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Andrey Sitnikov
Multi Bifacial Solar Cells Multi Bifacial Solar Cells Multi Bifacial Solar Cells Multi Bifacial Solar Cells in comparison with Bifacial in comparison with Bifacial
mono cells and modulesmono cells and modules3D Solar AG 3D Solar AG Solar Wind LtdSolar Wind Ltd
Solar Wind Ltd experience (Since 1997): If Bifacial solar modules are used as standard modules,it provides power gain of 7-9%
There are systems, emphasizing the advantages of double-sided modules
The gain is up to 30%
Solar Wind Ltd experience (Since 1997): If Bifacial solar modules are used with special tracking system, it provides power gain of up to 30%
The test results of bifacial modules on «TRAXEL», show a significant advantage in compare with standard modules of similar capacity
to 30%
Bifacial modules advantages realization Czech Republic, Crumlov SOLAR PARK 0.43 MWtTRAXEL system with the trackers
Standard bifacial modules parametersProducing power is up to 178 & 250 W/м2
MSW Side Standard AM1,5
conditions – 178 W/ м2 Cells,
125x125 mm LWT, mm
Weight, kg
Additional 70% rear illumination – 250 W/ м2
Isc, A Uoc, V Pmax, W Umpp, V Impp , A Isc, A Uoc, V Pmax, W Umpp , V Impp , A
85/50 Front 5,41 22,25 85 17,07 4,98
multi
9 x 4
1186
x 55
0 x 46
7,18
7,57 23,14 119 17,41 6,83
Rear 3,49 21,78 50 16,95 3,12
90/60 Front 5,51 22,39 90 18,00 5,01
mono
7,71 23,29 126 18,36 6,86
Rear 3,70 21,82 60 17,80 3,37
95/60 Front 5,69 22,50 95 18,20 5,22 7,97 23,40 133 18,56 7,16
1186
mono 95/60 Rear 3,80 21,96 60 17,80 3,37
100/70 Front 5,79 22,61 100 18,60 5,37 8,11 23,51 140 18,97 7,38
Rear 4,20 22,20 70 18,30 3,82
170/100 Front 5,41 44,51 170 34,14 4,98
multi
12 x 6
1575
x 8
07 x 4
6
14,05
7,57 46,29 238 34,82 6,83
Rear 3,49 43,56 100 33,90 3,12
190/120 Front 5,69 44,52 190 36,40 5,22
mono
7,97 46,30 266 37,13 7,16
Rear 3,80 43,92 120 36,00 3,37
195/130 Front 5,79 44,80 195 36,30 5,37 8,11 46,59 273 37,03 7,37
Rear 3,80 43,92 130 35,60 3,65
200/140 Front 5,79 45,22 200 37,20 5,37 8,11 47,03 280 37,94 7,38
Rear 4,20 44,40 140 35,60 3,82
Non-frame bifacial modules with the increased resource
Lisek & Solar Wind cooperationNon-frame bifacial module with the area 4,7 sq.m was made by LISEK (Austria) technology.
It contains 264 Solar Wind cells, laminated between two cells, laminated between two tempered glasses with thickness of 2.1 mm.
Such design, besides the increased resource has also other advantages to double-side application.
In particular, there is no shadowing by a frame.
Front power of the module – 711 W, rear – 433 W
Solar Wind standard bifacial mono crystalline solar cells
20%30%40%50%60%70%80%90%
100%ex
tern
al q
uant
um e
ffic
ienc
y [%
]
FaceRear
Mono Solar Wind SC №5
Calculated short circuit current, mA/cm 2
Face 38,6 Rear 25,99
Measured in PASAN with Fraunhofer Standard
0%10%20%
300 400 500 600 700 800 900 1000 1100 1200exte
rnal
qua
ntum
eff
icie
ncy
wavelength[nm] ОМЭ НИИЯФ МГУ 06.10.2011
Face 38,6 Rear 25,99
Voc Isc Pmax FF Vpm Ipm Eff
FaceAverage 0,626 5,761 2,879 79,821 0,537 5,365 18,621
± 0,003 0,021 0,019 0,515 0,004 0,037 0,123Best 0,629 5,766 2,910 80,38 0,540 5,398 18,82
RearAverage 0,619 4,002 1,989 80,36 0,536 3,714 12,87
± 0,001 0,092 0,047 0,68 0,004 0,093 0,30Best 0,621 4,126 2,070 80,950 0,544 3,813 13,39
Multi silicon as material for bifacial solar cells
It is believed that multi crystalline silicon is not entirely suitable for double-sided applications, entirely suitable for double-sided applications, due to the low minor carriers lifetime.
Let us consider in more detail the work of bi-facial solar cells and its dependence on the diffusion length
Dependence of the bifacial coeff. from the wavelength for monochromatic illumination and from the minor carriers diffusion length
0,50
0,60
0,70
0,80
0,90
1,00
bifa
cial
ity c
oeff
0,60
0,70
0,80
0,90
bifa
cial
ity c
oeff
32
28
24
40
idea
l AM
1,5
rear
cur
rent
, mA
/cm
2 fo
r 18
0 m
cm
0,00
0,10
0,20
0,30
0,40
200 400 600 800 1000 1200
bifa
cial
ity c
oeff
wavelength, nm100 mcm 200 mcm 300 mcm400 mcm 600 mcm 800 mcm1000 mcm
0,10
0,20
0,30
0,40
0,50
100 200 300 400 500 600 700 800 900 1000
Ln, mcm
160 mcm 180 mcm 200 mcm
21
17
12
7
idea
l AM
1,5
rear
cur
rent
, mA
/cm
Measurement of diffusion length on the real bifacial multi crystalline solar cells
0,3
0,35
0,4
0,45
0,5
0,55
0,6
0,65
0,7
0,75
0 10 20 30 40 50 60 70 80
Distance, mm
200 250 300 350 400 450 500 550 600
Ln, mcm
diffu
sion
leng
th, m
cm
bifa
cial
uty
coef
f
0,5
0,6
0,7
diffu
sion
leng
th, m
cm
bifa
cial
uty
coef
f
320
480
240
Test Series1: Multi crystalline solar cell
20%30%40%50%60%70%80%90%
100%ex
tern
al q
uant
um e
ffic
ienc
y[%
]
Face
Rear
Multy Solar Wind SC №2
Calculated short circuit current, mA/cm2
Face 34,29 Rear 24,3
Voc Isc Pmax FF Vpm Ipm Eff
F a c e Average 0,618 5,288 2,557 78,217 0,525 4,867 16,363
± 0,001 0,015 0,027 0,562 0,006 0,007 0,171 Best 0,621 5,295 2,610 79,34 0,537 4,855 16,70
R e a r Average 0,611 3,933 1,893 78,800 0,521 3,636 12,247
± 0,001 0,092 0,053 0,330 0,001 0,106 0,345 Best 0,611 4,116 2,00 79,46 0,520 3,847 12,937
0%10%20%
300 400 500 600 700 800 900 1000 1100 1200
exte
rnal
qua
ntum
eff
icie
ncy
wavelength [nm] ОМЭ НИИЯФ МГУ 06.10.2011
Face 34,29 Rear 24,3
Measured in PASAN with Fraunhofer Standard
MONO = MULTI ?
The diffusion length in multi silicon is quite suitable formanufacturing of bifacial solar cells. The overwhelming part of ithas diffusion length more than 300 microns that considerablyexceeds standard wafer thickness (180-200 microns).
Actually multi silicon diffusion length doesn't differ from the mono.
At the same time, if the relation of back currents for the multi andAt the same time, if the relation of back currents for the multi andmono makes 93 %, for obverse currents this relation decreasesto 89 %.
Except insufficient antireflection properties of an acid texturedstructure there is one more mechanism, able to make essentialimpact on an obverse current of short circuit. It is the mechanismknown as «light trapping» it is connected with design features ofcells and it is shown in a long-wave part of radiation.
Refraction and reflection in different cells design
“Light trapping” effect manifestation on the transmission of various structures
The result of “light trapping” action in various structures
Calculated Isc without optical losses
for 180 mcm thickness wafer with Ln 500 mcm, mA/cm2
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
Isc
spect
ral d
ensi
ty,
mA
/nm
cm
2
AM1,5
Pyr. EVA Ref
Pyr. EVA no Ref
Pyr. Air Ref
Pyr. Air no Ref
Smooth Ref
Smooth no Ref
0,00300 400 500 600 700 800 900 1000 1100 1200Is
c sp
ect
ral d
ensi
ty,
mA
/nm
cm
wavelength, nm
0,00
0,10
0,20
0,30
0,40
0,50
0,60
900 950 1000 1050 1100 1150 1200
Isc
spe
ctra
l de
nsi
ty, m
A/n
m
cm2
wavelength, nm
AM1,5
Pyr. EVA Ref
Pyr. EVA no Ref
Pyr. Air Ref
Pyr. Air no Ref
Smooth Ref
Smooth no Ref
Thank you for your attention!