TY - JOUR

T1 - Rear side dielectrics on interdigitating p +-(i)-n +back-contact solar cells-hydrogenation vs. charge effects

AU - Rienäcker, Michael

AU - Larionova, Yevgeniya

AU - Krügener, Jan

AU - Wolter, Sascha

AU - Brendel, Rolf

AU - Peibst, Robby

N1 - Funding Information: The authors thank the state of lower Saxony and the Federal Ministry of Economic Affairs (BMWi) for funding this work, which was performed in the framework of the research project “27Plus6” (FKZ03EE1056A). We are grateful to Hilke Fischer, Sarah Spätlich and Renate Winter (all from ISFH) as well as Raymond Zieseniss and Guido Glowatzki (both from Institute of Electronic Materials and Devices) for sample processing. We thank Felix Haase and Christina Hollemann for fruitful discussions.

PY - 2021/11/9

Y1 - 2021/11/9

N2 - Polysilicon-on-oxide (POLO) passivating contacts and interdigitated back-contact (IBC) cell technologies have recently attracted a lot of interest as candidates for the implementation in the next generation of solar cells. An IBC cell with POLO junctions for both polarities-a POLO2-IBC cell-has to electrically isolate the highly defective p+ and n+ poly-Si regions on the rear side of the cell to avoid parasitic recombination. Inserting an initially undoped, intrinsic (i) region between the p+ and n+ poly-Si regions was demonstrated to successfully prevent the parasitic recombination in the transition region of ISFH's 26.1%-efficient POLO2-IBC cell. In order to further improve the conversion efficiency towards 27%, we apply hydrogen-donating dielectric layer stacks to the p+-(i)-n+ POLO interdigitating rear side to enhance the passivation quality of the POLO junctions. We indeed show a significant improvement of POLO junctions on symmetrical full-Area homogenously doped reference samples, but when we apply a hydrogen-donating layer stack on the p+-(i)-n+ POLO interdigitating rear side, we observe a strong degradation in the performance of the POLO2-IBC cell. We attribute this to the formation of a conductive channel between the p+ and n+ poly-Si regions due to the strong negative charge density of the hydrogen-donating layer stack.

AB - Polysilicon-on-oxide (POLO) passivating contacts and interdigitated back-contact (IBC) cell technologies have recently attracted a lot of interest as candidates for the implementation in the next generation of solar cells. An IBC cell with POLO junctions for both polarities-a POLO2-IBC cell-has to electrically isolate the highly defective p+ and n+ poly-Si regions on the rear side of the cell to avoid parasitic recombination. Inserting an initially undoped, intrinsic (i) region between the p+ and n+ poly-Si regions was demonstrated to successfully prevent the parasitic recombination in the transition region of ISFH's 26.1%-efficient POLO2-IBC cell. In order to further improve the conversion efficiency towards 27%, we apply hydrogen-donating dielectric layer stacks to the p+-(i)-n+ POLO interdigitating rear side to enhance the passivation quality of the POLO junctions. We indeed show a significant improvement of POLO junctions on symmetrical full-Area homogenously doped reference samples, but when we apply a hydrogen-donating layer stack on the p+-(i)-n+ POLO interdigitating rear side, we observe a strong degradation in the performance of the POLO2-IBC cell. We attribute this to the formation of a conductive channel between the p+ and n+ poly-Si regions due to the strong negative charge density of the hydrogen-donating layer stack.

KW - Charge

KW - Hydrogenation

KW - IBC

KW - Passivating contact

KW - POLO

KW - Polysilicon

KW - Recombination

UR - http://www.scopus.com/inward/record.url?scp=85119094617&partnerID=8YFLogxK

U2 - 10.1051/epjpv/2021007

DO - 10.1051/epjpv/2021007

M3 - Article

AN - SCOPUS:85119094617

VL - 12

JO - EPJ Photovoltaics

JF - EPJ Photovoltaics

M1 - 6

ER -