TY - JOUR
T1 - Gettering in PolySi/SiOx Passivating Contacts Enables Si-Based Tandem Solar Cells with High Thermal and Contamination Resilience
AU - Assar, Alireza
AU - Martinho, Filipe
AU - Larsen, Jes
AU - Saini, Nishant
AU - Shearer, Denver
AU - Moro, Marcos V
AU - Stulen, Fredrik
AU - Grini, Sigbjørn
AU - Engberg, Sara
AU - Stamate, Eugen
AU - Schou, Jørgen
AU - Vines, Lasse
AU - Canulescu, Stela
AU - Platzer-Björkman, Charlotte
AU - Hansen, Ole
PY - 2022
Y1 - 2022
N2 - Multijunction solar cells in a tandem configuration could further lower the costs of electricity if crystalline Si (c-Si) is used as the bottom cell. However, for direct monolithic integration on c-Si, only a restricted number of top and bottom cell architectures are compatible, due to either epitaxy or high-temperature constraints, where the interface between subcells is subject to a trade-off between transmittance, electrical interconnection, and bottom cell degradation. Using polySi/SiOx passivating contacts for Si, this degradation can be largely circumvented by tuning the polySi/SiOx stacks to promote gettering of contaminants admitted into the Si bottom cell during the top cell synthesis. Applying this concept to the low-cost top cell chalcogenides Cu2ZnSnS4 (CZTS), CuGaSe2 (CGSe), and AgInGaSe2 (AIGSe), fabricated under harsh S or Se atmospheres above 550 °C, we show that increasing the heavily doped polySi layer thickness from 40 to up to 400 nm prevents a reduction in Si carrier lifetime by 1 order of magnitude, with final lifetimes above 500 μs uniformly across areas up to 20 cm2. In all cases, the increased resilience was correlated with a 99.9% reduction in contaminant concentration in the c-Si bulk, provided by the thick polySi layer, which acts as a buried gettering layer in the tandem structure without compromising the Si passivation quality. The Si resilience decreased as AIGSe > CGSe > CZTS, in accordance with the measured Cu contamination profiles and higher annealing temperatures. An efficiency of up to 7% was achieved for a CZTS/Si tandem, where the Si bottom cell is no longer the limiting factor.
AB - Multijunction solar cells in a tandem configuration could further lower the costs of electricity if crystalline Si (c-Si) is used as the bottom cell. However, for direct monolithic integration on c-Si, only a restricted number of top and bottom cell architectures are compatible, due to either epitaxy or high-temperature constraints, where the interface between subcells is subject to a trade-off between transmittance, electrical interconnection, and bottom cell degradation. Using polySi/SiOx passivating contacts for Si, this degradation can be largely circumvented by tuning the polySi/SiOx stacks to promote gettering of contaminants admitted into the Si bottom cell during the top cell synthesis. Applying this concept to the low-cost top cell chalcogenides Cu2ZnSnS4 (CZTS), CuGaSe2 (CGSe), and AgInGaSe2 (AIGSe), fabricated under harsh S or Se atmospheres above 550 °C, we show that increasing the heavily doped polySi layer thickness from 40 to up to 400 nm prevents a reduction in Si carrier lifetime by 1 order of magnitude, with final lifetimes above 500 μs uniformly across areas up to 20 cm2. In all cases, the increased resilience was correlated with a 99.9% reduction in contaminant concentration in the c-Si bulk, provided by the thick polySi layer, which acts as a buried gettering layer in the tandem structure without compromising the Si passivation quality. The Si resilience decreased as AIGSe > CGSe > CZTS, in accordance with the measured Cu contamination profiles and higher annealing temperatures. An efficiency of up to 7% was achieved for a CZTS/Si tandem, where the Si bottom cell is no longer the limiting factor.
KW - Tandem
KW - Gettering
KW - Chalcogenides
KW - Si
KW - TOPCon
U2 - 10.1021/acsami.2c00319
DO - 10.1021/acsami.2c00319
M3 - Journal article
C2 - 35297597
SN - 1944-8244
VL - 14
SP - 14342
EP - 14358
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 12
ER -