Microstructure evolution and passivation quality of hydrogenated amorphous silicon oxide (a-SiO x :H) on and -orientated c-Si wafers

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 (tau(eff)) of 4743 mu s and corresponding implied open-circuit voltage (i V-oc) of 724 mV are obtained on < 100 & rang;-orientated c-Si wafers. While tau(eff) of 2429 mu s and i V-oc of 699 mV are achieved on < 111 & rang;-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 equivalent to Si- Si, and O-3 equivalent to 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%.