Microstructure evolution and passivation quality of hydrogenated amorphous silicon oxide (a-SiOx:H) on 〈100〉- and 〈111〉-orientated c-Si wafers**Project supported by the National Key Research and Deveopment Program of China (Grant No. 2018YFB1500402), the National Natural Science Foundation of China (Grant Nos. 61674084 and 61874167), the Fundamental Research Funds for Central Universities, China, the Natural Science Foundation of Tianjin City, China (Grant

Abstract

Hydrogenated amorphous silicon oxide (a-SiOx:H) is an attractive passivation material to suppress epitaxial growth and reduce the parasitic absorption loss in silicon heterojunction (SHJ) solar cells. In this paper, a-SiOx:H layers on different orientated c-Si substrates are fabricated. An optimal effective lifetime (τeff) of 4743 μs and corresponding implied open-circuit voltage (i Voc) of 724 mV are obtained on 〈100〉-orientated c-Si wafers. While τeff of 2429 μs and i Voc of 699 mV are achieved on 〈111〉-orientated substrate. The FTIR and XPS results indicate that the a-SiOx:H network consists of SiOx (Si-rich), Si– OH, Si– O– SiHx, SiO2≡Si– Si, and O3 ≡S– Si. A passivation evolution mechanism is proposed to explain the different passivation results on different c-Si wafers. By modulating the a-SiOx:H layer, the planar silicon heterojunction solar cell can achieve an efficiency of 18.15%.