Distribution - Jet Propulsion Laboratory 1st Ann... · Distribution Category UC -63 ... Nine more contractors have been selected to perform ,additional tech- ... Simplified energy

E R D A / J P L / ~ o ~ ~ - ~ ~ / ~ , Distribution Category UC -63 ' i

OF T H E

LOW - C O S T S I L I C O N S O L A R A R R A Y P R O J E C T ,.., - ;. .,, - f 3 ..a& .,

F O R T H E P E R I O D

J A N U A R Y 1 9 7 5 - M A R C H 1 9 7 6

' JPLDocument 5101-3

Published - August 9, 1976

NOTICE

lpoarod by the United SUtu G o m l u ~ n t . N&lm th. United Stltsr nor the United S h t a Energy W c h d M o p w n t AdadniUntion. nor my of hair empbym, nor 8tlg of their mntactars, sabmnmdon, or th& slnployca. lnhr my

eXpNM or impbd, Or ~~1 any l& %ability or rccp~ndbility for the acmmcy, mmpkrmma or ueIulncm of my infornution, rppantm, produn or pi.,- dhdord, or rrplaCnt1 Uut it1 ulo wc.uld not

This work w a s performed by the J e t Propulsion Laboratory. California Institute of Technology, under National Aeronautics and Space Administration Contract NAS7-100, f o r the U. S. Energy Research and Development Administration (ERDA), Division of Solar Energy.

The Low-Cost Silicon Solar Ar r ay Projec t is funded by ERDA and forms pa r t of the ERDA Photovoltaic Conversion Program to initiate a major effort toward the development of low-cost so la r arrays. , . . . I

I ,

L 4 ' .

J E T P R O P U L S I O N L A B O R A T O R Y

C A L I F O R N I A I N S T I T U T E O F T E C H N O L O G Y

P A S A D E N A , C A L I F O R N I A

A B S T R A C T

In r e s p o n s e t o t h e - n e e d t o f ind n e w m e t h o d s of e c o n o m i c a l l y g e n e r a t i n g e n o u g h e l e c t r i c a l p o w e r t o m e e t f u t u r e r e q u i r e m e n t s , t h e P h o t o v o l t a i c C o n v e r s i o n P r o g r a m of E R D A ' s D i v i s i o n of S o l a r E n e r g y w a s e s t a b l i s h e d it1 J a n u a r y 1975 . T h e o v e r a l l P r o g r a m o b j e c t i v e s a r e ( 1 ) t o d e v e l o p t h e t e c h n o l o g y f o r l o w - c o s t p h o t o v o l t a i c p o w e r and ( 2 ) t o s t i m u l a t e i n d u s t r y t o p r o d u c e , m a r k e t , a n d d i s t r i b u t e p h o t o v o l t a i c s y s - t e m s f o r w i d e s p r e a d r e s i d e n t i a l , c o m m e r c i a l , a n d g o v e r n m e n t a l u s e . T h e L o w - C o s t S i l i c o n S o l a r A r r a y P r o j e c t (LSSA) w a s e s t a b l i s h e d a t t h e J e t P r o p u l s i o n L a b o r a t o r y as p a r t of t h e E R D A P r o g r a m . I t s g o a l is t o g r e a t l y r e d u c e t h e p r i c e of s o l a r a r r a y s by t h e i m p r o v e n l e n t of m a n u - f a c t u r i n g t e c h n o l o g y , by a d a p t a t i o n of m a s s p r o d u c t i o n t e c h n i q u e s , a n d b y h e l p i n g a c h i e v e m e n t of u s e r a c c e p t a n c e . T h e ~ r o j e c t"s a p p r o a c h ,

i n c l u d e s t h c d e v e l o p m e i l t of t e c h n o l o g y , i t s t r a n s f e r b y i n d u s t r y t o c o m - m e r c i a l p r a c t i c e , t h e e v a l u a t i o n of t h e e c o n o m i c s i n v o l v e d , a n d t h e s t i m u l a t i o n of m a r k e t g r o w t h .

T h e a c t i v i t i e s a n d p r o g r e s s of t h e L S S A P r o j e c t d u r i n g i t s f i r s t y e a r a r e d e s c r i b e d i n t h i s d o c u m e n t . I t i s t h e f i r s t P r o j e c t d o c u n l e n t i n t e n d e d f o r w i d e d i s sen . i i r i a t ion a n d is a r e p o r t c o v e r i n g a l l P r o j e c t a c t i - v i t i e s , w i t h p r i m a r y e m p h a s i s o n t h e t e c h n i c a l p l a n s a n d a c c o n ~ p l i s h t n e n t s . T h e d e v e l o p m e n t of m a n u f a c t u r i n g t e c h n o l o g y is n o w a n d w i l l c o n t i n u e t o b e p e r f o r m e d p r i n c i p a l l y by i n d u s t r i e s a n d universities. T o d a t e , 24 c o n t r a c t o r s are w o r k i n g o n n e w s i l i c o n - r e f i n e m e n t p r o c e s s e s , s i l i c o n - s h e e t - g r o w t h t e c h n i q u e s , e n c a p s u l a n t s , a n d a u t o m a t e d - a s s e m b l y s t u d i e s . N i n e m o r e c o n t r a c t o r s h a v e b e e n s e l e c t e d t o p e r f o r m , a d d i t i o n a l t e c h - n o l o g y i n v e s t i g a t i o n s a n d t h e i r c o n t r a c t s are b e i n g n e g o t i a t e d . A d d i - t i o n a l c o n t r a c t s w i l l b e i s s u e d i n t h e f u t u r e as p r o m i s i n g i d e a s a p p e a r .

I n d u s t r y , t h r o u g h i n v e s t m e n t i n m a n u f a c t u r i n g a n d s u p p l e m e n t a r y a c t i v i t i e s , is i n c r e a s i n g i t s r o l e i n P r o j e c t - s u p p o r t e d a c t i v i t i e s . F i v e c o m p a n i e s are m a n u f a c t u r i n g "off t h e s h e l f " s o l a r a r r a y s t h a t a re b e i n g p u r c h a s e d f o r E R D A ' s t e s t a n d d e m o n s t r a t i o n a c t i v i t i e s . T h i r t e e n p r o - p o s a l s , s u b m i t t e d i n r e s p o n s e t o a R e q u e s t f o r P r o p o s a l , a re b e i n g e v a l u - a t e d f o r t h e p r o c u r e m e n t of a l a r g e r q u a n t i t y of s e m i s t a n d a r d i z e d s o l a r a r r a y s . P l a n s a r e b e i n g . f o r m u l a t e d f o r f u t u r e p u r c h a s e s of i n c r e a s i n g q u a n t i t i e s of s o l a r a r r a y s m a n u f a c t u r e d w i t h t h e e v o l v i n g s t a t e - o f - t h e - a r t t e c h n o l o g y a n d s e l l i n g a t d e c r e a s i n g u n i t c o s t s .

T h e E R D A P r o g r a m is d e r i v e d f r o m t w o d e c a d e s of e x t e n s i v e r e s e a r c h , . d e v e l o p m e n t , a n d u s e of s i l i c o n s o l a r c e l l s by i n d u s t r i e s , u n i v e r s i t i e s , p r i v a t e o r g a n i z a t i o n s , NASA, N S F , a n d o t h e r g o v e r n m e n t a l a g e n c i e s . T h e P r o g r a m p l a n n o w b e i n g i m p l e m e n t e d o r i g i n a t e d u n d e r N S F a n d w a s t h o r o u g h l y r e e v a l u a t e d b y E R D A i n c o n j u n c t i o n w i t h i n d u s t r y a n d o t h e r g o v e r n m e n t a g e n c i e s a n d c o n t i n u e s t o b e u p g r a d e d as t h e p r o - ject e v o l v e s .

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C O N T E N T S

Part . P a g e

I . SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A . P R O J E C T ANALYSIS A N D INTEGRATION

. . . . . . . . B . TECHNOLOGY D E V E L O P M E N T C O N T R A C T S

. . . . . . . . . . . . . . . . . . . . . C . SILICON MATERLAL TASK

. . . . . . . . . . . . . . D . L A R G E - A R E A SILICON S H E E T TASK

. . . . . . . . . . . . . . . . . . . . . . E . ENCAPSULATION 'TASK

. . . . . . . . . . . . . . . . F . A U T O M A T E D ASSEMBLY TASK ;

. . . . . . . . . . . . . . G . L A R G E - S C A L E PRODUCTION TASK

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I1 . INTRODUCTION

A . BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B . P R O J E C T M A N A G E M E N T

. . . . . . . . . . . . . . . 111 . P R O J E C T ANALYSIS AND INTEGRATION

. . . . . . . . . . . . . . . . . . . . . . . A . P R O J E C T ASSESSMENT

. . . . . . . . . . . . . . . . . . . . 1 . A l l o c a t i o n of C o s t G o a l s

. . . . . . . 2 . Def in i t i on of P r o j e c t A s s e s s m e n t F a c t o r s

. . . . . . . 3 . E v a l u a t i o n of A l t e r n a t i v e Des ign C o n c e p t s

4 . E s t i m a t i o n of t h e I m p a c t of R e s e a r c h E f f o r t s on . . . . . . . . . . . . . . . . . . . . . . . . . . . A r r a y C o s t s

. . . . . . . . . . . . . . . . . . . . . . B . P R O J E C T INTEGRATION

. . . . . . . . C . D E V E L O P M E N T O F ANALYTIC TECHNIQUES .a

1 . Uti l i ty -Owned S o l a r E l c c t r i c S y s t e m (USES) M o d e l . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 . S o l a r A r r a y M a n u f a c t u r i n g I n d u s t r y S i m ~ ~ l a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . (SAMIS) M o d e l

. . . . . . . . . . . . . . . . . . . . . . . D . COMMERCIALIZATION

. . . . . . . . . . . . . . . . . . IV . TECHNOLOGY D E V E L O P M E N T TASKS

TASK 1 . SILICON MATERLAL

. . . . . . . . . . . . . . . . . . . TECHNOLOGY B_4CI<GROUND

. . . . . . . . . . ORGANIZATION O F T H E TASK 1 EFE'OKT

T A S K 1 C O N T R A C T S . . . . . . . . . . . . . . . . . . . . . . . . .

CONTENTS (contd)

P a r t Page

D . TASK 1 TECHNICAL ACTIVITY . . . . . . . . . . . . . . . . . . 1 . P r o c e s s e s f o r Producing Semiconductor-Grade

Sil icon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Specif icat ions fo r So la r -Ce l l -Grade Si

. . . . . 3 . P r o c e s s e s f o r Producing Sola r -Cel l -Grade Si

4 . Evaluat ion of Si Product ion P r o c e s s e s . . . . . . . . . . . . . . . . . . . . . . . . L a m a r Univers i ty

. . . . . . . . . . . . . . . . 5 J P L T a s k 1 In-House Support

TASK 2 . LARGE-AREA SILICON SHEETS

. . . . . . . . . . . . . . . . . . . . . A TECHNICALBACKGROUND

. . . . . . . . . . . B 0.RGANIZATION O F THE TASK 2 E F F O R T

. . . . . . . . . . . . . . . . . . . . . . . . . . C TASK 2 CONTRACTS

. . . . . . . . . . . . . . . . . . TASK 2 TECHNICAL ACTIVITY

1 . Web-Dendri t ic Growth . Univers i ty of . . . . . . . . . . . . . . . . . . . . . . . . . . South Caro l ina

2 . E F G Growth . Mobil-Tyco Sola r Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . Corpora t ion

. . . . . . . . . . . . . . . . . . . . . . . 3 . E F G Growth IBM

. . . . . . . . . . . . Inver ted Stepanov Technique RCA

L a s e r -Zone Growth i n a Ribbon-to-Ribbon . . . . . . . . . . . . . . . . . . . . . . . P r o c e s s Motorola

. . . . . . . . . CVD on Low-Cost Subs t ra tes Rockwell

Float ing Subs t ra te /CVD on Liquid . . . . . . . . . . . . . . . . . . . . . . . . . G e n e r a l E l e c t r i c

D;.p-Coating on Low-Cost Subs t r a t e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Honeywell

Heat Exchanger Method of Ingot Casting . . . . . . . . . . . . . . . . . . . . . . . . . C r y s t a l Systems

. . . . . . . . . Multiple -Wire Sawing C r y s t a l Sys t ems

. . . . . . . . . . . . . . . . . . Breadknife Sawing Var ian

. . . . . . . . . . . . . . . J P L In-Hause T a s k 2 Activity

TASK 3 . ENCAPSULATION

. . . . . . . . . . . . . . . . . . . . TECHNICALBACKGROUND

. . . . . . . . . . ORGANIZATION O F THE TASK 3 E F F O R T

CONTENTS (contd)

P a r t Page

. . . . . . . . . . . . . . . . . . . . . . . . . C . TASK 3 CONTRACTS

. . . . . . . . . . . . . . . . . . D . TASK 3 TECHNICAL ACTIVITY

1 . Identification of Candidate Encapsulant Mater ia l s . Battelle . . . . . . . . . . . . . . . . . . . . . .

2 . Conditions for Evaluating and Qualifying Encapsulant Mater ia l s . Battelle . . . . . . . . . . . . .

TASK 4 . SOLAR ARRAY AUTOMATED ASSEMBLY

. . . . . . . . . . . . . . . . . . . . A . TECHNICAL BACKGROUND

. . . . . . . . . . B . ORGANIZATION OF THE TASK 4 EFFORT

. . . . . . . . . . . . . . . . . . . . . . . . . C . TASK 4 CONTRACTS

. . . . . . . . . . . . . . . . . . . D TASK 4 TECHNICAL ACTIVITY

1 . M a n u f a c t u r i n g P r o c e s s e s A s s e s s r n e n t ~ M o t o r o l a . RCA. and Texas lns t rumcnts . . . . . . . . . . . . . . . .

2 . Elec t ron- Beam Solar Cel l Fabr ica t ion- . . . . . . . . . . . . . . . . . . . . . . Simulation Physic s

. . . . . . . . . . . . . . . . 3 A r r a y T e s t Evaluation Mi t re /' . . . . . . . . . . . . . . . 4 . A r r a y T e s t Evaluation Solarex

. . . . . . . . . . . . . . . . . . V . LARGE-SCALE PRODUCTION TASK

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . A . BAC,KGR.OUND

. . . . . . . . . . . B . ORGANIZATION OF. THE LSP EFFORT ;

. . . . . . . . . . . . . . . . . . . . C . . LSP TECHNICAL ACTIVITY

. . . . . . . . . . . . . 1 Large-Scale P rocu remen t Activity

. . . . . . . . . . . . . . . . . . . 2 Design and Tes't Activity

. . . . . . . . . . . . . . . . . 3 . Quality Assurance Activity

. . . . . . . . . . . . . . . . . . . . . . . . 4 . Fu tu re Activit ies

FIGURES

1.1 . Functional re la t ionships within the P r o j e c t and between . . . . . . . . . . . . . . . . . . . . . . . . the P r o j e c t and ERDA

2.1 . Organization c h a r t . Low-Cost Silicon Solar A r r a y P r o j e c t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.1 . T e r r e s t r i a l s o l a r a r r a y pr ice h i s tory . . . . . . . . . . . . . . vii

CONTENTS (contd) \

\ '

FIGURES

3 -2. T e r r e s t r i a l s o l a r a r r a y pr ice goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3. S t ruc tu re of USES model :

3 -4. - USES compar i son of levelized energy cost with . . . . . . . . . . . . . . . . . . . . . . . . . growing energy c o s t s

3 -5. A .SAMIS descr ip t ion of an industry based on Czochra lsk i ingots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

, 4-1. Pre . l iminary flow d iag ram lor the preparat ion of Si by Zn Reduction of .SiC14 . . . . . . . . . . . . . . . . . . . . . . . .

. . . . 4-2. - Conversion efficiency, 2 Zn t ~ i ~ l , ~ = 2 ZnC12 t Si

4 - 3. Schematic of unit f o r the preparat ion of Si by the Zn . . . . . . . . . . . . . . . . . . . (vapor f eed ) reduction of SiC14

4 -4. Simplified energy and m a t e r i a l flow' c h a r t fo r p repara t ion of 1 mo le of Si by reduction of SiC14 . . . . . .

4-5. P r e l i m i n a r y flow d iag ram for the prepara t ion of Si-f rom the hydrogen reduction pyrolysis of SiI made by the 4 . . . . . . . . . . . . . . . . i odination of SiO, /carbon mix tu re - .

4-6. ~ i m ~ l i f i ' e d energy and m a t e r i a l flow c h a r t fo r the prepara t ion of 1 mo le of Si by the rma l decomposit ion ofSi14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . Sc.hem.atic. f o r maxi -plant

. . . . . . . . . . . . Large A r e a Silicon s h e e t ~ a L k schedule

web-dendr i t i c growth . . . . . . . . :. . . . . . . . . . . . . . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . Capil lary die growth . .;

. . . . . . . . . . . . . . . . . . . . . . Inver ted Stepanov technique

. . . . . . . . . . . . . . . . . . . . L a s e r zone, crystall iz-ation. -. . . . . . . . . . . . . . . . . . . . . . . . . . . . Chemical vapor deposition

'. . . 4 .' . . . . . . . . . . . . . . . . . . . Floating subs t r a t e sheet growth

~ r o s ' s - s e c t i o n a l ' s k e t c h of basic shee t dip coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . growth faci l i ty < . . . . . . . C r y s t a l growth using the ~ e a t . ~ x c h a n ~ e r Method

Three- inch d i ame te r si l icon in Varian multiblade . wafer saw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Encapsulation T a s k schedule . . . . . . . . . . . . . . . . . . . . -

Page

viii 1 .

CONTENTS (contd)

FIGURES Page \

TABLES

. . . . . . . Solar A r r a y Automat'ed Assembly Task Schedule

Task 4 interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Silicon utilization

P r e s e n t state -of -the - a r t ma jo r manufacturing cos t es t imates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Concept of pulsed processing fo r automated ce l l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . production

. . . . . . . . . . . . . Large-Scale Production Task schedule

. . . . . . . . . . . . . . . . . . . Solar a r r a y procurement plan

. . . . . . . . . . . . . . . . Technology development contractors 1-8

. . . . . . . . . . . . . . Large -scale procurement cont rac tors 1-9

. . . . . . . . . . . . . . . . . . . . ~ r o j e ' c t cost goal allocations 3-6

. . . . . . . . . . . . . . . . . . . . Candidate a s ses smen t fac tors 3-7

Organization of the Task 1 effort . . . . . . . . . . . . . . . . . . . 4-3

Task 1 contractors . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Task 2 contractors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28

4 .4 . Task 3 contractors . . . . . . . . . . . . . . .'. . . . . . . . . . . 4-57

4.5 . Task 4 contractors . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-65

TH'IS PAGE

WAS INTENTJLONALLY

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FOREWORD

The activit ies and accomplishments pf the Low--Cost Silicon Solar Ar ray

P ro jec t (LSSA) during its f i r s t year a r e descr ibed ' in this document. These

activit ies a r e p a r t of the ERDA Photovoltaic Conversion P r o g r a m which i s '

responsible fo r the national effort directed toward the, development and util iza-

tion of ent i re photovoltaic power sys tems.

This repor t i s the f i r s t Pro jec t document intended f o r widespread d issemi-

nation, and i s pr imar i ly a technical repor t covering a l l the P ro jec t activit ies,

with emphasis on the technical plans and accomplishments. The majori ty of the

technical accomplishments 'relate to activit ies in the past t h ree months, because

the participating industr ies and universi t ies have been under contract for 'only

a few months. The repor t i s a r ranged in a functional manner and i s not s t r ic t ly

arranged as the Projec t i s organized.

The Pro jec t will be issuing Quar ter ly Reports s tar t ing with the f i r s t repor t

in May 1976. These Quar ter ly Reports and the future Annual Reports will

emphasize the technical accomplishments achieved during the i r respect ive

reporting periods. \

Genera l

CVD .

* DOD

EBIC

E F G

E P R I

ERDA

J P L

LASS

L e P C

L S P ,

LSSA

NASA

NSF ..

P A & I

chemica l vapor deposition

~ e p a r t m e n t of Defense

e l e c t r o n - b e a k ir iduced-current * e n e r g y d i spe r s ive analysi's of X- rays

edge-defined f i lm-fed growth

E l e c t r i c P o w e r R e s e a r c h Insti tute

Ene rgy R e s e a r c h and Developm,ent Adminis t ra t ion

. J e t Propuls ion 'Labora tory

L a r g e A r e a Silicon Sheet Task

Lewis' R e s e a r c h Cen te r . ,

L a r g e Sca l e Product ion Task

LOW-Cost Silicon So la r A r r a y p r o j e c t

National ~ e . r o n a u t i c s and Space Adminis t ra t ion

National Space Foundation:'

P r o j e c t Analysis and,1ntkgration T a s k

P r o j e c t Al ternat ive ' ~ e s i g ; Evaluation Model

RANN R e s e a r c h Applied t o National Needs

R F P Reques t f o r P roposa l ,

SAMIS s o l a r - a r r a y manufactur ing indus t ry ' s imulat ion

USES utility-ownkd so l a r - ene rgy s y s t e m -

Chemica l Symbols

A ,I a luminum

C carbon

Mg magnes ium

Mn manganese

C 1 chlor ine ' Ni - .

nickel

'Cu copper 0 oxygen

C r ch romium S i s i l icon

F f luor ine Sn t in

F e ' i r o n T i t i tanium

H hydrogen V vanadium

He he l ium Zn zinc

I iodine Z r z i rconium

P A R T I

SUMMARY

A c t i v i t i e s d i r e c t e d t o w a r d f u t u r e w i d e s p r e a d u s e of photovol ta i c s y s t e m s

f o r t h e g e n e r a t i o n of e l e c t r i c p o w e r w e r e i n i t i a t e d with t h e e s t a b l i s h m e n t , i n

J a n u a r y 1975, of t h e P h o t o v o l t a i c C o n v e r s i o n P r o g r a m of E R D A ' s D i v i s i o n of

S o l a r E n e r g y . T h e P r o g r a m ' s a c t i v i t i e s a r e p l a n n e d t o d e v e l o p a n d t o p r o m o t e

the u s e of pho tovo l t a i c s y s t e m s t o s u c h a n e x t e n t t h a t t h e p r i v a t e s e c t o r w i l l

p r o d u c e a n d u t i l i z e c o s t - c o m p e t i t i v e pho tovo l t a i c s y s t e m s . T h e ERDA P r o g r a m

p l a n is b a s e d o n y e a r s of, p r e v i o u s r e s e a r c h , deve lopmt?nt , a n d s t u d i e s . T h e '

o b j e c t i v e s of t h e ERDA P r o g r a m a r e :

T o d e v e l o p l o w - c o s t r e l i a b l e photovol ta ic s y s t e m s .

T o s t i m u l a t e t he c r e a t i o n of a v i a b l e i n d u s t r i a l and c o m m e r c i a l c a p a b i l i t y t o p r o d u c e and d i s t r i b u t e t h e s e s y s t e m s f o r w i d e s p r e a d u s e i n r e s i d e n t i a l , c o m m e r c i a l , and g o v e r n m e n t a l a p p l i c a t i o n s .

T h e L o w - C o s t S i l i con S o l a r A r r a y P r o j e c t (LSSA) , a p a r t of t he E R D A

P r o g r a m , w a s e s t a b l i s h e d a t J P L i n J a n u a r y 1975 . T h e LSSA P r o j e c t g o a l i s t o

r e d u c e the c o s t of s o l a r c e l l a r r a y s by i m p r o v i n g the t echno logy and by i n c r e a s -

i n g t h e s o l a r a r r a y p r o d u c t i o n c a p a b i l i t y and v o l u m e .

J P L ' s r o l e i n t he E R D A plan i s :

T o s u p p o r t s i l i c o n - s o l a r - a r r a y m a n u f a c t u r i n g t echno logy d e v e l o p - m e n t and i t s t r a n s f e r to i n d u s t r y .

T o e n c o u r a g e e x p a n s i o n of i n d u s t r i a l c a p a b i l i t y t o p r o d u c e s o l a r a r r a y s .

T o s u p p o r t m e t h o d s of p r o m o t i n g u s e r a c c e p t a n c e .

T h e s p e c i f i c J P L P r o j e c t g o a l f o r 1985-86 :

T o r e d u c e t o d a y ' s s o l a r a r r a y p r i c e s of $20, 000 to $25, 000 p e r k i l o w a t t i n a n n u a l q u a n t i t i e s of 100 k i l o w a t t s t o l e s s t h a n $500 p e r k i l o w a t t i n a n n u a l q u a n t i t i e s of 500, 000 k i l o w a t t s .

P r o g r , e s s t o w a r d t h e c o s t r e d u c t i o n g o a l s a c h i e v e d d u r i n g t h e p a s t y e a r

h a s b e e n n o t a b l e and h a s a c h i e v e d the p lanned g o a l s . T h e a c t i v i t i e s and a c c o m - \

p l i s h m e n t s of t he LSSA P r o j e c t a r e s u m m a r i z e d i n t h i s r e p o r t .

\

. . \

The approach being . implementid to achieve the Project1-s objectives .

cons i s t s of technology development, industry involvement, comrnerciali.zation, . .

and m a r k e t stimulation. Technology development i s directed toward the ex t r ac - I

tion and utilization of those i t e m s f r o m past arid cu r reh t r e s e a r c h act ivi t ies ' that .>

' . ' '

. 4

can reduce the cos t 'of producing so lar a r r a y s . Industry involvement i s being

fos t e red by part i=ipat ion i n the technology development, by the t ransfer-of tech-

nology to commerc ia l prac t ice , And by planned ea r ly l a rge annual procurements

of Solar a r r a y s . Market growth i s being supported and ~ t i m u 1 a t e d . b ~ the annual

s o l a r - a r r a y procurements , by ERDA1s photovoltaic power sys t em tes t s , by /

operat ional and economic evaluations of these a r r a y s , and by active participation - with a r r a y u s e r s i n defining requi rements and designing a r r a y s . Th'e P ro jec t

will conduc t ' so l a r -a r ray design and t e s t act ivi t ies and will manage and integrate

the s o l a r - a r r a y technolog-y develop'ment activit ies.

. .. Techno1o.g~ development involves tkie selection and support of potential - s o l a r - a r r a y manufactur ing cos t reduction efforts; continuing a s s e s s m e n t of the

technica l feasibi l i t ies of the evolving techniques and hardware; and verification - of the e,conomic viability of new manufacturing processes . These activit ies a r e

being acdomplished principally by industr ies and universi t ies and a r e divided

into four tasks :

1 ) Production of low-cost si l icon mater ia l . ,

2 ) Economical production of silicon in la rge-area-shee ts suitable for .. - the manufacture of so la r cel ls .

3 ) Development of kconomital encapsulation ma te r i a l s and techniques

f o r a r r a y l i fe t imes g rea te r than 20 yea r s .

' 4 ) Development of automated p rocesses and equipment for low-cost

- high-volume production of so lar a r r a y s .

. - The m a j o r s t eps to .be accomplished.by the four tasks and the interrelat ionship

of these t a s k s a r e shown i n Fig. 1 -1.

. The l a rge - sca le production activity involves the periodic purchase of

inc reas ing quantit ies of s o l a r a r r a y s a t decreasing unit p r i ces and with the

. . l a t e s t s t a t e -of -the.-art technology. The a r r a y s a r e being pro'curkd f r o m

JPL TASKS

AUTOMATEI) tXPtRlMENTAL

PRODUCTION

1

MATERIALS AND MATERIALS AND CONTINUING

PROCESSES PROCESSES . LIFE TIME - REOUllEMENTS DEFINED EVALUATION

. ,

I L I

TECHNOLOGY TRANSFER FROM ABOVE TASKS

I a a A

MANUFACTURING EXPERIENCE - - -

* ' PERIODIC WRCHASE OF ARRAYS PRODUCTION

f

PHOTOVOLTAIC SYSTEM TESTS AND DEMONSTKATIONS NASA/LsRC. DOD 6 OTHERS

TEST AND DEMONSTKATION RESULTS a - A - - - 1 a a

POWER SYSTEM REQUIREMENTS - - 7

3. TKHNOLOGY = -:'i'

1

POWER CONDITIONING h STORAGE

, MILITARY APPLICATIONS

NOVEL MATERIALS 6 DEVICES

TRANSFER OF: 1. INFORMATION - - '2. HARDWARE -

I

Fig. 1 - 1 . ' Functional relationships within the project and between the Project and ERDA

O T H ~ ERDA PHOTOVOLTAIC ACTIVITIES

SYSTEMS 6 APPLICATIONS

indus t ry on a comxn,ercial bas i s to mee t p,erforrnaric& specifications and . .

environmental requi rements f o r use in .ERDA photovoltaic power'system t e s t s .

and dem.onstrations. Hence, cu r ren t technology will be evaluated under numer - o u i and d ive r se environmental and operational conditions. This activity will

s t imula te an expansion of indus t ry ' s so la r - a r r a y manufacturing capabili t ies and

demonst ra te the ,resulting cos t reductions. It will a l s o m e a s u r e the benefits of !

incorporat ing the l a t e s t photovoltaic technology and facil i tate. ear ly detection of

manufacturi-ng problems. In conjunction with a r r a y manufac turers and users. ,

data will be obtained f o r establishing design, reliabili ty, . and performance . '.

improvements of s o l a r a r r a y s . The functional relationships within the LSSA

P r o j e c t and between the P r o j e c t and ERDA a r e shown in the preceding figure. * .

,

The project analysis .and integration (PA&I) effort focuses on the planning,

. integration, and overa l l p ro jec t analytical support which contributes to P ro jec t \

decis ion-making. This support will be irrjplemented by providing a s sessmen t s

of possible per formance and economic conse,quences of a l ternat ive P ro jec t , plans, developing the in te r face requirements among the ~ r o j e c t . t a s k s , support-

ing the establ ishment of the in te r face requirements . . between t,he LSSA Pro jec t , . .

and o ther ERDA ~ h o t o v o l t a i c - Conve.rsion P r o g r a m ac'tivities, .and by developing

.. the plans and procedures f o r integrating the tasks within the P ro jec t and between

the P r o j e c t activit ies and 'o ther e1emen.t~ of the P rogram.

The P ro jec t approach of conduct ingparal le l efforts within each. of the - technology development tasks and. the l a rge sca le production activit ies prov-ides

f o r examination of a l ternat ive approaches in.o.rder to obtain the most cost-

effective methods f o r a=hieving individual task. objective-s. Then, to optim'ize ,

the. overa l l project efforts, extensive examinations of the trade-offs between the . . .

t a sk approaches a r e pe r fo rmed . \

Considerable effort has been devoted to the P ro jec t in planning, imple-

menting, and administer ing these widely d iverse and complex procurement

act ivi t ies , involving universi t ies , l a rge industr ies , sma l l businesses , and

var ious governmental agencies. Many unsolicited proposals have been received . .

and a r e being evaluated *ith additional ones anticipated on a continuing basis.

In addit ion t o the contracted effort , J P L will u t i l ize in-house expe r t i s e

and faci l i t ies i n technical a s s e s s m e n t of the ma te r i a l s , devices , and p r o c e s s e s

which a r e being developed within the P r o j e c t a s well a s conduct l imi ted tech-

nology development.

The LSSA P r o j e c t was init iated on J a n u a r y 9, 1975; the in te rna l P r o j e c t

organizat ion was es tab l i shed in accordance with J P L P r o g r a m P l a n 1200- 18 1,

dated November 15, 1974. An indus t ry br ief ing was conducted on F e b r u a r y 5,

1975 to int roduce the P r o j e c t plans, objectives, schedules , and de ta i l s of

re la ted procurements . Approximately 300 pe r sons attended, represen t ing 105

companies. and 15 un ivers i t i es .

A m a j o r effor t dur ing this f i r s t y e a r ha s been to organize and coordinate

th i s d ive r se technical activity. In addition t o per iodic individual con t rac t

reviews, the f i r s t P r o j e c t Integrat ion Meeting was held J a n u a r y 13 and 14, 1976

a t J P L ; technical represen ta t ives of a l l the par t ic ipat ing organizat ions attended.

P a p e r s cover ing the P r o j e c t act ivi t ies we re presen ted a t the Second Semiannual

So l a r Photovoltaic Convers ion P r o g r a m Conference in Orlando, F lo r ida by J P L

r ep re sen t a t i ve s in J a n u a r y 1976. Cont rac tor represen ta t ives a l s o attended the

conference.

PROJECT ANALYSIS AND INTEGRATION

P r o j e c t Analysis and Integrat ion supports planning act ivi t ies by develop-

ing and implement ing techniques fo r a s s e s s i n g P r o j e c t plans and p r o g r e s s ; by

providing operat ional and economic ana lyses ; by determining internal and

ex te rna l in te r face requi rements ; and 'by contributing t o design requi rements .

These act ivi t ies provide f o r the integrat ion of P r o j e c t t a s k s a s well a s in tegra-

tion of the LSSA P r o j e c t ,with o ther e lements of the ERDA Photovoltaic P r o g r a m .

P r o j e c t a s s e s s m e n t methodologies continue t o be formulated and applied

t o decis ion prob lems . Informal in tegrat ion and in te r face meet ings have been

conducted with o the r e lements of the ERDA Photovoltaic P r o g r a m and the f i r s t

f o r m a l LSSA P r o j e c t / T a s k Integrat ion Meeting has been held.

O p e r a t i o n a l and . -economic a n a l y s e s a r e continuing u n d e r deve lopment :

t h e USES (ut i l i ty-owned s o l a r e n e r g y s y s t l & k ) r e q u i r e d - r e v e n u e m o d e l

( d e v e l o p e d jo in t ly with ERDA and t h e E l e c t r i c Powesr R e s e a r c h Ins t i tu te ) is

b e i n g p r e p a r e d f o r publ ica t ion; the SAMIS ( s ' o l a r - a r r a y manufac tu r ing i n d u s t r y

s i m u l a t i o n ) is being e v a l u a t e d a t t h i s t i m e .

B. TECHNOLOGY D E V E L O P M E N T CONTRACTS

R e q u e s t f o r P r o p o s a l ( R F P ) packages f o r the f o u r technology deve lopment

t a s k s w e r e m a i l e d i n M a r c h 1975 to a p p r o x i m a t e l y 272 o rgan iza t ions . In

r e s p o n s e to thebe f o u r R F P s 91 p r o p o s a l s w e r e r e c e i v e d by the end of Apr i l .

T h e p r o p o s a l s w e r e r e v i e w e d and evaluated on the b a s i s of compa t ib i l i ty wi th

t h e P r o j e c t ob jec t ives , t e c h n i c a l m e r i t , and p r i c e c o m p e t i t i v e n e s s . F u r t h e r

c l a r i f y i n g i n f o r m a t i o n w a s obta ined f r o m the o r g a n i z a t i o n s tha t s u b m i t t e d the

h i g h e s t p r i o r i t y p r o p o s a l s e i t h e r by v is i t ing t h e , o r g a n i z a t i o n o r by having r e p r e - ,--

se 'n ta t ives c o m e to J P L . Upon comple t ion of t h e s e s u r v e y s , e a c h t a s k a r e a w a s

r e v i e w e d and gu ide l ines w e r e p r e p a r e d wi th r e g a r d t o the n u m b e r of c o n t r a c t s

t h a t could be s e l e c t e d and the funding n e c e s s a r y to s u p p o r t t h e s e p r o c u r e m e n t s .

T h e f ina l c o n t r a c t o r s e l e c t i o n s w e r e m a d e by s e l e c t i n g the h ighes t p r i o r i t y

p r o p o s a l s to the e x t e n t p e r m i t t e d by the ant ic ipa ted P r o j e c t budget l e v e l s . Con-

t r a c t o r s w e r e notif ied i n the J u l y - S e p t e m b e r per iod a s t o w h e t h e r o r not they

had b e e n s e l e c t e d . Not i f ica t ions w e r e m a d e on the b a s i s of the funding ava i l ab le

t o c o v e r the c o n t r a c t s , on a n obl iga t ion b a s i s , and a s c o n s i s t e n t wi th the budget

s i tua t ion . F o r m a l c o n t r a c t negot ia t ions w e r e in i t ia ted wi th the o r g a n i z a t i o n s

.- s h o w n i n T a b l e 1-1 . Nine c o n t r a c t s w e r e negotiated and s igned by the end of

Oc tober . . T h e nego t i a t ion .and awarding' of m a n y of the r e m a i n i n g c o n t r a c t s w a s

d e l a y e d beizause of pa tent w a i v e r r e q u e s t s and o t h e r f a c t o r s . .

C. SILICON MATERIAL TASK

T h e ob jec t ive of t h e ~ i l i c o n ~ a t e r i a l T a s k is t o deve lop a capability,for -

p r o d u c i n g s i l i con , at a c o s t of l e s s than $10 p e r k i l o g r a m , t h a t is s u i t a b l e f o r

the m o s t e c o n o m i c a l f a b r i c a t i o n of s o l a r c e l l s . At p r e s e n t , s e m i c o n d u c t o r -

g r a d e s i l i c o n is u s e d f o r m a k i n g s o l a r c e l l s . . I t is known tha t s o l a r c e l l s c a n

b e f a b r i c a t e d f r o m l e s s p u r e s i l i c o n ; however , ce l l e f f ic iency m a y b e r e d u c e d

a s the quantities of impuri t ies increase. Therefore , s o l a r cell per formance

ve r sus sil icon impuri t ies and crystal l ine s t ruc tu re i s being investigated. The

evaluation of so la r cell performance ve r sus ma te r i a l / so la r cell p roper t ies and

cos t can be verified only through yea r s of analysis and testing. Consequently,

paral le l efforts a r e under way: ( 1 ) reduction of the production costs of s e m i -

conductor-grade silicon, (2) definition of a l e s s pure, l e s s costly so lar -ce l l -

grade silicon, and ( 3 ) development of an economical p rocess to produce this

so lar -ce l l grade silicon. In evaluating the above p rocesses a r e . d ~ ~ t i ~ n in

the consumption of energy required to produce the sil icon i s an impo;.:=.:t factor .

P r o c e s s e s that a r e being investigated with regard to the i r potential for the

low-cost production of semiconductor-grade silicon a r e a s follows: a method

of processing SiH the reduction of SiC14 and Si14, and a cyclic p rocess using 4'

S i F and metal lurgical grade Si ( s e e Table 1 - 1 ). Most of the accomplishments 4

to date in the Silicon Mater ial Task have been theoret ical analyses and the

preparat ion of experimental equipment. Some pre l iminary experimental resu l t s

have be-en obtained. The definition of so lar -ce l l -grade sil icon will resu l t f rom

evaluations of ma te r i a l s and so la r cel ls made f rom crys ta l s in which the silicon

, has been doped with a var ie ty of impuri t ies . The c rys t a l s will be grown by the

Czochralski, dendritic-web, and float zone methods. Many c rys t a l s of var ious

compositions have been grown and sliced. The method of preparing s o l a r cel ls

f rom these s l ices has been standardized. Mater ial and cell evaluation tech-

niques and plans a r e being prepared. Potential so la r - cel l -grade p rocesses that

will be investigated a r e a s follows: C reduction of S i 0 2 using a plasma, use of

C and SiO in an e lec t r ic a r c furnace followed by purification s teps , Na reduction 2

of SiF4, reduction of S i c 1 with alkali metals o r H using a p lasma a r c heater . 4 2

and reaction of H and S i c 1 in a nonequilibrium plasma jet. These efforts a r e 2 4

just s tar t ing. Supplementary studies of fluidized-bed technology and of the

relative commerc ia l potentials of the above p rocesses a r e being conducted.

D. ' LARGE-AREA SILICON SHEET TASK

The objective of the Large-Area Silicon. Sheet Task i s to develop an econ-

omical method of producing l a rge silicon shee ts that can be inexpensively made

r . . . C o n t r a c t o r 1 Tc.chnolou>- A r e a .

. . T A S ~ I . SILICOS XIATERIAL ( I I c o n t r a c t o r s )

;

S1.#lbironcl~8ctor-G1a~I1. S i l i c o n Prorl,tction P r o c r s e u s

B a t t ~ ~ 1 1 ~ ~ Xlcll,orial lns t i t t t te Si Iron!) SiCl , .or SiI C'ol88tlbh118. Ohio

Slotorola Phoenix . A r i z o n a

I'nion C a r h i d c S i s t c r s v i l l ~ ~ , \C. V i r g i n i a

l l o n a a n t o R e s r n r c h I st. I.0t.i~. \ l i s ~ o u r i

I i ~ v a t i n g h o u s e E l e c t r i c . Pittslmnrph. ~ r n n ' s y l v a n i a

Si us ing SiF, t r a n s f e r

I Si froen Sitl,

Inveat ipa t ion of ef fec ts 01 i m p u r i t i r s on s o l a r c e l l p e r f o r n > a n c e I l n v r s t i e a t i o n of c l l f c t a of i m p u r i t i e s on s o l a r c e l l p e r l o r t n a n c e ' I I S o l a r - C e l l - G r a d r Si l icon P r o d u c t i o n Procr.ssr.a I

' I Si Iron1 p u r e s o u r c e n ~ a t e r i a l s us inp a r c f u r n a c e p r o c e s s i n 0 I

1 Stamford R e s e a r c h I n ~ t i t u t e I Si by duplex ~ a ~ o r ~ e l e c t r o c h m ~ i . . ~ S l r n l o P a r k . C a l i f o r n i a c o n v e r s i p n 01 S i F I

I . A r r o C h e n ~ R e s e a r c h Labora tor ies : P r i n r r t o n . Sep. J e r s e y

I C 'o~tylwrcia l P o t e n t i a l of Processes

I ~ a ' ; t l a r V n i v e r i i t y . nra t tn>ont . T e x a s . .

S i by p l a s n , a - a r c - h y a t e r reduct ion 01 SiCI , with Hz and a l k a l i ~r ,era ls a a r rd l lc inc a r r n t s

F:valutale r e l a t i v e c o n , n > r r c i a l potent ia ls 01 Si product ion p r o . ceser .a <leveloped u n d e r T a s k I

TASK 2. LARGE ARE.4 SILICOZI S H E E T ( I I c o n t r a c t o r s )

Ril,b;on G r o w t h P r o c e a s e s

IBLl '

Hupewrl l Junct ion . New York

Xlobil - T y r o \\'althanr. S l a a s a c h u s e t t s

Slot0 r o l a Phoenis . A r i z o n a

RCA* P r i n c e t o n . S e w J e r i c y

Vniv. 01 So. C a r o l i n a Colunrbia. S. C a r o l i n a

S h e e t G r o w t h P r o c e a s e s

General E l e c t r i c Schenectady. S e w York

Eduv-defined. l i l m - l r d erowth

Edpc-def ined. f i l m - l e d prowth

L a s c r zone r ibhon growth

Inver ted Stepanov prowtb

U' rb-drndr i t ic prowth

Float ing s u b s t r a t e ( c h e n l i c a l v a p o r deposi t ion on liquid)

n i p - s s a t i n p (on low-cos t s u b s t r a t e s )

Rockwel l ' C h e m i c a l v a p o r deposi t ion ( o n low- Anahcinl. C a l i f o r n i a . I ' c o s t s u b s t r a t e s ) -

._/ lnvot G r o w t h a n d Cut t ing

C r y s t a l S y s t e m s S a l e m . Yaseachu.cttm

V a r i a n Lcs inpton. ~ l a s s a c h l m e t t e

Vniv. 01 ~ e n n m y l r a n i a ' Phi ladelphia . P e n n s y l v a n i a

Heat -eschan,grr inpot c a s t i n g and I n w l t i p l e w i i e sawin# I B r e a d k n i l e sawing

* c o n t r a c t t o be a w a r d e d in S p r l n p 01 1076. I

Table 1-1 (costd)

Table 1 -2. Large-scale procurement contractors (5)

'

46-KIV Solar A r r a y Prucnnrenncnt - k: \V

117 In ternat iona l A r l i ng ton I lu ichts , I l l i no i s 3 Sensor Trchnolouy C:hats\vorth. Ca l i f o rn i a 8

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:;olsreu Rockvi l lc.. L lary lant l /Q

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.

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Ba t t e l l e Llc,,torial In,st i tutr C o h ~ ~ r ~ b ~ t s . Ohio

DeBe l l and Richardson Enfield. Conn rc t i cu t -

RocL\r.ell -Anaheim. Ca l i f o rn i a

Sirnotlation ~ h ~ s i c a * Bur l inc ton. Massarhusct ts

Encapselant a s p c r i r n r e and rlcfiniticbn . o f env i r onmrh l : r n rapsu lan t t ea l

t,,r.thods anrl rsps1,i l i t ius

Polyn,sric prop.,rtiaa and a ~ i n c studies

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.

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Texas Inotr~un,ents Dallas. Tesas

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'C:ontract to I,c awar<ie<I i n Spr ing o f I l i b .

i n t o s o l a r c e l l s w i t h good e l e c t r i c a l and physica l p r o p e r t i e s . C o n t e m p o r a r y

s o l a r c e l l f a b r i c a t i o n r e q u i r e s the sawing of c r y s t a l s in to thin w a f e r s wi th

d i a m o n d s a w s follo-wed by polishing. Approx imate ly 75 p e r c e n t of the c r y s t a l

m a t e r i a l is w a s t e d . An i d e a l technique would b e to g r o w c r y s t a l l i n e s h e e t i n a

g e o m e t r y t h a t would r e q u i r e n e i t h e r cut t ing n o r polishing and yet would p roduce

a m a t e r i a l f r o m which high e f f i c i ency s o l a r c e l l s could be f a b r i c a t e d . As yet ,

no o n e t e c h n i q u e ' h a s b e e n developed, and pe r fec ted tha t a t t a i n s th is idea l

so lu t ion . However , the p r o g r e s s m a d e i n deve lopment w o r k on a n u m b e r of

g r o w t h t echn iques h a s b e e n suff icien-t to ind ica te tha t the idea l technique m a y be

a c h i e v a b l e . Consequen t ly , m a n y g r o w t h t echn iques a r e being ana ly t i ca l ly and

e x p e r i m e n t a l l y i n v e s t i g a t e d . Backup w o r k on c r y s t a l ingot g rowth and advanced

c u t t i n g t echn iques is a l s o being p e r f o r m e d ( s e e T a b l e 1 -1 ) . The in i t i a l w o r k

wi l l e m p h a s i z e d e t e r m i n a t i o n of the t echn ica l f eas ib i l i ty of the v a r i o u s p ro -

c e s s e s . T h e s u c c e s s f u l p r o c e s s e s wi l l then b e eva lua ted f o r t h e i r economic

f e a s i b i l i t y . The fo l lowing w o r k i s now being p e r f o r m e d by ~ a * ~ e - ~ r e a Si l icon

S h e e t T a s k c o n t r a c t o r s :

1) Ribbon g r o w t h f r o m a mol ten s o u r c e b a s e d on ( a ) c a p i l l a r y

ac t ion m o v e m e n t of m a t e r i a l th rough a d i e ( i . e . , the E F G

technique) and ( b ) g r a v i t y feed of m a t e r i a l f r o m a n i n v e r t e d

d i e ( i n v e r t e d Stepanov technique) .

2 ) W e b - d e n d r i t i c g r o w t h d i r e c t l y f r o m a m o l t e n s o u r c e wi th no

shap ing r e q u i r e d . -

3) L a s e r zone c r y s t a l l i z a t i o n of r ibbon m a t e r i a l ( r ibbon- to-

r ibbon p r o c e s s ) .

4) Vapor d e p o s i t i o n of thick f i l m m a t e r i a l on a low-cos t s u b s t r a t e

by c h e m i c a l v a p o r depos i t ion o r o t h e r me thods .

5) Shee t g r o w t h us ing novel techniques which inc lude dip-coating,

g rowth f r o m a s u p e r s a t u r a t e d b i n a r y mel t , and s t a t i c g rowth

of l a r g e ingo t s .

6) Ingot cu t t ing us ing mui t ip le -b lade and m u l t i p l e - w i r e s a w s ;

7 C h a r a c t e r i z a t i o n of m a t e r i a l s obta ined f r o m the above R & D

w o r k i n t e r m s of t h e i r su i t ab i l i ty f o r . f a b r i c a t i o n of high-

e f f i c i ency ( g r e a t e r than 10 p e r c e n t ) s o l a r c e l l s . (An a r r a y

ef f ic iency of a t l e a s t 10 p e r c e n t is d e s i r e d . )

In g e n e r a l , m o s t of the ac t iv i t ies to d a t e i n the L a r g e - A r e a Si l icon Shee t

T a s k have been t h e o r e t i c a l s tud ies , the p r e p a r a t i o n of the e x p e r i m e n t a l equip-

rhent, and in i t i a l g rowth exper imen t s . ' I m p r o v e m e n t s i n capi l la r 'y d i e d e s i g n

have been achieved which r e s u l t e d i n a reduc t ion i n s u r f a c e p a r t i c l e c o n t a m i n a -

t ion of the s i l i c o n r ibbon. A f a s t growth, edge-def ined, f i lm- fed g rowth ( E F G )

m a c h i n e is i n opera t ion . Seed c r y s t a l s t r u c t u r e e x p e r i m e n t s have y ie lded

knowledge which potential ly could r e s u l t i n , m o r e u n i f o r m c r y s t a l g rowth s t r u c -

t u r e . R e s u l t s t o da te , al though v e r y p r e l i m i n a r y , a r e s a t i s f a c t o r y and e n c o u r -

aging.

E . ENCAPSULATION TASK

- The ob jec t ive of the Encapsu la t ion T a s k is t o deve lop the capab i l i ty to

economica l ly e n c a p s u l a t e s o l a r a r r a y s f o r a 2 0 - y e a r l i f e t ime . Encapsu la t ion

m a t e r i a l s m u s t t r a n s m i t a m a x i m u m amount of sunl ight to the s o l a r c e l l s a s

we l l a s p r o t e c t the s o l a r c e l l s and e l e c t r i c a l c o n d u c t o r s f r o m the d e t r i m e n t a l

e f fec t s of a v a r i e t y of e n v i r o n m e n t a l condi t ions d u r i n g the l i fe of the a r r a y s .

They m u s t b e inexpens ive and e a s y t o p r o c e s s d u r i n g m a s s product ion of the

a r r a y s . T h e encapsu lan t m u s t b e c h e m i c a l l y s t a b l e o v e r a r a n g e of t e m p e r a -

t u r e s , and r e s i s t a n t t o f i r e , a b r a s i o n , i m p a c t , u l t r av io le t r ad ia t ion , and

m i c r o o r g a n i s m s .

of:

The f i r s t phase of the t a s k e f f o r t wi l l c o n s i s t of a s y s t e m a t i c a s s e s s m e n t

1) Po ten t i a l encapsu lan t m a t e r i a l s b a s e d on p a s t e x p e r i e n c e .

2) Defini t ion of the env i ronment .

3) P o t e n t i a l i m p r o v e m e n t of e n c a p s u l a n t m a t e r i a l s and p r o c e s s e s .

4) T e s t and ana ly t i ca l me thods r e q u i r e d t o eva lua te and v e r i f y

m a t e r i a l p e r f o r m a n c e .

In the second phase a su i t ab le .encapsulant s y s t e m wi l l be developed and

ve r i f i ed .

L i t e r a t u r e r e s e a r c h is be ing c o n d u c t e d t o l e a r n w h a t p a s t e x p e r i e n c e i n

t h e e n c a p s u l a t i o n of s e m i c o n d u c t o r d e v i c e s h a s b e e n . T o d a t e , m o r e t han 300

d o c u m e n t s ( o u t of a n e x p e c t e d 600) h a v e b e e n r e v i e w e d .

T h e e n v i r o n m e n t a l a n a l y s i s is b a s e d on n ine s i t e s , s e l e c t e d as r e p r e -

- s e n t a t i v e e x t r e m e s of Un i t ed S t a t e s c l i m a t o l o g i c a l c o n d i t i o n s . C l i m a t i c ,

i n s o l a t i o n , a n d a i r po l lu t ion d a t a f r o m t h e s e s i t e s are be ing a n a l y z e d t o d e t e r -

m i n e t h e r a t e s of o c c u r r e n c e of c o m b i n a t i o n s of c o n d i t i o n s wh ich m a y be d e t r i -

m e n t a l t o a r r a y l i f e t i m e s . E v a l u a t i o n of a c c e l e r a t e d l a b b r e v i a t e d t e s t i n g m e t h o d s

h a s o n l y r e c e n t l y s t a r t e d . As t he i n f o r m a t i o n f r o m i t e m s 1) and 2) b e c o m e s

a v a i l a b l e , w o r k o n i t e m s 3) and 4) w i l l c o m m e n c e . D u r i n g the n e x t f e y m o n t h s

a d d i t i o n a l c o n t r a c t s w i l l b e a w a r d e d , as o r i g i n a l l y p lanned ( s e e t a b l e above ) . I

. .

F. AUTOMATE'D ASSEMBLY TASK

T h e o b j e c t i v e of t h e A r r a y A u t o m a t e d A s s e m b l y ' T a s k is to d e v e l o p and . .

d e m o n s t r a t e t h e p r o c e s s and e q u i p m e n t t echno logy f o r t he m a s s ' p r o d u c t i o n of

- l o w - c o s t s o l a r a r r a y s . T h e p lan i s t o s t u d y and a s s e s s p r e s e n t a n d - p o t e n t i a l

p r o d u c t i o n p r o c e s s e s a n d t e c h n i q u e s t h a t a re a d a p t a b l e t o s o l a r a r r a y p r o d u c -

t i on ; d e s i g n a u t o m a t e d p r o d u c t i o n e q u i p m e n t ; a n d s t i m u l a t e - e x p a n s i o n of s o l a r

a r r a y p r o d u c t i o n f a c i l i t i e s . T ,h ree c o m p a n i e s have r e c e n t l y b e e n a w a r d e d

c o n t r a c t s t o a s s e s s t h e c u r r e n t s t a t e - o f - t h e - a r t t e chno logy and to i d e n t i f y ' t h o s e

areas of s o l a r c e l l t e chno logy w h i c h r e q u i r e d e v e l o p m e n t t o a c h i e v e l o w - c o s t ,

h i g h - v o l u m e p roduc t ion . P r o g r e s s t o dat'e, h a s c o n s i s t e d of e a c h c o n t r a c t o r , ' ,

. .

o r g a n i z i n g a t e a m , s u b m i t t i n g b a s e l i n e c o s t e s t i m a t e s and p l ans , and m a k i n g a

p r e l i m i n a r y e v a l u a t i o n of c u r r e n t s e m i c o n d u c t o r t echno logy as i t r e l a t e s t o t he

e c o n o m i c s of s o l a r ce lb m a n u f a c t u r i n g .

. .

I n ' r e s p o n s e - t o a n u n s o l i c i t e d p r o p o s a l J P L . . h a s dunded a c o n t r a c t w i t h

S i m u l a t i o n P h y s i c s t o d e t e r m i n e the po t en t i a l o f f e r e d b y a n i m p r o v e d ' p r o c e s s

f o r p r o d u c i n g high e f f i c i e n c y s o l a r c e l l s , a t r o o m t e m p e r a t u r e , a t v e r y h igh

p r o d u c t i o n r a t e s . T h i s p r o c e s s i n c l u d e s j unc t ion f o r m a t i o n by i o n - i m p l a n t a t i o n

and a n n e a l i n g of t h e j unc t ion d a m a g e by a b e a m of l o w e n e r g y e l e c t r o n s . A f t e r

e v a p o r a t i o n of the o h m i c c o n t a c t s and evapor . a t i on of a n a n t i r e f l e c t i v e c o a t i n g ,

t he s o l a r c e l l i s o n c e a g a i n ' s c a n n e d by a b e a m of l ow e n e r g y e l e c t r o n s . to s i n t e r

bo th the o h m i c c o n t a c t s and t h e a n t i r e f l e c t i v e c o a t i n g t o a c h i e v e m a x i m u m

bonding s t r e n g t h . T h e r e s u l t s to d a t e a r e e n c o u r a g i n g .

G. L A R G E - S C A L E PRODUCTION TASK

An R F P f o r 4 0 k i lowa t t s of ."off the s h e l f " s o l a r a r r a y s f r o m s e v e r a l

m a n u f a c t u r e r s w i th e x i s t i n g f a c i l i t i e s and p r o v e n d e s i g n s w a s i s s u e d i n Ju ly

1975. T h e R F P r e q u e s t e d i n f o r m a t i o n i n r e g a r d t o c u r r e n t d e s i g n s be ing p r o -

duced , qua l i t y c o n t r o l p r o c e d u r e s , . p r o d u c t f i e ld e x p e r i e n c e , and a n o m i n a l

5 wa t t , .9. 5 vol t m o d u l e d e s i g n . S ix p r o p o s a l s w e r e r e c e i v e d i n Augus t . T h e

p r o p o s a l s w e r e q u i t e v a r i e d i n m a n y r e s p e c t s - i nc lud ing c o s t s , wh ich r a n g e d

f r o m m o d e r a t e to high. In o r d e r to e s t a b l i s h a f i r m b a s i s f o r the f ina l s e l e c t i o n ,

e a c h p r o p o s e r ' s p lan t w a s v i s i t e d . F i v e c o n t r a c t o r s w e r e s e l e c t e d , w i th

d e l i v e r i e s s c h e d u l e d f o r F e b r u a r y t h r o u g h J u n e 1976 ( s e e T a b l e 1 - 2 above) .

D u r i n g the s e l e c t i o n , s t r o n g e m p h a s i s w a s p l aced o n p r e v i o u s e x p e r i e n c e and

p r e s e n t m a n u f a c t u r i n g ab i l i ty . T h e 'quant i ty to be p r o c u r e d f r o m e a c h c o n t r a c t o r

w a s nego t i a t ed w i t h the c o n t r a c t o r .on the b a s i s of p r i c e , s c h e d u l e , and e x p e r i -

e n c e . T h e pr ice ' s nego t i a t ed w i t h ' e a c h c o n t r a c t o r we . re d e p e n d e n t upon the

a m o u n t of t e s t i ng , i n s p e c t i o n , and d o c u m e n t a t i o n c o n s i d e r e d n e c e s s a r y as w e l l

as the b a s i c m a n u f a c t u r i n g c o s t of t he a r r a y s . T h e a v e r a g e nego t i a t ed p r i c e is

a p p r o x i m a t e l y $21 p e r pe.ak wa t t . T h e to ta l p r o c u r e m e n t w a s i n c r e a s e d to 4 6

k i l o w a t t s t o a l l dw f o r s p a r e s .

T h e i n i t i a l m o d u l e s h a v e b e e n f a b r i c a t e d and s u b j e c t e d t o p e r f o r m a n c e and

e n v i r o n m e n t a l t e s t s . C o n c e r n h a s a r i s e n as t o w h e t h e r s o m e of t he e a r l y

. m o d u l e s w i l l b e a b l e t o w i ths t and t h e t h e r m a l c y c l e t e s t s . T h e a d e q u a c y of t he

e n c a p s u l a n t m a t e r i a l s to w i ths t and t h e r i g o r o u s e n v i r o n m e n t a l cond i t i ons , the

c o r r e c t n e s s of m a n u f a c t u r i n g t e c h n i q u e s , . the a p p r o p r i a t e n e s s o f . t h e t e s t c o n -

d i t i ons , and the poten t ia l long r a n g e e f f e c t s of t h e s e p r o b l e m s are be ing e v a l u a t e d . ' ,

Module d e l i v e r i e s h a v e b e e n pos tponed a f e w w e e k s unt i l t he above i t e m s a r e

r e s o l v e d .

When the d e c i s i o n w a s . m a d e t o have a n e a r l y 40 -k i lowa t t p r o c u r e m e n t ,

i t w a s a l s o d e c i d e d t h a t a n ad.ditiona1 130 k i l o w a t t s of s o l a r a r r a y s would b e

p u r c h a s e d a p p r o x i m a t e l y a half y e a r l a t e r . I t w a s in tended tha t t h e s e l a t t e r

m o d u l e s would i n c o r p o r a t e s e l e c t e d d e s i g n i m p r o v e m e n t s to provide e a s i e r

i n s t a l l a t i o n , l e s s m a i n t e n a n c e , and i m p r o v e d in te rchangeab i l i ty in the f ie ld .

T h e module des ign r e q u i r e m e n t s and t e s t condi t ions have been i t e r a t e d wi th the

E R D A P r o g r a m Off i ce , NASA/LeRC, and 'DOD n u m e r o u s t i m e s . T h e d e s i r e s

and r e q u i r e m e n t s of the a r r a y u s e r s ( p r i n c i p a l l y L e w i s R e s e a r c h C e n t e r and

the D e p a r t m e n t of Defense ) , i n conjunction wi th l a b o r a t o r y and f ield t e s t r e s u l t s

plus d e s i g n s t u d i e s , have b e e n i n c o r p o r a t e d in to an R F P speci f ica t ion . T h e

130 k i l o w a t t - p r o c u r e m e n t R F P w a s r e l e a s e d to i n d u s t r y i n D e c e m b e r and i n c l u d e s

a s m a l l b u s i n e s s s e t - a s i d e of 40 k i lowat ts . A b r o a d e r s e g m e n t of i n d u s t r y w a s

s o l i c i t e d f o r th is p r o c u r e m e n t than f o r the in i t i a l buy. E a r l y i n F e b r u a r y 1976,

1 3 p r o p o s a l s w e r e r e c e i v e d w i t h 6 r e p o r t i n g as s m a l l b u s i n e s s . P r o p o s a l

e v a l u a t i o n is p roceed ing on schedu le . D e l i v e r i e s a r e schedu led f o r l a t e 1976

and e a r l y 1977.

In i t ia l planning f o r a t h i r d buy - of 150 ki lowat ts - w a s s t a r t e d . The

s p e c i f i c a t i o n s f o r t h e s e m o d u l e s will be , fo rmula ted f r o m the r e q u i r e m e n t s and

r e s u l t s ga ined by f a b r i c a t i o n , t e s t , and u s e of the p r i o r p r o c u r e m e n t s .

PART I1

INTRODUCTION

A . BACKGROUND

Silicon, so lar ce l l s have been successfully utilized for remote t e r r e s t r i a l

e lec t r ica l power applications for two decades. During this t ime, the cost pe r

watt of so la r cel l a r r a y s has been decreasing and the s ize of the commerc ia l

market has grown, although i t i s st i l l minuscule relative to total e lec t r ica l

power generation. P r i o r to approximately 1972, t e r r e s t r i a i a r r a y s were con-

s t ructed utilizing so la r ce l l s that were re jec ts of the space program; however,

the growth of the market prompted the innovation af so la r a r r a y desigps which

were specifically oriented for the technical and economic requirements o f a

t e r r e s t r i a l applications market . A "price breakthrough" that i s mainly a t t r i ,

buted to the utilization of l a r g e - a r e a round o r wafer ce l l s reduced the pr ice

f r o m $90 per peak watt to $30 per peak watt. The round ce l l s a r e produced

with s imi l a r sunlight-to-electricity conversion efficiency but a r e produced m o r e

simply by requiring l e s s processing per watt of power output. Though the change

i s modest, the cos t i s reduced dramatical ly . Additional dramat ic pr ice reduc-

tions a r e anticipated a s a resul t of the ERDA Photovoltaic Conversion P r o g r a m

and LSSA Pro jec t activit ies.

Solar ce l l technology was init ially developed a t B e l l Telephone Laborato-

r i e s in the ear ly 1950s. In 1955, the f i r s t field t e s t was conducted in which

telephone ampl i f ie rs were successfully powered by silicon so la r cel ls . Exper i -

mental and special purpose t e r r e s t r i a l u s e s continued, but during the 1960s and

ea r ly 1970s spacecraf t e lec t r ica l power sys t ems were the m a j o r and only well-

known application for this technology. The Vanguard I Satellite, launched in

1958, operated for s ix yea r s ; Pioneer V I has been operating in so lar orbi t s ince

i t s 1965 launch. Various Mar iner spacecraf t have operated on so la r power f r o m '

the orbit of Mercury to beyond Mars . The l a rges t so lar photovoltaic sys t em t o

date was that of P ro jec t Skylab, designed for 21 -kilowatt capacity.

By the ear ly 1970s photovoltaic theory had been developed, and the sil icon

so la r -ce l l technology to support space applications and cost- l imited special '

,

-

t e r r e s t r i a l u s e s was well developed. However, the manufacturing of so la r ce l l s

was relat ively expensive. This. severe ly l imited widespread use, par t icular ly

where conventional e l ec t r i c -power sources were available. Solar ce l l s made '

f r o m other m a t e r i a l s have been and continue to be investigated and developed

i n va r ious labora tor ies . But the u s e of si l icon for so lar ce l l s maintained a

comlnanding lead over othe'r ma te r i a l s b e c a u s e of proven reliabili ty, the !

abundance of si l icon, and a n e.stab1ished although s m a l l si l icon ce l l industry.

R e s e a r c h and development act ivi t ies were supported by NASA, the NSF, the

. Department of Defense, and various, pr ivate institutions. 1

In 1971 the National Science Foundation's Research Applied to National .

Needs ( R A N N ) p r o g r a m established an R & D program in t e r r e s t r i a l applications ,'

of s o l a r energy. By mid-1 973 NSF was sponsoring some forty projects , eleven

of them in so la r photovoltaics,. and had collaborated with NASA in a m a j o r

a s s e s s m e n t .and, planning effort c a r r i e d out by a jointly-sopported Solar Energy

Panel . This led t o a m a j o r workshop on Photovoltaic Conversion of Solar Energy

for . T e r r e s t r i a l Applications, held at . Cher ry Hill, N. J. , in October 1973.

This G o r k s h . 0 ~ c ~ n s i s t e d ~ o f s ix working groups concerned with the technology,

panels concerned with the utilization of photovoltaic power sys tems, and the . . presentat ion of a group of invited papers . The working groups a s s e s s e d the

need fo r technology advances, the technical feasibility of achieving such ady.ances, \

and r e s e a r c h and delvelopment p rogram considerations for s ingle-crys ta l silicon

cel ls , . cadmium-sulf ide copper -sulfide cel ls , polycrystal silicon ce l l s , and

a l te rna t ive m a t e r i a l s and devices. Other; , factors considered were the de termina-

tion of t e r r e s t r i a l insolation, tes t and evaluation requi rements , and the need

.for photovoltaic s y s t e m s .studies, t e s t s , and design. The industry and utility . .

panels considered many aspec t s of future t e r r e s t r i a l solar-photovoltaic applica-

t ions, with emphas is on the need for a government-sponsored p rogram of

cons iderable duration.

A national photovo1taic plan was developed which considered inputs such

a s (1) the analysis of the conclusions and recommendations of the technical par t

of the C h e r r y Hill Workshop, ( 2 ) the photovoltaic conversion section in "The

Nation's Energy Future",, by Dr. D. L. Ray, and ( 3 ) a repor t of the Interagency

Pane.1 f o r T e r r e s t r i a l applications of Solar Energy by ~ . J P L t eam under NSF

sponsorship. This ini t ia l plan i s contained i n . J P L Special Publication .43 -1 1,

"Assessmt?nt of the Technology Required to Develop Photovoltaic Power Sys tems

for La rge -Scale National Energy Applications", published October 15, 1974.

The genera l 10-year goals of a s o l a r a r r a y p r i ce l e s s than 50 d per peak watt

and a production r a t e of 500 megawatts pe r y e a r were formulated. In addition,

act ivi t ies requi red in the a r e a s of technology development, photovoltaic power

sys t ems , and demonstrat ion w e r e outlined.

When ERDA was fo rmed i t acqui red m o s t of the responsibi l i t ies of the

e a r l i e r NSFIRANN so la r photovoltaic activity, including the foregoing plan.

Thereaf te r , ERDA, in conjunction with other government agenc ies , industry ,

and potential u s e r s , reviewed, reevaluated, and extended the or iginal plan .

during the formlllation of the ERDA Photovoltaic Conversion P r o g r a m . The

Low-Cost Silicon Solar A r r a y (LSSA) P ro j ec t a t J P L was init iated in January

1975 a s a m a j o r e l emen t of the new P r o g r a m . Its functional e lements c losely

cor respond to re levant e lements of the new plan. In F e b r u a r y 1975, a m a j o r

Industry Briefing was conducted jointly in Washington, D. C . , and Pasadena ,

California, to p r e p a r e fo r the init iat ion of a broad procurement p r o g r a m both

fo r so l a r a r r a y technology developmt-?nt and for the continuing acquisit ion of

s t a t e -o f - the -a r t si l icon s o l a r a r r a y s fo r var ious tes t s . In addition, ana lys i s ,

study, and technical data act ivi t ies were begun through the J P L P r o j e c t Office

which i s responsible f o r management of the en t i re LSSA Pro jec t .

B. PR.O.TECT MANAGEMENT

The P ro j ec t i s organized to support the ERDA P r o g r a m - specifically, to

m e e t the es tabl ished objectives, and to provide fo r the organization, manage-

ment, and integration of P r o j e c t act ivi t ies (F ig . 2-1). The management of the

P r o j e c t has been s t ruc tured to implement the plans descr ibed in the Summary .

The major functional act ivi t ies for which the P r o j e c t Manager i s responsible

a r e (1) technology development and t r a n s f e r to commercial izat ion, ( 2 ) p rocure-

ment of s ta te -of - the-ar t a r r a y s , ( 3 ) analysis and integrat ion of the Pro jec t , and

(4) P ro j ec t adminis t ra t ion. These activit ies a r e directed toward development

of the photovoltaic industry and st imulation of the marke t , with resul t ing pr ice

reductions .

LSSA PROJECT

MANAGER

PROJECT 1 1 P U N N I N G , ANALYSIS AND REPORTING, INTEGRATION DOCUMENTATION

PROCUREMENT RESOURCES ASSURANCE AND RELIABILITY

I TECHNOLOGY DEVELOPMENT I ---------

I

Fig. 2 -1. Organizat ion c h a r t - Low-Cost 's i l icon Solar .Array P r o j e c t

The P r o j e c t managemen t h a s es tab l i shed a m a j o r effor t fo r the interact ing

.of technology development with the engineer ing f o r c o m m e r c i a l 'production - the

ENGINEERING AND

TECHNOLOGY

function of technology t r a n s f e r . The Engineering and Technology Manager , who

is r e spons ib l e f o r both technology development and the p rocu remen t of a r r a y s .

He is supported by the Design and T e s t Engineer and backed by appropr ia te

I DESIGN

AND TEST

e x p e r t i s e n e c e s s a r y to p e r f o r m this function. The technology development work

has been divided into four key Tasks to provide f o r a m o r e d i r e c t and efficient

- .

- - - - - - - - - - - - d m - - -

, deve lopment e f for t to be conducted in these technology a r e a s : si l icon mater ia l ,

I - ---------

l a r g e s h e e t p roces s , encapsulation, and automated manufactur ing technology.

The La rge -Sca l e Produc t ion T a s k was es tabl ished to provide f o r the annual pro-

c u r e m e n t s of the s ta te -of - t he -a r t hardware . Task Managers a r e ass igned

respons ib i l i ty fo r t he i r r e spec t ive task a r e a s and a r e provided technical and

I I I

I - I I I I I 1

- admin i s t r a t i ve suppor t personne l including con t r ac t negot ia tors f o r theil' t a sks

I I I I

LARGE AREA SILICON SHEET

TASK

SILICON MATERIAL

TASK

ENCAPSULATlON TASK

AUTOMATED ARRAY ASSEMBLY

TASK

I I I

LARGE SCALE PRODUCTION

TASK

t o ma in ta in l e a d e r s h i p and c o n t r o l o v e r e a c h c o n t r a c t and a m o n g the v a r i o u s

c o n t r a c t s . Se lec ted in -house e f f o r t is a l s o a d m i n i s t e r e d by e a c h T a s k Manager .

T h e d e s i g n a n d t e s t ac t iv i ty w a s e s t a b l i s h e d t o (1 ) assist i n the deve lop- '.

m e n t of a n i n t e g r a t e d in -house t e s t e f for t , (2 ) p e r f o r m p a r a m e t r i c eng inee r ing

a n a l y s i s a n d d e s i g n of s o l a r a r r a y m o d u l e s f o r t h e deve lopment of m o r e opt i -

m i z e d h a r d w a r e , ( 3 ) deve lop and def ine m o d u l e des ign a n d t e s t r e q u i r e m e n t s ,

a n d coord ina te ac t iv i t i e s be tween J P L a n d L e R C r e g a r d i n g m o d u l e d e l i v e r i e s

f o r t h e T e s t a n d D e m o n s t r a t i o n P r o j e c t . I

The P r o j e c t Ana lys i s and In tegra t ion ( P A & I ) T a s k s u p p o r t s the planning,

in teg ra t ion and d e c i s i o n making a c t i v i t i e s of ,the P r o j e c t . T h i s s u p p o r t wi l l 6e i m p l e m e n t e d by providing a s s e s s m e n t s of poss ib le p e r f o r m a n c e and economic

c o n s e q u e n c e s of a l t e r n a t i v e P r o j e c t plans, developing the i n t e r f a c e r e q u i r e m e n t s

among the P r o j e c t t a s k s , suppor t ing the e s t a b l i s h m e n t of the i n t e r f a c e r e q u i r e -

m e n t s be tween the LSSA P r o j e c t and o t h e r ERDA Photovol ta ic C o n v e r s i o n P r o -

g r a m ac t iv i t i e s , and by developing the p lans and p r o c e d u r e s f o r in teg ra t ing the'

t a s k s within the P r o j e c t and between the P r o j e c t a c t i v i t i e s and o t h e r e l e m e n t s of

the P r o g r a m .

T h e Quali ty A s s u r a n c e and Rel iabi l i ty ac t iv i ty p rov ides f o r the i m p l e m e n -

ta t ion of a n effec't ive qual i ty p r o g r a m c o n s i s t e n t wi th the P r o j e c t o v e r a l l ob jec -

t ives and p rov ides the n e c e s s a r y inspec t ion and s u p p o r t pe r sonne l f o r the v a r i o u s

h a r d w a r e p r o c u r e m e n t s and r e l a t e d ac t iv i t i e s .

T h e P r o j e c t P lanning, Documenta t ion and Da ta Management funct ion pro-

v ides the e s s e n t i a l planning and documenta t ion n e e d e d t o a d m i n i s t e r and c o n t r o l

P r o j e c t ac t iv i t i e s . The acquis i t ion , o rgan iza t ion , and d i s s e m i n a t i o n of t echn ica l

in fo rmat ion , a key funct ion i n technology t r a n s f e r , is p e r f o r m e d by the P r o j e c t

D a t a C e n t e r .

, In the p r o c u r e m e n t ac t iv i t i e s , new, d i v e r s i f i e d and demanding r e q u i r e -

m e n t s have been f a c e d by the P r o j e c t and ERDA. T h e r e f o r e , e x p e r i e n c e d con-

t r a c t n e g o t i a t o r s w e r e a s s i g n e d t o the P r o j e c t and a ~ r o c u r e A e n t M a n a g e r

des igna ted t o a d m i n i s t e r the P r o j e c t ' s c o n t r a c t i n g a c t i v i t i e s i n t h e i r in i t i a l phase

of c o n t r a c t o r s e l e c t i o n and the l a t e r phase of c o n t r a c t management .

P r o j e c t f i n a n c i a l m a n a g e m e n t is a d m i n i s t e r e d by a R ' e s o u r c e s M a n a g e r

w i t h s u p p d r t i n g f i n a n c i a l and c o n t r a c t a n a l y s t s , m a k i n g m a x i m u m qse of the, . .

. e x i s t i n g <JPL ' f i nanc ia l r e p o r t i n g s y s t e m .

C

T h e c a p a b i l i t y t o a s i e s s t he p r o g r e s s be ing m a d e by the p r o j e c t and t h e

e v o l v i n g s o l a r a r r a y i n d u s t r y is u n d e r d e v e l o p m e n t f o r u s e i n the con t inua l

a d j u s t m e n t of the P r ' o j e c t ' s p l a n s i n v o l i ~ i n g &i t .her o r both m a n a g e m e n t Bnd tech.- . .

n i c a l a c t i v i t i e s , a s r e q u i r e d . T h i s - i n f o r m a t i o n wi l l a l s o b e u s e d to. d e t e r m i n e -. ' , . . . .

t he r e q u i r e m e n t s f o r e x p e r i m e n t a l . p r o d u ~ t ' i o n , ~ l a n t s a n d p roduc t ion p l an t s as , .

w e l l as the P r o j e c t g e n e r a l l e v e l of e f f o r t f o r cont inufng f u t u r e ac t iv i ty . A s the -

P r o j e c t a c t i v i t i e s con t inue , c o n t r a c t s a r e e x p e c t e d t o be added , modi f ied , and

s o m e t e r m i n a t e d t o o p t i m i z e t h e e n t i r e P r o j e c t e f f o r t i n a c c o r d a n c e wi th t h e

- P r o g r a m p l a n s and o b j e c t i v e s . J P L i n - h o u s e e f f o r t wi l l b e a p p l i e d . i n a n a d a p -

t i v e m o d e t o f l i r t t i e r a d j u s t t o t he P r o g r a m o r P r o j e c t n e e d s , w h i l e ma in t a in ing

a m o d e r a t e i n - h o u s e e f f o r t . T h i s wi l l p e r m i t n e c e s s a r y e x p e r t i s e to o p e r a t e

e f f e c t i v e l y in a d m i n i s t e r i n g to t he h ighly d y n a m i c p ro j ec t , w h i c h s e e k innova t ive ,

p r o d u c t i v e i d e a s f r o m i n d u s t r y , u n i v e r s i t i e s , a n d g o v e r n m e n t a l - a g e n c i e s . ,

P A R T I11

P R O J E C T ANALYSIS AND INTEGRATION TASK

T h e a c t i v i t i e s of t h e P r o j e c t A n a l y s i s a n d I n t e g r a t i o n T a s k i n c l u d e t h e

fo l lowing:

A s s e s s t h e g o a l s a n d p r o g r e s s of t he LSSA P r o j e c t .

C o n t r i b u t e t o t he g e n e r a t i o n a n d d e v e l o p m e n t of P r o j e c t p lans .

e. E s t a b l i s h s t a n d a r d s f o r e c o n o m i c c o m p a r i s o n s .

E n c o u r a g e e f f ec t ive c o m m u n i c a t i o n s a n d coord ina t ion .

D e v e l o p n e c c s s a r y a n a l y t i c a l c a p a b i l i t i e s .

T h e P r o j e c t A n a l y s i s a n d I n t e g r a t i o n T a s k f o c u s e s o n i n - h o u s e ac t iv i ty ,

c o n c e n t r a t i n g on p r o m o t i n g c o o r d i n a t i o n a m o n g t h e t echno logy d e v e l o p m e n t a n d

a r r a y p r o d u c t i o n t a s k s , a n a l y z i n g po ten t i a l P r o j e c t p l a n s a n d d e c i s i o n s , bu t

a l s o p r o v i d e s f o r t h e i n t e g r a t i o n of t h e P r o j e c t a c t i v i t i e s w i th t h e o t h e r e l e m e n t s

of t h e E R D A P r o g r a m .

D u r i n g t h i s i n i t i a l y e a r , t h e P A & I e f f o r t h a s c o n t a i n e d t h e fo l lowing f o u r

e l e m e n t s :

P r o j e c t a s s e s s m e n t . A p r e l i m i n a r y a l l o c a t i o n of c o s t g o a l s f o r

e a c h of t h e t echno logy d e v e l o p m e n t t a s k s h a s b e e n m a d e , a c t i v i t y

t o d e f i n e p r o j e c t a s s e s s m e n t f a c t o r s h a s b e e n s t a r t e d , a n d a

p r e l i m i n a r y m o d e l t o e v a l u a t e a l t e r n a t i v e a r r a y d e s i g n c o s t s h a s

b e e n deve loped ; a p r o c e d u r e t o e s t i m a t e t h e c o s t of a r r a y s r e s u l t i n g

f r o m de f ined m a n u f a c t u r i n g p r o c e s s e s i s now a v a i l a b l e .

F o s t e r i n g of c o m m u n i c a t i o n s a n d c o o r d i n a t i o n both a m o n g the t a s k s

wi th in the P r o j e c t a n d b e t w e e n the P r o j e c t a n d o t h e r e l e m e n t s of

t h e P r o g r a m . T h e f i r s t LSSA P r o j e c t T a s k I n t e g r a t i o n M e e t i n g w a s

held on J a n u a r y 12-14 , 1976, involv ing c o n t r a c t o r s , J P L , a n d

ERDA e l e m e n t s ; s i g n i f i c a n t i n t e r a c t i o n wi th ERDA h e a d q u a r t e r s ,

t h e E l e c t r i c P o w e r R e s e a r c h I n s t i t u t e ( E P R I ) , a n d u t i l i t y e q u i p m e n t

manufac tu re r s took place with r e spec t to development of the model

f o r analyzing utility-owned s o l a r e l ec t r i c power s y s t e m s (USES).

Development, adaptation, and implementation of techniques fo r

analyzing the re levant technological and economic processes . A

genera l model (USES) f o r es t imat ing the "busbar" energy cos t of

a l te rna t ive utility-owned s o l a r e l ec t r i c power sys t ems was developed

jointly with E R D A and EPRI, and i s being prepared f o r publication,

and a s imulat ion model of the s o l a r a r r a y manufacturing industry

(SAMIS) has been developed to e s t ima te the cos t s of manufacturing.

Considerat ion of b a r r i e r s to commercial izat ion. The exis tence of

b a r r i e r s to commerc ia l iza t ion of photovoltaic power has been

recognized, and effor ts have been initiated to obtain a n improved

unders tanding of the b a r r i e r s , with the objective of identifying,

reducing,. avoiding, o r otherwise overcoming them.

1. Alloca-tion of Cos t Goals

In o r d e r to provide one of the bases for measur ing the p r o g r e s s of the

P r o j e c t toward achieving i t s goals, a p re l iminary detailed allocation of cost

goals f o r each of the m a j o r manufacturing s teps fo r each yea r of the P r o j e c t

has been made. This allocation was s t rongly influenced by projections of the

r e s u l t s of the technology development tasks now in p rog res s . The detailed

ra t ionale i s descr ibed below.

The general philosophy of the a s sumed cos t reduction p roces s i s shown

in Fig. 3 -1. Two ma jo r s t eps a r e anticipated, each followed by a period of m o r e

gradua l subsequent p r i c e reduction. The f i r s t s t ep i s based on the assumption

tha t the focused m a r k e t provided by the ERDA P r o g r a m procureme'nts of s o l a r

a r r a y s will p romote s o m e s tandardizat ion and regular i ty in the industry. The

second s t e p is based on the assumption that the resu l t s of the technology develop-

m e n t act ivi t ies will be t r a n s f e r r e d to production prac t ices .

INDIVIDUAL MANUFACTURER'S

LSSA PROJECT COST GOAL

INGOT SHEET TECHNOLOGY TECHNOLOGY .

C------3 AUTOMATION

CALENDAR YEAR

Fig. 3- 1. Terres t r ia l solar a r r ay price history

The allocation of the cos t goal t rends i s depicted in Fig. 3 - 2 ; the numerical

detai ls of these allocations a r e l is ted in Table 3 - 1 . This allocation i s intended

to be p re l imina ry and i s expected to be refined ( o r possibly changed completely)

a s the r e su l t s a r e i t e ra t ed with the manufacturing industry and a s the technology

development tasks mature .

2. ~ e f i n i t i o n of P r o j e c t Assessment Fac to r s

This effort i s intended to support LSSA Pro jec t decision-making through

evaluation, par t icular ly by identifying the nature and importance of factors

which m a y influence P ro jec t success . I t is being ca r r i ed out in th ree in te r -

acting a r e a s : factor identification, development of a factor-processing method-

ology, and acquisit ion of prac t ica l experience through the solution of special

trade-off problems which a r i s e in P ro jec t operations. The approach i s derived

in p a r t f rom aspec t s of fl ight-project mission analyses , and the goals and

c r i t e r i a a r e being i terat ively redefined in this ea r ly stage of development. -

A portion of a f i r s t - cu t listing of candidate a s s e s s m e n t fac tors , categorized

by the segment of the P ro jec t to which they apply, i s given in Table 3-2.

This l ist ing i s expec,ted to be added to.and edited by the operation of the

fac tor -process ing methodology, which includes extensive. inte raction with LSSA

and ERDA a s well a s external information and judgement sources in various

interview and crit ique processes . The proces.sing methodology cal ls for four

phased s teps: .x

1 ) Determining which fac tors impact P ro jec t success , on the basis

of P ro jec t goal association, 'posi t ive o r negative impact, and

definition of s u c c e s s c r i t e r i a ; interacting with P r o j e c t / P r o g r a m

elements to improve the f i r s t -cu t list.

2) Evaluating factor impacts , developing and valuing a s e t of c r i te r ia ,

and weighting and ordering the fac tors , again with c r i t ica l in te r -

action.

3) Quantifying the impacts of the factors , with special methods for

those fac tors on which evaluation,consensus i s not reached (in

20' - - - @ ARRAY FABRICATION -

@ CELL MANUFACTURE - @ SLlClNG

15 - @ INGOT/SHEET GROWTH -

- @ SILICON MATERIAL C

2 - 3 - M W

10 - V)'

!!! - INGOT SHEET

d a - TECHNOLOGY TECHNOLOGY P -

6 - -

AUTOMATION

- 4 -

- 2 -

- 0.1 I

1 976 1 978 1 980 1982 1984 1986

CALENDAR YEAR

Fig. 3-2. T e r r e s t r i a l colar a r r a y pr ice goals

Table 3 - 1. Project- cost goalallocationb (a l l cbats in "1975 dollars)

2

CALENDAR YEAR

SILICON MATERIAL

Slllcon Mater lar

$/kg

$/w

Sem~conduc to r Grade Solar Grade

INGOTISHEET GROW Ti-!

Process ing Value Added - $ 1 ~

Wafer M a t e r ~ a l - $Iw

10

0.05

6 0

1 . 9

7

0.03

40

0.65

50

I. 1

C z o c h r a l s k ~ Ingots-*-- Large Area Sheet

IS'

0 .09

4.8

6.7

INGOT SLICING

Processing Value Added - S l w

Wafers - $lw

2.1

3.2

3.7

10.4

0.52

0.57

CELLMANUFACTURE

0.14

0.17

1.6

2.2

0.6

3. 8

Mate r ra l s Added (Contacts , rtc. ) - $lw

J.

Proceas lng Value Added - $/w

Ce l l s - $ 1 ~

1.9

2.0

0.5

2.7

S ~ l v e r C o m m e r c ~ a l Conductor

ARRAY FABRICATION

0.01

2.0

0.07 0. 8

M a t e r ~ a l s Added (Encapsulat~on, F ramlng , etc. ) - $/w

0

0. 57

0. 20

Mostly Manual Automated

0. 5 0 .5

0

0.17

0.08 0.4

Processing Value Added - $/w

L

ARRAY PRICE GOALS - $/w

0. 35

0. 3

0. 25

2.45

0.09

0.72

S l l ~ c o n mate r i a l ~n flnal product 27% 30% 38% 7 8% 87% 91%

Total processing value added 84% 71% 7 5% 87% 7 3% 6 4%

Watts lkg of s i l lcon m a t e r l a l 32 47 6 2 162 187 203

Cel l e f f i c~ency (AM1 ) 11% 11.5% 12% 12.5% 13% 13.5%

Cel l t h ~ c k n e s s - m l l s I 5 I 2 12 10 10 1 0

Mostly Manual Automated

0. 85

3.9

0.06

0. 30

4. 3

15.5

0.10

1.2

5.4

4.0

20

0.08

1.1

7

0.08

0.12

I

0.50 L L

0.18

1

0 .8

5

0.45

3

Table 3-2. Candidate a s s e s s m e n t f ac to r s

s t ep 2 above); obtain expert - interview data a s , a s t ruc tu red

para l le l , t r ack re la t ive t o in te rna l quantification (and evaluation

and determinat ion a s appropria te) .

4) Determining what actions m u s t be taken to i nc rease favorable

impacts and reduce negative impacts ; weighting actions re la t ive

t o f ac to r s and using es tabl ished fac tor quantifications and, a s

above, employing internal and ex te rna l c r i t i ca l in teract ions .

p r o j e c t Segment

The development of this methodology is expected to b e influenced by the

experience in developing and adjusting trade-off f ac to r s in s tudies c a r r i e d

out t o suppor t decis ions on special p roblems which a r i s e in var ious tasks of

the LSSA Pro jec t . The f i r s t special -problem study has begun with r e spec t to

the question, in the LSSA Large-Scale Product ion Task, of whether a n d / o r how

much of the future 150-kilowatt p rocurement should be held a t the technology

leve l of the 130-kilowatt p rocurement in o r d e r t o c r e a t e an appropr ia te t i m e

interval f o r adequate evaluation, analysis , and feedback f r o m both the previous

46-kilowatt p rocurement and the design act ivi ty of the 130-kilowatt buy.

3-7

Commercialization. . .

A r r a y Cost

P e r f o r m a n c e

Standardization

Subsidies

' U s e r Acceptance

Capital Investment

Marke t S ize

A r r a y Design and Test ing

Reliabil i ty

Maintainability

~ t a n d a r d i z a - tion

Test ing Load

C h a r a c t e r -

i s t i cs

.

P r o j e c t Admi.nistration

Schedule

Planning

Manpower

Budget

Fac i l i t i es

.

.

Technical Development

A r r a y Cost

Reliability '

Per fo rmance

Test ing

Environmental

Impacts

.

3. ' Evaluation of Alternative Design Concepts . .

A Pro jec t Al.ternative Design Evaluation Model (PADEM) to compare the

ove ra l l per formance of a l ternat ive sil icon s o l a r a r r a y designs is being developed.

Owing to the wide var ie ty of s o l a r power applications, types of e lectr ical . ,

loads, and operat ing.environments , a single normative performance index value

does not appear to be suitable. Rather, there must be many such values,

ta i lored to different applications, loads, and environments.

Study of a number of c r i t e r i a by which the performance of an a r r a y design

can be evaluated has led to the conclusion that the performance index can be

adequately charac ter ized by three s u m m a r y components: total cost, e lec t r ica l

per formance , and convenience. The total cost includes acquisition and instal la-

t ion .costs , operating and maintenance costs , and the t ime value of-money. A

procedure f o r express ing total cost on an annualized basis has been,developed.

The e l ec t r i ca l per formance calculation i s complicated by the likelihood that the '

per fo rmance of eac'h a r r a y . des,ign . may va ry differently according to varying

e n v i r ~ ~ r n e n t a - 1 factors . The mode .of such performance variations and

the i r integration has not been defined fur ther than the requirements fo r tegting

each module design under broadly differing conditions. It has been established,

however , that the appropriate measure of e lec t r ica l performance i s the total

( o r average) energy produced over the course of a year in the specified applica-

tion. . ,

Convenience fac tors a r e associated principally with specific sys tem .

applicat ions, , e. g. , lightweight f o r portable uses. Many of these factors a r e

not eas i ly 'measurable and a few may be difficult even to design. In no case

a r e they 'capable of 'normalizat ion .so that designs might be conlpared on t h i s .

bas is without specifying the application, Analysis of this s e t of fac tors , p re -

l imina ry a s yet, suggests that w,hile, in general, , evaluation and selection from

among al ternat ive designs of a "standard"~configuration .is. possible.on the

bas is of per formance/cos t c r i te r ia , selection of nonstandard designs for con-

venience will keep such designs in the market for spec.ia1 applications.

4. E s t i m a t i o n of t h e I m p a c t of R e s e a r c h E f f o r t s o n A r r a y C o s t s

T h r o u g h u s e of t h e S o l a r A r r a y M a n u f a c t u r i n g I n d u s t r y S i m u l a t i o n (SAMIS)

m o d e l , w h i c h wi l l b e d e s c r i b e d i n d e t a i l below, t h e m a x i m u m i m p a c t o n t h e

c o s t of m a n u f a c t u r i n g s o l a r a r r a y s t h a t c a n r e s u l t f r o m a n y of t h e t echno logy

d e v e l o p m e n t t a s k s c a n b e e s t i m a t e d . It is e x p e c t e d t h a t t h i s c a p a b i l i t y wi l l b e

u s a b l e i n t h e a l l o c a t i o n of LSSA P r o j e c t r e s o u r c e s .

B. P R O J E C T INTEGRATION

T h e f i r s t P r o j e c t I T a s k I n t e g r a t i o n Mee t ing w a s conduc ted i n m i d - J a n u a r y

1976 ( t h e P r o c e e d i n g s w e r e publ i shed e a r l y i n M a r c h ) . T h e f o c u s of t h i s m e e t -

i ng w a s P r o j e c t and t a s k planning and s t a t u s , t o g e t h e r w i th i n t r a - t a s k i n t e r f a c e

m a t t e r s . T h e f o c u s e s t a b l i s h e d f o r t he s e c o n d , P r o j e c t I n t e g r a t i o n Mee t ing ,

s c h e d u l e d f o r l a t e Apr i l , a l s o inc luded i n t e r - t a s k i n t e r f a c e s a n d i n t e g r a t i o n

. w o r k , a s w e l l a s i n t e r f a c e s w i th o t h e r e l e m e n t s of t he P h o t o v o l t a i c P r o g r a m .

T h e LSSA P r o j e c t i n t e r f a c e s w i th the ERDA P r o g r a m Off ice , t he S y s t e m

Def in i t ion P r o j e c t , , t h e T e s t .and emo on strati on P r o j e c t , and the M i s s i o n A n a l y s i s

s t u d i e s w e r e e x a m i n e d and l a id o u t i n p r e l i m i n a r y f a sh ion , and then w e r e i t e r -

a t e d t h r o u g h i n t e g r a t i o n planning m e e t i n g s conduc ted w i t h Sand ia L a b o r a t o r i e s

( S y s t e m s . D e f i n i t i o n ) , NASA'Lewis R e s e a r c h C e n t e r , D e p a r t m e n t of D e f e n s e

MERADCOM ( T e s t and D e m o n s t r a t i o n ) , and A e r o s p a c e C o r p o r a t i o n (M.j.ssion

A n a l y s i s ) . T h e s e i t e r a t i o n s con t inue t h r o u g h ad hoc m e e t i n g s and t h r o u g h the

ERDA P r o g r a m Of f i ce ' s q u a r t e r l y r e v i e w l i n t e r f a c e m e e t i n g s .

C . D E V E L O P M E N T O F ANALYTIC TECHNIQUES

1. Uti l i ty -Owned S o l a r E l e c t r i c S y s t e m (USES) Model

T h i s e c o n o m i c eva lua t ion m o d e l i s d e s i g n e d t o o p e r a t e o n c o s t f i g u r e s

r e s u l t i n g f r o m the acqu i s i t i on , i n s t a l l a t i o n , , and m a i n t e n a n c e of a s o l a r e n e r g y

s y s t e m ( n o t l i m i t e d t o photovol ta ics ) by a public o r p r i v a t e u t i l i ty , and t o d e r i v e

t h e e n e r g y " p r i c e " n c e s s a r y to r e c o v e r t h o s e c o s t s , a s s u m i n g s c a l e and load

f a c t o r s . I t h a s bee.n d e v e l o p e d joint ly w i t h E R D A and the E l e c t r i c P o w e r

R e s e a r c h I n s t i t u t e t o p r o v i d e e n e r g y a n a l y s t s a s i m p l e , conven ien t , and s t a n d a r d

too l f o r r a n k i n g c a n d i d a t e s y s t e m s i n o r d e r of c o s t - e f f e c t i v e n e s s . D o c u m e n -

t a t i o n of t h e m o d e l is i n . p r e p a r a t i o n .

T h e m o d e l is d e s i g n e d t o a c c o m m o d a t e e n e r g y s y s t e m s w i t h d i f f e r e n t

. t e c h n i c a l and e c o n o m i c f e a t u r e s , bu t no t t o b e s o s e n s i t i v e to s y s t e m - s p e c i f i c

d e t a i l s as t o p r e c l u d e p l ann ing - l eve l e v a l u a t i o n and c o m p a r i s o n s . It i s c o m -

p a t i b l e w i t h c o n v e n t i o n a l b u s i n e s s p r a c t i c e s f o r c o s t p r o j e c t i o n and c a p i t a l . .

budge t ing .

T h e b a s i c s t r u c t u r e of t h e m o d e l i s g i v e n in t h e f low d i a g r a m of Fig. 3 -3.

T h e fo l lowing d i s c u s s i o n s u m m a r i z e s t h e s e q u e n c e of ca l cu la t ions . T h e c o s t

of c a p i t a l t o t he u t i l i t y a n d i t s a n n u a l i z e d f ixed c h a r g e r a t e a r e c o m p u t e d f r o m

t h e s e e q u a t i o n s , w h e r e the s y m b o l s a r e de f ined in F ig . 3-3:

T h e p r e s e n t v a l u e s of t h e i n i t i a l a n d r e c u r r e n t c a s h f lows a r e ob ta ined f r o m

C I P v = ( 1 + gld [CI, (*TI t

I I INPUT DATA I COMPUTATIONS

- - - - - - - I - . - - - - - - - - - - - - - - - - - - I OUTPUT -1 1

ruTILITY DESCRIPTION DATA ( u D D 1 I

I 1 .

MISCELLANEOUS COST RATES B1,fi2 ( 8 1 t 8 2 1 1

I I N SYSTEM LIFETIME (FROM SDD) N I

1 I I

-

I k T EFFECTIVE INCOME TAX RATE I

I I I D c - P 1 , 4 < 4 V *

CAPITAL STRUCTURE - > COMPUTE

I I I V,.V, V I COMPUTE COST OF COMPLJTE CAPITAL C R F k t ~ ANNUALIZED

RATES OF RETURN hd,, kc, kp 1 CAPITAL TO UTILITY b RECOVERY FACTOR I FIXED CHARGE RATE

1 I I I I

I GENERAL ECONOMIC CONDITIONS .- I ESCALATION RATES "g" I

L - - - - - - - - -1- - - - - - SYTEM DESCRIPTION DATA

CASH FLOWS

CAPITAL INVESTMENT Cl,

OPERATING COSTS O P,

MAINTENANCE COSTS MNT,

FUEL COSTS FL+

I COMPUTE PRESENT VALUES [

- C R F k , ~ FCR

OF CASH FLO'WS

PRESENT VALUE OF C1 p v CAPITAL INVFSTM~NT

h +

PRESENT VALUES OF I RECURRENT COSTS

SYSTEM LIFETIME N I I

COMPUTE ANNUALIZED

SYSTEM - RESULTANT COST

COMWE LEVELIZ~D 1 :,+ SYSTEM ENERGY OUTPUT MWHA BUSBAR ENERGY COST BBEC

I

Fig . 3-3 . S t ruc ture of USESmodcl

w h e r e X i s r e p l a c e d by OP, M N T , o r -FL, . a s a p p r o p r i a t e ; d = n u m b e r of y e a r s

f r o m p r i c e i n f o r m a t i o n t o s t a r t of c o m m e r c i a l o p e r a t i o n ; and j . = n u m b e r of

y e a r s f r o m s t a r t of c o m m e r c i a l dpe- ra t ion to t he o c c u r r e n c e of c a p i t a l i n v e s t -

m e n t .

. . T h e a n n u a l i z e d c o s t is ob ta ined f r o i n . .

- - . ' A C = F C R ' C I ' 4- C R F k , N - O P t MNT t FL

P v PV PV P v

, . a n d i s t h e n d iv ided b i t h e s y s t e m t s energy- ou tpu t t o p r o d u c e a n e s t i m a t e of t h e

l e v e l i z e d b u s b a r , e n e ? g y ; c o s t :

Th ' is I e v e l i z e d c h a r g e , w h i c h p r o d u c e s a d e q u a t e r e v e n u e t o r e c o v e r s y s t e m c o s t s ,

i s a s i n g l e r i u m b e r s u m m a r i z i n g t h e l i k e l y d i s t r i bu t io r? of rea- l ' and d i f f e r e n t r a t e s ,

a s r e p r e s e h t e d i n - F i g . 3-4. 1 t c o v e r s ' i n t e r e s t a n d p r o f i t , a s t he f low d i a g r a m

T h e i n t e r a c t i o n s of a s o l a r - e n e r g y s y s t e m wi th o t h e r supp ly s y s t e m s a n d

t h e c o n s t i t u e n c y of u s e r s a c r o s s t he whole . u t i l i t y a r e not t a k e n u p b y t h i s mode l .

T h u s o n l y if t h e e f f e c t s on t h e u t i l i t y a r e c o m p a r a b l e c a n c ' ompar i son be tween two . .

( d i f f e r e n t - s y s t e n l s u s i n g t h i s m o d e l be c o n s i d e r e d e n t i r e l y val id . . ,

- 2. S o l a r A r r a y M a n u f a c t u r i n g I n d u s t r y S i m u l a t i o n (SAMIS) Mode l

. , T h e p u r p o s e of ' SAMIS is t o - p r o v i d e ,an uilde r s tanding of t he poten t ia l r-

b i n e f i t s of s c i e n t i f i c r e s e a r c h i n t o the m a t e r i a l s and p r o c e s s e s involved in t h e . I

- . m a n u f a c t u r e of, a r , . rays f o r t he photovol ta ic c o n v e r s i o n of s o l a r e n e r g y . T h e

p r o c e d u r e w h i c h is be ing d e v e l o p e d f o r t h i s p u r p o s e a l s o a l l d w s . s tudy of the

e f f e c t s of v a r i o u s f i S c a l p o l i c i e s of m a n u f a c t u r e r s and of p o s s i b l e g o v e r n m e n t a , l

a c t i o n s .

Fig. 3-4 . Compar i son of levelized energy cos t with growing 'energy cos t s

3 - 1 3

z ? V)

2 4

v, I-

8 u -

BBEC > 0 LIL W

5 BBEC 0

LEGEND - BBEC = LEVELIZED BUSBAR BBEC+

ENERGY COST

Yco = FIRST YEAR OF COMMERCIAL OPERATION

N = SYSTEM LIFETIME

- - - - -

-----'Y

Y ,,+N

TIME, YEAR

1 ,

T o a c c o m p l i s h i t s purpose , SAMIS is a t h r e e - p a r t e f fo r t . The f i r s t i s the

c o n s t r u c t i o n of a c o m p u t e r p ' r ~ ' ~ r a r n tha t wiil unders t and a d e s c r i p t i o n of the , , . . .

s t r u c t u r k 0 f . a m a n u f a c t u r i n g indus t ry , then s i m u l a t e the r e s p o n s e o f ' t h a t ind'ustry . , . ,

t'o a n o r d e r f o r a spe.cif ied quant i ty of i t s end product . T h e second ' p a r t of the

SAMISieffor t i s the d e s c r i p t i o n - o f the i n d u s t r y s t r u c t u r e s that would rCsult f r o m

the u s e of p a r t i c u l a r t echno log ica l p r o c e s s e s f o r t h e m a n u f a c t u r e of photovoltaic , ,

s o l a r a r r a y s . T h e t h i r d p a r t is the u s e of the SAMIS c o m p u t e r p r o g i a m to

- i n v e s t i g a t e the s e n s i t i v i t y of the p r i c e of s o l a r photovoltaic power capabi l i ty . .

- ( and , p e r h a p s , t h e v a l u e s of ' o t h e r quan t i t i e s of i n t e r e s t , s u c h a s the e n e r g y

payback t i m e ) to v a r i a t i o n s in the technologica l p r o c e s s e s and i n t h e va1;es of

p a r a m e t e r s tha t d'escribe i n d u s t r i a l po l i c i e s , g o v e r n m e n t a l . ac t ions , a n d / o r t h e \

c o s t s of ' r e q u i r e d goods and s e r v i c e s .

T h e SAMIS C o m p u t e r P r o g r a m a s s u m e s tha t the i n d u s t r y c a n b e r e p r e -

s e n t e d a s a collkc'tion of s i h g l e - p r o d u c t manufac tu r ing f i r m s . The end p roduc t

of t h e i n d u s t r y ( t h a t i s , , a n n u a l newly- ins ta i led s o l a r photovoltaic power p r o -

- ' duc t ion capab i l i ty ) i s a s s u m e d t o - b e 'produced by a m a n u f a c t u r e r . w h o require .?

c e r t a i i o t h e r , p r o d i ~ c t & and s e r v i c e s a s input. 'SAMIS a s s u m - e s tha t e a c h of t h e s e

o t h e r p r o d u c t s and s e r v i c e s i s p roduced by a n o t h e r m a n u f a c t u r e r , E a c h o f .

t h e s e rninufacturikig f i r m s k e q u i r e s addi t ional p r o d u c t s and s e r v i c e s , and s o on.

Eventual ly , produ,c ts o r r a w m a t e r i a l s a r e identif ied f 0 . r .which the m a r k e t

s i m p l y supp l i e s . a p r i c e . T h e i n d u s t r y d e s c r i p t i o n m u s t supply SAMIS with h o w ,

m u c h of e a c h r e q ~ ~ i r e d p r o d u c t and s e r v i c e i s needed a s a function of how m u c h

of e a c h r e q u i r i n g p r o d u c t i s t o be produced.

.- ' - Since i t i s ' b e i n g a s s u m e d tha t fa p a r t i c u l a r s e t of technologica l p r o c e s s e s -

i s be ing u s e d , SAMIS d o e s not need to know the p r i c e s of t h e in't 'ermediate p r o - '.

d u c t s when i t is ca lcu la t ing the quant i t ies . h his i s a n e c e s s a r y ~ a s s ~ u m p t i o n , . / -

because a t th i s point not a l l of the pric .es;are kno.wn. . ~ . £ t e r ' f o l l o w i n g the t r a i l ' ,

of o r d e r s to i t s e n d s , SAMIS's next s t e p i s to go back "up" the s t r u c t u r e , c o m -

puting p r i c e s . . -

.. - The. p r i c e of e a c h f i r m ' s p roduc t can b e computed by cons t ruc t ing a

m a t h e m a t i c a l mode l of t h e f i r m ' s f inances . Stich a m o d e l c.an be obtained by

s e t t i n g the f i r m ' s to ta l i n c o m e equa l to i t s to t a l outgo (which m u s t inilude . .

. .

earnings and investment), replacing t e r m s in that equation by successive sub-

models which contain parameters (such a s total capital required, legal minimum

lifetime for depreciation of equipment, and the required re turn on equity) that

will be used to descr ibe the f i rm, and solving for the unit price of the product.

This procedure causes some of the var iables that a r e resu l t s in the r ea l

world, such a s earnings, to .become inputs to the model. I t is this inversion of

the roles of such variables that makes it necessary to caution the u s e r of SAMIS.

In the r ea l world, the f i rm se t s the pr ice of i ts product, the amount of sales

e f for t , and a host of other facto.rs, and accepts whatever profit ( o r l o s s ) resul ts .

In SAMIS, the u s e r specifies the profit, the in te res t ra te for corpora te bonds,

the ratio of debt to equity, and other pa ramete r s ; SAMIS then calculates the

quantity of ~ r ' o d u c t sold from the industry description supplied by the u s e r , and ' -

the product price. The "supply pr ice" est imated by SAMIS is that pr ice a t which

the manufacturer would just meet a l l of his financial obligations,. including

profit, taxes, replacement of. capital goods, and so on, assuming that the quantity

sold is that which is implied by the industry description.

F o r rea l i sm in describing the industry, the submodels contained within

SAMIS allow a considerable amount of flexibility. F o r example, the following

pa ramete r s may be defined a s functions of quantity: the unit pr ices of purchased

goods and serv ices , the capital required by each manufacturing plant, and the

relat ive amounts of required goods and serv ices . In addition, each manufactur-

ing f i rm may have different values for the pa ramete r s that descr ibe i ts .f inancial

charac ter i s t ics .

SAMIS pr ice est imates depend upon a lot of user-suppl ied data, much of

which cannot be known precisely. To increase the usefulness of its resu l t s ,

SAMIS provides fo r consideration of uncertainties in the data by requir ing the

u s e r to s ta te minimum, median, and maximum values fo r a l l pa ramete r s and

then computing a (specifiable) number of Monte Carlo est imates . Means,

s tandard deviations, and his tograms of the pr ices and quantities can be d i s -

played. (If but a single t r i a l is specified, median values a r e used throughout

the computation. )

A typica l SAMIS i n d u s t r y d e s c r i p t i o n is i l l u s t r a t e d i n F i g . 3-5. F i g u r e

3-5 d o e s no t - show the v a l u e s of the f inancia l p a r a m e t e r s of the f i r m s , which

a re a l s o p a r t of the i n d u s t r y d e s c r i p t i o n inpub. Th i s d e s c r i p t i o n u s e s p r o c e s s e s

w h i c h a r e c o n s i s t e n t wi th the c u r r e n t s t a t e of the a r t , but no c u r r e n t manufac-

t u r e r d o e s things i n e x a c t l y the a s s u m e d fashcon. S o m e addi t ional modeling,

e x t e r n a l to the SAMIS c o m p u t e r p r o g r a m , i s r e q u i r e d t o produce the p a r a m e t e r s , I -

shown. F o r e x a m p l e t h e f i g u r e of 1. 32 w a f e r s / c e l l t a k e s into a c c o u n t b r e a k a g e ,

m e t a l i z a t i o n f a i l u r e , a n d s o on.

Addi t ional i n d u s t r y d e k c r ip t ions wi l l be d&eloped t o d e s c r i b e the s t r u c - ' , t u r e s t h a t would r & s u l t f r o m t h e ' u s e of o t h e r technologica l p r o c e s s e s , s u c h a s

t h o s e t h a t u s e m o n o c r y s t a l s i l i con r ibbons o r shee t s .

- T h e m o d u l a r i t y of S o l a r Pho tovo1 ta . i~ C o n v e r s i o n ~ ~ s t e m s ' (SPCS)' m a k e s i't'

' p o s s i b l e f o r t h e s e s y s t e m s t o h a v e app l i ca t ions ranging f r o m s m a l l , ?emote o r . .

porta.ble,power s y s t e m s , individual r e s i d e n t i a l o r c o m m e r c i a l ~ o w e r s y s t e m s , . .

t o l a r g e centr 'a l p0we.r plant<. Cons'equently, the potent ia l u s e r s of S P C S a r e ' n o t

n e c e s s a , r i l y r e s t r i c t e d t o p r i v a t e o r public p o w e r u t i l i t i e s , but e a s i l y inc lude

g o t e r n m e n t a l a g e n c i e s s u c h a s the U. S. F o r e s t S e r v i c e , t h e U. S. C o a s t Guard, .

f e d e r a l / s t a t e / l o c a l l a w e n f o r c e m e n t a g e n c i e s , w a t e r d i s t r i c t s , e tc . ; p r i v a t e

o r g a n i z a t i o n s s u c h a s t h e b u i l d i n g a n d c .ons t ruct ion indus t ry , i n d k s t r i a l p a r k s ,

c o m m e r c i a l shopping c e n t e r s , r e c r e a t i o n a l f ac i l i t i e s , etc . ; and individual

building o r h o m e o w n e r s . I

-

T h e wide r a n g e of p o s s i b l e u s e r s c r e a t e s a n e s p e c i a l l y d i f f icul t m a r k e t i n g

p r o b l e m f o r the s o l a r , a r r a y m a n u f a c t u r e r s i f t h e s e u s e r s r e p r e s e n t . t h e p u r -

c h a s e r s of s o l a r a r r a y s , o r . e v e n if t h e s e u s e r s . r e p r e s e n t a m a r k e t f o r a n u m b e r

of s y s t e m app l i ca t ion s u p p l i e r s who, in t u r n , a r e the p u r c h a s e r s of s o l a r

a r r a y s . I n - e i t h e r c a s e , the s o l a r a r r a y s u p p l i e r i n d u s t r y i s , in a l l l ikel ihood,

- . d

looking at a r e l a t i v e l y unknown a n d p o s s i b l y q u i t e d i s p e r s e d m a r k e t . The E R D A

P h o t o v o l t a i c C o n v e r s i o n P r o g r a m is seek ing t o iden t i fy , the .potent ia l m a r k e t by - ,

conduct ing v a r i o u s m i s s i o n a n d s y s t e m - s t u d i e s ; i t wil l begin t o a g g r e g a t e s o m e

ANNUAL NEW PHOTOVOLTAIC POWER CAPABILITY PEAK WATTS PER YEAR

SOLAR MODULES 0.00966 MODULES /PEAK WATT

ENCAPSULATION $492,000 CAPITAL FOR 4444 MODULES /YEAR SUBSTRATE MATERIAL (RTV) MATERIAL 2.38 POUNDS /MODULE I $~.OO/MODULE $2.50/POUND (

MISC. MATERIALS $19.20 /MODULE

/ SOLAR CELLS 225 CELLS/MODULE .

1

' LABOR 4.5 HR /MODULE W.OO/HR

$422,000 CAPITAL FOR 1,000,000 CELLS /YEAR SILVER

I MISC. MATERIALS

1. 14 GRAMS /CE $0.145/CELL $0.161 5/GRAM

w I c. TITANIUM -I $O.~~ /CELL

/ I ' LABOR SILICON WAFERS 1.32 WAFFERS /CELL 0.016 HR/CELL

I $4.00/HR $530,000 CAPITAL FOR 1,320,000 WAFERS /YEAR

I MISC. MATERIALS LABOR @.04/WAFER 0.019 HR /WAFER

$750,000 CAPITAL FOR 1594 INGOTS /YEAR MISC. MATERIALS

I LABOR

$88.90/INGOT 15.6 HR/INGOT $4.00/HR

HIGH GRADE POLYCRYSTAL SILICON 8.00 KG /INGOT

$65/KG

Fig. 3-5. A SAMIS description of a n industry based on Czochralski ingots

~ ' . of the. m a r k e t by c o o p e r a t i v e p r o g r a m s w i t h g o v e r n m e n t a l a g e n c i e s s u c h as the

~ k ~ a r t m e n t of D e f e n s e , U. S: F o r e s t S e r v i c e , U. S. C o a s t ~ u a r d , and with ' the - . . .

E l e c t r i c a l - P o w e r ~ e s e a r c t i ' I n s t i t u t e of t h e u t i l i ty i n d u s t r y . *

-, T h e LSSA P r o j e c t e l e m e n t of t h e E R D A P r o g r a m w i l l s e e k t o m i n i m i z e t he .

>

d i f f i c u l t i e s of c o m e r c i a l i z a t i o n - i n a d i v e r s e m a r k e t f o r t h e s o l a r a r r a y s u p p l i e r

i n d u s t r y by w o r k i n g w i t h t h e i n d u s c r y - t o d e v e l o p s t a n d a r d a r r a y ' d e s i g n s t o . c o v e r

as . m a n y a s poss-ible of t h e v a r i e t y of a p p l i c a t i o n s . his a p p r o a c h t r e a t s t h e ' .

. d i v e r s e , m a r k e t prob1e.m i n . t h e s a m e m a n n e r a s o t h e r c o m m e r c i a l (p roduct ' s

a d a p t a b l e t o d i f f e r e n t a p p l i c a t i o n s , n a m e l y by e s t a b l i s h i n g c o n f i g u r a t i o n l i m i t s , . .. -

m a t c h i n g i n t e r f a c e s , and i n t e r c h a n g e a b i l i t y s p e c i f i c a t i o n s , w h i l e a c c o m m o d a t i n g

m a n u f a c t u r e r - u n i q u e i n t e r n a l d e s i g n and p e r f o r m a n c e f e a t u r e s . I t a l s o w i l l

g i v e c o n s i d e r a t i o n to a r e a s w h e r e s p e c i a l a p p l i c a t i o n s r e q u i r e un ique d e s i g n s .

\ .

T h e , ~ A D E M ' m o d e l , d e s c r i b e d b r i e f l y i n 111-'A-3. above , .is be ing deve loped

to a n a l y z e t he t r a d e - o f f s as s ,oc i a t ed w i t h t he v a r i o u s - p r a r a m e t e r s wh ich m u s t be

c o n s i d e r e d i n e s t a b l i s h i n g d e s i g n s p e c i f i c a t i o n s f o r i n t e r c h a n g e a b l e s o l a r a r r a y s .

T h i s a n a l y t i c a l c a p a b i l i t y is. e x p e c t e d t o i n t e r a c t w i t h t h e USES and- SAMIS

m o d e l s , a l s o d e s c r i b e d b r i e f l y above , .and to i n t e r f a c e d i r e c t l y w i t h . a s o l a r . .

a r r a y e n g i n e e r i n g d e s i g n a n a l y s i s c a p a b i l i t y be ing d e v e l o p e d u n d e r t he LSSA

d e s i g n - a n d t k s t a c t i v i t y .

PART I V

TASK 1, SILICON MATERIA J,

-. The objective of the Silicon Materi'al Task i s t o establish, by 1984, an

installed plant capability f o r producing silicon suitable f o r so lar ce l l s a t a r a t e M

equivalent to 500 MW (peak) of so la r a r r a y s p e r y e a r a t a pr ice of l e s s than

$10 pe r kilogram. The p rogram formulated to achieve this objective i s based

on the conclusion that the pr ice goal can not be reached i f the process used i s . essentially the s a m e a s the present commerc ia l p rocess for producing s e m i -

conductor-grade silicon. Consequently, i t is necessa ry that e i ther a different

process be developed for producing semiconductor -grade sil icon o r a l e s s pure

and . less costly sil icon ma te r i a l (i. e. , a s.olar-cell-grade sil icon) be shown to

be utilizable.

A. TECHNICAL BACKGROUND

. Solar cel ls a r e present ly fabricated f rom semiconductor-grade silicon,

which has a marke t pr ice of about $65 pe r kilogram. A d ras t i c pr ice reduction

of mater ia l i s necessa ry to meet the economic objectives of the LSSA Project .

One means for meeting this requirement i s to devise a process fo r producing a

silicon mater ia l which is significantly l e s s pure than semiconductor-grade

silicon; the pr ice goal for this mater ia l is l e s s than $10 p e r kilogram. However,,

the allowance f o r the cost of silicon mater ia l in the overall economics of the

so la r a r r a y s f o r LSSA is dependent on optimization trade-offs, which concomi-

tantly t r e a t the effects of the pr ice of silicon mater ia l and the effects of ma te r i a l

propert ies on the performance of so la r cells. Accordingly, the program of the

Silicon Material Task is s t ruc tured to provide the information for the optimiza- , tion trade-offs and to develop processes f o r producing different impuri ty-grades

of silicon a t high volume and low cost.

B. ORGANIZATION OF THE TASK 1 EFFORT

-

The Task 1 effort is organized into five phases. As Table 4-1 indicates,

Phase I is divided into four parts. In Pa r t I the technical feasibility and

practicality of processes for producing semiconductor-grade silicon will be

demonstrated. In P a r t I1 the effects of impurities on the properties of single

c rys ta l silicon mater ia l and the performance characteristics of solar cells, a s

well a s the consequences of various processing procedures, will be investigated.

This body of infprmation will serve a s a guide in developing processes (in

P a r t 111) fo r the production of solar -cell-grade silicon. The process dtSvelop-

ments in P a r t s I and-III will be accomplished through chemical-reaction,

chemical-engineering, energy-use, and economic studies. In,Part IV of Phase

I, the relative co'mmercial potentials of the various gilicon-production pro-

ce s se s developed under P a r t s I and ILI will be evaluated. Thus, at, the end of

Phase I a body of information will have been obtained for optimization trade-off

studies and the most promising processes will have been selected. *

Phase I1 will be initiated to obtain scale-up information. This will be

derived f rom experiments and analyses involving mass and energy balances, -

process flows, kinetics, m a s s transfer , temperature and pressure effects, and

operating controls. The basic approach will be to provide fundamental scientific

'and engine'ering information f rom which valid extrapolations ;sable for plant

design can be made; applicable scale-up correlations will a lso be used. This

body of scale-up information will'then provide the necessary basis for the

design, construction, and operation of a large-scale production plant.

Since the installation anp operation of a commercial chemical process

t. plant that incorporates a new process involves high risks, experimental plants

will be used to obtain technical and economic evidence of large-scale production

potential. In the experimental plant phase (i. e. , Phase 111) there will be oppor- - tunities to correct design e r r o r s ; to determine energy consumption; to establish

practicaloperat ing p ~ o c e d u r e s and production conditions; and to 'more reali-

stically evaluate- the requirements for instrumentation, controls, and on-line

anaiys e s.

T a b l e 4- 1. Organ iza t ion of the Taslc 1 e f fo r t

In the f inal phase of T a s k 1 ( i . e . , P h a s e IV), a f u l l - s c a l e c o m m e r c i a l

plant c a p a b l e of mee t ing the product ion objec t ive wil l be des igned , ins t a l l ed ,

a n d opera ted . T h e e x p e r i m e n t a l p lant and t h e c o m m e r c i a l p lant wi l l b e o p e r a t e d

c o n c u r r e n t l y s o a s t o p e r m i t t h e u s e of t h e e x p e r i m e n t a l p lant f o r inves t iga t ions

of p lant opera t ions , i. e . , f o r p r o b l e m solving and f o r s t u d i e s of p r o c e s s opti-

miza t ion .

P h a s e I

P a r t I

P a r t 11

P a r t I11

, P a r t IV

P h a s e I1

. P h a s e I11

P h a s e IV

Addit ional b a s i c c h e m i c a l and eng inee r ing inves t iga t ions t o r e spond t o

p rob lem-so lv ing n e e d s of T a s k 1 wi l l be conducted i n suppor t ing e f fo r t s . T h e s e

suppor t ing s u b t a s k s wil l be a c c o m p l i s h e d u n d e r c o n t r a c t a n d by a n in -house J P L

p r o g r a m . 4 - 3

Objec t ive

D e m o n s t r a t e the t echn ica l f eas ib i l i ty and p r a c t i - ca l i ty of p r o c e s s e s f o r producing s i l i con .

~ s t a b l i s h the p rac t i ca l i ty of a p r o c e s s c a p a b l e of high vo lume product ion of s e m i c o n d u c t o r - g r a d e s i l i con a t a m a r k e d l y reduced c o s t .

Inves t iga te the e f fec t s of i m p u r i t i e s on the p r o p e r t i e s .of s ing le c r y s t a l s i l i con m a t e r i a l and the p e r f o r m a n c e c h a r a c t e r i s t i c s of s o l a r c e l l s as well a s the c o n s e q u e n c e s of v a r i o u s p ro - c e s s i n g p r o c e d u r e s .

' E s t a b l i s h the p rac t i ca l i ty of a p r o c e s s c a p a b l e of high vo lume production of s o l a r - c e l l - g r a d e s i l i con a t a p r i c e of l e s s than $10 p e r k i l o g r a m .

Eva lua te the r e l a t i+e c o m m e r c i a l potent ia ls of the s i l i con-produc t ion p r o c e s s e s developed under P h a s e I.

Obta in p r o c e s s s c a l e - u p in fo rmat ion .

Conduct e x p e r i m e n t a l p lant o p e r a t i o n s t o obta in t echn ica l and economic ev idence of l a r g e - s c a l e p roduc t ion potent ia l .

Design, ins t a l l , and o p e r a t e a f u l l - s c a l e c o m - t ~ ~ e r c i a l plant c a p a b l e of mee t ing the product ion objec t ive .

1

_ P r o p o s a l s f o r a p p r o p r i a t e p r o g r a m s to i m p l e m e n t P h a s e I of T a s k 1 w e r e -

s o l i c i t e d by m e a n s of R e q u e s t s f o r P r o p o s a l s (RFPs) . In addit ion, unso l i c i t ed - p r o p o s a l s h a v e been a n d a r e continuing to b e rece ived . Al l p r o p o s a l s a r e given

c a r e f u l evaluat ion . . ,/

he t e a m w h i c h e v a l u a t e d the p r o p o s a l s s u b m i t t e d in r e s p o n s e t o the s i l i - '

c o n m a t e r i a l R F P r e c o m m e n d e d tha t s e v e n c o n t r a c t s be negotiated: t h r e e f o r

P a r t I; two-fo? P a r t 11, ' a n d . t w o f q r P a r t 111. he c 6 n t r a c t o r s s e l e c t e d i r e

shown i,n T a b l e 4-2. Only the Dow Corn ing c o n t r a c t . r e m a i n s t o be negotiated.

A s t h e table ind ica tes , unso l i c i t ed p r o p o s a l s have thus f a r r e s u l t e d in a con-

t r a c t a w a r d . t o L a m a r U n i v e r s i t y a,nd t h r e e potent ia l a w a r d s .

. .

D. . TASK 1 TECHNJCAL ACTIVITY -. .-

T h e o b j e c t i v e s of P h a s e I of TBsk 1 are a s fol lows: P a r t I - E s t a b l i s h the 1

p r a c t i c a l i t y of a p r o c e s s ' capab le of the high vo lume* produc tioh of s e m i ~ ~ n d u c t o r -

. . g r a d e . s i l i c o n . a t a m a r k e d l y reduced c o s t ; . P a r t I1 - . ~ n v e s t i g a t e the e f fec t s of

i m p u r i t i e s o n the p r o p e r t i e s of s ing le c r y s t a l s i l i c o n m a t e r i a l and the perf6i.&

a.nce c h a r a c t e r i s t i c s of so l .a r c e l l s as wel l a s the c o n s e q u e n c e s of v a r i o u s pro- '

c e s s i n g p roc .edures ; and P a r t I11 - E s t a b l i s h the p r a c t i c a l i t y of a p r o c e s s capab le

of the high v o l u m e p roduc t ion of s o l a r - c e l l - g r a d e s i l i c o n a t p r i c e l e s s than $10 .

., .

pe? k i l o g r a m ; and P a r t IV - Eva lua te the r e l a t i v e c o m m e r c i a l . p r a c t i c a l i t y of the .

s i l i c o n - p r o d u c t i o n ~ p r o c e s s e s developed u n d e r P h a s e I of T a s k 1.

1. P r o c e s s e s , f o r P r o d u c i n g S e m i c o n d u c t o r - G r a d e 'Silicon

T h e a p p r o a c h used f o r P a r t I i n c o r p o r a t e s t h e o r e t i c a l s tudies- involving - - , - t h e r m o d y n a m i c s , r e a c t i o n c h e m i s t r y , and c h e m i c a l eng inee r ing ; c h e m i c a l

reaction..investigations c o n s i s t i n g of the . exper imen ta l determinations.of-reaction

kinet?cs , y ie lds , -and s.uitable p r o c e s s condi t ions ; a c h e m i c a l eng inee r ing e f fo r t

f o r s e c u r i n g a n e x p e r i m e n t a l d a t a b a s e f o r p r e l i m i n a r y p r o c e s s model ing; and

e n e r g y - u s e and e c o n o m i c ca lcu la t ions f o r p r e l i m i n a r y p r o c e s s m o d e l s . ' In e a c h

T a b l e 4-2. T a s k 1 c o n t r a c t o r s

Note : All T a s k 1 c o n t r a c t s , c u r r e n t o r p roposed , a r e f o r w o r k u n d e r P h a s e I

C o n t r a c t o r Techno logy A r e a

SEMICONDUCTOR-GRADE PRODUCTION P R O C E S S E S ( P a r t I of P h a s e I)

B a t t e l l e M e m o r i a l In s t i t u t e , C o l u m b u s , Oh io

Moto ro la , Phoen ix , A r i z o n a

Union C a r b i d e , S i s t e r s v i l l e , W. V i r g i n i a

S i f r o m SiC14 o r Si14

S i u s ing S i F 4 t r a n s f e r

S i f r o m SiH4

S O L A R - C E L L - G R A D E S P E C I F I C A T I O N S ( P a r t I1 of P h a s e I)

M o n s a n t o R e s e a r c h , St. L o u i s , M i s s o u r i

W'es t i nghouse E l e c t r i c , . ,

P i t t s b u r g h , P e n n s y l v a n i a

Inves t iga t ion of e f f e c t s of i m p u r i t i e s o n s o l a r c e l l p e r f o r m a n c e

Inves t iga t ion of e f f e c t s of i m p u r i t i e s o n s o l a r c e l l p e r f o r m a n c e

S O L A R - C E L L - G R A D E PRODUCTION P R O C E S S E S , ( P a r t I11 of P h a s e I)

Dow C o r n i n g , Hemlock , Mich igan

T e x a s ~ n ' s t r u m e n t s , D a l l a s , T e x a s

S tan fo rd R e s e a r c h Ins t i t u t e M e n l o P a r k , C a l i f o r n i a

~ e s t i nghouse E l e c t r i c 1 , 2

P i t t s b u r g h , P e n n s y l v a n i a

A e r o C h e m R e s e a r c h L a b o r a - t o r i e s l * 2, P r i n c e t o n , New J e r s e y

.

S i f r o m p u r e s o u r c e m d t e r i a l s u s ing '

a r c f u r n a c e p r o c e s s i n g

S i f r o m C r e d u c t i o n of S iO us ing p l a s m a p r o c e s s i n g 2

S i by d u p l e x v a p o r - e l e c t r o c h e m i c a l c o n v e r s i o n of S i F 4 S i b y p l a s m a - a r c - h e a t e r r e d u c t i o n of SiC14 w i t h H and a l k a l i m e t a l s

2 as r e d u c i n g a g e n t s

S i by u s e of a n o n - e q u i l i b r i u m p l a s m a j e t

COMMERCIAL P O T E N T I A L O F P R O C E S S E S ( P a r t IV of P h a s e I)

L a m a r U n i v e r s i t y , 2 Beaumont , T e x a s

E v a l u a t e r e l a t i v e c o m m e r c i a l potenti 'als of S i - p roduc t ion p r o c e s s e s deve loped u n d e r T a s k 1

' C o n t r a c t t o b e a w a r d e d i n S p r i n g of 1976.

' u n s o l i c i t e d p r o p o s a l .

. , . ..

c a s e , t h e c o n t r a c t r , e q u i r e s a d e m o n s t r a t i o n of t e c h n i c a l f e a s i b i l i t y and ' a - p r o j e c t i o n o f ' c o m m e r c i a l p r a c t i c a l i t y , involv ing the p r e l i m i n a r y a n a l y s i s of

s u i t a b i l i t y f o r a s c a l e - u p s t u d y . T h e e v a l u a t i o n of e a c h p r o c e s s as a c a n d i d a t e -

f o r t h e P h a s e I1 s c a l e - u p s t u d i e s i s s c h e d u l e d f o r e a r l y 1977.

a. S e m i c o n d u c t o r - G r a d e S i P r o d u c t i o n b y (a) Z n Reduct i0 .n of S iC14, (b') 'Reduc t ion of S i I 4 w i t h - H 2 a n d ( c ) T h e r m a l D e c o m p o s i t i o n of Si14 - B a t t e l l e M e m o r i a l I n s t i t u t e

T h e o b j e c t i v e of t h e p r o g r a m a t t h e B a t t e l l e M e m o r i a l I n s t i t u t e i s t o J,

( d e t e r m i n e t h e p r a c t i c a l i t y of u t i l i z ing t h e ~ n " . r e d u c t i o n of S iC14 o r t h e t h e r m a l

d i s . soc i a t i on , o r r e d u c t i o n b y H2, of S i I t o m e e t t h e goa l of P a r t I. P r a c t i - 4

c a l i t y w i l l b e d e m o n s t r a t e ' d by t h e o p e r a t i o n ,of a s m a l l p r o c e s s i n g uni t . S e l e c -

t i o n of t h e p r o c e s s , t o b e u s e d f o r ' t h e un i t wi l l b e b a s e d o n the r e s u l t s of a n a l y s e s

a n d c . o m p a r i s o n s of t h e . t e chno logy , economic.^, and e n e r g y u s e of t h e . p r o c e s s -

c a n d i d at-e s . . .

T h e f i r s t w o r k u n d e r t h i s c o n t r a c t i nc luded c a l c u l a t i o n s of e q u i l i b r i u m

y i e l d s f o r a s s u m e d p r a c t i c a l o p e r a t i n g c o n d i t i o n s , f o r m u l a t i o n of pre1iminar .y (

. pr0ces . s f low s h e e t s , c a l c u l a t i o n s of m a s s and e n e r g y b a l a n c e s , and e x p e r i -

m e n t a l i n v e s t i g a t i o n s of. o p t i o n s f o r t he two ' p r o c e s s e s . . -

. .

F o r t h e l i t e r a t u r e s e a r c h , the r e a c t i o n s t o b e s t u d i e d w e r e u s e d a s 6

g u i d e l i n e s : t h e Z n r e d u c t i o n - of SiC14, t h e t h e r m a l d e c o m p o s i t i o n of Si14, t h e -

H r e d u c t i o n of Si14, t h e e l e c t r o l y s i s of ZnC12, t h e f o r m a t i o n of S i I by 2 . 4 . . r e a c t i n g I2 w i t h r n e t a l i u r g i c a l g r a d e S i o r w i th a m i x t u r e of S iOZ and C , and I2

r e c o v e r y p r o c e s s e s . T h e c h a r a c t e r i s t i c s t o be i nc luded i n t he i n v e s t i g a t i o n

w e r e t h e r m o d y n a m i c p r o p e r t i e s , r e a c t i o n k i n e t i c s , p r o c e s s t echno logy and

c o s t s , m a t e r i a l s of cons . t ruc t ion , ene r ' gy -use , c .he 'mical analyses , , and the

e f f e c t s of ~n as a n i m p u r i t y i n Si . . .

* Z i n c . F o r i d e n t i f i c a t i o n of c h e m i c a l s y m b o l s , see L i s t of A b b r e v i a t i o n s .

Z n Reduc t ion of SiC14: T h e p r e l i m i n a r y p r o c e s s - f l o w d i a g r a m f o r t he

Z n r e d u c t i o n of S i C l ( F i g . 4 -1 ) w a s d e v i s e d t o i l l u s t r a t e s o m e of t he opt ions a n d 4 o p e r a t i n g cond i t i ons wh ich need t o b e c o n s i d e red . T h i s p r o c e s s i n c o r p o r a t e s

s e c t i o n s f o r i n v e s t i g a t i o n s of (1 ) Zn and SiC14, wh ich r e a c t i n the f lu id i zed bed

d e p o s i t i o n a t a b o u t 900°C, ( 2 ) the r e c o v e r y of Z n C I Z and the s u b s e q u e n t r e g e n -

e r a t i o n of Z n by e l e c t r o l y s i s , and ( 3 ) the r e c o v e r y and pu r i f i ca t ion by d i s t i l l a -

t ion of SiC14. A l t e r n a t i v e s t e p s of the p r o c e s s wi l l be i n t r o d u c e d and a s s e s s e d

when n e c e s s a r y .

T h e r m o d y n a m i c c a l c u l a t i o n s w e r e m a d e to e x a m i n e e q u i l i b r i u m y i e l d s

f o r s e v e r a l cond i t i ons and to p r o v i d e a b a s i s f o r the s u b s e q u e n t e n e r g y b a l a n c e

d e t e r m i n a t i o n . At the s t a r t a d i f f e r e n c e b e t w e e n the f r e e e n e r g i e s of f o r m a t i o n

of ZnC1 a s c a l c u l a t e d f r o m the e n t r o p y , en tha lpy , and h e a t c a p a c i t y d a t a and 2 f r o m the f u s e d s a l t emf d a t a w a s found. T h i s w a s r e s o l v e d by s u b s t i t u t i n g

a n o t h e r s e t of e x p e r i m e n t a l d a t a f o r t he m e l t i n g point and t h e h e a t and e n t r o p y

of fus ion . Us ing t h e s e da t a , v a l u e s ' f o r -AGO w e r e c a l c u l a t e d f o r t he ' t e m p e r a -

t u r e r a n g e of 300" to 1 5 0 0 ° K : T h e s e v a l u e s w e r e then u s e d i n the c a l c u l a t i o n s

of the e q u i l i b r i u m c o n v e r s i o n e f f i c i ency v a l u e s of t he r e d u c t i o n r e a c t i o n . T h e

r e s u l t s a r e shown in Fig. 4-2, wh ich a l s o i l l u s t r a t e s t h e e f f e c t of a d i l u e n t gas .

T h e o p e r a t i n g t e m p e r a t u r e , b a s e d on t h e s e d a t a , is l i k e l y t o b e b e t w e e n t h e

d e w po in t of ZnC12 a t 1005 OK a n d 1300 OK. T h e f ina l d e t e r m i n a t i o n wi l l r e s u l t

p r i m a r i l y f r o m c o n s i d e r a t i o n s of t h e e x p e r i m e n t a l r a t e a n d y i e l d da t a . . .

E x p e r i m e n t s involving the i n t r o d u c t i o n of Zn as a so l id , wh ich is p a s s e d

t h r o u g h a h igh t e m p e r a t u r e zone p r i o r to r e a c t i o n w i t h S i c 1 i n a f lu id i zed bed, 4 h a v e f a i l ed t o y i e ld depos i t i on of S i i n t he bed . T h e r e a c t i o n i n v a r i a b l y o c c u r s

. above the bed and r e s u l t s i n a b lockage of t he p r e h e a t e d zone . AS a c o n s e q u e n c e ,

t h i s m o d e h a s b e e n e l i m i n a t e d f r o m f u r t h e r c o n s i d e r a t i o n .

T h e e x p e r i m e n t s i n which Zn w a s i n t r o d u c e d as a v a p o r .were p e r f o r m e d

in a n a p p a r a t u s shown in Fig. 4-3 , which u t i l i z e s a f lu id i zed bed d e p o s i t i o n

r e a c t o r . T h e r e s u l t s i n d i c a t e t h a t f l u id i za t ion c a n be ach ieved , t h a t t he pro-

c e s s w i l l p r o v i d e a r e l a t i v e l y h igh c o n v e r s i o n e f f i c i ency of a t l e a s t 45% a t

-1- SiCI4

PREHEATER I AND I

VAPORIZER J,

- 2 2 c -

BLEED(g) BLEED(g) BLEED (g ) SiCl, ( e l sic1 (g )

aC14 ( 9 ) BLEED (g ) ZnCI2 (8 ) (1) Zn ( l ) 5c14 (g)

Si (s) Zn ( r ) BLEED(^) , - - - - - - - ----- n ( ~ ) znC14(g) SiC14(g) I

60°C Zn(s) Si (I)

320°c I I 60% 1 I 60 O c 1 I IMPURITIES

Fig. 4- 1. P r e l i m i n a r y flow d i a g r a m f o r the p repara t ion of Si by Zn reduct ion of S i c 14

t

DISTILLATION COLUMN

SiC14

CONDENSER -u0c

DUST SEPARATOR

60Oc

900%

PREHEATER SECTION

ZnCIZ

CONDENSER

ZnC 1 AND Zn -

1

I 20 O c t si(s) SiCl,(l)

320°c

DEPOSITION SECTION

fn(l) + .

ZnCl, (1)

4- I

Zn(%)

CONDENSER 45&

OPTIONAL

BLEED(g) zn(g)

9 1 0 ~ ~

ZnC12 (1) Si (0

BY PRODUCT C l2 (9 )

, SLUDGE ( I )

t PURIFIED s iC14U)

w

SUPPLY PRODUCT

INERT BLEED GAS SUPPLY I SiC14(g) 250°c

BLEED(g) + TRACE + Sicl4(g)

20°c 20°c

I 250°c .I- LA,---------------------------

250 OC BLEED (g) -+ SiC14(g) sic14 SUPPLY- - 4 --- OPTIONAL SYSTEM PROVIDING FOR THE L

' RECIRCULATION OF SiC14 WITHOUT PURIFYING

SiC14

VAPORIZER

4500C ZINC RECOVERY I INERT ( BLEED Zn(P) 450%

(ELECTROLYTIC)

1 GAS

L+ - I.

850 TO 950 '~

Zn VAPORIZER

I

TEMPERATURE, OK

-

Fig . 4-2. C o n v e r s i o n e f f i c i ency , 2 Zn t SiC14 = 2 Z n C I Z t Si

CARRIER GAS I iC14 AND -11

SiC14 CONDENSER (DRY ICE /ACETONE)

CARRIER GAS

Fig . 4-3. S c h e m a t i c of unit f o r the prepara t i .on of Si by the Zn ( v a p o r f eed) r educ t ion of SiC14

4-10

d e p o s i t i o n t e m p e r a t u r e s l e s s t he 1000" C, and t h a t t h e Z n / Z n C 1 2 c o n d e n s a t e

c a n be hand led a t 500" C . T h e e l e c t r o l y t i c . r e c o v e r y of Zn f r o m ZnC 1 h a s b e e n 2

p r o v e n to b e c o m m e r c i a l l y prac ' t i ca l , w i t h 8970 e l e c t r o c h e m i c a l e f f i c i e n c y us ing

4 . 53 k i lowa t t - h o u r s p e r k i l o g r a m of Si.

P r e l i m i n a r y c a l c u l a t i o n s of t he ene . rgy and m a s s b a l a n c e s have b e e n m a d e

u s i n g a s i m p l i f i e d f l ow c h a r t , shown i n F ig . 4-4. F o r t h e cond i t i on t h a t no

s e n s i b l e h e a t i s r e c o v e r e d , t h e t o t a l e n e r g y r e q u i r e m e n t s w e r e d e t e r m i n e d to

b e a b o u t 14. 8 k i l o w a t t - h o u r s p e r k i l o g r a m of S i p r o d u c e d ; if a l l of t h e h e a t i s

r e c o v e r e d , t h e v a l u e b e c o m e s a b o u t 7 k i l o w a t t - h o u r s p e r k i l o g r a m .

T h e t h e o r e t i c a l and e x p e r i m e n t a l r e s u l t s t o d a t e have indicate .d no t e c h -

n i c a l b lock t o t he Zn v a p o r - S i c 1 p r o c e s s . A m u c h m o r e c o m p l e t e e x a m i n a - 4

t i on of t h e d e p o s i t i o n s t e p i n the f l u id i zed bed is i n p r o g r e s s . T h e p a r a m e t e r s

of t e m p e r a t u r e , s t o i c h i o m e t r y , g a s f l o w s , r e a c t o r d e s i g n , and p r o c e s s a s s e m b l y

wi l l b e u s e d to s t u d y the p r o c e s s c h a r a c t e r i s t i c s of r a t e , y i e ld , and e n e r g y u s e .

T h e m a s s and e n e r g y - u s e b a l a n c e s w i l l b e p e r i o d i c a l l y i t e r a t e d . T h e p r o d u c t

of the n e x t p h a s e of t h i s w o r k wi l l be a m u c h b e t t e r u n d e r s t a n d i n g of t h e o p e r a t -

i n g c h a r a c t e r i s t i c s , e c o n o m i c s , and e n e r g y u s e of the p r o c e s s .

D e c o m p o s i t i o n and R e d u c t i o n of Si14: T h e r e s u l t s of p r e l i m i n a r y c o n -

s i d e r a t i o n . of t he op t ions and o p e r a t i n g c o n d i t i o n s f o r a p r o c e s s f o r t h e d e c o m -

pos i t i on and r e d u c t i o n of Si14 ( w h i c h i n c l u d e s t he i od ina t ion of a s i o 2 / C m i x t u r e

t o f o r m Si I and s u b s e q u e n t r e d u c t i o n by H of t he S i I ) a r e s h o w n i n F ig . 4-5. 4 Z 4 T h e r e a c t i o n s con ta ined i n t h i s f low d i a g r a m are t h e i od ina t ion ; t he r e c y c l i n g

s t e p f o r t h e 12; t he p u r i f i c a t i o n of t he Si14 by d i s t i l l a t i o n ; the S i d e p o s i t i o n a t

g r e a t e r t h a n 1 0 0 0 ° C ; a n d t h e r e c o v e r y of t h e b y - p r o d u c t s , I2 and HI, and of t h e

u n r e a c t e d Si14 and Hz . T h e op t ions f o r t h e d e p o s i t i o n s t e p a r e ho t w i r e , hot

w a l l , and f l u id i zed b e d ; t he f l u id i zed bed o p e r a t i o n w i l l r e q u i r e t he l e a s t e n e r g y

i n p u t and is p r e d i c t e d t o have t h e b e s t e f f i c i ency . T h i s p r o c e s s w i l l b e a s s e s s e d

s e c t i o n by s e c t i o n , and a l t e r n a t i v e s t e p s w i l l b e i n t r o d u c e d as r e q u i r e d .

T h e r m o d y n a m i c c a l c u l a t i o n s w e r e m a d e t o p r o v i d e a b a s i s f o r p r e d i c t i n g

y i e l d s and t h e e f f e c t s of t h e p r o c e s s p a r a m e t e r s of t e m p e r a t u r e , c o m p o s i t i o n ,

and p r e s s u r e . T h e d e t e r m i n a t i o n of t h e d e p e n d e n c e of e q u i l i b r i u m Si y i e l d by

Fig . 4-4. Simpl i f ied e n e r g y and m a t e r i a l flow c h a r t f o r p r e p a r a t i o n of I m o l e of Si by reduc t ion of SiC14

Si (s) (1.ooo)

bEPOS),TlON UNIT (1200 K, 72.4 % CONVERSION )

- 5.050

Si ( s ) (1.000) *

ZnCI2(g ) (2.000)

Zn(g ) (762) Zn (Q) SiCI4(g) (0.381)

(0.762)

ZnCI2(g) (0.006)

- 1

COOLER ' CONDENSER (298OK) I (773'~) 1 s iC l4 (9 ) -5.37 1 - 101.368

I (0.381)

SiC14 VAPORIZER

(331°K) +7.906

t - S T R I P ~ E R

(591 K ,

- 1.929

4 t s ic14( f , SiC14 (1)

( 1.000) I 1 t

Sic14(g)

-)i0.381 591°K )

ZnC12(t)

( 1.994) c12(g ) +

(2.000 591 OK)

ZnCI2 ( 1 )

(0.006)

r

STRIPPER (591°K)

4

- 4.189

ELECTROLYSIS CELL (773OK )

+ 193.891 (% ELECTRICAL - 74.4)

C O (2.000)

I

puRIFIER I STORtGE (3310K) 1 ( 2 9 8 K ) -68.113 1

I 4

C O SiCl4(g)

Z n ( f ) ( 2.762 )

(1.000) * , REACTOR ( I ~ O O O K ) +69.356

Zn VAPORIZER (IISIOK) +84.573

A 4

s i o 2 ( g ) ( 1 . m ( 2 . m c ( s ) C l 2 ( g ) (2.000 i (2.762 Zn ( g

298'~) 2984<) 591°K) 1 1 8 1 " ~ )

Fig. 4-5. P r e l i m i n a r y flow d i a g r a m f o r the p repara t ion of Si f r o m the hydrogen reduct ion pyrolys is of SiIq m a d e by the iodinat ion of SiO / c a r b o n m i x t u r e

-. 2

t h e r m a l d e c o m p o s i t i o n of S i I ( g ) on t e m p e r a t u r e , p r e s s u r e , and c o m p o s i t i o n , 4 r e v e a l e d a l a r g e e f f e c t of p r e s s u r e , whi ,ch is a r e s u l t of t h e i n c r e a s e i n v o l u m e

c a u s e d by t h e f o r m a t i o n of m o n a t o m i c i od ine . A m o n g t h e o t h e r c o n d i t i o n s c o n - /

s i d e r e d w e r e : o p e r a t i o n a t a t o t a l p r e s s u r e of o n e a t m o s p h e r e , w h e r e t h e d a t a

i n d i c a t e i n e f f i c i e n t c o n v e r s i o n a t d i l u t i ons b e l o w 99 / I e x c e p t a t 1600 OK; b p e r a - '

t i o n a t a t o t a l p r e s s u r e of o n e a t m o s p h e r e u s i n g H2 a s a r e d u c t a n t , w h e r e t h e -

y i e l d d e c r e a s e s r a p i d l y a t Hz d i l u t i o n s b e l o w 1 9 / 1 ; t h e f o r m a t i o n of S i I l by t h e

i o d i n a t i o n of SiO - C m i x t u r e s , w h e r e thk y i e l d s a r e l ow be low 1 6 0 0 ° K ; and t h t 2 . .

. i o d i n a t i o n of S i , w h e r e t h e r e a c t i o n is e s s e n t i a l l y c o m p l e t e , a m i x t u r e

of Si14, Si12, SiH13, and S iH I in- t h e t e m p e r a t u r e r a n g e of 800 to 1800" K. T h e 2 2 e f f e c t s of t h e add i t i on of H2 and a d i l u e n t g a s w e r e c o n s i d e r e d i n s e v e r a l c a s e s .

. .

T h e r m a l D e c o m p o s i t i o n of Si14: P r e l i m i n a r y c a l c u l a t i o n s of t h e e n e r g y

and, mass b a l a n c e s w e r e m a d e f o r t h e p r e p a r a t i o n of Si t h r o u g h the t h e r m a l

d e c o m p o s i t i o n of S i I a s s h o w n in Fig., 4-6. When no h e a t r e c o v e r y i s p r o v i d e d 4' f o r , t h e e n e r g y r e q u i r e m e n t i s a b o u t 13. 3 k i l o w a t t - h o u r s p e r k i l o g r a m of S i ;

i f a l l ' t h e h e a t i s r d c o v e r e d , t h e v a l u e i s a b o u t 6 . 3 k i l o w a t t - h o u r s p e r k i l o g r a m

of S i .

T w o p r o c e d u r e s f o r t h e f o r m a t i o n of SiI w e r e e v a l u a t e d . The. i od ina t ion 4 of a SiO -C m i x t u r e h a s b e e n abandoned b e c a u s e of a h igh r e a c t i o n t e m p e r a t u r e '

2 . , (>1600%) and a p r e d i c t e d c o s t l y r e c y c l e and s e . p a r a t i o n p r o c e d u r e . ~ c c o r d i n ~ l y ,

' ..

t h e i o d i n a t i o n of m e t a l l u r g i c a l g r a d e Si, w h i c h h a s a c o n v e r s i o n e f f i c i e n c y of

abo.ut 10.0% 'will b e s t u d i e d . . .,

T h e o p e r a t i n g c 0 n d i t i 0 . n ~ - c o n s i d e r e d w e r e i ne r tLgas d i l u t i on and r e d u c e d

p r e s s u r e f o r t he t h e r m a l d e c o m p o s i t i o n r e a c t i o n and Hz r e d u c t i o n o n a hot w i r e ,

a h o t w a l l , and a f lu id i zed bed . T h e e x p e r i m e n t a l d a t a f o r the HZ r e d u c t i o n

r e a c t i o n i n d i c a t e t h a t t h e e f f i c i e n c i e s a r e r e l a t i v e l y high and t h a t a n y of t he .

depos i t i ' on m e t h o d s c o u l d b e u s e d .

. .

R e m a r k s : S e v e r a l p r o c e s s f a c t o r s r e m a i n t o b e d e t e r m i n e d b e f o r e a

c o m p a r i s o n c a n b e m a d e b e t w e e n t h e d e c o n l p o s i t i o n of S i I 4 and . t h e .. Z n r e d u c t i o n

. of S iC14. A m o n g t h e s e a r e t h e c o s t of t h e I r e c o v e r y ; t h e p r o c e d u r e f o r 2 . -

Fig. 4-6. Simplif ied e n e r g y and m a t e r i a l flow c h a r t f o r p r e p a r a t i o n of 1 m o l e of Si by t h e r m a l decompos i t ion of SiI 4

4-1 5

f

DISTILLATION UNlT (458/5n0u)

-39; 393

COOLER (577'~)

-10.789

S14 (9) b

I2 (a) (2.000) +

4

4si14 (9)

(1

l2 VAPORIZER (458 OK

t20.050

sil, ( a ) ( 1 . 7 9

7 (577 K)

S i 1 VAPORIZER (577'~) +19.998

IODINATION (1000'~) -44.846

I 4 12 (9)

(2. 4

S i ( I )

(1 .Ow st14 ( 9 ) (1.424)

v COOLER/ STORAGE

(298 OK) -27.122

4 I

S i (1 .om)

DEPOSITION UNlT (130O0K, 0.001 atm

58% CONVERSION) 90.250

L

A si(m) l 2 ( 9 ) (1.000) (2.000)

si14 ( 9 ) (0.724

v . - REACTOR

(2000 OK) +191.988

COOLER/COMPRESSOR '

(WOK) -29.260

- i

A A S i 0 2 (s) C ( 0

(2. ow (l.@W (298 OK) (298 %

handl ing the HI; the p e r f o r m a n c e of the f lu id ized bed; and the e c o n o m i c e n e r g y

and y ie ld f o r the S i I p r o c e s s . Although the S i c 1 p r o c e s s a p p e a r s t o be b e t t e r 4 4 a t t h i s s t a g e , the f ina l d e c i s i o n a s to which p r o c e s s wil l b e s e l e c t e d f o r a: pro-

c e s s i n g uni t wil l depend upon a n a n a l y s i s of the s e t s of d a t a now being obtained.

b. P r o d u c t i o n of SiH4 by Red i s t r ibu t ion of Ch lo r ina ted S i l a n e s - Union C a r b i d e

T h e ob jec t ive of th i s p r o g r a m i s to d e m o n s t r a t e the p r a c t i c a l i t y of p ro -

duc ing SiH4 a t a c o s t of $3 to $5 p e r k i l o g r a m us ing a s the b a s i c p r o c e s s the

r e d i s t r i b u t i o n of a m i x t u r e of c h l o r i n a t e d s i l a n e s to yield SiH T h e r e d i s t r i - 4 '

but ion i s a c c o m p l i s h e d by us ing a t e r t i a r y a m i n e ion exchange r e s i n ( R o h m and

~ a ' a s A m b e r l y s t A-21) f o r the ca ta ly t i c d i sp ropor t iona t ion . T h i s is followed

by t h e pur i f i ca t ion of SiH4 by f r a c t i o n a l d is t i l la t ion , the c h l o r i n a t e d s i l a n e s

be ing r e c y c l e d and r e p r o c e s s e d . . A second m a j o r e f fo r t is d i r e c t e d toward

ach iev ing d i r e c t s y n t h e s i s of S iH2Cl to provide a n e n r i c h e d feed f o r the r e d i s - 2

t r i b u t i o n p r o c e s s s t e p . T o d e t e r m i n e t echn ica l feas ib i l i ty , the e f f e c t s of t e m -

p e r a t u r e , p r e s s u r e , and feed c o m p o s i t i o n on r a t e , yield, se l ec t iv i ty , and pur i ty

wi l l b e inves t iga ted . T h e s e r e s u l t s wil l be i n c o r p o r a t e d in to the ca lcu la t ions of

m a s s and e n e r g y b a l a n c e s , the model ing of the ful l p r o c e s s , and economic and

e n e r g y - u s e a n a l y s e s . The f i r s t d e m o n s t r a t i o n of the p r o c e s s wi l l be conducted

u s i n g a mini -p lant , c o n s i s t i n g of one r e d i s t r i b u t i o n r e a c t o r and one d i s t i l l a t ion

c o l u m n , to p roduce SiH a t the r a t e of 10 pounds p e r day f o r 10 d a y s . The f inal 4

d e m o n s t r a t i o n wi l l u t i l i ze a m a x i - p l a n t of two r e d i s t r i b u t i o n r e a c t o r s and t h r e e

d i s t i l l a t i o n c o l u m n s wi th the s a m e product ion goal . A s c h e m a t i c of the max i -

p lan t i s shown in Fig. 4-7. \

L a b o r a t o r y inves t iga t ions a r e u n d e r way f o r s tud ies of the r e d i s t r i b u t i o n

of S ~ H C ~ and S iH2Cl to SiH4, f o r the r e a c t i o n of C u l S i wi th HC 1 and H2 using 2

a f lu id ized bed r e a c t o r to produce a SiH2C1 - e n r i c h e d m i x t u r e , and f o r the 2

r e a c t i o n of Si wi th H2 and SiC14 to g e n e r a t e SiHC13 us ing a f lu id ized bed. In

the f i r s t of th is s e r i e s of s t u d i e s i t h a s been shown that the yield on one p a s s

w a s 13. 5 m o l e p e r c e n t f r o m a SiH C1 feed a t 1 a t m o s p h e r e and 60" C, a r e s u l t 2 2

w h i c h e s s e n t i a l l y c o r r o b o r a t e d e a r l y Union C a r b i d e data . The recyc l ing of

u n r e a c t e d SiH C1 and by-produc t SiHC1 led to a s t o i c h i o m e t r y of the o v e r a l l 2 2 3

STILL 1 . R E A C T O R 1 STILL '2 R E A C T O R 2 STILL 3 ABSORBER

F i g . 1 -7 . S c h e m a t i c for m a x i - p l a n t

d i s p r o p o r t i o n a t i o n w h i c h ' c a n b e - w r i t t e n as : 3SiH2C 1 - 2 SiHC13 + SiH4;

Bas 'ed on t h e s e d a t a , t h e SiH4 p roduc t ion r a t e w a s 0 . 2 7 pounds p e r h o u r p e r

' pound of A-21 r e s i n w i t h a f e e d of 4 . 2 pounds of S iH2C12 p e r h b u r . I t i s a n t i -

c i p a t e d t h a t t h i s v a l u e , w h i c h i s abou t 60% of the c a l c u l a t e d r a t e , c a n be

i n c r e a s e d w i t h i m p r o v e d c o m p o n e n t s e p a r a t i o n s . ,

T h e d e s i g n a n d p lanning f o r the m i n i - p l a n t have p r o c e e d e d o n s c h e d u l e .

In s u p p o r t o f the f r a c t i o n a t i o n s tudy , a c o m p i l a f i o n of i n f o r m a t i o n on the phys i ca l

p r o p e r t i e s of the c h l o r i n a t e d s i l a n e s and S iH h a s b e e n m a d e . T h e d a t a f o r h e a t 4 -

c a p a c i t i e s h a v e b e e n c o m p i l e d i n t o e q u a t i o n s by a l e a s t - s q u a r e s t r e a t m e n t . T h e -,

s i t e i s b e i n g p r e p a r e d and t h e p r o c u r e m e n t s of m a j o r e q u i p m e n t have b e e n m a d e .

T h e p l an t i s s c h e d u l e d t o b e i n o p e r a t i o n i n mid -1976 . .

c. S e m i c o n d u c t o r - G r a d e Si P i -oduc t ion by S i F q - ' S i F T r a n s p o r t - ~ M o t o r o l a C o r p o r a t i o n

2

A c o n t r a c t h a s b e e n n e g o t i a t e d f o r t he d e v e l o p m e n t of t h e p r o c e s s t o

p r o d u c e S i b ~ . the r e a c t i o n of S i F 4 with m e t a l l u r g i c a l - g r a d e S i t o f o r m S i F 2 a s

t h e t r a n s p o r t s p e c i e s a n d t h e n t o d e p o s i t s e m i c o n d u c t o r - g r a d e S i f r o m a S i F 2 p o l y m e r , S i F c o n c u r r e n t l y r e g e n e r a t i n g S i F T h e f i r s t p h a s e of w o r k u n d e r 2 3' - t h i s c o n t r a c t \\.ill b e d i re ' c ted t o w a r d t h e e s t a b l i s h m e n t of c h e m i c a l f e a s i b i l i t y ,

u s i n g t h e c r i t e r i a of y i e l d , r a t e , a n d p u r i t y . In th; s e c o n d p h a s e c h e m i c a l

e n g i n e e r i n g c a l c u l a t i o n s wi l l b e e m p l o y e d t o p r o v i d e e v i d e n c e f o r p r a c t i c a l i t y ,

e n e r g y - u s e , a n d e c o n o m i c a n a l y s e s .

- 2b S p e c i f i c a t i o n s f o r s o l a r - c e l l - ~ r a d e S i

T h e o b j e c t i v e of P a r t I1 of P h a s e I ( s e e T a b l e 4-1) i s to d e t e r m i n e the

e f f e c t s of i m p u r i t i e s in s i n g l e c r y s t a l S i o n t h e p r o p e r t i e s of t h e m a t e r i a l a n d on

t h e c h a r a c t e r i s t i c s of s o l a r c e l l s . T h i s e f f o r t w i l l invol\:e i n v e s t i g a t i o n of t h e

i n t e r p l a y of i m p u r i t i e s a n d t h e p r o c e s s e s f o r p r e p a r i n g s i n g l e c r y s t a l S i a n d f o r

f a b r i c a t i n g c k l l s . ( A c o n c u r r e n t e f f o r t i n P a r t s I and I11 w i l l b e d i r e c t e d t o

s t u d i e s of t h e i m p a c t of s p e c i f i c i m p u r i t i e s o n c h e m i c a l r e a c t i o n s , pu r i f i ca t ion

r e q u i r e m e n t s , p r o d u c t i o n e n g i n e e r i n g , e n e r g y u s e , a n d p r i c e . ) A s e r i e s of

t r a d e - o f f s w i l l be r e q u i r e d t o e s t a b l i s h t h e o v e r a l l o p t i m i z a t i o n of t h e t e c h n i c a l

and e c o n o m i c f a c t o r s . A p r e l i m i n a r y d e s c r i p t i o n of t he i n f l u e n c e of p a r t i c u l a r

i m p u r i t i e s o n m a t e r i a l and c e l l c h a r a c t e r i s t i c s i s s c h e d u l e d f o r e a r l y 1977 .

W e s t i n g h o u s e E l e c t r i c and M o n s a n t o R e s e a r c h a r e c o n d u c t i n g p r o g r a m s

to d e v e l o p t h i s i n f o r m a t i o n . T h e s e p r o g r a m s a re n e a r l y p a r a l l e l i n many-

r e s p e c t s . T h u s , i n e a c h p r o g r a m doub ly and m u l t i p l y doped s i n g l e c r y s t a l s , a re

b e i n g g r o w n t h a t c o n t a i n o n e o r m o r e s p e c i f i c i m p u r i t i e s i n a d d i t i o n t o t he b a s e

dopan t . T h e i m p u r i t y m a t r i c e s c o n t a i n t h e e l e m e n t s C r , Mn, Ni, F e , T i , V,

Mg, Zn, and Z r . T h e s e c r y s t a l s a r e t o b e c h a r a c t e r i z e d i n a s e r i e s of c h e m i c a l ,

m e t a l l u r g i c a l and e l e c t r i c a l m e a s u r e m e n t s ; s o l a r c e l l s a r e t o be f a b r i c a t e d and

e v a l u a t e d ; c o r r e l a t i o n s a re t o be o b t a i n e d b e t w e e n t h e i m p u r i t i e s and i m p u r i t y

c o n c e n t r a t i o n s v i s - a - v i s t he c r y s t a l m a t e r i a l and s o l a r c e l l p r o p e r t i e s ; and

i m p u r i t y t h r e s h o l d l e v e l s a r e to b e e s t a b l i s h e d . T h e p r o g r a m s d i f f e r i n t he

fo l lowing r e s p e c t s : W e s t i n g h o u s e w i l l s t u d y t h e e f f e c t s of r e l a t i v e l y r a p i d c r y s t a l

g r o w t h u s i n g the d e n d r i t i c - w e b t e c h n i q u e alid C u i s i n c l u d e d i n i t s m a t r i x .

M o n s a n t o w i l l u t i l i z e t he f l o a t - z o n e t e c h n i q u e to c o n t r a s t w i t h t h e C z o c h r a l s k i -

g r o w n c r y s t a l s i n o r d e r t o i n v e s t i g a t e t he c o n s e q u e n c e s of 0 and C c o n c e n t r a -

t i o n s ; w i l l e x a m i n e t h e e f f e c t i v e n e s s of a s a w e d s u r f a c e f o r g e t t e r i n g ; and wi l l

i n c l u d e A1 i n t h e i m p u r i t y m a t r i x .

T h e a n a l y s e s t o be p e r f o r m e d on t h e Si i ngo t i n c l u d e d e t e r m i n a t i o n s of

i m p u r i t y c o n c e n t r a t i o n s , l ong i tud ina l r e s i s t i v i t y , r a d i a l r e s i s t i v i t y , d i s l o c a t i o n

d e n s i t y , and C and 0 c o n c e n t r a t i o n s . The w a f e r s c u t f r o m the i n g o t s a r e t o

be e v a l u a t e d b e f o r e and a f t e r p r o c e s s i n g . T h e e v a l u a t i o n s m a d e b e f o r e p r o -

c e s s i n g c o n s i s t of s p r e a d i n g r e s i s t a n c e f o r c o m p o s i t i o n h o m o g e n i t y ; o p t i c a l

m i c r o s c o p y , X - r a y topography , and s c a n n i n g e l e c t r o n m i c r o s c o p y f o r m i c r o -

s t r u c t u r e a n a l y s i s ; and pho toconduc t ive d e c a y l i f e t i m e m e a s u r e m e n t s . A f t e r

c e l l f a b r i c a t i o n , the p e r f o r m a n c e c h a r a c t e r i s t i c s of the c e l l a r e t o be d e t e r m i n e d

by m e a s u r e m e n t s of l i f e t i m e , o p e n c i r c u i t vo l t age , s h o r t c i r c u i t c u r r e n t , f i l l

f a c t o r , s p e c t r a l r e s p o n s e , and e f f i c i e n c y .

a. I n v t r s t i g a t i o n of E f f e c t s of I l l>p! l r i t ies o n S o l a r C e l l P e r f o r m a n c e - M'es t - ing l~o l~sc , Ez lec t r i c C o r p o r a t i o n

W e s t i n g h o u s e E l e c t r i c h a s c o m p l c t e d p r e p a r a t i o n of t h e f i r s t g e n e r a t i o n

i n g o t s u s i n g t h e e l e m e n t s i n t h e i m p u r i t y t n a t r i x w i t h t h e e x c e p t i o n of M g . T h e 3 3 d o p i n g l e v e l w a s 1 0 1 5 a t o m s / c m , e x c e p t f o r N i w h i c h w a s 1 0 1 4 a t o m s l c m .

A d i f f i c u l t y w h i c h o c c u r r e d i n f i r s t a t t ' empt t o d o p e w i t h Ni w a s s u b s e q u e n t l y

o v e r c o m e b y t h e u s e of a Ni w i r e as t h e d o p i n g n ~ a t e r i a l i n p l a c e of Ni p o w d e r .

T h e e \ r a l u a t i o n s of s o l a r c e l l s f r o m w a f e r s c o n t a i n i n g C r , M n , C u , a n d Ni 3 ( 1 0 1 4 a t o m s / c m ) ha \ -e b e e n c o m p l e t e d . T h e \ - a l u e s of c o n r . r e r s i o n e f f i c i e n c y

o b t a i n e d t h t ~ s f a r a r e : 9 . 791 w i t h o u t i m p u r i t y d o p i n g ; 6 . 6 t o 9. 570 f o r M n - d o p e d ;

8. 5 t o 9. 5O;;, f o r N i - d o p e d ; a n d 9. 0 t o 9 . 8";) f o r C u - d o p e d . In a d d i t i o n , w a f e r s

f1-otn b a s e l i n e Si a n d C r - , M n - , N i - , a n d C u - d o p e d i n g o t s w e r e d e l i v e r e d t o JPL

f o r e v a l ' u a t i o n s .

In t h e n e x t p h a s e W e s t i n g h o u s e w i l l p r e p a r e s e c o n d - g e n e r a t i o n i n g o t s

w i t h i m p u r i t y c o n c e n t r a t i o n s s e t a t 2 x l o L 4 a t o m s / c m 3 . T h e m a t e r i a l a n d

s o l a r c e l l e v a l u a t i o n s o n t h e w a f e r s f r o m t h e ' f i r s t - a n d s e c o n d - g e n e r a t i o n i n g o t s

w i l l p r o c e e d .

b. I n v e s t i g a t i o n of E f f e c t s of I m p u r i t i e s o n S o l a r C e l l P e r f o r m a n c e - h ' l o n s a n t o R e s e a r c h C o r p o r a t i o n

M o n s a n t o h a s c o m p l e t e d p r e p a r a t i o n of c r y s t a l s b y f l o a t - z o n e t e c h n i q u e s 3 3

i n c o r p o r a t i n g C, F e a t o m s / c r n ) Ni (10" a t o m s / c m , V ( 5 x 1 0 1 5

3 3 a t o m s l c m ), A1 (10" a t o m s / c m ) a n d i r ( n o t y e t d e t e r m i n e d ) , a n d h a s s h i p p e d

s l i c e s t o JPL f o r c o r r o b o r a t i n g e v a l u a t i o n s . S o l a r c e l l s h a v e b e e n p r e p a r e d a n d

c h a r a c t e r i z e d ; t h e e f f i c i e n c y m e a s u r e d f o r t h o s e p r e p a r e d f r o m b a s e l i n e m a t e r i a l

w a s a b o u t 8%.

I n t h e n e x t p h a s e M o n s a n t o w i l l c o m p l e t e t h e s c h e d u l e d p r e p a r a t i o n s of

c r y s t a l s a n d w i l l p r o c e e d w i t h t h e m a t e r i a l a n d s o l a r c e l l c h a r a c t e r i z a t i o n s .

, 3. P r o c e s s e s f o r P r o d u c i n g S o l a r - C e l l - G r a d e S i

T h e a p p r o a c h u s e d f o r P a r t 111 of P h a s e I ( s e e T a b l e 4 - 1 ) i n c o r p o r a t e s

t h e o r e t i c a l s t u d i e s i n v o l v i n g t h e r m o d y n a l n i c s , r e a c t i o n c h e m i s t r y , , a n d c h e m i c a l

e n g i n e e r i n g ; c h e m i c a l r e a c t i o n i n v e s t i g a t i o n s c o n s i s t i n g of t h e e x p e r i m e n t a l

d e t e r m i n a t i o n s of r e a c t i o n k i i l e t i c s , . y i e l d s , and s u i t a b l e p r o c e s s c o n d i t i o n s ; a -'

c h e m i c a l e n g i n e e r i n g e f f o r t f o r s e c u r i n g a n e x p e r i m e n t a l d a t a b a s e f o r p r e l i m -

i n a r y p r o c e s s mode l ing ; . and e n e r g y - u s e and e c o n o m i c c a l c u l a t i o n s f o r p r e l i m -

i n a r y p r o c e s s m o d e l s . In e a c h c a s e t he c o n t r a c t r e q u i r e s a d e m o n s t r a t i o n of

t e c h n i c a l f e a s i b i l i t y and a p r o j e c t i o n of c o m m e r c i a l p r a c t i c a l i t y , i nvo lv ing the

p r e l i m i n a r y a n a l y s i s of the s u i t a b i l i t y f o r a s c a l e - u p s t u d y . T h e e v a l u a t i o n of

e a c h p r o c e s s as a c a n d i d a t e f o r t h e s c a l e - u p s t u d i e s ( P h a s e 11 of T a s k 1) is

s c h e d u l e d f o r e a r l y 1977.

a. S o l a r - C e l l - G r a d e S i P r o d u c t i o n by S u b m e r g e d - A r c - F u r n a c e a n d V a c u u m - E v a p o r a t i o n P r o c e s s e s - Dow C o r n i n g C o r p o r a t i o n

A c o n t r a c t w i l l be nego t i a t ed w i t h Dow C o r n i n g f o r i n v e s t i g a t i o n s of the

s u b m e r g e d - a r c - f u r n a c e and v a c u u m - e v a p o r a t i o n p r o c e s s e s f o r p roduc ing s o l a r -

c e l l - g r a d e Si . T h e s u i t a b i l i t y of u s i n g p u r e r r a w m a t e r i a l s w i l l be e x p l o r e d

u s i n g a d e v e l o p m e n t - s i z e a r c f u r n a c e . T h e a p p l i c a t i o n of t he v a c u u m - e v a p o r a t i o n

t e c h n i q u e w i l l b e e x a m i n e d u s i n g the p r o d u c t s of the s u b m e r g e d - a r c - f u r n a c e

o p e r a t i o n a s t he r e a c t a n t s . T h e f i n a l p h a s e w i l l i n c l u d e e n e r g y - u s e , p r o d u c t

c h a r a c t e r i s t i c s , and c o s t a n a l y s e s f o r t h e s e p r o c e s s e s .

b. S o l a r - C e l l - G r a d e S i P r o d u c t i o n b y D u p l e x V a p o r - E l e c t r o - C h e m i c a l C o n v e r s i o n o f S i F - S t a n f o r d R e s e a r c h I n s t i t u t e , Inc.

4

A c o n t r a c t w i l l be nego t i a t ed w i t h S t an fo rd R e s e a r c h I n s t i t u t e f o r t he

i n v e s t i g a t i o n of a d u p l e x v a p o r - e l e c t r o c h e m i c a l s y s t e m f o r t he u s e of a n a l k a l i

m e t a l t o r e d u c e S i F to s o l a r - c e l l - g r a d e Si. T h e d e p e n d e n c e of t he y ie ld and 4 p u r i t y of t he p r o d u c t on r a t e s of r e a c t i o n s , m a s s t r a n s f e r , e n e r g y u s e , t e m -

p e r a t u r e , p r e s s u r e , f low r a t e s , and r e a c t o r c o n f i g u r a t i o n w i l l b e d e t e r m i n e d .

C h e m i c a l - e n g i n e e r i n g , e c o n o m i c , a n d . e n e r g y - u s e s t u d i e s w i l l fo l low t h e p h a s e

t o e s t a b l i s h t e c h n i c a l f ea s ib i l i t y .

c. S o l a r - C e l l - G r a d e S i P r o d u c t i o n b y C R e d u c t i o n of S iO2 in a n Induc t ion P l a s m a T o r c h - T e x a s I n s t r u m e n t s C o r p o r a t i o n

T h i s c o n t r a c t wi th T e x a s I n s t r u m e n t s i s f o r t h e e s t a b l i s h m e n t of t h e

f e a s i b i l i t y of u s i n g a n i nduc t ion p l a s m a t o r c h t o p r o d u c e s o l a r - c e l l - g r a d e Si

f r o m a reaction in which SiO is reduced by C . The influence of 'C fo rms , 2 gaseous environment, intimacy of mixing, ra te of tempera ture r i se , coo'ling, '

stoichiometry, thermodynamics, and kinetics on the yield and purity of the

p ~ o d u c t will be investigated. A phase for chemical engineering s tudies i s to

follow the initial chemis t ry phase provided suitable reaction cha rac te r i s i t c s

have been obtained. A final phase will be f o r energy and economic analyses .

4. Evaluation of Si Production P r o c e s s e s - L a m a r University \

- Under P a r t IV o'f ask I ( see Table + - I ) , L a m a r University is to pe r fo rm

investigations and analyses of the silicon- production processes being developed , .

under Task 1 . The objective of the program i s to evaluate the rela-tive com-

m e r c i a l -potentials of t h e s e processes . The economic evaluations a r e to be J , based upon analyses of p r o c e s s - sys tem propert ies , chemical engineering

ana lyses , and costing-economics. .. .

The plan to be used' for these eval'uatio.ns involves the ~ t i l ' i za t ion of the '

r e su l t s of the three analysis-sect ions f o r technical and economic comparisons

of the alte'rnative p i o c e i d e s . The.planning sequence then leads f rom these'

compar isons to the p rocess selections and then to the phases of the task pro-

g r a m fo r scale-up, for experimental plants, and fo r the commerc ia l plant. At

e a c h s tage, these analyses and evaluations a r e to continue, utilizing the new

information which'-becomes available f rom the various .process -development' .- .

cont rac ts .

The analyse's of the process- 'system proper t ies - which a r e to be performed

.will l ead to physical and chemical descriptions of the processes . Data a r e being

cbllected f rom the , l i t e ra tu re , independent sources , and f rom labora to ry measure -

rnktits -on , vap6r . p r e s s u r e , l a k i t heat of vap'orization,. heat capacity, - density,

viscosi ty , thermal conductivity, enthalpy.of formation, and ~ i b b ; f r e e energy . . .

.of formation. T h e subsequent analyses of engineering design,. construction,

sta.rt-up, operation, a i d process optimization will make use of this information . .

base. . -

\

T h e c h e m i c a l e n g i n e e r i n g a n a l y s e s t o b e c o n d u c t e d w i l l be u s e d to

c a l c u l a t e t he k i n e t i c and p r a c t i c a l y i e ld p r o p e r t i e s of t he p r o c e s s . T h e s e

a n a l y s e s w i l l i n c l u d e p r e l i m i n a r y p r o c e s s f low d i a g r a m s , d e s c r i p t i o n s of the

r e a c t i o n s , k i n e t i c r a t e d a t a , m a j o r e q u i p m e n t a c t i v i t i e s , c h e m i c a l e q u i l i b r i u t n

c o n s i d e r a t i o n s , m a s s t r a n s p o r t , h e a t t r a n s f e r , c o n c e n t r a t i o n e f f e c t s , t e m -

p e r a t u r e e f f e c t s , a n d r e a c t o r c o n f i g u r a t i o n s . I n v e s t i g a t i o n s l e a d i n g t o t h e

c o n d i t i o n s f o r o p t i m i z i n g t h e c o m m e r c i a l p r o d u c t i o n p r o p e r t i e s of p r o c e s s e s wi l l

be b a s e d on the m o d e l s bu i l t frot.11 t h e s e c h e m i c a l e n g i n e e r i n g d a t a .

In p e r f o r m i n g the e c o n o m i c a n a l y s e s , the i t e m s to b e c o n s i d e r e d w i l l i n -

c l u d e p r o c e s s f low d i a g r a m s , c a p i t a l i n v e s t m e n t e s t i m a t e s , m a n u f a c t u r i n g

. c o s t s , r a w m a t e r i a l c o s t s , m a t e r i a l b a l a n c e s , e n e r g y b a l a n c e s , c o n s t r u c t i o n

and m a i n t e n a n c e , and s ta f f ing . T h e e c o n o m i c m o d e l s w i l l b e o p t i m i z e d , f o r l ow

p r i c e and low e n e r g y u s e a s w e l l as h igh p roduc t ion .

T h e p r e l i m i n a r y d a t a c o l l e c t i o n f r o m d o m e s t i c s o u r c e s f o r the p r o c e s s -

s y s t e m p r o p e r t i e s a n a l y s e s i s n e a r i n g c o m p l e t i o n f o r t he Si s o u r c e m a t e r i a l s

a s s o c i a t e d w i t h t h e SiH4, SiC14, and S i I p r o c e s s e s . R e q u e s t s f o r i n f o r m a t i o n 4 f r o m f o r e i g n s o u r c e s h a v e b e e n i s s u e d . An add i t i ona l e f f o r t d e a l i n g w i t h t h e

S i F t r a n s p o r t p r o c e s s h a s b e e n i n i t i a t e d . 4

A s p a r t of t he c h e m i c a l - e n g i n e e r i n g - a n a l y s i s e f fo r t , a n e x t e n s i v e i n f o r -

m a t i o n e x c h a n g e w i t h t h e T a s k 1 c o n t r a c t o r s i s u n d e r w a y ; t h i s w a s s t a r t e d a t

t h e r e c e n t P r o j e c t I n t e g r a t i o n Mee t ing . T h e fo l lowing s e t of b a s e l i n e c o n d i t i o n s

w a s e s t a b l i s h e d f o r u s e i n t he a n a l y s i s of 'a c o m m e r c i a l p lan t t o p r o d u c e s o l a r

c e l l g r a d e Si: ( 1 ) p lan t s i z e - 1000 m e t r i c t o n s p e r y e a r ; ( 2 ) c o s t i n d e x - c a p i t a l

e q u i p m e n t c o s t is t o be b a s e d on the J a n u a r y 1975 c o s t - i n d e x va lue , 430 ; (3 )

o p e r a t i n g r a t i o - t he o p e r a t i n g r a t i o shou ld be s e l e c t e d b a s e d o n the a s s u m e d

o p e r a t i n g d a y s p e r y e a r .

In t he e c o n o m i c a n a l y s i s e f f o r t , a c o n s i d e r a b l e a m o u n t of d a t a f o r u s e i n

c a p i t a l c o s t e s t i m a t i o n w a s ob t a ined . An e x t e n s i v e l i s t of e q u i p m e n t u s a b l e

i n t h e p r o c e s s e s to b e a n a l y z e d h a s b e e n a s s e m b l e d . T h e a s s i g n m e n t s of t he

e q u i p m e n t t o t h e v a r i o u s p r o c e s s e s and t h e c a l c u l a t i o n s f o r p r e l i m i n a r y . m o d e l s

of t h e p r o c e s s e s a r e cont inu ing .

The next period wi l l include e f fo r t s to comple te the compila t ion of da t a

s o u r c e s on Si s o u r c e m a t e r i a l s ; to perfor111 additional da t a ana lyses f o r physical ,

t h e r n i o d y n a n ~ i c , and t r a n s p o r t p rope r t i e s ; to proceed \vith da t a assen ib ly and

p r e l i m i n a r y de sc r i p t i ons of the va r ious p r o c e s s e s ; and to review methods fo r

e s t i n ~ a t i n p plant fixed capita! i nves tmen t based on ma jo r p roce s s e q ~ ~ i p t n e n t

c ap i t a l c o s t s .

5. JPI, Tasli 1 In-House Suppor t

S u b p r o g r a n ~ s which a r e c o n ~ p l e m e n t a r y and suppor t ing to the contractcial

e f fo r t s will be under way a t J P L t h r o ~ ~ g h o u t the Task 1 p r o g r a m . These sub-

progratms include t ~ ~ e a s u r e m e n t s and evaluat ions of ( a ) m a t e r i a l s and c e l l s

a s soc i a t ed with the con t r ac t s of P a r t I1 and ( b ) c h e n ~ i c a l in te rn ied ia tes and

p roduc t s f r o m the react ion-s under d e v e l o p n ~ e n t in the con t r ac t s of P a r t s I and

111. In addit ion s t ud i e s of the fluidized bed p roce s s will be conducted in coope ra -

t ion mlith the deve lopment con t r ac t s of P a r t s I and 111, which i nco rpo ra t e th i s

p r o c e s s technique.

The m e a s u r e m e n t of the p r o p e r t i e s of Si m a t e r i a l s and ce l l s p rov ides an

independent s e t of da t a t o be u s e d to c o r r o b o r a t e the co r r e l a t i ons obtained by

t he c o n t r a c t o r s . T h r e e categ0rie.s of m e a s u r e m e n t s will be used: chemica l ,

m e t a l l u r g i c a l , and e l ec t r i c a l .

Chemica l ~ ~ ~ e a s u r e m e n t s will be f o r the purpose of de t e rmin ing the chemica l

compos i t ion of reac t ion p roduc t s in the p r o c e s s developments and of ingots and

s l i c e s in the s o l a r c e l l g r a d e definition effor t . The sens i t iv i ty needed i s in the

ppba to pplna range. Th i s sens i t iv i ty can be obtained f o r d i f fe ren t groups of

e l e m e n t s us ing s p a r k s o u r c e m a s s spec t ro scopy , a t omic absorp t ion spec t roscopy ,

and neu t ron act ivat ion ana ly s i s .

A4etallurgical ana ly se s =.ill be p e r f o r m e d fo r the purpose of co r r e l a t i ng . ..

the s t r u c t u r a l p r o p e r t i e s of s l i c e s and ce l l s with the chemica l consti tut ion of

the m a t e r i a l and \ ~ . i t h the e l e c t r i c a l p e r f o r m a n c e c h a r a c t e r i s t i c s of s o l a r c e l l s .

These analyses requi re the use of optical microscopy (dislocation density and

s t ruc tu re ) , t ransmiss ion electron microscopy (c lus t e r s , vacancies, and p re -

cipitates), scanning electron microscopy (topographic defects), Laue ,X-ray

diffraction ( c rys t a l orientation), and X-ray topography ( s t ruc tu re defects).

E lec t r ica l measurements will be made fo r the purpose of cor re la t ing the. . e lec t r ica l pa ramete r s important to so la r cel l performance with chemical con-

sitution and s t ruc tura l propert ies .

Studies of fluidized bed technology form the second m a j o r in-house sub-

program, s ince a fluidized bed r eac to r i s a p r i m a r y element in the S i deposition

s t ep of the process developments by Battelle and Union Carbide. The common

bas is for this emphasis i s the recognition of the inherent advantages of a fluid-'

ized bed reac tor for some p rocesses when compared with the commerc ia l CVD

p rocess for the deposition of S i . These advantages include ve ry sma l l heat

l o s ses , tempera ture uniformity, the capability of l a r g e production ra tes because

of the l a rge sur face a r e a and high gas flow ra t e s which can be used, and the

1 I suitability fo r continuous operation. The J P L in-house program in this field

will be designed to support and be complementary to the contractual efforts.

Some of the aspects to be investigated at J P L will be as follows: (1)

theoretical t h e r ~ o d y n a m i c a n d kinetic studies of fluidized bed SiH deposition 4

react ions; ( 2 ) models for fluidized bed operation, especially for smal l particle

s i ze seeds ; ( 3 ) t empera ture profile measurements ; (4) character izat ion of par-

t icles as a function of t ime and operating conditions; (5) studies of f!uidization

conditions not covered by the cont rac ts ; and ( 6 ) determinations of chemical

engineering data, which can be used for m a s s and heat balances, ' react ion

kinetics, Si deposition modeling, and engineering cos t es t imates . The . resul ts

of these investigations will be evaluated concurrently with the progress under

the contracts and should provide the information bask for more complete develop-

ment efforts in this field. .

The in-house subprograms a r e under way. P re1 imina r~ ' f lu id ized bed

'studies a r e being accomplished in the a r e a s of basic feasibil i ty analyses;

fluidized bed models; bench sca le experiments; and theoret ical studies of

reaction kinetics, chemical analyses , m a s s and heat t r ans fe r , and fluid

mechanics. - 4-25

\

T h e i n - h o u s e m e a s u r e m e n t s i nc lude t h e d e t e r m i n a t i o n s of m i n o r i t y

c a r r i e r l i f e t i m e s i n c e l l b l a n k s a n d in p r o c e s s e d s o l a r c e l l s , of r e s i s t i v i t y

p r o f i l e s , a n d of s o l a r c e l l p e r f o r m a n c e c h a r a c t e r i s t i c s , e. g . , I , e f f i c i e n c y , S C

a n d s p e c t r a l r e s p o n s e .

TASK 2. L A R G E - A R E A SILICON S H E E T S

T h e o b j e c t i v e of t he L a r g e - A r e a S i l i con S h e e t (LASS) T a s k i s to d e v e l o p

a n d d e m o n s t r a t e t h e f e a s i b i 1 i . t ~ of s eve ' r a l a l t e r n a t i v e p r o c e s s e s f o r p roduc ing

l a r g e a r e a s of s i l i c o n s h e e t m a t e r i a l s u i t a b l e f o r l o w - c o s t , h igh e f f i c i ency s o l a r

pho tovo l t a i c e n e r g y c o n v e r s i o n . T o m e e t t he o b j e c t i v e of the LSSA P r o j e c t ,

s u f f i c i e n t r e s e a r c h and d e v e l o p m e n t m u s t be p e r f o r m e d on a n u m b e r of p ro -

c e s s e s t o d e t e r m i n e the c a p a b i l i t y of e a c h f o r p roduc ing l a r g e a r e a s of c r y s t a l -

l i z e d s i l i c o n . T h e f i n a l s h e e t - g r o w t h c o n f i g u r a t i o n s m u s t be s u i t a b l e f o r d i r e c t

i n c o r p o r a t i o n i n t o a n a u t o m a t e d s o l a r - a r r a y p r o c e s s i n g s c h e m e .

A. T E C H N I C A L BACKGROUND

C u r r e n t s o l a r c e l l t e chno logy i s b a s e d o n the u s e of s i l i c o n w a f e r s ob ta ined

b y s l i c i n g l a r g e C z o c h r a l s k i o r f l o a t - z o n e ingo t s ( u p to 12 . 5 c e n t i m e t e r s i n

d i a m e t e r ) , u s ing s i n g l e - b l a d e i n n e r - d i a m e t e r ( ID) d i a m o n d s a w s . T h i s me thod

of o b t a i n i n g s i n g l e c r y s t a l l i n e s i l i c o n w a f e r s i s t a i l o r e d to the n e e d s of l a r g e

v o l u m e s e m i c o n d u c t o r p r o d u c t s ( i . e . , , i n t e g r a t e d c i r c u i t s plus d i s c r e t e power

a n d c o n t r o l d e v i c e s o t h e r t han s o l a r c e l l s ) . Indeed , t he s m a l l m a r k e t o f f e r e d

b y p r e s e n t s o l a r c e l l u s e r s d o e s not jus t i fy the d e v e l o p m e n t of s i l i c o n " r e a l

e s t a t e " p r o d u c t i o n t e c h n i q u e s wh ich would r e s u l t i n l o w - c o s t e l e c t r i c a l e n e r g y .

G r o w t h of s i l i c o n c r y s t a l l i n e m a t e r i a l i n a g e o m e t r y wh ich d o e s not r e q u i r e

c u t t i n g t o a c h i e v e p r o p e r t h i c k n e s s i s a n obv ious w a y t o e l i m i n a t e c o s t l y p r o -

c e s s i n g and m a t e r i a l w a s t e . G r o w t h t e c h n i q u e s s u c h a s edge -de f ined f i l m - f e d

g r o w t h ( E F G ) , w e b - d e n d r i t i c g rowth , c h e m i c a l v a p o r d e p o s i t i o n (CVD), e t c . ,

a r e p o s s i b l e c a n d i d a t e s f o r t h e g r o w i n g of s o l a r c e l l m a t e r i a l . T h e g r o w i n g of

l a r g e i n g o t s wi th o p t i m u m s h a p e s f o r s o l a r c e l l n e e d s ( e . g . , hexagona l c r o s s -

s e c t i o n s ) , r e q u i r i n g v e r y l i t t l e m a n p o w e r and m a c h i n e r y would a l s o a p p e a r

p laus ib l e . H o w e v e r , i t a p p e a r s t h a t the cu t t i ng of the l a r g e i n g o t s i n t o w a f e r s

m u s t b e done us ing m u l t i p l e r a t h e r t han s i n g l e b l a d e s i n o r d e r to be c o s t - '

e f f ec t ive .

B. ORGANIZATION O F T H E TASK 2 E F F O R T

At the t i m e 'the LSSA P r o j e c t w a s i n i t i a t e d , i n J a n u a r y 1975, a n u m b e r of

m e t h o d s poten t ia l ly s u i t a b l e f o r g r o w i n g s i l i c o n c r y s t a l s f o r s o l a r c e l l m a n u f a c -

t u r e w e r e known. S o m e of t h e s e w e r e u n d e r d e v e l o p m e n t ; o t h e r s e x i s t e d only

i n concep t . D e v e l o p m e n t w o r k o n the m o s t p r o m i s i n g m e t h o d s i s now be ing -. funded . A f t e r a pe r iod of a c c e l e r a t e d d e v e l o p m e n t , t he v a r i o u s m e t h o d s wil l

b e e v a l u a t e d and the b e s t s e l e c t e d f o r a d v a n c e d d e v e l o p m e n t . A s the g r o w t h

m e t h o d s a r e r e f ined , m a n u f a c t u r i n g p lan ts w i l l be d e v e l o p e d f r o m which the

m o s t c o s t - e f f e c t i v e s o l a r c e l l s c.an be m a n u f a c t u r e d .

T h e T a s k 2 e f f o r t i s o r g a n i z e d i n t o f o u r p h a s e s : r e s e a r c h and d e v e l o p -

m e n t o n s h e e t g r o w t h m e t h o d s (1975-77) ; a d v a n c e d d e v e l o p m e n t of s e l e c t e d

g r o w t h m e t h o d s (1977-80) ; d e v e l o p m e n t , f a b r i c a t i o n , a n d o p e r a t i o n of p r o d u c -

t ion g r o w t h p l an t s (1983- 86) .

C . TASK 2 C O N T R A C T S

T h e p u r s u i t of o p t i m a l t e c h n i q u e s f o r g r o w i n g s i l i c o n c r y s t a l l i n e m a t e r i a l

f o r s o l a r c e l l p r o d u c t i o n h a s l c d to t h e a w a r d i n g of R & D c o n t r a c t s t o 10 o r g a n i -

za t ions . T h e p r o c e s s e s be ing d e v e l o p e d by t h e s e c o n t r a c t o r s a r e shown. in

T a b l e 4-3.

F i g u r e 4 -8 s h o w s t h e s c h e d u l e f o r e a c h c o n t r a c t a s i t w a s in i t i a l l y

negot ia ted . Fo l low-on w o r k a n t i c i p a t e d for e a c h c o n t r a c t i s i n d i c a t e d by the

c r o s s - h a t c h e d h o r i z o n t a l b a r s . R e s e a r c h a n d d e v e l o p m e n t w o r k w i l l 'cont inue

t h r o u g h the e n d of F Y 1977, by which t i m e i t is e x p e c t e d t h a t t e c h n i c a l f e a s i -

b i l i ty w i l l h a v e b e e n d e m o n s t r a t e d . I t i s a n t i c i p a t e d t h a t two a d d i t i o n a l R & D

c o n t r a c t s wi l l b e a w a r d e d d u r i n g l a t e F Y 1976 o r e a r l y F Y 1977 f o r o t h e r

g r o w t h p r o c e s s c a n d i d a t e s . S e l e c t i o n of " p r e f e r r e d " g r o w t h m e t h o d s f o r f u r t h e r

de-ve lopment duri .ng F Y 1978-80 i s p l anned f o r l a t e F Y 1977 o r e a r l y F Y 1978.

B y 1980, bo th t e c h n i c a l a n d e c o n o m i c f e a s i b i l i t y s h o u l d be d e m o n s t r a t e d by

ind iv idua l g r o w t h m e t h o d s . 4-27


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F l o a t i n g s u b s t r a t e ( c h e m i c a l v a p o r d e p o s i t i o n o n l i qu id )

D i p - c o a t i n g ( o n l o w - c o s t s u b s t r a t e s )

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F i g u r e 3-8 a l s o i n d i c a t e s t h e r e c e i p t o f . s i l i c o n " s h e e t " s a m p l e s a n d s o l a r

c e l l s f r o m t h e v a r i o u s g r o w t h - p r o c e s s R & D p r o g r a m s . T h e s e s a m p l e s / s o l a r

cells w i l l b e c h a r a c t e r i z e d / e v a l u a t e d a t J P L .

D. TASK 2 T E C H N I C A L ACTIVITY

I n f o r m a t i o n r e g a r d i n g e a c h g r o w t h - p r o c e s s R & D c o n t r a c t i s g iven i n t h e

f o l l o w i n g p a g e s . E a c h p r o c e s s i s b r i e f l y , d e s c r i b e d , , t o g e t h e r w i th a s h o r t

a c c o u n t of w h a t t h e i n d i v i d u a l c o n t r a c t s a r e d e s i g n e d t o a c c o m p l i s h in o r d e r t o

d e m o n s t r a t e t e c h n i c a l f e a s i b i l i t y . A c c 6 m p l i s h m e n t s t o d a t e p l u s f u t u r e p l a n s

a r e also' g i v e n ( e x c e p t f o r R C A , w h o s e c o n t r a c t i s s t i l l u n d e r nego t i a t i on a t t h e

. t i m e of t h i s wr i t i ng ) .

1. W e b - D e n d r i t i c G r o w t h - U n i v e r s i t y of Sou th C a r o l i n a

W e b - d e n d r i f i c g r o w t h m a k e s i t s own g u i d e s of s i l i c o n , w h e r e a s m o s t

o t h e r r i b b o n p r o c e s s e s m u s t r e l y o n m a t e r i a l s o t h e r . than s i l i c o n f o r t he g u i d e s

( i . e . , d i e s ) ( F i g . 4-9) . T h e g u i d e s a r e thin d e n d r i t e s t h a t g r o w a h e a d of t h e

s h e e t and s u p p o r t t h e m o l t e n s i l i c o n b e t w e e n t h e m t o f o r m t h e s h e e t . T h e

d e n d r i t e g u i d e s g r o w i n a v e r y p r e c i s e o r i e n t a t i o n d i c t a t e d by t h e i r un ique

g r o w t h habi t . T h u s t h e o r i e n t a t i o n of t he s h e e t wh ich g r o w s b e t w e e n t h e m t a k e s

o n t h i s p r e c i s e o r i e n t a t i o n . T h e twin p l ane r e e n t r a n t e d g e m e c h a n i s m ( T P R E M ) < c o n t r o l s t h e g r o w t h of t h e e d g e d e n d r i t e s , g iv ing t h e m t h e i r un ique and i n t e r n a l l y -

c o n t r o l l e d g r o w t h d i r e c t i o n a l l owing t h e m to g r o w a h e a d of t he s h e e t and t h u s

a c t s as g u i d e s .

T h e b a s i c s t e p s , then , i n w e b s h e e t g r o w t h a r e ( 1 ) d i p a s e e d of the p r o p e r

. o y i e n t a t i o n i n t o a s l i g h t l y u n d e r c o o l e d m e l t , ( 2 ) hol'd t he s e e d s t a t i d n a r y wh i l e

g r o w t h t a k e s p l a c e l a t e r a l l y on the s u r f a c e of t he m e l t , f o r m i n g w h a t is t e r m e d

t h e bu t ton a n d (3) w h e n t h e l a t e r a l g r o w t h h a s p r o c e e d e d to t he d e s i r e d wid th ,

s t a r t t h e pul l ing. A s t h e pul l ing p r o c e e d s , two c o p l a n a r d e n d r i t e s g r o w down-

w a r d f ro ,m e a c h e n d of t h e bu t ton , p r o p a g a t i n g t o a d e p t h of 1 - 3 m i l l i m e t e r s

b e n e a t h t h e s p r f a c e of t he m e l t . A s t he bu t ton and i t s d e n d r i t e s e m e r g e f r o m

t h e m e l t , s i l i c o n is pul led u p b e t w e e n t h e m by s u r f a c e t e n s i o n , a n d t h e r e s u l t i n g

s h e e t s o l i d i f i e s j u s t a b o v e the m e l t s u r f a c e . T h e unique o r i e n t a t i o n and s l i g h t

u n d e r c o o l i n g to i n s u r e f a c e t e d gro,wth g i v e t h e s h e e t i t s a l m o s t m i r r o r - f l a t s u r -

f a c e f i n i s h .

MOLTEN SILICON

F i g . 4-9. W e b d e n d r i t i c g r o w t h

T h e o v e r a l l goa l of t h i s c o n t r a c t is t o d e v e l o p a b e t t e r u n d e r s t a n d i n g of

t he w e b - d e n d r i t i c p r o c e s s and d e f i n e i n g r e a t e r d e t a i l t he b a s i c l i m i t a t i o n s of

t h e p r o c e s s ( e s p e c i a l l y t h e m a x i m u m g r o w t h r a t e and wid th) . T h i s w i l l be

a c c o m p l i s h e d by d e v e l o p m e n t of a m u l t i v a r i a t e s e m i e m p i r i c a l m o d e l o f t h e web-

d e n d r i t i c g r o w t h p r o c e s s b a s e d upon g r o w t h e x p e r i m e n t s and t h e o r y .

T h e c o n t r a c t o r h a s s e t up t h e c r y s t a l g r o w t h a p p a r a t u s and h a s g r o w n s o m e

. small w e b - d e n d r i t e r i b b o n s ! T h e m a j o r p r o b l e m t o d a t e h a s b e e n i m p r o p e r

t h e r m a l g r a d i e n t s i n t he m e l t , c a u s i n g n u c l e a t i o n of a t h i r d d e n d r i t e . Modi f i -

c a t i o n s t o c h a n g e the t h e r m a l g r a d i e n t s h a v e begun. A c o n c u r r e n t a n a l y s i s of

t h e r m a l s t a b i l i t y of t he m e n i s c u s u n d e r s t a t i c c o n d i t i o n s h a s b e e n m a d e . In

t h e c h ' a r a c t e r i z a t i o n a r e a , s o l a r c e l l s h a v e b e e n m a d e f r o m c o m m e r c i a l

C z o c h r a l s k i w a f e r s . S o m e p r e l i m i n a r y w o r k h a s b e e n s t a r t e d on t r a n s m i s s i o n

and s c a n n i n g e l e c t r o n m i c r o s c o p e s t o m e a s u r e twin s p a c i n g .

P l a n s f o r t h e n e x t - q u a r t e r i n c l u d e d e f i n i n g t h e t h e r m a l g e o m e t r y f o r

g r o w i n g w i d e r r i b b o n . T h i s w i l l i n c l u d e a n a L y t i c a l h e a t f l o w a n a l y s i s a n d c o r r e -

, . l a t i o n of t h e h e a t t r a n s f e r r a t e w i t h c r y s t a l l i z a t i o n k i n e t i c s a n d s e e d i n g r e q u i r e -

m e n t s . M o r e d e t a i l e d c h a r a c t e r i z a t i o n of b u l k w e b s i l t c o n a n d s o l a r c e l l f a b r i -

c a t i o n f r o m w e b m a t e r i a l i s s c h e d u l e d f o r t h e n e x t q u a r t e r .

2. E F G G r o w t h - ~ M o b i l - T y c o S o l a r E n e r g y C o r p o r a t i o n

E f f o r t s u n d e r t h i s c o n t r a c t a r e d i r e c t e d t o w a r d e x t e n d i n g t h e c a p a c i t y of

E F G g r o w t h of s i l i c o n s h e e t t o s p e e d s of 3 i n c h e s a m i n u t e a n d w i d t h s of 3

i n c h e s ; w o r k b e g a n N o v e m b e r 1975 ( F i g . 4 - 10). T h e i n i t i a l s t a g e s w i l l i n v o l v e

i n d e p e n d e n t d e v e l o p m e n t of h i g h - s p e e d g r o w t h ( w i t h a p p r o p r i a t e t h i c k n e s s e s ) .

a n d i m p r o v e d w i d t h . L a t e r s t a g e s w i l l a t t e m p t t o i n t e g r a t e t h e s e t w o a p p r o a c h e s .

T h e e x p e r i m e n t a l p r o g r a m i n v o l v e s t w o m a c h i n e s a n d w i l l b e s u p p o r t e d by

a p p r o p r i a t e t h e o r e t i c a l a n a l y s e s of t h e l i q u i d l s o l i d d i e c o n f i g u r a t i o n a n d t h e

t h e r m a l g e o n ~ e t r y s u r r o u n d i n g t h e c r y s t a l l i z a t i o n a n d c o o l i n g of t h e r i b b o n .

A p p r o p r i a t e c h a r a c t e r i z a t i o n a n d s o l a r c e l l p r e p a r a t i o n is i n c l u d e d .

A t p r e s e n t , t h e E F G gr .pwth m a c h i n e f o r t h e d e v e l o p m e n t of f a s t e r g r o w t h

of a p p r o p r i a t e t h i c k n e s s e s i s p r o d u c i n g r i b b o n a t s p e e d s a p p r o a c h i n g the ' p l a n n e d

3 i n c h e s p e r m i n u t e . T h e s e r i b b o n s a r e h i g h l y s t r e s s e d a n d n o t f u l l - w i d t h ( l e s s

t h a n 1 i n c h ) , bu t a r e i n d i c a t i v e of s i g n i f i c a n t p r o g r e s s . S t u d i e s o n t h i s m a c h i n e

h a v e d e m o n s t r a t e d t h a t t h e (1. ! C ; -: 2 11> o c i e n t ~ t i o n o f f e r s a s p e c i f i c a d v a n t a g e

f o r E F G g r o w t h i n t h a t s e e d i n g m a y b e a c h i e v e d w i t h t h i s o r i e n t a t i o n . A

p a r a l l e l t w i n s t r u c t u r e i n t h e g r o w n r i b b o n is s t i l l o b t a i n e d r e g a r d l e s s of w h e t h e r

t h e s e e d i s a s i n g l e c r y s t a l o r ' t w i n n e d , a n d p e r t u r b a t i o n s t o t h i s p a r a l l e l t w i n

s t r u c t u r e ' a r e s t i l l b e i n g i n t r o d u c e d b y t h e s i l i c o n c a r b i d e p a r t i c l e s c o m i n g f r o m

t h e d i e . H o w e v e r , t h e s e r e s u l t s d o i n d i c a t e t h e h i g h e r s t a b i l i t y of t h i s s t r u c -

t u r e a n d o r i e n t a t i o n . T h e o r e t i c a l s t u d i e s a r e p r e s e n t l y a d d r e s s i n g t h e p r o b l e m

of s t r e s s w i t h i n t h e r i b b o n a n d r e s u l t s t h u s f a r s u g g e s t i t t o b e a s i g n i f i c a n t

p r o b l e m f o r h i g h - s p e e d g r o w t h . O t h e r e f f o r t a t t h i s t i m e i n v o l v e s t h e i n i t i a l

d e s i g n f o r t h e s e c o n d m a c h i n e , plann,ed t o d e m o n s t r a t e 3 - i n c h w i d e g r o w t h .

T h e s e c o n d m a c h i n e w i l l h a v e a h o r i z o n t a l c o n f i g u r a t i o n c o n s i s t e n t w i t h e v e n t u a l

m e l t r e p l e t l i s h n l e n t s t u d i e s .

MOLTEN SILICON

F i g . 4-10. C a p i l l a r y d i e g r o w t h

N e a r - t e r , m - p l a n s involve f u r t h e r e f f o r t s toward i m p r o v i n g the q u a l i t y of

the f a s t - g r o w n r ibbon by i n c o r p o r a t i n g i m p l i c a t i o n s of the s t r e s s and' t h e r m a l

a n a l y s i s in to the e x p e r i m e n t a l conf igura t ion , C h a r a c t e r i z a t i o n and s o l a r c e l l

is ' ,under way and preli-minar.y r e s u l t s wi l l be .evaluated soon . A

f i n a l d e s i g n f o r the w i d e - r i b b o n m a c h i n e wi l l b e s e l e c t e d and cons t ruc ' t ion begun. . .

3. E F G G r o w t h - IBM

T h e c o n t r a c t is d i r e c t e d toward the a s s e s s m e n t of E F G as a m e a n s of

p roduc ing sil 'icon r i b b o n s u i t a b l e f o r s o l a r c e l l s , c h a r a c t e r i z a t i o n of tha t r ibbon,

/ a n d e c o n o m i c a n a l y s i s of a n u m b e r of m e a n s of pro.ducing s i l i c o n s h e e t (Fig. 4-

10). T h e r i b b o n g r o w t h b y E F G invo lves both e x p e r i m e n t a l a n d t h e o r e t i c a l I

s t u d i e s of t h e p r o c e s s . T h e c h a r a c t e r i z a t i o n is p r i m a r i l y e l e c t r i c a l a n d s t r u c -

t u r a l b u t d o e s not s p e c i f i c a l l y i n c l u d e s o l a r c e l l p r e p a r a t i o n . C h a r a c t e r i z a t i o n

a l s o i n c l u d e s t h e d e v e l o p m e n t a n d a s s e s s m e k t of new techniques . T h e economic

s t u d i e s i n c l u d e d e v e l o p m e n t of s o f t w a r e f o r t h e a s s e s s m e n t of po ten t i a l c o s t s

f o r p roduc ing s i l i c o n and r ibbon s h e e t s a s a funct ion of input and p r o c e s s i n g

p a r a m e t e r s .

T h e p r o g r a m has 'been u n d e r way s i n c e May 1975, and the.>EFG w o r k a t -

- p r e s e n t i n c l u d e s the c a p a c i t y t o g r o w nomina l ly 1- inch-wide m a t e r i a l but has

inc luded the g rowth o'f tubes a*d a n ' a s s e s s r n e n t of ' the v e l o c i t y / t h i c k n e s s r e l a -

t i o n s h i p u n d e r s u c h g rowth . ' s t u d i e s a l s o inc lude s e v e r a l a l t e r n a t e d i e m a t e r i a l s ;

h o w e v e r , r e s u l t s in th is a r e a have not y-et been conc lus ive .

C h a r a c t e r i z a t i o n w o r k a t p r e s e n t has' identif ied the c a r b i d e p a r t i c 1 . e ~

f o r m e d wi th in the r ibbon a s B e t a s i l i con c a r b i d e , and a b rownish f i l m on the

s u r f a c e SiO plus Si r e s u l t i n g f r o m the decompos i t ion pf SiO. ~ l e c t r o n

, c h a n n e l i n g t echn iques have a l s o bee; inves t iga ted a s a m e a n s of s t r u c t u r e d e t e r -

mina t ion . T h e c o m p u t e r w o r k a t p r e s e n t has r e s u l t e d i n s o f t w a r e f o r economic

a n a l y s i s of E F G growth and w o r k h a s begun o n C z o c h r a l s k i g rowth .

N e a r - t e r m plans wi l l i nc lude s t u d i e s of s t r e s s d i s t r i b u t i o n and c r y s t a l

p e r f e c t t o n a s a funct ion of the t h e r m a l g e o m e t r y s u r r o u n d i n g the ribbon.,

C h a r a c t e r i z a t i o n e f f o r t w i l l e m p h a s i z e c o r r e l a t i o n of s t r u c t u r a l d e f e c t s i n the

E F G r i b b o n wi th l i f e t i m e as m e a s u r e d f r o m MOS c a p a c i t o r s . Work on the

e c o n o m i c m o d e l s f o r v a r i o u s s h e e t g r o w t h t e c h n i q u e s w i l l con t inue .

4. I n v e r t e d S tepanov T e c h n i q u e - R C A

I n t h i s p r o g r a m e m p h a s i s i s p l aced on t h e d e v e l o p m e n t of t h e g r o w t h of

r i b b o n - s h a p e d s i l i c o n us ing a ' Inon-wet ted ' ' d i e ( F i g . 4-1 1). T h e u s e of t h e "non-

w e t t e d " d i e p r o v i d e s the p o s s i b i l i t y of m i n i m i z i n g the r e a c t i o n be tween the

m o l t e n s i l i c o n and t h e d i e m a t e r i a l . R e a c t i o n be tween m o l t e n s i l i c o n and we t t ed

d i e s is o n e s o u r c e of d e g r a d a t i o n i n the c r y s t a l l o g r a p h i c q u a l i t y of s i l i c o n g r o w n

us ing a w e t t e d d i e ( i . e . , t h e edge -de f ined f i l m - f e d g r o w t h m e t h o d ) . T h e i n t r o -

d u c t i o n of the f eed f r o m a b o v e and the g r o w t h of the s i n g l e c r y s t a l i n a down-

w a r d d i r e c t i o n ( t h e i n v e r t e d S tepanov t echn ique ) i n p a r t c o m p e n s a t e s f o r t h e

h y d r o d y n a m i c d r a g i n the s l o t and f o r the l a c k of c a p i l l a r y r i s e . ( T h e c a p i l l a r y

rise f e e d s t h e m a t e r i a l to t he d i e e d g e i n the E F G me thod . ) T h e i n v e r t e d g e o m -

e t r y a l s o l e a d s t o c o n s i d e r a b l e f l ex ib i l i t y i n the g r o w t h c o n f i g u r a t i o n when the .-_

f e e d i s i n t r o d u c e d f r o m a ' m o l t e n z o n e a t t he end of a s o l i d s i l i c o n r o d .

T h e p r i m a r y o b j e c t i v e of the p r o g r a m i s to i n v e s t i g a t e t he b a s i c s e e d i n g

a n d g r o w t h p r o c e s s e s involved i n t he g r o w t h of s i l i c o n s h e e t f r o m "non-wet ted"

d i e s . T h e goa l i s t o . e s t a b l i s h w h e t h e r o r no t s i g n i f i c a n t i m p r o v e m e n t i n t he

c r y i t a l l o g r a p h i c p r o p e r t i e s of the s i l i c o n c a n be r e a l i z e d by t h e u s e of "non-

w e t t e d " r a t h e r t h a n "wetted" s h a p i n g d i e s . S i l i c a and b o r o n n i t r i d e s h a p i n g d i e s

w i l l b e u s e d . Me thods wi l l b e s o u g h t t o c o m p e n s a t e f o r t he l a c k of m e c h a n i c a l

s t r e n g t h of s i l i c a a t the g r o w t h t e m p e r a t u r e . Although b o r o n n i t r i d e l e a d s to

u n a c c e p t a b l e doping of the g r o w n s i l i c o n r ibbon , i t i s m o r e r i g i d than s i l i c a and

t h e r e f o r e i s u se fu l i n the i d e n t i f i c a t i o n of f u n d a m e n t a l l i m i t i n g f a c t o r s i n the

S t e p a n o v g r o w t h method.

5. L a s e r - Z o n e G r o w t h i n a R ibbon- to -R ibbon P r o c e s s - M o t o r o l a C o r p o r a t i o n

T h e r ibbon- to - r i bbon p r o c e s s is b a s i c a l l y a f l o a t - z o n e c r y s t a l g r o w t h

m e t h o d i n which t h e f e e d s t o c k is a p o l y c r y s t a l l i n e s i l i c o n r ibbon ( F i g . 4-12) .

FEED

POLYCRYSTAL FEEDSTOCK

MOLTEN POOL

NON-W ETTED- D I E

SHAPING ORIFICE

PULL

'RIBBON PRODUCT

Fig . 4-1 1. Inverted Stepanov technique - R C A

4 - 3 6

THIN, SINGLE-CRYSTAL / RIBBON

COORDINATED SPEED OUT ? 11 v ZONE OF MELTING A N / RECRYSTALLIZATION

/ . , HEAT SOURCE

Fig. 4- 12. Laser zone crystalliaatiot~

T h e p o ~ l y s i ~ i c o ' n r i b b o n is fed i n t o a p r e h e a t e d r e g i o n w h i c h i s a d d i t i o n a l l y h e a t e d

. , b y a f o c u s e d l a s e r b e a m , m e l t e d , and c r y s t a l l i z e d . T h e l iqu id s i l i c o n , i s held

i n p l a c e b,y i t s o w n s u r f a c e t ens ion . . T h e s h a p e of the r e s u l t i n g c r y s t a l i s de f ined

b y t h e s h a p e o f t h e f e e d s t o c k atid t h e o r i e n t a t i o n i s d e t e r m i n e d by. t hh t of a s e e d . .

s i n g l e - c ' r y s t a l r i b b o n .

T h i s i s a c o n t r a c t of 1 5 m o n t h s d u r a t i o n ; t he p r i m a r y e f f o r t s . u n d e r i t . .

a r e t o :

Mod i fy a n d e v a l u a t e t he e x i s t i n g r ibbon- to : r ibbon g r o w t h f a c i l i t y

t o m e e t t h e c o n t r a c t goa ls .

O p e r a t e t h e f a c i l i t y on a r e g u l a r b a s i s to s t u d y and o p t i m i z e t h e

g r o w t h c a p a b i l i t i e s of t h e R T R p r o c e s s w i t h p a r t i c u l a r e m p h a s i s

o n t h e r m a l e n v i r o n m e n t , s e e d i n g , r i b b o n ve loc i ty , l a s e r i npu t

c o n f i g u r a t i o n , and th roughpu t .

P e r f o r m c h a r a c t e r i z a t i o n s / t e s t s o n r i b b o n s a m p l e s f r o m e a c h

g r o w t h r u n .

F a b r i c a t e a n d c h a r a c t e r i z e s o l a r c e l l s .

- 1

T h i s c o n t r a c t w a s e n t e r e d in to o n F e b r u a r y 4, 1976. T o d a t e , M o t o r o l a

h a s s u b m i t t i d the p r o g r a m p l an d e t a i l i n g the v a r i o u s e f f o r t s l i s t e d a b o v e . T h e

p l a n i s b e i n g r e v i e w e d by J P L .

T h e p l a n s f o r t he n e x t q u a r t e r c a l l f o r c o m p l e t i o n and e v a l u a t i o n of the

R T R g r o w t h f a c i l i t y . S o m e of t h e p a r t i c u l a r m o d i f i c a t i o n s whic.h w i l l be c o m - I

p le t ed and e v a l u a t i o n s w h i c h w i l l be p e r f o r m e d are :

, • ~ e s i g n and i m p l e m e n t a t i o n of a u x i l i a r y hea t ing t e c h n i q u e s . - • 1ns ta l la t i0 ,n of a n e w c a m e r a - v i e w i n g - s y s t e m w h i c h w i l l a l l o w

s . a m p l e v i ewing f r o m f ron t , r e a r and a t l e a s t o n e s i d e

s . imul t a n e o u s l y . -

e. ~ n s t a l l a t i o n and c a l i b r a t i o n of o p t i c a l p y r o m e t e r and photodiode . .

t e m p e r a t u r e s e n s o r s .

C o m p l e t i o n of t r a n s l a t i o n p r o g r a m m e r n e c e s s a r y f o r h ig t ie r

s p e e d g r o w t h r u n s .

I n s t a l l a t i o n of a r e m o t e m i r r o r o r i e n t a t i o n c o n t r o l s y s t e m to

e n s u r e ab i l i t y of a l i g n m e n t of l a s e r s c a n s .

\

D u r i n g t h i s t i m e v a r i o u s o t h e r a s p e c t s of t he s y s t e m wi l l be e v a l u a t e d t o

e n s u r e p r o p e r o p e r a t i o n ; e . g . , r i b b o n t r a n s l a t i o n s t ag ing , l a s e r o p e r a t i o n a l

c h a r a c t e r i s t i c s ' ( b e a m p r o f i l e s , p o w e r o p t i m i z a t i o n , power c o n t r o l , e t c . ) and

the o p t i c a l s y s t e m .

6. CVD o n L o w - C o s t S u b s t r a t e s - Rockwel l C o r p o r a t i o n

T h e p u r p o s e of t h i s c o n t r a c t i s t o e x p l o r e t h e c h e m i c a l v a p o r depos i t i on

(CVD) m e t h o d f o r t he g r o w t h of s i l i c o n s h e e t on i n e x p e n s i v e s u b s t r a t e m a t e r i a l s

( F i g . 4 - 13). T h e w o r k w i l l be c a r r i e d ou t a t t h e Rockwe l l E l e c t r o n i c s R e s e a r c h

Div i s ion i n A n a h e i m , but a l s o invo lves e x p e r i m e n t a l s o l a r c e l l f a b r i c a t i o n and

e v a l u a t i o n by the P h o t o e l e c t r o n i c s G r o u p to O p t i c a l Coa t ing L a b o r a t o r y , I n c . ,

i n C i t y of I n d u s t r y , C a l i f o r n i a . T h e c o n t r a c t p r o v i d e s f o r a n 18-mo.nth e f fo r t .

Work s t a r t e d o n D e c e m b e r 29, 1975; t h i s r e p o r t c o v e r s the f i r s t 2 m o n t h s .

T h e C V D method a s app l i ed t o s i l i c o n s h e e t g r o w t h invo lves p y r o l y s i s , o r

r educ t ion , of a s u i t a b l e s i l i c o n c o m p o u n d a t e l e v a t e d t e m p e r a t u r e and a p p r o x i -

m a t e l y a t m o s p h e r i c p r e s s u r e i n a f l o w - t h r o u g h (open- tube ) d e p o s i t i o n c h a m b e r

i n wh ich the s u b s t r a t e i s moun ted o n a s i l i c o n c a r b i d e - c o a t e d c a r b o n p e d e s t a l

h e a t e d by rf f r o m o u t s i d e the c h a m b e r . T h e p r o p e r t i e s of t he s i l i c o n s h e e t a r e

d e t e r m i n e d by d e p o s i t i o n t e m p e r a t u r e , r e a c t a n t c o n c e n t r a t i o n s , t he n a t u r e of

t he c a r r i e r g a s , the s i l i c o n s o u r c e compound used , g r o w t h r a t e , dop ing i m p u r -

i t i e s ( a d d e d by i n t r o d u c t i o n of a p p r o p r i a t e c o m p o u n d s i n t o the c a r r i e r g a s

s t r e a m ) , and the p r o p e r t i e s of the s u b s t r a t e .

T h e s p e c i f i c t e c h n i c a l g o a l s e s t a b l i s h e d f o r t h e c o n t r a c t i nc lude the

fo l lowing:

S i l i con s h e e t :

A r e a ( p e r s a m p l e )

Depos i t i on r a t e

30 c m 2

5 pm p e r m i n u t e

Fig . 4 - 13. C h e m i c a l v a p o r depos i t i on (CVD) - Rockwel l I n t e r n a t i o n a l

T h i c k n e s s

C r y s t a l s t r u c t u r e

I n t r a g r a i n d i s l o c a t i o n d e n s i t y

20 t o 100 p m

1 0 0 p n ~ a v e r a g e g r a i n s i z e 4 < 10 p e r c m 2

T h e c o n t r a c t p r o g r a m i s s t r u c t u r e d i n . t e r m s of six m a i n t e c h n i c a l t a s k s ,

as fo l lows :

o Modi f i ca t i on a n d t e s t of a n e x i s t i n g C V D r e a c t o r s y s t e m .

Iden t i f i ca t i on a n d / o r d e v e l o p m e n t of s u i t a b l e i n e x p e n s i v e s u i -

s t r a t e m a t e r i a l s .

E x p e r i m e n t a l i n v e s t i g a t i o n of C V D p r o c e s s p a r a m e t e r s u s i n g

v a r i o u s ' c a n d i d a t e s u b s t r a t e m a t e r i a l s .

. P r e p a r a t i o n of s i l i c o n s h e e t s a m p l e s f o r v a r i o u s s p e c i a l s t u d i e s ,

i nc lud ing s o l a r c e l l f a b r i c a t i o n .

e E v a l u a t i o n of t h e p r o p e r t i e s of t h e s i l i c o n s h e e t m a t e r i a l p r o -

d u c e d by the C V D p r o c e s s . -

F a b r i c a t i o n a n d e v a l u a t i o n of e x p e r i m e n t a l s o l a r cell s t r u c t u r e s

by O p t i c a l C o a t i n g L a b o r a t o r i e s , Inc . ,' u s i n g s t a n d a r d s a n d n e a r -

s t a n d a r d p r o c e s s i n g t e c h n i q u e s .

D e s i g n d e t a i l s of m o d i f i c a t i o n s t o t h e C V D r e a c t o r h a v e b e e n f i n a l i z e d a n d

. a l l of t he p a r t s r e q u i r e d h a v e b e e n o r d e r e d ; h o w e v e r , b e c a u s e of l ong d e l i v e r y

t i m e s , t he m o d i f i c a t i o n s m a y no t b e c o t n p l e t e un t i l A p r i l . T h i s s h o u l d n o t

i m p a c t t h e p r o g r a m b e c a u s e the unmod i f i ed r e a c t o r w i l l b e a d e q u a t e un t i l t he

' : f ine- tun ing" s t a g e of p r o c e s s c o n t r o l i s r e a c h e d .

S e v e r a l c a n d i d a t e s i i b s t r a t e m a t e r i a l s ( g l a s s e s a n d c e r a m i c s ) h a v e b e e n

a c q u i r e d and D r . H. M a n a s e v i t h a s v i s i t e d s e v e n po ten t i a l s l i p p l i e r s i n s e a r c h .

of m o r e . S e v e r a l of t h e m e x p r e s s e d s t r o n g i n t e r e s t i n s u p p l y i n g n o n s t a n d a r d

g l a s s e s , c e r a m i c s , g l a z e s , and m e t a l l i z e d m a t e r i a l s . A s sotme of t h e s u b -

s t r a t e s t e s t e d s o far havc , p r o v e d t o be r e a c t i v e i n a n H. c a r r i e r g a s bu t n o t - i n 2 '

He, d e p o s i t i o n p a r a m e t e r s f o r t h e l a t t e r a r e be ing e s t a b l i s h e d .

By the end of the n e x t q u a r t e r , t h e r e a c t o r m o d i f i c a t i o n s h o u l d b e coni--

p l e t e and e x p e r i m e n t s t o d e f i n e t he d e p o s i t i o n and dop ing p a r a m e t e r s w e l l \ ~ . ~ n d e r .

I

4 -41

I

w a y . T e c h n i q u e s f o r X - r a y and. sc.anning-electron-microsco,pe d e t e r m i n a t i o n of ,

g r a i n s i z e and o r i e n t a t i o n shou ld b e e s t a b l i s h e d and s p r e a d i n g - r e ~ i s t a n c e m e a - , . - s u r e m e n t c a p a b i l i t y a c q u i r e d .

I

. , , 7. Flo.ating ~ u b s t r a t e / C ~ ~ o n L i q u i d - G e n e r a l E l e c t r i c

T h e of t h i s c o n t r a c t T i s t o d e m o n s t r a t e t h e f e a s i b i l i t i of a f lba t ing

- s u b s t r a t e ~ h e e t ' ~ r o w t h p r o c e s s f o r ' t h e f a b r i c a t i o n of s i l i c o n s h e e t ( F i g . 4-14). .

T h e p r o c e s s i s a n , a p p r o a c h t o the f o r m a t i o n of s i n g l e - c r y s t a l s i l i c o n by d i r e c t

- ' e p i t a x i a l c o n v e r s i o n f r o m g a s e o u s s i l a n e . In a n a p p r o p r i a t e . r e a c t o r , s i l a n e

, i s p a s s e d o v e r s i l i c o n s u b s t r a t e wh ich i s s u p p o r t e d . o n a t h i n - f i l m of m b l t e n t in .

S ing le c ' r y s t a l s t l i c o n g r o w s t o the d e s i l ' e d - t h i c k n e s s by v a p o r p h a s e epi taGy. -. ~ u c l e a t i o n of f r e s h - s u b s t r a t e s i l i c o n t a k e s p l a c e a t cine end of t he r e a c t o r w'here, -

t h e e d g e of t he g r o w i n g s h e e t . i s i n c o n t a c t w i t h a r e g i o n of t h e t i n w h i c h i s s u p e r -

s a t u r a t e d - w i t h s i l i c o n . T h e p r o c e s s l e n d s i t s e l f t o cont inuo 'us o p e r a t i o n , w i t h

thk fi'n-ished s h e e t b e i n g w i t h d r a w n f r0 .m the o p p o s i t e end ,of the g r o w t h zone .

T h e c o n t r a c t c o v e r s a 1 5 - m o n t h p r o g r a m in t ended to p r o v i d e a f e a s i b i l i t y -

o f - c o n c e p t - d e m o n s t r , a t i o n . T h e m a j o r p o r t i o n of t he p r o g r a m wi l l f o c u s o n

n u c l e a t i o n s t u d i e s and t h e r a p i d g r o w t h of s i l i c o n s u b s t r a t e f r o m s u p e r c o o l e d

m e l t s . T h e s e e f f o r t s shou ld l e a d to a shee.t g r o w t h d e m o n s t r a t i o n by the e n d of , . t h e f i r s t c o n t r a c t y e a r and. a d e s i g n and c o s t a n a l y s i s fo r . a p ro to type s h e e t '

g r o w t h a p p a r ' a t u s b y c o n t r , a c t c l o s e . E x p l i c i t s t u d i e s f o r the c o n t r a c t i nc lude :

. , S u p e r c o o l i n g i n Sn-Si m e l t s .

I C r y s t a l g r o w t h f r o m a s u p e r c o o l e d Sn-Si m e l t .

~ i l i c ' o n up take bjr t i n f r o m s i l a n e s . I

S u r f a c e g r o w t h .

P r o t o t y p e d e s i g n a n d c o s t a n a l y s i s .

T h e t e c h n i c a l g o a l s f o r t h e c o n t r a c t r e q u i r e g r o w t h of a s i n g l e q r y s t a l of

s i l i c o t i hav ing a n a r e a of 0 . 5 c m 2 and the d e t e r m i n a t i o n of the propagat ion

v e l o c i t y of sin.gl.e c r y s t a l s i l i c o n g r o w t h a long a s u p e r s a t u r a t e d hot t i n m e l t

s u r f a c e .

DIRECTION O f SHEET TRAVEL -

TEMPERATURE PROF1 E

SILICON

FLOATING SUBSTRATE SIL ICON S H W GROWTH

\ :TNE GROWTH

I -I

I SILICON CVD DEPOSITION ZONE

ENLARGED SCHEMATIC VIEW OF GROWING EDGE OF SHEET. (a = FIRST FEW ATOR\IC LAYERS OF EPlTAXlALLY DEPOSITED SILICON, b = THIN LOLVER LAYER FORMED BY GRO\'JTH FROM SIL ICON SOLUTION, c = SURFACE OF L IQUID T I N SUPERSATURATED \VITH SIL ICON BY DEPOSITION FRO/\\ VAPOR PHASE. AND d = LEADING EDGE)

F i g . 4-14. F l o a t i n g s u b s t r a t e s h e e t g r o w t h - C E R e s e a r c h a n d D e v e l o p m e n t C e n t e r

T o d a t e , t h e e x p e r i m e n t a l a p p a r a t u s f o r the s u p e r c o o l i n g ' a n d k i l ane uptak.e.

e x p e r i m e n t : h a v e b e e n d e s i g n e d and f a b r i c a t e d . T h e s u p e r c o o l i n g a p p a r a t u s h a s - . been a s s e m b l e d , i s o p e r a t i o n a l , and e x p e r i m e n t s a r e u n d e r way . T h e s i l a n e

I , u p t a k e a p p a r a t u s is i n f i n a l a s s e m b l y : P r o g r e s s ap 'peaks s a t i s f a c t o r y . . ?

- S c h e d u l e d a c t i v i t i e s ' f o r t h e ' n e x t q u a r t e r i n c l u d e c o m p l e t i o n of the b a s i c

s t u d i e s . , of s u p e r c o o l i n g a n d s i l i>con up take f r o m s i l a n e s a n d the i n i t i a t i o n , of - . . s t u d i e s of c r y s t a l g r o w t h f r o m supe rcoo ' l ed Sn-Si m e l t s .

. ~

8 \

8.- ' D i p - C o a t i n g on L o w - C o s t S u b s t r a t e s - Honeywe l l C o r p o r a t i o n

T h i s p rog ra . ln i s d i r e c t e d t o w a r d the e v a l u a t i o n of s i l i c o n f i i m s c r y s t a l - . ' ,

l i z e d - f r o m t h e m e l t on l o w - c o s t c e r a m i c s u b s t r a t e s ( F i g . 4- 15). C e r a f n i c s h a v e

be.en s e l e c t e d b e c a u s e of t h e i r s u p e r i o r t h e r m a l e x p a n s i o n m a t c h w i t h s i l i c o n

a n d the g r e a t e r e a s e w i t h w h i c h t h i s ex6a t i s ion m a y b e a d j u s t e d . T h e c e r a m i c s

will .b 'e, c o a t e d w i t h a f i l m of c a r b o n o r s i l i c o n c a r b i d e to e n h a n c e the a d h e s i o n .

T h e c o n c e p t h a s b e e n d e m o n s t r a t e d p r e v i o u s l y . : T h e to t a l p r o g r a m i n c l u d e s

c o n s t r i i c t i o n of a d ipp ing f a c i l i t y , s e l e c t i o n and e v a l u a t i o n of s u b s t r a t e s and

a's s o c i a t e d c o a t i n g s , p roduc- t ion df d i p f i l m s - and t h e i r c h a r a c t e r i z a t i o n . by v a r i - , .

011s s t r u c t u r a l , c h e n ~ i c - d a n d s o l a r . c e l 1 p e r f o r m a n c e m e t h o d s . T h e s o l a r c e l l s .

w i l l r e q u i r e s o m e s p e c i a l i z e d t e c h n i q u e s b e c a u s e of the nonconduc t ive n a t u r e of

t h e s u b s t r a t e .

- - ,The' p i - o g r a m was. i n i t i a t e d i n l a t e O c t o b e r and t o d a t e h a s e m p h a s i z e d the

d e s i g n a n d c o n s t r u c t i o n of t h e d ipping f a c i l i t y . It h a s b e e n comple te .d and h a s

m e l t e d s o m e s i l i c o n , a l t h o u g h m i n o r d i f f i c u l t i e s w i t h t h e ' p o w e r s 'upply have

pr-evehted m e l t i n g a fu l l c h a r g e a t t h i s t ime; Effor ' t h a s a l s o b e e n expended i n ~!

t h e p r o c u r e m e n t a n d p r e p a r a t i o n of ' su i t ab l e c e r a m i c s u b s t r a t e s . A p p r o x i m a t e l y

2 5 d i f f e r e n t s u b s t r a t e s t r u c t u r e s and c o m p o s i t i o n s h a v e . b e e n o b t a i n e d , r a n g i n g . I

f r o m d e n s e p o l y c r y s t a l s t o p r e s s e d p a p e r s . -In add i t i on , s o m e e f f o r t h a s .been . ,

exper ided o n the ' d e v e l o p m e n t of s o l a r c e l l f a b r i c a t i o n t e c h n i q u e s s u i t a b l e f o r .

- f q o n t l s i d e c o n t a c t i n g . H o w e v e r , t h i s w o r k i s p r e s e n t l y i n c o m p l e t e .

N S h o r t - t e r m p l a n s p r o v i d e f o r beg inn ing the d i p - c o a t i n g o p e r a t i o n , a s s o o n

as t h e m i n o r p o w e r s u p p l y p r o b l e m h a s b e d n c o r r e c t e d . 1n i t ia i s u b s t r a t e s w i l l . \. . .

cQ UARTZ TUB1 NG ( 5 in. D I A )

)- GAS I NLETS

\tt20 INLET

Fig. 4-1 5. C ros s - s ec t i ona l ske tch of bas ic shee t d ip coating growth lac i l i ty - Honeywell Co rpo ra t e R e s e a r c h C e n t e r

b e c a r b o n c b a t e d b y m e c h a n i c a l s c r u b b i n g t o r e p r o d ~ c e p a s t e f f b r t s . O t h e r I'

c o a t i n g t e c h n i q u e s w i l l b e u s e d -to p r o v i d e a m a t r i x o f . . v a r i a b l e s . o f s u b s t r a t e s

a n d c o a t i n g s . I n t h i s m a n n e r t h e c o n t r o l l i n g f e a t u r e s of n u c l e a t i o n a n d g r o w t h ,

c a n b e a s c e r t a i n e d . E f f o r t s i n v o l v i n g t h e c e l l p r e p a r a t i o n m e t h o d s w i l l a l s o (

c o n t i n u e .

9. H e a t E x c h a n g e r ~ e t h o d ' o f I n g o t C a s t i n g - C r y s t a l S y s t e m s , Inc . .

t

T h e S c h m i d - V i c c h n i c k i t e c h n i 4 u e ( h e a t - e x c h a n g e r m e t h o d ) h a s b e e n

d e v e l o p e d t o g r o w l a r g e s i n g l e - c r y s t a l s a p p h i r e ( F i g . 3 -16) . H e a t is - r e m o v e d

f r o m t h e c r y s t a l b y m e a n s of a h i g h - t e m p e , r a t u r e h e a t e x c h a n g e r . T h e h e a t " r e m o v a l i s c o n t r o l l e d b y t h e f l o w of heliu.171 g a s ( t h e c o o l i n g m e d i u m ) t h r o u g h

t h e h e a t e x c h a n g e r . h his e l i m i m a t e s . t h e n e e d f o r m o t i o n of t h e c r y s t a l , c r u c i b l e ,

o r h e a t zone. . In e s s e n c e t h i s m e t h o d i n v o l v e s d i r e c t i o n a l s o l i d i f i c a t i o n f r o m

t h e m e l t w h e r e ' t h e t e m p e r . a t u r e g r a d i e n t i n t h e s o l i d ' m i g h t b e c o n t r o l l e d b y t h e

h e a t e x c h a n g e r a n d t h e g r a d i e n t i n t h e l i q u i d c o n t r o l l e d . b y t h e f u r n a c e t e m p e r -

a t u r e .

, .

. T h e o v e r a l l g o a l of t h i s p r o g r a m i s t b d e t e r m i n e if t h e h e a t - e x c h a n g e r . i n g o t c a s t i n g m e t h o d ' c a n g r o w l a r g e s i l i c o n c r y s t a l s ( 6 i n c h e s i n d i a m e t e r b y

4 i n c h e s i n h e i g h t ) i n a f o r m s u i t a b l e f o r t h e e v e n t u a l f a b r i c a t i o n of s o l a r ' c e l l s .

T h i s g o a l i.5 t o b e a c c o m p l i s h e d by t h e t r a n s f e r of s a p p h i r e g r o w t h t e c h n o l o g y

( 5 0 - p o u n d i n g o t s h a v e a l r e a d y b e e n g r o w n ) , a n d by t h e o r e t i c a l c o n s i d e r a t i o n of

s e e d i n g , c r y s t a l l i z a t i o n k ine t i cs ' , f lu id d y n a m i c s , a n d h e a t f l o w f o r s i l i c o n . - ..

F i v e s i l i c o n - c r y s t a l c a s t i q g s h a v e b e e n m a d e t o d a t e . C r y s t a l s y s ; e m s .

- - h a s m e l t e d a n d f r o z e n as m u c h a s 2 5 0 0 g r a m s of s i l i c o n , b u t h a s n o t y e t p r o -

d u c e d a s i n g l e - c r y s t a l . c a s t i n g . D i r e c t i o n a l . f r e e z i n g of o n e s a m p l e d e m o n s t r a t e d

l a r g e d i r e c t i o n a l l y - t e x t u r e d g r a i n s . Sinc,e t h e c a s t i n g is b e i n g d o n e u n d e r p a r t i a l

v a c u i l n l p r e s s u r e , t h e c o n t r a c t o r h a s m a d e s o m e t h e o r e t i c a l c a l c u l a t i o n s of t h e

o x y g e n a n d C O p r e s s u r e s v e r s u s t e m p e r a t u r e .

- D u r i n g t h e n e x t q u a r t e r t h e e s t a p l i s h m e n t of s e e d i n g c o n d i t i o n s f o r ' g r o w -

i n g 6 x 4 i n c h s i n g l e c r y s t a l s w i l l b e u n d e r t a k e n . T h e condi t - ions w i l l b e

a c h i e v e d t h r o u g h a s e m i - e m pi r i c a l a p p r o a c h t h a t c o n s i d e r s k n o w n s a p p h i r e

COVER

., d , - T , \ MATERIAL I , . I - . * - >-< -.' ,

. . \ .. I L . .; :fl ) i i J

SEED HEAT 4 EXCHANGER ( a )

4

1 NTERFACE (,I

3

GROWTY OF A CRYSTAL BY THE HEAT EXCHANGER METHOD (HEM). (a) .CRUCIBLE, COVER, STARTING MATERIAL, AND SEED PRIOR TO MELTING; (b) STARTING MATERIAL MELTED; ( c ) SEED P A R T I A L L Y MELTED TO INSURE GOOD NUCLEATION; (dl GROWTH O F CRYSTAL COMMENCES;.(e) GROWTH O F CRYSTAL COVERS CRUCIBLE BOTTOM; ( f) LIQUID-SOLID INTERFACE EXPANDS IN NEARLY ELLIPSOIDAL FASHION; (g) LIQUID-SOLID INTERFACE BREAKS LIQUID SURFACE; (h) CRYSTAL GROWTH COMPLETED

Fig. 4-16. C r y s t a l growth u s i n g t h e H e a t Exchanger Method (HEM) C r y s t a l S y s t e m s Inc.

t e c h n o l o g y , s i l i c o n w e t t i n g t echno logy , h e a t t r a n s f e r , and c r y s t a l l i z t i o n

k i n e t i c s .

10. M u l t i p l e - W i r e Sawing - C r y s t a l S y s t e m s , Inc.

T o d a y m o s t s i l i c o n i s s l i c e d i n t o w a f e r s w i t h a n i n s i d e d i a m e t e r s a w , o n e

w a f e r a t a t i m e b e i n g s l i c e d f r o m t h e c r y s t a l . T h i s is a b ig c o s t f a c t o r i n

p r o d u c i n g s o l a r cel ls . T h e l e s s e r - u s e d m u l t i b l a d e s l i c e r c a n be u t i l i z e d t o

s l i c e s i l i c o n . T h e m u l t i b l a d e s l i c e r h a s no t b e e n d e v e l o p e d f o r t h e s e m i c o n d u c t o r

i n d u s t r y s i n c e t h i s m e t h o d p r o d u c e s bow and t a p e r u n a c c e p t a b l e f ~ r i n t e g r a t e d -

c i r c u i t a p p l i c a t i o n s .

T h e o v e r a l l g o a l of t he s l i c i n g p r o g r a m is to o p t i m i z e m u l t i b l a d e ( w i r e )

s i l i c o n s l i c i n g , i n v e s t i g a t i n g t h e fo l lowing p a r a m e t e r s i n p a r t i c u l a r :

R a t e of m a t e r i a l r e m o v a l and k e r f r e m o v a l .

S l i c e t h i c k n e s s , w i r e b l a d e d i m e n s i o n s , cu t t i ng , f o r c e s ,

w i r e / b l a d e tens i ,on , and o t h e r m a c h i n e v a r i a b l e s .

W i r e s v e r s u s b l a d e s as a c u t t i n g tool .

V a r i a t i o n of r o c k i n g m o t i o n .

I n t r o d u c t i o n of a b r a s i v e d u r i n g s l i c i n g o p e r a t i o n .

E f f e c t of s u r f a c e c o n d i t i o n of tool , inc lud ing c o n s i d e r a t i o n

of h a r d n e s s and nnethod of p la t ing .

E f f e c t of d i a m o n d a b r a s i v e p a r t i c l e s i z e and type .

E f f e c t of c u t t i n g f luid c o m p o s i t i o n .

A r o c k i n g m e c h a n i s m w e i g h i n g on ly 1 / 1 0 of t he o r i g i n a l s a m p l e h o l d e r

m e c h a n i s m h a s b e e n f a b r i c a t e d . T h i s m o d i f i c a t i o n w a s r e q u i r e d s i n c e the

o r i g i n a l m e c h a n i s m w a s too heavy , c a u s i n g l a r g e i n e r t i a a n d h igh f r ic ' t ion

d u r i n g s l i c i n g of t h e s a m p l e . A d i a p h r a g m s e a l w i t h low f r i c t i o n i s u t i l i z ed t o

c o n t r o l t h e f o r c e w h i c h t h e w o r k p i e c e e x e r t s o n t h e w i r e .

D u r i n g the n e x t q u a r t e r , i n v e s t i g a t i o n wi l l e m p h a s i z e t h i s r o c k i n g

m e c h a ~ l i s n l t o s t u d y t h e p a r a m e t e r s l i s t e d a b o v e . A s p e c i a l e m p h a s i s w i l l be

placed on including sodium hydroxide in the cutting media a t temperatures g r e a t e r

than room temperature to increase the cutting rate. Wire s i zes (50 wires/run)

will be 0. 003 and 0. 008 inch.

1 1. Breadknife Sawing - Varian Corporation

The purpose of this cdntract is to develop a multiple-blade sawing process

that will significantly reduce the cos t of cutting wafers f rom ingots o r blocks of -

single crystal silicon f o r so la r cel l fabrication and has the potential to be scaled

up f o r eventual la rge production environments (Fig. 4-17). The major portion of

the program consists -of a systematic experimental investigation of:

a Variation in cutting loads.

Speed of slicing head.

a Blade dimensions. . I . -

a Abrasive, size, and concentrations.

a Blade material properties and costs.

Lubricants.

a Specimen mountings.

The investigations will be conducted on a Varian 686 wafering machine

which will be modified fo r experimental studies. It will be supplemented by a

parallel theoretical effort to parametr ize sys tem performance as affected by

modified abrasive wear and to establish practical l imits to wafer accuracy and

thickness, blade instability, abrasive blunting, etc. The major technical goals

for the program are :

Wafer thickness:

Slicing ra te :

a Kerf loss:

a Number of parallel slices:

Stock size:

5 mils

10 mils per minute

5 mils

100

4 inches

Work to date includes (1) modification of a Varian 686 wafering machine

f o r cleaner s lu r ry drainage; stronger, shock-free drive system; and a smoother

Fig. 4-17. Three-inch diameter s i l i con in Varian multiblade wafer saw

a c t i n g v e r t i c a l f e e d ; (2 ) i n i t i a t i on of t h e o r e t i c a l s t u d i e s f o r s l u r r y s a w i n g ; a n d

( 3 ) , p r e l i m i n a r y d e s i g n c o n s i d e r a t i o n s f o r a l o a d - b a l a n c i n g d y n a m o m e t e r f o r t h e

w a f e r i n g mach ine . T h e f i r s t i n g o t s f o r w a f e r i n g h a v e b e e n p u r c h a s e d a n d

s l i c i n g e x p e r i m e n t s a r e u n d e r way.

T h e n e x t q u a r t e r ' s a c t i v i t i e s wi l l b e t o c o m p l e t e t h e s a w m o d i f i c a t i o n s

( inc lud ing t h e d y n a m o m e t e r ) , con t inue w i t h t h e s l i c i n g t e s t s a n d t h e o r e t i c a l

m o d e l i n g of a b r a s i v e w e a r , a n d i n i t i a t e d e v e l o p m e n t of a f e e d b a c k c o n t r o l s y s -

t e m t o r e g u l a t e cu t t i ng r a t e a n d f o r c e i n t e r a c t i o n s .

12. JPL I n - H o u s e T a s k 2 Ac t iv i ty

a. s i l i c o n ~ h a r a ' c . t e r i z a t i o n

S t r u c t u r a l a n d e l e c t r i c a l c h a r a c t e r i z a t i o n of m a t e r i a l s a m p l e s r e c e i v e d

f r o m t h e g r o w t h c o n t r a c t s ( s e e F ig . 4-8) wi l l b e p e r f o r m e d a t J P L . T h e b a s i s

f o r t h i s w o r k i s t h e de f in i t i on of c h a r a c t e r i z a t i o n t e c h n i q u e s wh ich m e e t t h e

ind iv idua l n e e d s of e a c h g r o w t h m e t h o d be ing d e v e l o p e d f o r h igh e f f i c i e n c y 5,

s o l a r -pho tovo l t a i c e n e r g y c o n v e r s i o n . C h a r a c t e r i z a t i o n t e s t s wi l l be r u n o n

ind iv idua l s a m p l e s u s i n g a t l e a s t the fo l lowing techniqu 'es :

S t r u c t u r a l C h a r a c t e r i z a t i o n .

X - r a y ( L a u e , t opography , D e b y e - S c h e r r e r , e tc . )

Scann ing e l e c t r o n m i c r o s c o p e ( r e f l e c t i 6 n . EBIC, EDAX

( i m p u r i t i e s ) ) .

O p t i c a l m i c r o s c o p y ( g r a i n s t r u c t u r e , d e f e c t s , s u r f a c e topo-

g r a p h y , e t c . ).

( 2 ) E l e c t r i c a l C h a r a c t e r i z a t i o n .

L i f e t i m e / d i f f u s i o n l e n g t h ( c a p a c i t i v e t i m e - d e l a y , s u r f a c e

photovol tage , e l e c t r o n vol tage) .

R e s i s t i v i t y ( s p r e a d i n g r e s i s t a n c e , f o u r - p o i n t p r o b e ) .

H a l l m e a s u r e m e n t : ; ( m o b i l i t y , c a r r i e r c o n c e n t r a t i o n ) .

" T h e r m a l " s p e c t r o s c o p y ( d e e p l e v e l t r a p s p e c t r o s c o p y ;

t h e r m a l l y s t i m u l a t e d c u r r e n t o r capa 'c i tance) .

O t h e r a n a l y t i c a l t e c h n i q u e s .w i l l b e a d d e d as d e e m e d n e c e s s a r y d u r i n g the p r o g r a m

(e . g . , t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y , e l e c t r o r e f l e c t a n c e , e t c . ) . R o u t i n e

c h a r a c t e r i z a t i o n of m a t e r i a l u s i n g s p e c i f i c t e c h n i q u e s w h i c h wi l l have b e e n d e t e r -

m i n e d t o b e m e a n i n g f u l f o r s p e c i f i c f o r m s of s i l i c o n ( e . g . , EBIC f o r e x a m i n i n g

g r a i n b o u n d a r i e s i n C V D l a y e r s ) w i l l be d o n e o n a c o n t r a c t b a s i s . T h i s w i l l a l l ow

f o r a l a r g e r s a m p l i n g of m a t e r i a l t h a n i s e i t h e r p o s s i b l e o r n e c e s s a r y d u r i n g the

i n i t i a l s t a g e s of e a c h g r o w t h c o n t r a c t .

TASK 3. ENCAPSULATION

The objective of the Encapsulation Task i s to develop and qualify a so la r

a r r a y module encapsulation system that has a demonstrated high reliabili ty and

a 20-year l ifetime expectancy in t e r r e s t r i a l environments, and is compatible

with the low-cost objectives of the Project ,

The s.cope of the Encapsulation Task includes developing the total sys t em

required to protect the optically and electr ical ly active elements of the a r r a y

f rom the degrading effects of t e r r e s t r i a l environments. The most difficult '

technical problem is expected to be developing the element of the encapsulation

sys tem for the sunlit side; this e lement must maintain high t ransparency for the

20-year l ifetime, while a l so providing protection f rom adver se environments.

In addition, significant technical problems a r e anticipated a t interfaces between

the encapsulation sys tem and the active a r r a y elements , and a t points where

the encapsulation sys tem is penetrated for external e lec t r ica l connections.

Selection of the element fo r the r e a r s ide (i. e. , the s ide opposite to the sunlit

s ide) of the encapsulation sys tem will be based pr imar i ly on cost, functional

requirements , and compatibility with the other pa r t s of the encapsulation sys tem

and with the s o l a r cells.

Depending on the final so la r a r r a y design implementation, the encapsula-

tion sys tem may a lso s e r v e other functions, e. g. , s t ruc tura l , e lectr ical , etc. - in addition to providing the essent ial protection.

At present , options a r e being kept open a s to what form tke t ransparent

e lement of the encapsulation sys tem will take - glass o r polymer sheet , polymer

f i lm, sprayable polymer, castable polymer, etc. The t ransparent e lement may

contain m o r e than one mater ia l and may be integral with the photovoltaic device,

o r be bonded to it, o r installed a s a window o r lens remote f rom the device.

A. T E C H N I C A L BACKGROUND

, Photovoltaic devices (solar cells ) and the associated electrical conductors

which together constitute solar a r r ays must be protected f rom exposure to the

environment. Exposure. would cause severe degradation of electrical performance

a s .a . resul t of corrosion, contamination, and mechanical damage.

In the' recent past, limited testing by JPL, NASA-LeRC, the U. S. Coast

-Guard, and solar ce l l manufacturers has clearly demonstrated that a r r ays must

be protected from the t e r r e s t r i a l environment and confirmed that spacecraft

a r r a y encapsulation sys tem designs.db not provide adequate protection. At the

s a m e t ime this t e s t experience has indicated that there a r e no known technical

b a r r i e r s to. designing encapsulation systems which will withstand longlife te r -

rest.ria1 exposure. To be acceptable, the encapsulation system must be compati-

ble wi th .10~-cos t , high-volume cell and a r r a y production methods.

.B. ORGANIZATION O F T H E TASK 3 E F F O R T

he approach to be used in achieving the overall objective of Task 3 will

include an appropriate combination of contractor and JPL in-house efforts. The

contractoF efforts will be carr ied out in two phases.. Within ?ach phase some

paral le l investigations will be conducted to assure timely accomplishment~of

objectives.

During -Phase I the contractor and the JPL in-house effort will consist

pr imari ly of systematic assessment and documentation of the following items:

• Potential candidate encapsulant materials based on past experience

with the encapsulation of silicon and other semiconductor devices

and on availa.ble information on the properties and stability of other

potential encapsulant materials and processes.

. • The environment which the encapsulation system must withstand..

The properties, environmental stability, and potential improve-

ment of potential encapsulant materials and processes.

• Test and analytical methods required. to evaluate performance and

predict and/or verify lifetime of encapsulant materials and encap-'

sulation systems.

4- 54

The resu l t s of this effort will then be used to specifically define additional

r e sea rch , development, and evaluation required during the subsequent phase.

Throughout the task atypical o r unique approaches to solving the

encapsulation sys tem problem will be sought and evaluated. F o r example,

Phase I will include an evaluation of the feasibility of utilizink electrosti*=icd!.v-

bonded integral g lass cove,rs a s par t of the encapsulation system.

In Phase 11, contractor and J P L in-house efforts will be conducted to

idcntify and/or develop one o r m o r e potentially suitable encapsulation sys t ems

and then verify the expected lifetime and reliability of these sys tems. Depending

on the resu l t s of Phase I, the contractor effort in this phase will include an

appropriate combination of some of the following i t ems :

Evaluate, develop, and/or modify tes t and analytical methods

and then validate these methods.

P e r f o r m mate r i a l s and interaction testing, using these methods to

evaluate candidates and demonstrate the reliability of encapsulation

sys tems.

Modify ma te r i a l s and processes used in encapsulation sys t ems

to improve automation and cost potential.

Modify potential encapsulation sys t em mate r i a l s to optimize

nlechanical, thermal and aging propert ies .

Implement r e s e a r c h and development on new encapsulant mater ia l s .

C. TASK 3 CONTRACTS

During the past year a contract with Battelle Columbus Laborator ies was

initiated to perform the following investigations :

1 ) Identification of candidate encapsulant mater ia l s based on a

review of ( a ) worldwide experience with encapsulation sys tems

for si l icon so la r cells and related devices and (b) the propert ies

of other available mater ia l s .

2 ) Def in i t i on of cond i t i ons f o r e v a l u a t i n g a n d qua l i fy ing e n c a p s u l a n t

m a t e r i a l s b a s e d o n a n a l y s i s of e n v i r o n m e n t a l i n f o r m a t i o n .

3 ) E v a l u a t i o n of t e s t m e t h o d s a n d d e t e r m i n a t i o n of p r o p e r t i e s of

c a n d i d a t e e n c a p s u l a n t m a t e r i a l s .

4 ) D e v e l o p m e n t of a c c e l e r a t e d a n d / o r a b b r e v i a t e d t e s t a n d a n a l y t i c a l

m e t h o d s f o r e v a l u a t i n g e n c a p s u l a t i o n s y s t e m s .

Add i t iona l c o n t r a c t o r s ( s e e T a b l e 4 - 4 ) h a v e been s e l e c t e d f o r t h e fo l lowing

a c t i v i t i e s , s c h e d u l e d t o beg in a p p r o x i m a t e l y A p r i l 1 , 1976:

D e B e l l a n d R icha rds0 .n . A s t u d y of t h e p r o p e r t i e s , p r o c e s s i n g ,

a n d a g i n g of p o l y m e r i c e n c a p s u l a n t m a t e r i a l s a n d t h e u s e of h igh -

s t r e s s t e s t i n g t o e v a l u a t e e n c a p s u l a t i o n s y s t e m s u t i l i z ing t h e s e

m a t e r i a l s .

R o c k w e l l I n t e r n a t i o n a l . An e x p e r i m e n t a l eva lua t ion of a c c e l e r a t e d /

a b b r e v i a t e d t e s t i n g m e t h o d s . T h i s wi l l c o m p l e m e n t the a n a l y t i c a l l y

o r i e n t e d e f f o r t a t Ba t t e l l e .

S i m u l a t i o n P h y s i c s , Inc. An e x a m i n a t i o n of t h e f e a s i b i l i t y of

u t i l i z i n g e l e c t r o s t a t i c a l l y - b o n d e d i n t e g r a l g l a s s c o v e r s a s t h e

t r a n s p a r e n t p a r t of t h e e n c a p s u l a t i o n sys t e rn .

T h e s e q u e n c e of t h e s e a c t i v i t i e s d u r i n g the P h a s e I i s shown in Fig. 4-18.

D u r i n g t h e f i r s t y e a r t h e on ly c o n t r a c t o r a c t i v i t i e s h a v e been in f i r s t two

s t u d i e s u n d e r the B a t t e l l e c o n t r a c t .

D. TASK 3 T E C H N I C A L ACTIVITY

1. Iden t i f i ca t ion of C a n d i d a t e E n c a p s u l a n t M a t e r i a l s - B a t t e l l e M e m o r i a l I n s t i t u t e

In t h i s s tudy , p o s s i b l e e n c a p s u l a t i o n s y s t e m r e q u i r e m e n t s w e r e r e v i e w e d

t o b r a c k e t t he p o s s i b l e r a n g e of r e q u i r e m e n t s f o r e n c a p s u l a n t m a t e r i a l s . S o m e

of t h e m o s t w ide ly u s e d e n c a p s u l a n t m a t e r i a l s w e r e ident i f ied . B a s e d on t h i s

i n f o r n l a t i o n a n d s e l e c t e d k e y w o r d i d e n t i f i e r s , a m a j o r l i t e r a t u r e s e a r c h h a s been

u n d e r t a k e n t o i den t i fy a n d r e t r i e v e r e l e v a n t i n f o r ~ n a t i o n . V a r i o u s s t a n d a r d

Table 4-4. Task 3 contractors

data bases , a s well a s seve ra l special bibliographies, have been interrogated.

The output of these sea rches has been reviewed by ma te r i a l s special is ts t o

identify and select documents for detailed review. T o date over 600 documents

have been identified and ordered; approximately 500 have been received and

200 reviewed.

r

Contractor

Battelle Memorial Institute C olurnbu s , Ohio

.C

DeBell and Richardson-" Enfield, Connecticut

.I.

R~ckwell-" , Anaheim, California .I. -,-

Simulation Physics Burlington, Massachuset ts

The magnitude of this review requi res that relevant data be extracted

Technology Area

Encapsulant experience and definition of environment; encapsulant t e s t methods and capabili t ies

1

Polymeric proper t ies and aging studies

~ c c e l e r a t e d ~ a b b r e v i a t e d testing .

Bonded integral g lass covers .

the f i r s t t ime through each document. At the same t ime the cu r ren t lack of

::: Contracts to be awarded in spring of 1976.

definition of the final a r r a y configuration (concentration, tracking, flat, etc. )

makes i t necessa ry to extract information on a broad spec t rum of mater ia l s .

ACTIVITY CY 75 CY 76 CY n 0 1 ~ 1 ~ J ~ F ~ M ~ A I M I J ~ J ~ A ~ S ~ O ~ N ~ D J IF IM/A IM[J IJ IA IS [O~N~D

PHASE I

DEFINITION OF CONDITIONS FOR I I

EVALUATING AND QUALIFYING I I ENCAPSULANT MATERIALS - BATTELLE I I

I I IDENTIFICATION OF CANDIDATE I ENCAPSULANT MATERIALS - BATTELLE

I I I

EVALUATION OF MATERIAL I I PROPERTIES AND TEST METHODS - I I BATTELLE I 1

STUDY OF PROPERTIES, PROCESSING, I I

AND A G I N G OF ENCAPSULANT I MATERIALS - DeBELL AND RICHARDSON I I I!_ ANALYSIS OF ACCELERATED/ I I ABBREVIATED TEST METHODS - BAllELLE - EXPERIMENTAL EVALUATION OF I I ACCELERATED/ABBREVIATED TEST I METHODS - ROCKWELL

I 1 I EVALUATION OF FEASIBILITY OF I I ELECTROSTATICALLY-BONDED GLASS COVERS - SIMULATION PHYSICS

I I I -I

PHASE II . IDENTIFICATION AND /OR DEVELOP- MENT OF ONE OR MORE POTENTIALLY

I I SUITABLE ENCAPSULATION SYSTEMS; I I VERIFY EXPECTED LIFETIME AND I I RELIABILITY I

I

Fig. 4 - 18. E n c a p s u l a t i o n t a s k s c h e d u l e

2. Conditions fo r Evaluating and Qualifying Encapsulant Mater ia l s - Battelle Memo r i a l Insti tute

I n this study, the expected frequency and. d ~ l r a t i o n of combinations of

environmental conditions during the 20-year a r r a y l i fe t ime will be used to

es tab l i sh t e s t conditions fo r the encapsulation sys tem. Since combinal ior~s of

conditions govern degradation, r a the r than individual e x t r e m e s o r dis t r ibut ions ,

h i s tor ica l r eco rd data f rom selected s i t e s a r e being ana1yze.d f o r the s imultaneous

occur rences . Twenty-year predictions will be developed using s tandard s ta t i s t i -

ca l mcthods.

The following nine s i t e s were selected because ( 1 ) they a r e represen ta t ive

of United States climatological ex t r emes and of geographical a r e a s where l a r g e

s c a l e photovoltaic installat ions might be used and ( 2 ) suitable data about them

i s available:

Phoenix

Albuquerque

Miami

Bismarck

Cleveland

Los Angeles l River s ide

Fa i rbanks

San Antonio o r Brownsville

Boston/Blue Hill

Semiar id , high insolation, modera t e alt i tude

Semiar id , high insolation, high alt i tude

Semitropical , mar ine , high humidity, high

ave rage t empera tu re

Low winter t empera tu re s , l a r g e seasona l

var ia t ions

Pollution, high humidity, snow, c l imat ic

mix tu re s

Pollution, high d iurna l t empera tu re var ia t ion

Low ave rage t empera tu re , ex t r eme

low t empera tu re s , l a r g e seasona l var ia t ions

W a r m cl imate , high insolation

Moderately cold, humid, fog, m a r i n e

Af t e r evaluating possible approaches, an exist ing p rog ram, the Stat is t ical

P r o g r a m f o r the Social Sciences (SPSS), was selected fo r u s e in the ana lys i s o f .

h i s tor ica l data. With this p rog ram the range of each cl imat ic 'condition

( t e m p e r a t u r e , , re la t ive humidity, etc. ) can be divided into selected intervals and

the s t a t i s t i c s of s imul taneous occu r rence (of var ious combinations and t r ans i -

t i ons ) de te rmined .

During the pas t yea r a t r i a l ana lys i s of one of the s i t e s was completed

f o r t e m p e r a t u r e , re la t ive humidity, wind velocity, and insolation. Of the 600

poss ib le combinations (with se lec ted in te rva ls ) , l e s s than 200 occu r red during

the 10 -yea r per iod analyzed. (This confi rmed the expectation that considerably

f e w e r than 600 should occu r , s ince c l imat ic conditions a r e not ' independent

va r i ab l e s . ) ~ u r t h e r m o r e , of a p re l imina ry s e t of 34 "abusive" conditions (i. e . ,

combinat ions of conditions that would be expected to cause above-average

degrada t ion of the encapsulat ion sys t em) , only 12 occu r red during the 10-year

per iod and r ep re sen ted approximately 5 - 1 /2 percent of the total t ime . Thus,

f o r th i s s i t e , the ( p r e l i m i n a r y ) "abusive" conditions would r ep re sen t slightly

o v e r 1 yea r dur ing the 20-year a r r a y l ifetime.

Since the p a r a m e t e r s , combinations, and in te rva ls can eas i ly be changed

f o r a va r i e ty of appl icat ions , the methodology that has been developed i s

expected to be useful to the P r o j e c t Analysis and Design and T e s t portions of

the P r o j e c t . To accommodate these act ivi t ies and to permi t analysis of addi-

t ional s i t e s (if requi red a f t e r the Battelle study of the conditions fo r evaluating

and qualifying encapsulant ma te r i a l s i s completed), p rog rams have been

o r d e r e d and J P L expe r t i s e will be established.

TASK 4. SOLAR ARRAY AUTOMATED ASSEMBLY -

The o v e r a l l ob jec t ive of T a s k 4 i s to u s e t h e r e s u l t s and e x p e r i e n c e

gained f r o m T a s k s 1 , 2, 3 , a n d 5 t o f a b r i c a t e s o l a r a r r a y s of 10% o r b e t t e r

c o n v e r s i o n ef f ic iency a t a p r i c e of $0. 50 /wa t t o r l e s s a t a r a t e of 500 m e g a -

w a t t s p e r y e a r with a 2 0 - y e a r o p e r a t i n g life. P h a s e I ( t echno logy a s s e s s m e n t )

o-f t h i s t a s k h a s t h e s e spec i f i c ob jec t ives : -

T o identify the r e q u i r e m e n t s f o r e c o n o m i c a l manufac tu r ing p r o c e s s e s

and fac i l i t i e s .

T o a s s e s s the c u r r e n t technology u s e d in the m a n u f a c t u r e and

a s s e m b l y p r o c e s s e s tha t could be app l i ed to s o l a r a r r a y s .

T o d e t e r m i n e the l e v e l of technology r e a d i n e s s to a c h i e v e the

high-volur .~-~e, l o w - c o s t production.

T o p r o p o s e p r o c e s s e s f o r development .

A. TECHNICAL BACKGROUND

The m a n u f a c t u r e of s o l a r c e l l s and a r r a y s i s p r e s e n t l y p e r f o r m e d by

ba tch p r o c e s s e s , p r i m a r i l y u n d e r the d i r e c t judgment and c o n t r o l of individual

o p e r a t o r s . E e c a u s e of the l i m i t e d quan t i t i e s of s o l a r c e l l s and a r r a y s p r o -

duced, c o s t s a r e high. T h e outs tanding s u c c e s s of the s e m i c o n d u c t o r i n d u s t r y

in applying au tomat ion s e r v e s a s a n i ? lus t ra t ion of the potent ia l ga ins f r o m high

volui-ne production. Automa.tion a c c o m p l i s h e s m o r e than the obvious reduc t ion in

the a m o u n t of l abor . In addi t ion , au tomat ion c a u s e s a u n i f o r m i t y of p r o c e s s i n g

which r e s u l t s in a m o r e u n i f o r m produc t and p r o d u c e s a c o r r e s p o n d i n g reduc t ion

in w a s t e d u e to r e j e c t e d product .

B. ORGANIZATION O F T H E TASK 4 E F F O R T

T a s k 3 i s d iv ided into f ive p h a s e s , o c c u r r i n g o v e r a 1 0 - y e a r p e r i o d of

tirise; the p h a s e s a r e :

I. T e c h n o l o g y a s s e s s m e n t .

11. P r o c e s s d e v e l o p m e n t .

111. F a c i l i t y a n d e q u i p m e n t des ign .

IV. E x p e r i m e n t a l p l a n t c o n s t r u c t i o n .

V. C o n v e r s i o n t o m a s s prod(1ction p l an t ( b y 1986).

F i g u r e 4 - 1 9 p r e s e n t s t h e o v e r a l l s c h e d u l e of t h i s t a s k a n d , f o r P h a s e s I a n d 11,

i d e n t i f i e s s o m e of t h e a c t i v i t i e s t h e s e p h a s e s wi l l inc lude .

M a n y o f t h e d e c i s i o n s t h a t m u s t be m a d e d u r i n g the T a s k 4 e f f o r t c a n n o t

bc n ~ a d e independen t ly . T h e y wi l l r e s u l t f r o m t r a d e - o f f s wi th o t h e r d e c i s i o n s

t h a t a r e m a d e both wi th in t h e t a s k a n d in con junc t ion wi th t h e o t h e r t a s k s of t h e

P r o j e c t . T a s k 4 h a s a p a r t i c u l a r l y l a r g e n u m b e r of i n t e r f a c e s , bo th wi th in a n d

o u t s i d e of t h e t a s k . F i g u r e 4 - 2 0 s h o w s the e l e m e n t s of T a s k 4 which r e q u i r e

d e c i s i o n s . E l e n ~ e n t s j o ined by a l i n e c o n s t i t u t e a n i n t e r f a c e . Any g iven e l e m e n t

c a n n o t b e t o t a l l y r e s o l v e d u n t i l i t s i n t e r f a c i n g e l e m e n t s ( c o n n e c t e d by l i n e s ) a r e

c o n s i d e r e d .

F i g u r e 4 - 2 0 i d e n t i f i e s t h e e l e m e n t s wi th t h e t a s k s i nvo lved by m e a n s of

s y m b o l s . S i n c e a l l of t h e e l e m e n t s shown invo lve T a s k 3 , e a c h h a s a c i r c l e

( t h e s y m b o l of T a s k 4) . E l e m e n t s wh ich a r e a l s o a c t i v i t i e s of o t h e r t a s k s h a v e

t h e a d d i t i o n a l t a s k s y m b o l s s u p e r i m p o s e d upon t h e c i r c l e s of T a s k 4. T h i s

m e a n s t h a t , in a d d i t i o n t o a l l t h e i n t e r f a c e s w i th o t h e r e l e m e n t s shown by l i n e s ,

t h e r e a r e s i g n i f i c a n t i n t e r f a c e s wi th the a c t i v i t i e s of t h e o t h e r t a s k s . T h i s

i n t e r f a c e d i a g r a m i s s u b j e c t t o upda t ing a s t h e P r o j e c t d e v e l o p s .

C. TASK 4 C O N T R A C T S

P h a s e I c o n t r a c t s h a v e b e e n a w a r d e d t o t h r e e c o n t r a c t o r s ( M o t o r o l a , RCA,

a n d T e x a s I n s t r u m e n t s ) t o p e r f o r m p a r a l l e l e f f o r t s ( T a b l e 4-5) . T h e th - r ee -

c o n t r a c t o r p a r a l l e l e f f o r t ph i lo sophy w a s s e l e c t e d t o o b t a i n t h e b r o a d e s t p o s s i b l e

v i e u , of r e c o m m e n d a t i o n s a n d c o n c l u s i o n s upon wh ich t o b a s e t h e c o n t r a c t u a l

e f f o r t s of P h a s e I1 ( F i g . 4 -19) . D u r i n g P h a s e I t h e s e c o n t r a c t o r s wi l l a d d r e s s

t h e a r e a s of de f in ing t h e r e q u i r e m e n t s f o r a u t o m a t i o n a s a p p l i c a b l e to s o l a r c e l l

m a n u f a c t u r i n g by e v a l u a t i o n of p r o c e s s e s which a r e now u s e d , a n d how t h e s e

ASSESSMENT FACTURING PROCESSES

Determine priori'ty for pro- c e s s development

Identify c o s t s of p ro- • Identify a r e a s where new c e i s i n g and test ing technology must be developed

Develop p r o c e s s e s and demon- .@ Develop c o s t effective s t r a t e technology read iness

approaches and identify options available

Identify the manufacturing

Identify cos t /manufac- t u r e obs tac les

Update conceptual design Conceptual solutions td developed Phase I these obs tac les

Update the c o s t analysis

Define the conceptual approach that a p p e a r s mos t c o s t effect ive for

F i g . 4-20 . Task 4 interfaces

4 - 64


p r o c e s s e s could be mod i f i ed f o r h i g h - v o l u m e , l o w - c o s t p roduc t ion . C o s t

a n a l y s e s wi l l b e p e r f o r m e d t o p r o v i d e e c o n o m i c g u i d e l i n e s t o m a i n t a i n a n

C o n t r a c t o r

M o t o r o l a , P h o e n i x , A r i z o n a

RCA, P r i n c e t o n , N e w J e r s e y

. T e x a s I n s t r u m e n t s , D a l l a s , T e x a s

S i m u l a t i o n P h y s i c s , Bur l ing ton , -~as-s=azc=hu=s=e t tcs

M i t r e C o r p o r a t i o n M c L e a n ; V i r g i n i a

.I, -0- _

T e x a s I n s t r u m e n t s D a l l a s , T e x a s

So la r e x Rockv i l l e , M a r y l a n d

.'I I-

o v e r a l l v i e w of LSSA P r o j e c t ob jec t ives .

T h e p r i n c i p a l a c t i v i t i e s a n d a v e n u e s of i n q u i r y t o be u n d e r t a k e n by the

C o n t r a c t t o be a w a r d e d i n S p r i n g of 1976.

T e c h n o l o g y A r e a

M a n u f a c t u r i n g p r o c e s s e s a s s e s s m e n t

M a n u f a c t u r i n g p r o c e s s e s a s s e s s m e n t .

manufacturing p r o c e s s e s a s s e s s m e n t

E l e c t r o n - b e a m s o l a r c e l l f a b r i c a t i o n

1

A r r a y t e s t eva lua t ion

C z o c h r a l s k i g r o w t h a n d w a f e r i n g i m p r o v e m e n t s

A r r a y t e s t eva lua t ion

..

t h r e e c o n t r a c t o r s i n P h a s e I wi l l be :

'1.. ., '.

C o n s i d e r a t i o n of t he v a r i o u s " f o r m s " of s i l i c o n s u c h a s r i bbon ,

s h e e t , w a f e r s , e tc . '

C o n s i d e r a t i o n of t h e po ten t i a l e f f e c t s upon m a n u f a c t u r i n g if c o n -

c e n t r a t o r s a r e u sed .

T r a d e - o f f s t u d i e s of n e w m a n u f a c t u r i n g technology.

a S t u d i e s of i n - p r o c e s s t e s t i n g r e q u i r e m e n t s and p r o c e d u r e s .

S t u d i e s of s o l a r c e l l i n t e r c o n n e c t i n g t e c h n o l o g y .

S t u d i e s of t h e a p p l i c a b i l i t y of s t a t e - o f - t h e - a r t t e c h n o l o g y t o

a n a u t o m a t e d f a c i l i t y .

D e t a i l e d c o s t a n a l y s e s of e a c h p o t e n t i a l m a n u f a c t u r i n g s t e p .

C o n c e p t u a l a p p r o a c h e s f o r p r o c e s s i n g m a t e r i a l s .

I n a d d i t i o n t h e c o n t r a c t o r s w i l l p a r t i c i p a t e i n t e c h n i c a l r e -v iews a n d a w o r k s h o p

t o b e h e l d a t J P L f o r r e p r e s e n t a t i v e s of g o v e r n m e n t , i n d u s t r y , a n d t h e i n t e r e s t e d .

a c a d e m i c c o r n m u n i t y .

S i m u l a t i o n P h y s i c s i s c a r r y i n g o u t a p r o g r a m t a d e v e l o p h i g h r a t e ,

e n e r g y e f f i c i e n t s o l a r c e l l p r o c e s s i n g t e c h n i q u e s b a s e d o n i o n i m p l a n t a t i o n a n d

t h e e l i m i n a t i o n of all c o n v e n t i o n a l t h e r m a l o p e r a t i o n s . M i t r e a n d S o l a r e x a r e

e v a l u a t i n g a r r a y t e s t m e t h o d s .

D. T A S K 4 T E C H N I C A L A C T I V I T Y

1. h 4 a n u f a c t u r i n g P r o c e s s e s A s s e s s r n e n t - M o t o r o l a , R C A , a n d T e x a s I n s t r u r n e n t s

D u r i n g t h e 1 s t T a s k I n t e g r a t i o n M e e t i n g , e a c h c o n t r a c t o r ( T a b l e 3 - 5 )

p r e s e n t e d t h e s p e c i f i c d e t a i l s of t h e i r i n d i v i d u a l a p p r o a c h e s t o t h e P h a s e I

e f f o r t . V e r y s h o r t l y e a c h w i l l p r e s e n t a d e t a i l e d p r o g r a m p lan , w h i c h is t h e

f i r s t c o n t r a c t u a l m i l e s t o n e . A l t h o u g h t h e b a s i c o b j e c t i v e i s t h e s a m e f o r a l l

t h r e e c o m p a n i e s , t h e r e a r e v a r i a t i o n s i n t h e i r i n d i v i d u a l a p p r o a c h e s . F o r

i n s t a n c e , T e x a s I n s t r u m e n t s i s p u t t i n g e m p h a s i s o n s i l i c o n s h e e t w h i c h c o t n e s

f r o m a m o d i f i e d C z o c h r a l s k i p r o c e s s . Motorola is b a s i n g t h e i r e f f o r t u p o n t h e

s t a t e d a v a i l a b i l i t y of l o w - c o s t s i l i c o n s h e e t b e i n g s i i p p l i e d by a n e w as y e t

u n d e v e l o p e d m e t h o d . R C A i s d e l i b e r a t e l y n o t f a v o r i n g a n y t y p e of s i l i c o n s o u r c e .

A n a n a l y s i s h a s b e e n m a d e of t h e c o s t s p r e s e n t l y i n v o l v e d i n t h e m a n u -

f a c t u r i n g of t e r r e s t r i a l s o l a r m o d u l e s . B y c o n s i d e r i n g t h e v a r i a t i o n s i n d e s i g n

a n d m a n u f a c t u r i n g m e t h o d s u s e d b y t h e d i f f e r e n t m a n u f a c t u r e r s , a c o m p o s i t e

d e s i g n a n d m e t h o d h a s b e e n d e v e l o p e d . T h i s m e t h o d is n o t f o l l o w e d b y a n y

c u r r e n t m a n u f a c t u r e r . a l t h o u g h e a c h s t e p is u s e d b y a t l e a s t o n e m a n u f a c t u r e r

a n d cou ld b e u s e d b y all. A s new m e t h o d s d e v e l o p i n t h e c o u r s e of t h i s p r o j e c t ,

t h e i n f luence upon c o s t c h a n g e m a y b e c a l c u l a t e d u s i n g t h i s s t a t e - o f - t h e - a r t

b a s i c mode l .

A t p r e s e n t , a p p r o x i m a t e l y 3 7 p e r c e n t of t h e c o s t of a m o d u l e i s d u e t o

t h e r e f i n e d s i l i c o n u s e d as r a w m a t e r i a l . f o r t h e s o l a r c e l l s . In c u r r e n t m e t h o d s , '

a b o u t f o u r - f i f t h s of t h i s s i l i c o n is w a s t e d d u r i n g p r o c e s s i n g . T h e m o s t w a s t e -

fu l p r o c e s s a t p r e s e n t i s t h e s l i c i n g of the s i l i c o n a f t e r i t h a s b e e n g r o w n i n t o - --- -- s i 1 e c r y s t~lli~gBt-s~-T=h-e=ke=~f=w=i=ddt-hhiisSa bboOu ttteeq9u a to t he s 1 i c e t h i c k n e s s ; c o n -

_I_-____ --- -

s e q u e n t l y , half t he m a t e r i a l w h i c h r e a c h e s t he s l i c i n g o p e r a t i o n i s w a s t e d a s

s m a l l p a r t i c l e s . F i g u r e 1 - 2 1 s h o w s t h e l o s s e e of s i l i c o n in g r a p h i c f o r m . T h e

ind iv idua l c a t e g o r i e s a r e o v e r l a p p e d t o i l l u s t r a t e t h e f a c t t h a t t h e p e r c e n t a g e s

l o s t a t e a c h o p e r a t i o n a p p l y on ly t o t he m a t e r i a l w h i c h h a s s u r v i v e d the p r e -

c e d i n g o p e r a t i o n s and t h e i r l o s s e s . T h e f i g u r e i l l u s t r a t e s , by p r o p o r t i o n a t e

a r e a s , the i n c r e a s e i n p r o d u c t s u r v i v a l if a s p e c i f i c l o s s i s e l i m i n a t e d .

T h e e c o n o m i c m o d e l of t he s t a t e - o f - t h e - a r t i n c l u d e s t h e c o s t s of m a t e r i a l s ,

l a b o r , s u p p l i e s , and i n t e r e s t and d e p r e c i a t i o r l on c a p i t a l e q u i p m e n t . T h e m a n u -

f a c t u r i n g p r o c e s s is b r o k e n up i n t o f o u r s u b p r o c e s s e s w h i c h c a n b e and p r e s e n t l y

i n s o m e c a s e s a re pe r fo ' rmed i n s e p a r a t e f a c i l i t i e s o r c o m p a n i e s . T h e s e s u b -

p r o c e s s e s are:

S ing le c r y s t a l i ngo t g r o w t h .

S i l i con s l i c i n g .

S o l a r c e l l m a n u f a c t u r e .

A s s e m b l y i n t o s o l a r pane l m o d u l e s .

-- F i g u r e 4 -22 s h o w s g r a p h i c a l l y t h e p r o p o r t i o n a t e c o s t s of t h e s e s u b p r o c e s s e s and

t h e i r b r e a k d o w n i n t o c o s t e l e m e n t s . O v e r h e a d h a s no t b e e n p r o p o r t i o n e d o r ,

i f you p r e f e r , t he o v e r h e a d h a s b e e n u n i f o r m l y a p p l i e d i n p r o p o r t i o n to t h e c o s t s .

P r e s e n t i n d u s t r y p r a c t i c e v a r i e s w i d e l y w i th r e g a r d t o o v e r h e a d and o v e r h e a d

d i s t r i b u t i o n a n d d e p e n d s upon s e v e r a l f a c t o r s , o n e of w h i c h i s w h e t h e r o r n o t '

o t h e r p r o d u c t s a r e p r o d u c e d i n t h e s a m e f a c i l i t y .

1975 STATE-OF-THE-ART 0.010 INCH THICK CELL

F i g . 4-21 . Silicon u t i l i z a t i o n

4 - 6 8

BASED ON S A ~ ~ I S * COhlPUTER PROGRAhl 1 ID3 I

* SOLAR ARRAY ~\ANUFACTURII\C INDUSTRY SlhlUlATION

Fig. 4 - 2 2 . Present state-of-the-art major manufacturing cost estimates

4-69

2. Elec t ron -Beam S o l a r Cel l Fabr ica t ion - Simulation Phys i c s

The object ive of th is p r o g r a m i s to develop high r a t e , energy efficient

s o l a r c e l l p roces s ing techniques based on ion implantat ion and the e l iminat ion

of a l l conventional t h e r m a l operat ions . Some specif ic object ives under this

p r o g r a m include:

No etching o r c leaning operat ions .

No batch p r o c e s s opera t ions .

No consumable m a t e r i a l s o the r than those of ce l l

components .

F i g u r e 4 - 2 3 shows the pr inc ipa l p a r t s of th is concept in d i ag ram form. The

p r o c e s s i s intended to be appl icable to a wide va r i e ty of s i l icon f o r m s . The

d i r e c t p rocess ing e n e r g y will be l e s s than 5 c a l o r i e s pe r s q u a r e cen t ime te r of

s o l a r c e l l a r e a . The total p rocess ing t ime f r o m s i l i con wafer to finished c e l l

will be l e s s than 30 seconds p e r s q u a r e cen t ime te r .

Ce l l s have been made using a p r o c e s s sequence which includes conventional

f u r n a c e heating. Ce l l s l ike t he se will be used a s s t anda rds f o r compar i son of

the pulsed- e l ec t ron-beam- p roces sed ce l l s . Some ce l l s have been made using

the e l e c t r o n beam ins tead of the furnace . These c e l l s did not have ant i ref lect ive

coa t ings on t hem but t he i r power generat ing capabi l i ty looks ve ry promising.

They have about t h r ee - fou r th s of the output of conventionally processed ce l l s and

a r e expected to be cons iderab ly be t t e r a f t e r ant i ref lect ive coating has been

applied.

During the next q u a r t e r the p r o g r a m will demons t r a t e the abil i ty to pro-

duce c e l l s without t h e r m a l p rocess ing . These c e l l s will have an efficiency of '

m o r e than 1 2 pe rcen t when the sun i s d i r ec t l y overhead (11 percen t efficiency

above the a tmosphe re ) . This work will include the identif ication of the opt imum

p a r a m e t e r s f o r the e lec t ron- b e a m annealing and s in te r ing p roces se s .

PULSED ELECTRON BEAM IMPLANT PULSED

JUNCTION ION ANNEAL AND FRONT

ELECTRON AR

IMPLANTATION THERMoMECH- CONTACT COATING BEAM SINTER ANICALSIZING EVAPORA- EVAPORA-

TION TION

ENTRANCE CHAMBER

bb I 4 C

- - - - --

- MOVING BELT WAFER HOLDER

t

VACUUM lNT ERLOCK

\ ' I

VACUUM EVAPORA- ELECTRON CHAMBER BEAM SlNTER

F i g . 4 - 2 3 . C o n c e p t of pu lsed p r o c e s s i n g f o r a u t o m a t e d cell produc t ion - Simula t ion P h y s i c s

, 3 . A r r a y T e s t Evahiation - ' ~ i t i e c o r ~ o r a t i ~ n . . -

. . 5

\ . , . ( '

, , . ' Work unde r this cont rac t h a s been concluded and- the final r epo r t i s in

4. A r r a y T e s t ~ v & l u a t i o n - ~ o l a r e x Corporat ion , .

.War-k unde r this cont rac t h a s b e e n con'ciuded and the final repor t h a s

been writ ten.

"- -

- P A R T V '

L A R G E - S C A L E P R O D U C T I O N TASK

T h e o b j e c t i v e of -the L a r g e - S c a l e P r o d u c t i o n T a s k ( L S P ) i s t o p r o d u c e

s i l i c o n s o l a r - a r r a y m o d u l e s t o s u p p o r t t h e E R D A Pho tovo l t a i c T e s t and D e m o n -

s t r a t i o n P r o j e c t i n p r o g r e s s i v e l y g r e a t e r q u a n t i t i e s and a t p r o g r e s s i v e l y l o w e r

c o s t .

T h e t a s k i s e x p e c t e d to b r i n g a b o u t i m p r o v e d d e s i g n s i n o r d e r t o ach i e \ - e

p r o d u c t i o n and c o s t i m p r o v e m e n t s . T h e w o r k w i l l . b e c a r r i e d oiit by p r o d u c t i o n

c o n t r a c t o r s , u n d e r P r o j e c t s p o n s o r s h i p . In add i t i on , w h e n e v e r and w h e r e v e r

p r a c t i c a l , t h i s t a s k w i l l a p p l y t echno logy i m p r o v e m e n t s a c h i e v e d i n o t h e r t a s k s

of t he P r o j e c t t o l a r g e - s c a l e p roduc t ion , p r i n c i p a l l y t o a i d i n t he a c h i e v e m e n t

of t a s k o b j e c t i v e s , bu t a l s o t o t e s t t h e n e w t echno logy i n t he c o n t e x t of a c t u a l

c o m m e r c i a l m a n u f a c t u r i n g c o n d i t i o n s .

P r i c e g o a l s f o r l a t e r m o d u l e p r o d u c t i o n are $5 p e r w a t t by F Y 1979, $2

p e r w a t t by 1981 , and $1 p e r w a t t by F Y 1983. In i t i a l q u a n t i t i e s to be ' p r o c u r e d

are 46 k i l o w a t t s of s t a t e - o f - t h e - a r t t e chno logy a r r a y m o d u l e s and 130 k i l o w a t t s

of a d v a n c e d - t e c h n o l o g y m o d u l e s ( a n t i c i p a t e d f o r d e l i v e r y i n F Y '1977) .

A . BACKGROUND

At t he i n c e p t i o n of t he LSSA p r o g r a m i n J a n u a r y 1975, t he s o l a r c e l l

m a n u f a c t u r i n g i n d u s t r y i n the United S t a t e s w a s i n d e c l i n e . A s o l a r c e l l p r o -

duc t ion c a p a c i t y of abou t 10 k i l o w a t t s p e r yeai- , f o r u s e i n s p a c e , had b e e n

r e a c h e d i n 1970 , a t the peak of t he NASA p r o g r a m . P r o d u c t i o n of s o l a r c e l l s

f o r s p a c e c r a f t h a s b e e n d e c l i n i n g s i n c e . B y c o m p a r i s o n , the p roduc t ion of c e l l s

f o r t e r r e s t r i a l a p p l i c a t i o n w a s v e r y low and i n c r e a s i n g a t a v e r y s l o w r a t e .

Only a f e w s m a l l c o m p a n i e s w e r e m a k i n g t e r r e s t r i a l m o d u l e s . T h e s e c o m p a n i e s

cou ld be c o n s i d e r e d a s o f f shoo t s of t he l a r g e U. S. s e m i c o n d u c t o r i n d u s t r y . S i l i -

c o n s o l a r c e l l s w e r e m a d e of s e m i c o n d u c t o r - g r a d e s i l i c o n w h i c h h a s b e e n

u n n e c e s s a r i l y e x p e n s i v e f o r l a r g e - s c a l e t e r r e s - t r i a l u s e . L a r g e v a r i a t i o n s i n '

a v a i l a b i l i t y a n d ' p r i c e . of p u r e . s i l i c o n h a s b e e n a f e a t u r e of t h e - d y n a m i c -.se.mi-

c o n d u c t o r i n d u s t r y . A s s m a l l c o n s u m e r s of s i l i c o n w i t h l i m i t e d r e s o u r c e $ , t h e

s m a l l e ; k o m p a n i e k i n t h e s o l a r c e l l i n d u s S t r y w e r e o c c a s i o n a l l y s u b j e c t t o s t r o n g . t

. e c o n o m i c f o r c k s r e s u l t i n g i n i n s t a b i l i t y .

T h e m a r k e t i n t e r v e n t i o n of ' t h e L a r g e - S c a l e P r o c u r e m e n t T a s k of t h e . L S S A i n t o t h i s i n d u s t r y s h o u l d p r o v i d e . a ' s t r o n g s t a b i l i z i n g f o r c e a n d l a r g e c o s t

Geduc t i o n s . An a s s u r e d a n d g r o w i n g m a r k e t f o r s o l a r m o d u l e s . s h o u l d

t h e i n c e n t i v e s f o r p r i v a t e c a p i t a l i n v e s t m e n t , p r o c e s s d e v e l o p m e n t , i m i p r o v e d

a v a i l a b i l i t y of r a w m a t e r i a l s a t lowe ' r p r i c e s , a n d l o w e r p r o d u c t c a s t s f r o m

i n c r e a s e d s c a l e of p r o d u c t i o n . * A d d i t i o n a l c o s t r e d u c t i o n s w i l l r e s u l t w h e n t h e . ,

. . . . d e v e l o p m e n t s - g e n e r a t e d b y t h e t e c h n o l o g y d e v e l b p m e n t t a s k s of t h e LSSA P r o j e c t

1

a r e i n c d r p o r a t e d i n t o t h e f i n a l p r o d u c t d u r i n g t h e c o m i n g decade , .

B . O R G A N I Z A T I O N O F T H E L S P E F F O R T

T h e L a r g e - S c a l e P r o d u c t i o n T a s k i n v o l v e s t h e p e r i o d i c p u r c h a s e of

i n c r e a s i n g q u a n t i t i e s of s o l a r a r r a y s a t d e c r e a s i n g u n i t p r i c e s and w i t h t h e

l a t e s t s t a t e - o f - t h e - a r t t e c h n o l o g y . T h e a r r a y s w i l l b e ' p r o c u r e d f r o m i n d u s t r y

o n a c o m m e r c i a l b a s i s t o m e e t p e r f o r m a n c e s p e c i f i c a t i o n s a n d e n v i r o n m e n t a l

r e q ~ ~ i r e m e n t s f o r u s e i n n u m e r o u s a n d d i v e r s e E R D A t e s t s a n d d e o m o n s t r a t i o n s .

M u l t i p l e c o n t r a c t s w i l l b e a w a r d e d t o i n d u s t r y t h r o u g h a c o m p e t i t i v e b i d -

d i n g p r o c e s s f o r t h e p r o d u c t i o n of l a r g e q u a n t i t i e s o f s o l a r c e l l m o d u l e s . .-A

s u m m a r y s c h e d u l e f o r t h e L S P T a s k i s s h o w n i n F i g . 5 - 1 ; a p l a n f o r t h e p r o - ,

c i ~ r e m e n t is g i v e n i n F i g . 5 - 2 . T h e c o n t r a c t s w i l l b e a w a r d e d o n e s s e n t i a l l y

a n a n n u a l b a s i s f o r p r o g r e s s i v e l y i n c r e a s i n g q u a n t i t i e s of h a r d w a r e . I t is I

a n t i c i p a t e d t h a t t h e p r o c u r e m e n t s c h e d u l e s h o w n i n F i g . 5 - 2 w i l l b e e m p l o y e d

a n d , as i n d i c a t e d , t w o m a j o r s u b t a s k a r e ' a s a r e i d e n t i f i e d f o r F Y 1 9 7 6 : ( 1 ) t h e

4 6 - k i l o w a t t p r o c u r e m e n t of s t a t e - o f - t e c h n o l o g y s o l a r - a r r a y m o d u l e s a n d ( 2 ) t h e %

1 3 0 - k i l o w a t t p r o c u r e m e n t o f a d v a n c e d - d e s i g n s o l a r - a r r a y m o d u l e s . B e g i n n i n g

w i t h t h e 1 3 0 - k i l o w a t t p r o c u r e m e n t , s m a l l b u s i n e s s c o n c e r n s w i l l b e s o l i c i t e d

t h r o u g h a - s e t - a s i d e p r o c e d u r e .

-

- . - PROTOTYPE - FAB. AND TEST

ESTIMATED WORK MILESTONE COMPLETION v INITIATED 1 1

MILESTO.NE RESCHEDULE V

MILESTONE COMPLETE

I

F i g . 5 - 1 Iaargr-Scal t : I . ' , - ! ! r i : : ~ t i o n Task s c h e d n l e

I . , FY76 FY77 ' i FY78 FY79 FY80 - \ F Y 8 1 ~ FY82 1 FY83 .

, " ' I i ' ' . . . . . I

I 1 ' '

, i : i . ; I :

1 ' I I . I _ I

i l 2 ' 3 4 1 IOG 30 ! ' 1 1 1 . '

1': 176 Lw-E:.T. $20/w '! I '

# j I ( . . i

\ , I

. ! 2. 420 kw-€Sf. $15/w ; .

, . . . . .

.. . i 1

- 3. 1520 kw-E5T.S10/w , ! , . 1010

; , . , . ! . . . .

i :

I 4. 2000 kw-EST. S5/w : , .

: . , - . ,

L . . . , , . . . . , . . ! .

, . . , . . . . a 51 3000 kw-EST. S3/w '

. ,

, . . . . :

. . : I . . .. . ! . , I :

6. 4000 kw-EST. S2/w ' I ! .I ( :

I ANNUAL DELIVERY (kw) I 46 1 130 1 315 I ' 6 1 5 I 1010 I 2& I ;KO. , I I I . NOTES:

, . , .

NUMER1CAL:VALUES ARE KILOWATTS

30 . . DELIVERY O F INDICATED QUANTITY

4 * DESIGN' R~QUIREMENTS DEFINED . , -, ,

A

F i g . 5 - 2 . ~ t i l a r a r r a y prociirc.n~t-111. plan

T h e a p p r o a c h of t he L a r g e - S c a l e P r o c u r e m e n t Ac t iv i t y w a s c h a n g e d i n

1975 . O r i g i n a l l y , s o l a r m o d u l e s w e r e to be pro \ - ided f o r a 2 0 0 - k i l o w a t t d e n i o n -

s t r a t i o n p lan t by 1977. I t w a s p lanned to p r e p a r e s o l a r - c e l l - g r a d e m a t e r i a l

s p e c i f i c a t i o n s l e a d i n g t o a p r o t o t y p e m o d u l e i n 1976 . P r o d u c t i o n c o n t r a c t s would

t h e n be l e t p rov id ing 200 k i l o w a t t s by mid--1977. An H F P p a c k a g e t o r the e a r l y

c o n t r a c t e f f o r t w a s p r e p a r e d . H o w e v e r , i n M a y 1975, th.e g o a l s w e r e c h a n g e d

and a c c e l e r a t e d . E R D A adop ted a n e a r l i e r d e m o n s t r a t i o n p lan . A s a r e s u l t of

r e s t r u c t u r i n g of t he E R D A d e m o n s t r a t i o n p lan , t he e x i s t i n g R F P w a s t e r m i n a t e d .

T w o R F P p a c k a g e s took i t s p l ace . T h e f i r s t w a s f o r 40 k i l o w a t t s o f \ s t a t e - o f -

t h e - a r t s o l a r m o d u l e s t a r g e t e d f o r d e l i v e r y s t a r t i n g i n F e b r u a r y 1976 and

e x t e n d i n g t h r o u g h J u l y 1976 . T h i s q u a n t i t y w a s r e v i s e d l a t e r t o 4 6 k i l o w a t t s

t o p r o v i d e s p a r e s . T h i s s c h e d u l e f o r d e l i v e r y t o t he de tmons t r a t i on p r o g r a u i w a s

v e r y t igh t . I t r e q u i r e d e x p e d i t e d p r o c u r e m e n t f r o m c o m p a n i e s w i th n i anu fac -

t u r i n g e x p e r i e n c e i n m o d u l e s of p r o v e n d e s i g n t o e n s u r e m e e t i n g d e l i v e r y s c h e d -

u l e s and p e r f o r m a n c e . In i t i a l l y , t he m o d u l e s p r o d u c e d would be u s e d i n a p p l i -

c a t i o n s requi ' r ing l ow p o w e r , s u c h as f o r i s o l a t e d i n s t a l l a t i o n s of t h e D e p a r t m e n t

of D e f e n s e . A l o n g e r r a n g e a p p l i c a t i o n w o ~ ~ l d be f o r s y s t e m s t e s t i n g f o r u l t i m a t e

t i e - i n of a photovol ta ic p o w e r s o u r c e t o a c o m m e r c i a l p o w e r g r i d .

T h e seco'nd R F P i s f o r 130 k i l o w a t t s and wi l l i n c o r p o r a t e d e s i g n c h a n g e s

to o b t a i n a , m o r e u n i f o r m d e s i g n p rov id ing g r e a t e r f l e x i b i l i t y i n t he d e n i o n s t r a -

t i o n s w h i l e e n c o u r a g i n g f u r t h e r c o s t r e d u c t i o n s . T h i s p r o c u r e m e n t w i l l be m o r e

wide ly s o l i c i t e d t o t h e m a n y c o m p a n i e s p r e s e n t l y p r e p a r i n g o r e x t e n d i n g m a n u -

f a c t u r i n g c a p a b i l i t y .

A n o t h e r m o d i f i c a t i o n to t he o r i g i n a l c o n c e p t i s a p lan t o t e s t s a m p l e s f r o m

a l l p r o c u r e m e n t b l o c k s . T h e R F P wi l l r e q u i r e t h e c o n t r a c t o r s to p e r f o r m c e r -

t a i n t e s t s . =. . T h e s e t e s t s w i l l b e r e p e a t e d at J P L f o r c o n f i r m a t i o n and o t h e r t e s t s

a ,dded. *, ,

A P r o j e c t D e s i g n a n d T e s t Ac t iv i t y w a s e s t a b l i s h e d i n t h e F a l l of 1975 f o r

t h e p u r p o s e of ( 1 ) a s s i s t i n g i n t he d e v e l o p m e n t of s o l a r a r r a y m o d u l e d e s i g n

s p e c i f i c a t i o n s and p e r f o r m a n c e c r i t e r i a and ( 2 ) a s s i s t i n g i n t e c h n i c a l i n t e r f a c i n g

wi th o t h e r E R D A p r o g r a m p a r t i c i p a n t s and c o o r d i n a t i n g i n - h o u s e d e s i g n and t e s t

a c t i v i t i e s .

9 .

T h e quali , ty e f f o r t w h i c h h a s b e e n i n i t i a t e d f o r t h e LSSA P r o j e c t p r ima . r i l y

- s u p p o r t s t h e p r o c u r ' e m e n t of s o l a r a r r . a y s and' h g s t h r e e m a i n o b j e c t i v e s i n a d d i - . t i d n t o t h e n o r m a l q u a t i t y t a s k s : ( 1 ) t o e v a l u a t e t h e s t a t e -o f - the . - a r - t of the . . /

., c o m m e r c i a l i n s p e c t i o n s y s t e m s p r e s e n t l y e m p l o y e d by the co 'mmerc ia l s o l a r

m o d u l i m a n u f a c t u r e r s , (2) t o e v a l u a t e and e s t a b l i s h m i n i m u m i n s p e c t i o n c r i t e r i a .

a n d w o r k m a n s h i p s t a n d a r d s f o r u s e on f u t u r e p r o c u r e m e . n t s , a n d ' ( 3 ) t o e s t a b l i s h

a n d i r r i p l e m e n t a p r o b l e m f a i l u r e r e p o r t i n g s y s t e m tha t w i l l y ie ld f i e ld u s e d a t a .

.Th,e R F P f o r t h e i n i t i a l p r o c u r e m e n t s p e c i f i e s t he t e m p e r - a t u r @ cy'cling and

h u m i d i t y r e q u i r e m e n t ' s t h a t t h e r n ~ o d u l e s m u s t m e e t . Qua l i fy ing t h e m o d u l e s to . -

t h e s e r e , q u i r e m e n t s is t h e r e s p o n s i b i l i t y of t he su ,pp l ie r : At J P L , s a m p l e

m o d u l e s w i l l be s u b j e c t e d t o t h e s e e n v i r o n m e n t s and t h e i r p e r f o r m a n c e w i l l be

e v a l u a t e d . In add i t i on , t h e m o d u l e s wiJl be e x p o s e d to o t h e r e n v i r o n m e n t s t-hey '

are l i k e l y t o m e e t d u r i n g t h e E R D A d e m o n s t r a t i o n p r o g r a m . T h e s e a r e h u m i d i t y -

f r e e z i n g , r a i n - h e a t , s a l t fog, . and f u n g u s . A l s o , s a m p l e s ' wi'll be s e t u p i n r a c k s

a t J P L as a f ie ld t e s t i n t h e ~ a s a d e n a , C a l i f o r n i a e n v i r o n m e n t .

T h e . 130 -k i lowa t t p r o c u r e m e n t R F P is n o t l i m i t e d t o s t a t - e - o f - t h e - a r t

m o d v l e s of e x i s t i n g d e s i g n . A c o n t r a c t p e r i o d f o r d e s i g n u p g r a d i n g i s p r6v ided . .

, and d e s i g n c r i t e r i a a re g i v e n . Module d e s i g n s a r e s p e c i f i e d t ha t w i l l f i t i n t o a

. 4 by 4 - f o o t s u b a r r a y . O t h e r R E P r e q u i r e m e n t s are :

- T h e

\

A m i n i m u m of 60 w a t t s of p o w e r b a s e d on the 4 by 4 - foo t a r r a y .

O n e h u n d r e d th , e rma l c y c l e s f r o m - 4 0 to 110" C .

F i v e t e m p e r a t u r e c y c l e s a t h i g h - r e l a t i v e humid i ty .

O n e - h u n d r e d c y c l i c a l a p p l i c a t i o n s of s t r u c t u r a l l o a d s .

/

s c h e d u l e f o r t h e 130- k i l owa t t p r o c u r e m e n t . i s :

D e t a i l e d d e s i g n d e v e l o p e d

P r o c e d u r e s and s p e c i f i c a t i o n

p r e p a r e d

F : a b r i c a t i o n a n d t e s t of

p ro to type . m o d u l e s

, ,Module p r o d u c t i o n 1

2 m o n t h s f r o m c o n t r a c t s t a ' r t

2 m o n t h s f r o m c o n t r a c t s t a r t

6 m o n t h s f r o m , c o n t r a c t s t a r t

J a n u a r y 1977: 100 k i l o w a t t s

F e b r u a r y 1977 : 30 ki low,at ts

!

C . L S P T E C H N I C A L A C T I V I T Y -

. 1 . L a r g e - S c a l e P r o c u r e m e n t A c t i v i t y

A s u r v e y m a d e e a r l y i n t h e L S S A P r o j e c t s h o w e d t h a t t h e r e w a s no

s t a n d a r d i z a t i o n of s o l a r m o d u l e s . A l s o , t h e r e w e r e s i g n i f i c a n t c o n f l i c t i n g

c l a i m s c o n c e r n i n g m o d u l e p e r f o r m a n c e a n d p r i c e w h i c h n e e d e d t o b e u n d e r -

, s t o o d . l ' h e r e w a s a n u r g e n t n e e d f o r a s t a n d a r d m e t h o d of m o d u l e p e r f o r m a n c e

e v a l u a t i o n . I t is i n t e n d e d t h a t t h e L a r g e - S c a l e P r o d u c t i o n A c t i v i t y b e b e n e f i c i a l

i n p r o v i d i n g g u i d a n c e a n d b e a s t a b i l i z i n g f o r c e i n t h e s e a r e a s .

'The L a r g e - S c a l e P r o c o r e r r ~ e n t A c t i v i t y w a s e s s e n t i a l l y o n s c h e d u l e t h r o t ~ g h

J a n u a r y 1 9 7 6 . A l l c o n t r a c t s f o r t h e -16-ki lowat t p r o c u r e m e n t had b e e n a w a r d e d

by J a n l i a r y 1 9 7 6 . T h e f o l l o w i n g f i v e c o m p a n i e s w e r e s e l e c t e d t o p r o d t ~ c e t h e

i n d i c a t e d s t a t e d q u a n t i t i e s of s o l a r a r r a y ( s e e F r o n t i s p i e c e ) :

K i l o w a t t s

M7 I n t e r n a t i o n a l 3

S e n s o r T e c h n o l o g y 8

1 0 S p e c t r o l a b

S o l a r P o w e r 1 5

S o l a r e x 1 0

T h e a r r i v a l a t J'PL of t h e f i r s t s a m p l e m o d u l e s f o r t e s t w a s d e l a y e d . T h e

i n i t i a l t e s t i n g of t h e s e e a r l y m o d u l e s h a s u n c o v e r e d p r o b l e m s w i t h t h e e n c a p s u -

l a n t . S o l u t i o n s t o t h e s e p r o b l e m s a r e b e i n g i n v e s t i g a t e d w i t h t h e c o n t r a c t o r s .

T h e m o d u l e d e l i v e r y s c h e d u l e h a s b e e n d e l a y e d a f e w w e e k s . P r o d u c t i o n of

m o d u l e s w i l l c o m m e n c e w h e n t h e s e p r o b l e m s a r e r e s o l v e d . T h e p r o c u r e m e n t

w i l l b e c o m p l e t e d i n 6 m o n t h s .

T h e R F P f o r t h e 1 3 0 - k i l o w a t t p r o c u r e m e n t w a s r e l e a s e d t o i n d u s t r y ' o n

D e c e m b e r 15, 1 9 7 5 . Of t h e 130 k i l o w a t t s , 40 k i l o w a t t s a r e s e t a s i d e f o r p r o -

c u r e m e n t f r o m s m a l l b u s i n e s s a n d 9 0 k i l o w a t t s f r o m l a r g e b u s i n e s s w i t h s t i p u -

l a t i o n t h a t s m a l l b u s i n e s s cAn bid o h t h e t o t a l q u a n t i t y of 1 3 0 k i l o w a t t s . P r o p o s a l s

' t

i n r e s p o n s e t o the R F P w e r e r e c e i v e d F e b r u a r y 2,- 1976 and a r e i n the eva lua t ion

p r o c e s s . I t is e x p e c t e d tha t c o n t r a c t s t a r t i n g d a t e s f o r the 130-ki lowat t p r o c u r e -

m e n t wi l l be i n J u l y 1976. A t e s t plan f o r e n v i r o n m e n t a l t e s t of the s a m p l e , I

m o d u l e s h a s been c o m p l e t e d . Deta i led t e s t p r o c e d u r e s f o r s e t A modules ( t e m -

p e r a t u r e c y c l i n g and humid i ty t e s t ) have been c o m p l e t e d a l s o . E q u i p m e n t and

l a b o r a t o r y a r e a s have b e e n s e t up f o r t h e s e e n v i r o n m e n t a l e x p o s u r e s . A module

e v a l u a t i o n a r e a i s r e a d y . E leckr ica l eva lua t ion wi l l be done wi th the L a r g e r A r e a \

P u l s e d S o l a r s i m u l a t o r t h a t h a s r e c e n t l y b e e n i n s t a l l e d and checked .bu t . P h y s i c a l

inspect ionyand module c o n t r o l ' a r e a s have b e e n m a d e r e a d y . P r e p a r a t i o n f o r .

h u m i d i t y - f r e e i i n g and f u n i u s t e s t i n g Should be c o m p l e t e d by the t i m e the s a m p l e

. - m d u l e s a r r i v e . , Sa l t fog e q u i p m e n t and r a i n - h e a t t e s t i n g equ ipment should be

r e a d y by A p r i l 1, 19761 . ,

.- r

, . 2 . Des ign and T e s t Activi ty I .

P r i m a r y d e s i g n and t e s t t echn ica l a c c o m p l i s h m e n t s . r e l a t e t o the develop-

m e n t of s o l a r a r r a y d e s i g n r e q u i r e m e n t s and p e r f o r m a n c e t e s t c r i t e r i a . Specif ic

\ a c t i v i t i e s h a v e c e n t e r e d i n the fol lowing f ive areas: a r r a y conf igura t ion ; module ,

elecfr . ica1 p e r f o r & a n c e ; s o l a r c e l l , module , and s u b a r r a y i n t e r c o n n e c t i o n s ;

t h e r m a l d e s i g n ; and s t r u c t u r a l d e s i g n .

/

, A r r a y conf igura t ion inves t i ,ga t ions have b e e n conducted to e v a l u a t e module1

,- s u b a r r a y g e o m e t r i c r e q u i r e m e n t s , ' s o l a r c e l l packing ef f ic iency v e r s u s module

g e o m e t r y and c e l l s i z e , m o d u l e ground handl,ing r e q u i r e m e n t s , and ins ta l l a t ion r

and r e m o v a l , and s i m i l a r cons ide;a t ions . S a m p l e 4 by 4-foot s u b a r r a y s t r u c - ,

t ,ures and v a r i o u s m o c k u p module conf igura t ions have bee,n des igned and f a b r i -

c a t e d t o a l low t x p e r i m e n t a l asseSss .ment of conf igura t iona l and handling c h a r a c -

. t e r i s t i c s . -

' M o d u l e e l e c t r i c a l p e r f o r m a n c e .ac t iv i ty i s c e n t e r e d on m o d u l e l a r r a y

e l e c t r i c a l , . r e q u i r e m e n t s i n the a r e a s of s e r i i s l p a r a l l e l i n g c o n s i d e r a t i o n s in -

eluding a n a l y s i s of "hot spo t " e f fec t s and e f f e c l s o f m i s o l a t c h i n module a,nd

. c e l l e l e c t r i c a l c h a r a c t e r i s t i c s and o p e r a t i n g t e m p e r a t u r e s .

S o l a r ce l l , module, and s u b a r r a y e l e c t r i c a l i n t e r c o n n e c t i o n s are a n

i m p o r t a n t e l e m e n t of s o l a r a r r a y l i f e t i m e and re l i ab i l i ty . V a r i o u s module e l e c -

t r i c a l t e r m i n a t i o n s c h e m e s a r e c u r r e n t l y being f a b r i c a t e d i n p r e p a r a t i o n f o r

e n v i r o n m e n t a l t e s t ing evaluat ion and the g e n e r a t i o n of f u t u r e e l e c t r i c a l t e r m i n a -

t ion r e q u i r e m e n t s .

T h e r m a l d e s i g n ac t iv i ty inc ludes a n a l y s i s and t e s t ing d i r e c t e d a t under -

s t and ing m o d u l e / s o l a r a r r a y t h e r m a l p e r f o r m a n c e c o n s i d e r a t i o n s , t h e r m a l

d e s i g n c r i t e r i a , and t e s t me thods . T h e r m a l _ a n a l y s e s and t e s t s of v a r i o u s s o l a r

a r r a y module d e s i g n s have been conducted and m e a s u r e m e n t s have been m a d e to

a c c u r a t e l y d e t e r m i n e t h e r m a l photo-optical p r o p e r t i e s . E x p e r i m e n t s conducted

d u r i n g p r e l i m i n a r y t h e r m a l t e s t s ind ica te tha t module open c i r c u i t vol tage ( V ) OC

a n d s h o r t c i r c u i t c u r r e n t ( I ) m a y proGide a r e l i a b l e m e a s u r e of s o l a r c e l l S C

t e m p e r a t u r e when used toge the r i n the fol lowing re la t ionsh ip :

C e l l t e m p e r a t u r e = a + bV + cloglO(Isc) OC

Cons tan t s a , b, and c a r e c a l i b r a t e d d u r i n g t e s t s i n which t h e r m a l g r a d i e n t s

within the module a r e min imized o r e l i m i n a t e d . Such a n i n d i r e c t m e a s u r e m e n t

technique i s v e r y d e s i r a b l e b e c a u s e of the g e n e r a l diff icul ty i n a t t ach ing t h e r m o -

coup les d i r e c t l y to encapsu la ted s o l a r c e l l s .

S t r u c t u r a l des ign ac t iv i ty inc ludes a n a l y s i s and t e s t ing d i r e c t e d a t under-

s tanding m o d u l e l s u b a r r a y s t r u c t u r a l loading c r i t e r i a and t e s t ms thods . An

au tomat ic ' module s t r u c t u r a l loading m a c h i n e h a s been des igned and f a b r i c a t i o n

in i t i a t ed . F u t u r e t e s t s wi l l inc lude d e t e r m i n a t i o n of the l o a d - c a r r y i n g capabili.ty

and load-cyc le - l i f e c h a r a c t e r i s t i c s of v a r i o u s module d e s i g n s .

In addi t ion to the in -house inves t iga t ions d e s c r i b e d above, c l o s e l i a i s o n

is mainta ined wi th the NASA L e w i s R e s e a r c h C e n t e r d e m o n s t r a t i o n ac t iv i t i e s ,

the Sandia L a b o r a t o r i e s s y s t e m a n a l y s i s ac t iv i t i e s , and the d e m o n s t r a t i o n a c t i -

v i t i e s of the D e p a r t m e n t of Defense . Design r e q u i r e m e n t s e m a n a t i n g f r o m t h e s e

s t u d i e s a r e i n c o r p o r a t e d in to the s o l a r a r r a y : equ i rements ac t iv i ty on a con-

t inuous b a s i s . D i s c u s s i o n s wi th module m a n u f a c t u r e r s and potential and pas t

pho'tovoltaic u s e r s a l s o provide valuable i n f o r m a t i o n which i s i n c o r p o r a t e d in to

s o l a r a r r a y r e q u i r e m e n t s .

3 . Qua l i ty A s s u r a n c e Activi ty

- T h e p r e l i m i n a r y e v a l u a t i o n of c o m m e r c i a l s o l a r m o d u l e m a n u f a c t u r e r s

c o m m e r c i a l i n s p e c t i o n s y s t e m s w a s u n d e r t a k e n d u r i n g the r e v i e w of the 40 kW

p r o p o s a l and on s u b s e q u e n t s i t e v i s i t s . I t w a s found t h a t the i n s p e c t i o n s y s t e m s

r a n g e d f r o m v e r y m i n i m a l s y s t e m s t o o n e s a l m o s t e q u a l to t h o s e f o r a e r o s p a c e

a p p l i c a t i o n s .

T w o s o l a r m o d u l e s f r o m e a c h of s i x c o m m e r c i a l s u p p l i e r s w e r e p r o c u r e d

a n d i n s p e c t e d i n t h e " a s r e c e i v e d ' ' cond i t i on to d e t e r m i n e the p r e s e n t s t a t e - o f -

t h e - a r t - w o r k m a n s h i p ' s t a n d a r d s u t i l i zed by e a c h of the s u p p l i e r s . T h e w o r k - -

m a n s h i p e v i d e n c e d by the p a n e l s p a r a l l e l e d the r e s u l t s found i n r e l a t i o n t o ' t h e

i n s p e c t i o n s y s t e m s . S o m e m o d u l e s had v e r y l i t t l e u n i f o r m i t y i n w o r k m a n s h i p

a n d o t h e r p a n e l s w e r e of a l m o s t a e r o s p a c e qua l i t y .

T h e r e s u l t s of t h e i n s p e c t i o n s y s t e m e v a l u a t i o n s a n d . t h e s o l a r m o d u l e

i n s p e c t i o n , both t h e i n i t i a l two p a n e l s and the s u b s e q u e n t i n s p e c t i o n s a t e a c h of

- t h e s u p p l i ~ r s wi l l b e u s e d t o f o r m u l a t e m i n i m u m i n s p e c t i o n c r i t e r i a and w o r k -

m a n s h i p +. s t a n d a r d s f o r f u t u r e p r o c u r e m e n t s so. t ha t e v e n t u a l l y s o l a r m o d u l e ' h a r d w a r e of u n i f o r m q u a l i t y f r o m s u p p l i e r to s u p p l i e r c a n be ob ta ined .

A p r o b l e m / f a i l u r e r e p o r t i n g s y s t e m - hasv .been~ devekoped- t h a t h a s two .ma in

db jec t i \ l e s : ( 1 ) to o b t a i n f ie ld d a t a f r o m s i t e i n s t a l l a t i o n s , i n r e a l t i m e , o n the . -

s o l a r . m o d u l e s p r o d u c e d d u r i n g the 40 k i lowa t t and s u b s e q u e n t p r o c u r e m e n t s and

( 2 ) t o p r o \ ~ i d e a d a t a bank w h e r e the i n f o r m a t i o n c a n be s t o r e d and e a s i l y obta ined

w h e n r e q u i r e d . I t i s i n t e n d e d t o u s e the d a t a bank to co r . r e l a t e i n f o r m a t i o n o n

f i e ld p r o b l e m s o r f a i l u r e s w i t h the i n s p e c t i o n r e p o r t s of t he m o d u l e s ob ta ined

d u r i n g m a n u f a c t u r e a t e a c h of the s u p p l i e r s . In t h i s w a y the i n s p e c t i o n c r i t e r i a

a n d w o r k m a n s h i p s t a n d a r d s e m p l o y e d by e a c h of t he s u p p l i e r s of c o m m e r c i a l -

s o l a r m o d u l e ? c a n be e v a l u a t e d f o r t h e i r a p p l i c a b i l i t y and s u b s e q u e n t l y changed ,

w h e r e n e c e s s a r y . T h e i n f o r m a t i o n w i l l a l s o a s s i s t i n p r e p a r a t i o n of the m i n i -

m u m c r i t e r i a and s t a n d a r d s p r e v i o u s l y d i s c u s s e d .

\

4 . F u t u r e A c t i v i t i e s

1 ) F u t u r e a c t i v i t i e s w i l l a s s i s t i n t he d e v e l o p m e n t of m o d u l e c o n -

f i g u r a t i o n r e q u i r e m e n t s w i t h e m p h a s i s on r e q u i r e m e n t d i f f e r e n c e s

a s s o c i a t e d wi th t h e g e n e r a l s o l a r a r r a y a p p l i c a t i o n s :

U n i \ - e r s a l l o w - c o s t a r r a y s t yp i ca l of the m a j o r i t y of

p r e s e n t d a y a p p l i c a t i o n s .

R e s i d e n t i a l a r r a y s w h i c h i n c o r p o r a t e a r c h i t e c t u r a l f e a t u r e s

a p p r o p r i a t e f o r r e s i d e n t i a l d w e l l i n g s .

L igh twe igh t a r r a y s w h i c h a d d r e s s n e e d s f o r c o m p a c t n e s s

and mob i l i t y t y p i c a l of m i l i t a r y and s i m i l a r a p p l i c a t i o n s .

2) P r e p a r a t i o n s a r e be ing m a d e f o r r e c e i v i n g s a m p l e m o d u l k s , i n s p e c t -

ing , e l e c t r i c a l eval. tration, and e n \ - i r o n m e n t a l t e s t s . D e s i g n s of the

f i e l d t e s t and r a i n - h e a t t e s t a re u n d e r w a y . T h e t e s t e q u i p m e n t w i l l

t h e n b e f a b r i c a t e d and i n s t a l l e d . T e s t p r o c e d u r e s w i l l be g e n e r a t e d

f o r t h e s e p lus t h e fungus , s a l t fog , and h u m i d i t y - f r e e z i n g t e s t s . 7

F u t u r e a c t i v i t i e s w i l l s t u d y r e q u i r e m e n t s f o r l i gh tn ing p r o t e c t i o n and

d i o d e c i r c u i t p r o t e c t i o n wi th in s o l a r a r . r ay m o d u l e s .

3) C o n t r a c t m o n i t o r i n g a c t i l ~ i t y s t a r t e d i n J a n u a r y and wi l l b e i n c r e a s e d

i n t he nex t q u a r t e r . P l a n t \ - i s i t s w i l l be m a d e t o c h e c k p r o g r e s s

and a s s i s t i n p e r f o r m a n c e e v a l u a t i o n and s t a n d a r d i z a t i o n . In- h o u s e

m o n i t o r i n g ac t i \ - i t i e s i n c l u d e l i a i s o n b e t w e e n c o n t r a c t o r s , J P L and

L e R C . An a c c o u n t a b i l i t y s y s t e m f o r a l l m o d u l e s w i l l be s e t up o v e r

t h e n e x t s e v e r a l m o n t h s .

4) I n t e n s i v e p r o p o s a l e v a l u a t i o n a c t i v i t y w i l l be c a r r i e d o n f o r the 130-

k i l o w a t t p r o c u r e m e n t w i th a t a r g e t d a t e f o r c o m p l e t i o n by A p r i l 1976.

C o m p l e t i o n of c o n t r a c t n e g o t i a t i o n s and r e l e a s e s a r e s c h e d u l e d f o r /

J u n e 1976 .

5) Preparat ion of t he 150 -k i lowa t t R F P f o r 1977 w i l l r e c e i v e i n c r e a s i n g

a t t e n t i o n w i t h a t a r g e t r e l e a s e d a t e of e a r l y 1977 . T e c h n o l o g i c a l

a n d a d m i n i s t r a t i v e i m p r o v e m e n t s r e s u l t i n g f r o m the e x p e r i e n c e of

t h e f i r s t two p r o c u r e m e n t s w i l l b e i n c o r p o r a t e d i n t h i s R F P .

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