Light-induced activation of boron doping in hydrogenated amorphous silicon for over 25% efficiency silicon solar cells

by Wenzhu Liu, Jianhua Shi, Liping Zhang, Anjun Han, Shenglei Huang, Xiaodong Li, Jun Peng, Yuhao Yang, Yajun Gao, Jian Yu, Kai Jiang, Xinbo Yang, Zhenfei Li, Wenjie Zhao, Junlin Du, Xi Song, Jun Yin, Jie Wang, Youlin Yu, Qiang Shi, Zhixin Ma, Haichuan Zhang, Jiajia Ling, Lujia Xu, Jingxuan Kang, Fuzong Xu, Jiang Liu, Hanyuan Liu, Yi Xie, Fanying Meng, Stefaan De Wolf, Frédéric Laquai, Zengfeng Di, Zhengxin Liu

Article Year: 2022 DOI: https://doi.org/10.1038/s41560-022-01018-5

Bibliography

Liu, W., Shi, J., Zhang, L., Han, A., Huang, S., Li, X., Peng, J., Yang, Y., Gao, Y., Yu, J., Jiang, K., Yang, X., Li, Z., Zhao, W., Du, J., Song, X., Yin, J., Wang, J., Yu, Y., Shi, Q., Ma, Z., Zhang, H., Ling, J., Xu, L., Kang, J., Xu, F., Liu, J., Liu, H., Xie, Y., Meng, F., De Wolf, S., Laquai, F., Di, Z., Liu, Z.

Abstract

Recent achievements in amorphous/crystalline silicon heterojunction (SHJ) solar cells and perovskite/SHJ tandem solar cells place hydrogenated amorphous silicon (a-Si:H) at the forefront of photovoltaics. Due to the extremely low effective doping efficiency of trivalent boron in amorphous tetravalent silicon, light harvesting of aforementioned devices is limited by their fill factors (FFs), a direct metric of the charge carrier transport. It is challenging but crucial to develop highly conductive doped a-Si:H with minimal FF losses. Here we report that light soaking can efficiently boost the dark conductance of boron-doped a-Si:H thin films. Light induces diffusion and hopping of weakly bound hydrogen atoms, which activates boron doping. The effect is reversible and the dark conductivity decreases over time when the solar cell is no longer illuminated. By implementing this effect to SHJ solar cells, we achieved a certified total-area power conversion efficiency of 25.18% with a FF of 85.42% on a 244.63 cm2 wafer.

Keywords

Devices for energy harvesting Solar cells