monoPolyTM Technology Platform: Implementation of

1SERIS is a research institute at the National University of Singapore (NUS). SERIS is supported by the National University of Singapore (NUS), the National Research Foundation Singapore (NRF) and the Singapore Economic Development Board (EDB).

Note: You can replace this image to match the theme of your presentation

Shubham DUTTAGUPTA, Naomi NANDAKUMAR, John RODRIGUEZSolar Energy Research Institute of Singapore (SERIS), NUS, Singapore

SNEC 2020: 14th Global Advanced PV Technology Conference7-9 Aug 2020

monoPolyTM Technology Platform: Implementation of Passivated Contacts in PERC/T Production Lines


Introduction of the Speakerq Dr Shubham Duttagupta is the Deputy Director of the Silicon Solar

Cells & Modules (SSCM) Cluster at SERIS and also heads the Advanced Silicon Solar Cells Group inside the SSCM Cluster.

q The scientific-technical aim of the research cluster is to develop technologies that target the limit of silicon based single-junction cell & module efficiency while keeping the overall process cost-competitive.

q The research cluster collaborates with several solar cell/module, equipment, automation and material companies to jointly develop next-generation processes.

q Dr Duttagupta’s PhD research focused on the development of advanced multifunctional passivation materials required for high-efficiency crystalline silicon wafer solar cells.

q Recently his research team has won an APVIA Technological Achievement Award at SNEC 2019 and a Research Partner Award at World Solar Congress (WSC) 2019 – both for the monoPoly© high-efficiency silicon solar cell technology.


About SERISSolar Energy Research Institute of Singapore

q National Lab founded at NUS in 2008; supported by NRF & EDB

q Focuses on applied solar energy research(solar cells, PV modules, PV systems)

q > 160 staff & adjunct researchers; state-of-the-art labs, ISO certified (9001, 17025)

q Close collaborations with industry & government agencies

q Strategic priorities: To develop & commercialise solar technologies suited for urban and tropical applications, and support industry development and the energy transformation towards higher solar adoption

SERIS

Solar cells

PV modules

Solar PV

systems


Main R&D areas of SERIS

Solar cells:§ Silicon solar cells (various

cell architectures)§ Perovskite/silicon tandem

solar cells§ Characterisation &

simulation

Solar PV systems:§ System technologies,

incl. Floating solar§ PV grid integration§ Solar potential & energy

meteorology§ Urban Solar, incl. BIPV§ Quality assurance of PV systems

PV modules:§ Module development § Module testing (indoor &

outdoor)§ Characterisation & simulation§ Module reliability studies,

failure root cause analysis§ Module recycling


Outlineq Motivation

q PERC innovation & evolution q Need for and transition to passivated contact

q SERIS’ bifacial monoPoly™ cell technology

q Strategic vision for evolutionary pathq The monoPolyTM process/platform

q monoPolyTM cells using inline single-side PECVD deposition

Ø monoPolyTM process flowØ monoPolyTM layer propertiesØ I-V results for thinner n+:poly-Si

q Late News: initial results of biPolyTM cells

q Summary


PERC innovation to industrialisationPassivated Emitter & Rear Cell

~25% efficiency, late 1980s/1990s Industrial Process, 2008 – 2010

~680 mV, ~22%

TEX

ANNEAL

DIF

WET

PRINT

r + f.PECVD

FIRING

Stabilisation

LASER

Blakers, Zhao, Green et al. (UNSW)

New ProcessOptimisedKnobloch, Aberle et al. (Fraunhofer ISE)


PERC/T Cells[pPERC]

680 mV, ~22.5% 670 mV, ~22%

TEX

WET

DIFF

DIF

WET

PRINT

r + f.PECVD

FIRING

[nPERT] q PERC: Passivated Emitter & Rear Cell

q Capacity (today): ~90 GW [1]

q Cost (today): $0.24 – 0.28/Wp [1]

q PERC cell efficiency:

Ø 5 – 12 BB eff. PERC cells today are at 22.5 ± 0.5% (best bin, golden line)

Ø May or may not include selective emitter

Ø Record cell reported in R&D: 24% (press-release [2])

TEX

ANNEAL

DIF

WET

PRINT

r + f.PECVD

FIRING

Stabilisation

[1] ITRPV 2019, [2] LONGi press release (2018/19)


PERC – with Passivated ContactsBeyond standard PERC/PERT

Ø Passivated Contacts: Voc of ≥ 700 mV due to lower surface recombination losses (J0,metal + J0,passivated)

REQUIREMENTØHigh-throughput, low-cost,

established process techniques for passivated contacts

Ø Easy upgrades to existing PERC/PERT production lines

Ø Thermally stable screen-printed, fire-through metallization

ITRPV 2020


q Best efficiency on small-area cells: 25.7% (TOPCon), 26.1% (ISFH IBC-POLO)q Industry soon catching up on large-area cells: 24.79% (JinkoSolar) q Still significant gaps for the transfer of technology to mass production!

Poly-Si/SiOx passivated contacts


PERC/PERT

SINGLE-SIDE PASSIVATED CONTACT

Vision “beyond PERC/T”

Ø Based on classical PERC/PERT device structure

Ø Low absorbing poly-Si at either-side

Ø Voc at 680 mV today

Ø Voc of >700 mV is not easy

22.5%


PERC/PERT

SINGLE-SIDE PASSIVATED CONTACTØ Based on classical

PERC/PERT device structure




22%

24.5%



PERC/PERT




Ø PECVD method to increase bifaciality and very high throughput





PERC/PERT




Ø PECVD method to increase bifaciality and very high throughput



PERC

Upgraded PERC



PERC/PERT



Ø Low absorbing poly-Si at either side

Ø Ultra high deposition speed (2 nm/s)



PERT

Vision beyond “standard” PERC/T

Upgraded PERT / TOPCon


Industrial Platform: monoPolyTM

Passivated Emitter & Rear Cell~25%, late1980s/1990s

Industrial platform ~2017

710 mV, ~23.5%

TEX

DIF

WET

PRINT

r. n-doped layer

FIRING

Anneal

r. + f. Passivation/ARC

Feldmann, Glunz et al. (Fraunhofer-ISE)

TOPCon~25.7% efficiency, ~2013

New ProcessOptimised

Ø Screen-printing &Ø High-T fired contactsØ Bifacial cell Ø Industrial processØ 2 nm/sec dep. rate

Blakers, Zhao, Green et al. (UNSW)

PERT


SERIS’ monoPolyTM celle.g. rear-side monoPolyTM scheme

Front PECVD passivation/ARC stack

Screen-printed (& fired) rear metal

contact

Diffused junction

Screen-printed (& fired) rear

metal contact

Rear PECVD layer

n-type or p-type 6” Cz-Si

n+:monoPolyTM layer

Interfacial oxide


LPCVD

PECVD

APCVD

Industrial Tools for monoPolyTM cell


SDE + Texture

In-situ oxide + n+:a-Si

Annealing

HF dip

B-diffusion

Rear side etch

n-type

n-typen-typep+

p+

Rear etch

n-typen-type

p+

Thin oxide Poly-Si (n+)

cn-type

p+ emitter

Thin oxide Poly-Si (n+)

Front ARC

SiNx

Solar cell process flow8-step process with inline PECVD poly-Si

[2] Duttagupta et al., SOLMAT 187 (2018)[3] Nandakumar et al., Prog. in Photovolt. 27 (2019)

cn-type

p+

ARC + passivation


SDE + Texture


Annealing

HF dip

Screen-printing + Firing

B-diffusion

Rear side etch

8 ST

EPS

Solar cell process flow8-step process with inline PECVD poly-Si

[2] Duttagupta et al., SOLMAT 187 (2018)[3] Nandakumar et al., Prog. in Photovolt. 27 (2019)

ARC + passivation


monoPolyTM layer propertiesin-situ interfacial oxide layer

Symmetric test structure τeff (µs) iVoc at 1 Sun (mV) J0,pass per side

(fA/cm2)J0,metal per side

(fA/cm2)No oxide formation 1700 711 8.9 -In-situ oxide formed 3000 740 3.0 20

n-Si

SiNx

n+:poly-Sioxide

oxiden+:poly-Si

SiNx

With oxide

n-Si

SiNx

n+:poly-Si

n+:poly-SiSiNx

W/o oxide growth

Test sample structuren+:poly-Si

SiOx

c-Si

5 nm


Ø Reason for low parasitic absorption: High O-content in poly-Si layer!

Ø Poly-SiOx widens bandgap making layer transparent to long wavelength light4

monoPolyTM layer propertiesLow absorbing n+:poly-Si

4Yang et al., APL, 112 (2018)

ED

S A

real

Map

s

LPCVD poly-Si

Si substrate

SiNx

PECVD poly-Si

Si substrate

SiNx


I-V resultsImprovements in B-emitter and Si wafer

Best group (busbarless) Voc (mV) Jsc (mA/cm2) FF (%) η (%)Batch median 705 41.1 79.2 23.0Best cell 707 41.1 79.7 23.2



η [%]

Isc [mA]

Voc [mV]

FF [%]

Cell area [cm²]

Jsc [mA/cm²]

23.20 9868 707.9 81.20 244.44 40.37*Measurement with rear full-area brass chuck

q External verification at ISFH CalTec



Cell precursor iVoc to cell Voc drop Reverse current characteristics

q Lowly doped emitter shows a higher drop due to higher recombination at the metal contact

q Thinner wafers with lowly doped emitters show lower Irev at -12 V


monoPolyTM efficiency progress Poly-Si deposited using an advanced PECVD tool

Record Batch Voc (mV)

Jsc (mA/cm2)

FF (%)

η (%)

Record batch (Aug 2019)

708 40.37 81.2 23.2

SDE + Texture


Annealing

HF dip

Screen-printing + Firing

B-diffusion

Rear side etch

8 ST

EPS

ARC + passivation

qRapid progress – LR of 1%abs/year

qPilot-scale production ongoing with strategic technology partners

Independently Certified by


Initial Module ResultsmonoPolyTM inside

352 W

60 cellsWhite Back Sheet

monoPolyTM inside

TUV

Cer

tifie

d


Upgraded PERT/monoPolyTM PlatformPassivated Emitter & Rear Cell

monoPolyTM Industrial Platform ~2017

710 mV, ~23.5%

TEX

DIF

WET

PRINT

PECVD n-doped layer*

FIRING

Anneal


Ø Screen-printing &Ø High-T fired contactsØ Bifacial cell Ø Industrial process

690 mV, ~23.0%

TEX

DIF

WET

LPCVD poly-Si POCl3

pClean process*

PECVD Process* LPCVD Process*

PRINT

FIRING


*SERIS proprietary


PERC/PERT

BACK-SIDE PASSIVATED CONTACT

FRONT & BACK-SIDE PASSIVATED CONTACTS

Late News: Vision “beyond PERC/T”

Ø Based on classical HJT device structure

Ø poly-Si at both sides to increase Jsc Ø PECVD layers to enable “thin,

stable and contactable” front-layers

Ø Alternative metallisation pastes to reduce cost and increase stability

Ø Based on classical PERT device structure

Ø Low absorbing poly-Si at rear sides to increase VOC

Ø Voc limits at 680 mV today

Ø Voc of >700 mV is difficult

Advancement - 1

Advancement - 2

25.5%

24.5%


q Firing-stable “semi-transparent” poly-Si thickness on front ~20 nm q Firing-stable “standard” poly-Si thickness on the rear ~ 50 nm

iVoc [mV]

Jsc* [mA/cm2]

iFF [%]

h max

[%]Cell “precursor“ (244.3 cm2) 730 40.5 85.1 25.1

* parameters for an assumed Jsc of 40.5 mA/cm2

Upgraded high-temperature “heterojunction” cell



Summaryq SERIS’ monoPolyTM platform presents a “unique” industrial

solution for PECVD and LPCVD processes suitable for mass production

q Inline, single-side PECVD deposition (CAiA®). q 8-step process flow easily adaptable for mass production.q Low parasitic absorption due to higher O-content in poly-Si.q Thinner PECVD poly-Si layers (20-120 nm) show good

results q Best efficiency using 80-100 nm PECVD n+:poly-Si with no

loss in Jsc

q Peak efficiency of 23.5%, with Voc of ~710 mV!q First modules have power of 345 W (60 cells)q After monoPolyTM; SERIS is strategizing towards biPolyTM

cell development potential is beyond 25% cell efficiency


Thank you for your attention!SERIS is a research institute at the National University of Singapore (NUS). SERIS is supported by the National University of Singapore (NUS), the National Research Foundation Singapore (NRF) and the Singapore Economic Development Board (EDB)

More information at www.seris.sgWe are also on:

Documents

monoPolyTM Technology Platform: Implementation of