Details
| Original language | English |
|---|---|
| Article number | 104509 |
| Journal | Journal of applied physics |
| Volume | 107 |
| Issue number | 10 |
| Publication status | Published - 15 May 2010 |
Abstract
Currently, the emitter-wrap-through (EWT) design of Si solar cells is being intensively investigated as a potential candidate for cheap, low-quality Si materials. So far, experimentally achieved energy conversion efficiencies have stayed unexpectedly far below the expectations of common device theory. Therefore, we analyze fabricated EWT cells in detail and refine device theory to account for the limiting loss mechanisms present only in EWT cells. By means of rigorous three-dimensional numerical device modeling, we show that the fill factor (FF) is significantly reduced, primarily due to a effect we call the via-resistance induced recombination enhancement effect. The FF is only secondarily reduced by the resistive losses in the vias where the emitter is wrapped through the cell. This implies that lowering the base resistivity will improve cell efficiency more effectively than lowering the resistance in the vias. Our simulations predict that the EWT design with a nonpassivated rear emitter and a homogeneous emitter diffusion leads to an efficiency improvement of about 1% absolute, as compared to the common front-junction design. This is so for excess carrier lifetimes in the bulk between 1 and 100 μs, which means also for multicrystalline cells.
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In: Journal of applied physics, Vol. 107, No. 10, 104509, 15.05.2010.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Loss analysis of emitter-wrap-through silicon solar cells by means of experiment and three-dimensional device modeling
AU - Ulzhöfer, Christian
AU - Altermatt, Pietro P.
AU - Harder, Nils Peter
AU - Brendel, Rolf
N1 - Funding Information: Funding was provided by the State of Lower Saxony.
PY - 2010/5/15
Y1 - 2010/5/15
N2 - Currently, the emitter-wrap-through (EWT) design of Si solar cells is being intensively investigated as a potential candidate for cheap, low-quality Si materials. So far, experimentally achieved energy conversion efficiencies have stayed unexpectedly far below the expectations of common device theory. Therefore, we analyze fabricated EWT cells in detail and refine device theory to account for the limiting loss mechanisms present only in EWT cells. By means of rigorous three-dimensional numerical device modeling, we show that the fill factor (FF) is significantly reduced, primarily due to a effect we call the via-resistance induced recombination enhancement effect. The FF is only secondarily reduced by the resistive losses in the vias where the emitter is wrapped through the cell. This implies that lowering the base resistivity will improve cell efficiency more effectively than lowering the resistance in the vias. Our simulations predict that the EWT design with a nonpassivated rear emitter and a homogeneous emitter diffusion leads to an efficiency improvement of about 1% absolute, as compared to the common front-junction design. This is so for excess carrier lifetimes in the bulk between 1 and 100 μs, which means also for multicrystalline cells.
AB - Currently, the emitter-wrap-through (EWT) design of Si solar cells is being intensively investigated as a potential candidate for cheap, low-quality Si materials. So far, experimentally achieved energy conversion efficiencies have stayed unexpectedly far below the expectations of common device theory. Therefore, we analyze fabricated EWT cells in detail and refine device theory to account for the limiting loss mechanisms present only in EWT cells. By means of rigorous three-dimensional numerical device modeling, we show that the fill factor (FF) is significantly reduced, primarily due to a effect we call the via-resistance induced recombination enhancement effect. The FF is only secondarily reduced by the resistive losses in the vias where the emitter is wrapped through the cell. This implies that lowering the base resistivity will improve cell efficiency more effectively than lowering the resistance in the vias. Our simulations predict that the EWT design with a nonpassivated rear emitter and a homogeneous emitter diffusion leads to an efficiency improvement of about 1% absolute, as compared to the common front-junction design. This is so for excess carrier lifetimes in the bulk between 1 and 100 μs, which means also for multicrystalline cells.
UR - http://www.scopus.com/inward/record.url?scp=77953009048&partnerID=8YFLogxK
U2 - 10.1063/1.3373612
DO - 10.1063/1.3373612
M3 - Article
AN - SCOPUS:77953009048
VL - 107
JO - Journal of applied physics
JF - Journal of applied physics
SN - 0021-8979
IS - 10
M1 - 104509
ER -