Hard mask processing of 20% efficiency back-contacted silicon solar cells with dopant-free heterojunctions

• Published in: Nano energy Vol. 66; p. 104116
• Main Authors: Wang, Jiajia, Lin, Hao, Wang, Zilei, Shen, Wenzhong, Ye, Jichun, Gao, Pingqi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2019
• Subjects: Dopant-free carrier-selective contacts; Interdigitated back contact; Silicon heterojunction; Solar cells; Solar cells; Dopant-free carrier-selective contacts; Silicon heterojunction; Interdigitated back contact
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2019.104116

Single junction crystalline silicon (c-Si) solar cells featuring a conventionally doped interdigitated back contact heterojunction (IBC-SHJ) structure has approached a record efficiency of 26.6%, which is very close to the practical limit. However, integrating the interdigital p- and n-type amorphous silicon (a-Si:H) layers on the rear surface of Si substrate is of such complexity, posing problem of heavy dependences on expensive manufacturing techniques including plasma-enhanced chemical vapor deposition and photolithography. Its commercial potential is thus always being questioned, and to seek an alternative fabrication procedure, which adapts to cost-effective deposition parallel with simple patterning characteristics, has been a primary research target of related subjects. Here, we demonstrated 20.1% efficiency dopant-free IBC-SHJ solar cells by combining evaporated carrier-selective materials (MoOx and LiFx) and two-steps hard masks alignments, delivering substantial simplifications in the architecture and fabrication procedures. We investigated the effect of intrinsic a-Si:H films with different thicknesses on the passivation and contact resistance for both a-Si:H/MoOx and a-Si:H/LiFx contacts, showing 4 nm a-Si:H is better for high efficiency IBC-SHJ solar cells. We also found that the position of the metal target (electrode definition step) and isolation in between the busbar and the Si substrate are highly relevant to leakage and recombination and have great impact on the device performance. The dopant-free IBC-SHJ solar cells demonstrated here manifest enough confidence in our hard mask based fabrication procedure, with great potential for high performance-to-cost ratio in future. [Display omitted] •IBC-SHJ solar cells was shown by combining evaporated carrier-selective materials and two-steps hard masks alignments.•Without doping process, without lithographic method, an IBC-SHJ solar cell with PCE of 20.1% was achieved.•Well tuning the position of the metal target and adding isolation between the busbar and n-Si are beneficial to the PCE.