This document summarizes a study evaluating different cell interconnection architectures for bifacial PV modules. Four interconnection schemes were tested: standard 3-bus, 4-bus, 3-bus with cells interconnected every half-cell ("3-bus - 1/2 cell"), and a new smartwire technology. Testing showed the smartwire design had the best front and bifacial performance, with high module bifaciality of 95.7% and power gains very close to the albedo ratio. The 3-bus - 1/2 cell and 4-bus architectures also performed well. The smartwire technology was found to be particularly attractive due to enabling both higher module performance and lower cell manufacturing costs.

1. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
1
Cell interconnection challenges for
bifacial modules
M. Joanny, B. Soria, A. Bettinelli, P. Lefillastre, B. Novel, H. Robin, R.
Monna, Y. Veschetti, G. Razongles, E. Gerritsen and CEA team
- maryline.joanny@cea.fr
Direction of Technological Research
Solar Technologies Department
Laboratory of PhotoVoltaic Modules

2. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
2
1) Module architecture
2) Front performance
3) Bifacial performance
4) Conclusion
Cell interconnection challenges for bifacial modules
Objective :
Content :
To find the best cell interconnection architecture
for bifacial module

3. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
3
1) Module architecture
2) Front performance
3) Bifacial performance
4) Conclusion

4. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
3 bus
interconnect ribbon
1.5 mm
4
1) Module architecture
• Interconnection schemes evaluated
n-type bifacial cells 156 mm pseudo square (INES PERT technology 20% efficiency)
encapsulant EVA standard / EVA UV clear
glass-glass structure 36 cm x 36 cm x 3 mm
4 bus
interconnect ribbon
1.2 mm
3 bus - ½ cell
interconnect ribbon
1.5 mm
2) Front performance
3) Bifacial performance
4) Conclusion
* interconnection material provided by Meyer Burger (smartwire technology)
smartwire*
wires with PET film
x 36

5. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
5
• Interconnection schemes evaluated
3 bus
interconnect ribbon
1.5 mm
4 bus
interconnect ribbon
1.2 mm
wires with PET film
x 36
interconnect ribbon
1.5 mm
2) Front performance
3) Bifacial performance
4) Conclusion
1) Module architecture
smartwire*3 bus - ½ cell
n-type bifacial cells 156 mm pseudo square (INES PERT technology 20% efficiency)
encapsulant EVA standard / EVA UV clear
glass-glass structure 36 cm x 36 cm x 3 mm
* interconnection material provided by Meyer Burger (smartwire technology)

6. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
6
1) Module architecture
2) Front performance
3) Bifacial performance
4) Conclusion

7. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
7
• STC performance
2) Front performance
3) Bifacial performance
4) Conclusion
1) Module architecture
mask
same total transparent area for all architectures
→ Isc (A), FF (%), Pmax (W)
⇒ CTMIsc (%), CTMFF (%), CTMPmax (%)

8. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
8
• STC performance
EVA standard
2) Front performance
3) Bifacial performance
4) Conclusion
1) Module architecture
EVA UV clear
→ 4 bus STC CTM Pmax is 1 % better than 3 bus
→ 3 bus - ½ cell and smartwire show better STC performance than standard 3 bus (respectively 3 %
and 6 %)
≈ 3 % better
≈ 6 % better
≈ 4,5 % better
≈ 5 % better
Isc (A)

9. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
9
• Front performance
→ CTMFF slopes are comparable for 3 bus and 4 bus interconnection schemes
→ The lowest CTMFF slope is obtained for the smartwire module
→ Smartwire then 3 bus - ½ cell show the best CTMFF especially at high irradiance
≈ 3,5 % better
≈ 5,5 % better
EVA UV clear
EVA standard
2) Front performance
3) Bifacial performance
4) Conclusion
FFmodule
FFcell @ 1000 W/m²
1) Module architecture
≈ 6,5 % better
≈ 4 % better
700 W/m²
1000 W/m²
1200 W/m²

10. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
10
• Front performance
White
screen
2) Front performance
3) Bifacial performance
4) Conclusion
1) Module architecture

11. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
11
• Front performance
4 modules with encapsulant EVA standard
2) Front performance
3) Bifacial performance
4) Conclusion
1) Module architecture
White
screen
1
2
→ Using a white screen enables to reach 1,5 to 2% more on Isc and Pmax performance

12. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
12
1) Module architecture
2) Front performance
3) Bifacial performance
4) Conclusion

13. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
13
• Module bifaciality in Pmax
2) Front performance
3) Bifacial performance
4) Conclusion
95,7 %
86,8 %
87,9 % 88,3 %
Bifaciality
1) Module architecture
Smartwire allows an
optimized design of the
rear side
1
2
→ Bifaciality obtained for the smartwire module is 95,7 %
→ Bifacialities of 86,8 to 88,3 % are obtained with the other interconnection schemes

14. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
14
• Bifacial indoor characterisation set up
aluminium mirrors
self-monitoring of irradiance with Isc
mesh filters → T ≈ 25% and 50%
reflective mirror
2) Front performance
3) Bifacial performance
4) Conclusion
1) Module architecture
mesh filter

15. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
15
• Bifacial performance
2) Front performance
3) Bifacial performance
4) Conclusion
1) Module architecture
Pmax @ 0% albedo
Pmax @ 23% albedo
Pmax @ 47% albedo
Pmax @ 100% albedo

16. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
16
• Bifacial performance
2) Front performance
3) Bifacial performance
4) Conclusion
1) Module architecture
y = 0,95 x (R² = 0,9993)
Linear regression
Pmax
Pmax1000 W/m²
- 1

17. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
17
• Bifacial performance
EVA UV clear
EVA standard
y ≈ 0,95 x
y ≈ 0,84 x
Y ≈ 0,78 x
y ≈ 0,80 x
2) Front performance
3) Bifacial performance
4) Conclusion
Pmax
Pmax1000 W/m²
- 1
→ The gain obtained on bifacial modules can reach 0.95 x albedo (smartwire), 0.84 x albedo (3
bus - ½ cell), 0.80 x albedo (4 bus) and 0.78 x albedo (3 bus)
1) Module architecture

18. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
18
1) Module architecture
2) Front performance
3) Bifacial performance
4) Conclusion

19. Imp 154 D - INESFREE DISTRIBUTION
bifi PV workshop 2014.05.26 Chambéry
Joanny, Maryline
19
• Summary and conclusion
2) Front performance
3) Bifacial performance
4) Conclusion
1) Module architecture
→ Foreseen follow up : upscale to real size module and characterisation
→ The best performance have been obtained for smartwire and ½ cell schemes
→ The smartwire technology appears very attractive due to both module higher performance
and lower cell price (lower quantities of Ag deposited on cell front (/3) and back (/2) sides)

20. 20
Alternative Energies and Atomic Energy Commission
INES RDI | Savoie Technolac – BP332 – 50 avenue du Lac Léman
F-73377 Le Bourget-du-Lac - FRANCE
T. +33 (0)4 79 79 23 17
Email : maryline.joanny@cea.fr
Public establishment with commercial and industrial character | RCS Paris B 775 685 019
Thanks for your
attention
Technological Research Division
Department of Solar Technologies
Photovoltaïc Modules Division
FREE DISTRIBUTION: This document may be distributed to other third parties as the contractors. It must be distributed unchanged
and in its entirety and include the issuer’s attribution and credit. This corresponds to the type of licence aa aaaaaaa defined by
http://creativecommons.org/licenses/. However, recipients are requested to exercise sound judgement when redistributing the
document.
Acknowledgements to MeyerBurger for providing the smartwire
materials