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Rear Side Dielectrics on Interdigitating p+-(i)-n+ Back-Contact Solar Cells – Hydrogenation vs. Charge Effects
M. Rienäcker, Y. Larionova, J. Krügener, S. Wolter, R. Brendel, R. Peibst
Recombination, Charge, Hydrogenation, IBC, POLO
Silicon Materials and Cells
Subtopic: High Temperature Route for Si Cells
Event: 38th European Photovoltaic Solar Energy Conference and Exhibition
Session: 2BO.12.2
154 - 157
ISBN: 3-936338-78-7
Paper DOI: 10.4229/EUPVSEC20212021-2BO.12.2
0,00 EUR
Document(s): paper, presentation


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.