p-type c-Si/SnO2/Mg heterojunction solar cells with an induced inversion layer
Qi Wang, Yurong Zhou, Yurong Zhou, Wanwu Guo, Yingguo Yang, Jiacheng Shang, Hu Chen, Haibo Mao, Tianyu Zhu, Yuqin Zhou, Yuqin Zhou, Fengzhen Liu
Abstract
Crystalline silicon/compounds heterojunction (SCH) solar cells using oxides or fluorides as the electron or hole transport layers present great low-cost potential. In this paper, c-Si/SnO2 SCH solar cells are based on p-type c-Si substrates and use SnO2, prepared by atomic layer deposition, as the electron transport layers are investigated. By optimizing the SnO2 thickness and the device annealing process, a Voc of 718 mV and an efficiency of 20.1% are achieved on a champion SCH solar cell with an optimized SnO2 thickness of 3 nm. By analyzing the dark J–V curves, transport mechanisms of the silicon/compound heterojunction are investigated. It is proved that a strong inversion layer is induced in the p-type Si substrate, and a high hole barrier exists in the heterojunction region, which makes it a minority-carrier device. The induced inversion layer at the Si surface and the carrier selective transport effect of the SnO2 layer together enable the devices to achieve a high Voc.