Role of polysilicon in poly-Si/SiO(x) passivating contacts for high-efficiency silicon solar cells

In this study, we focused on understanding the roles of a polysilicon (poly-Si) layer in poly-Si/SiO(x)/c-Si passivating contacts. Passivating contact formation conditions were varied by changing the doping method, annealing temperature and time, polysilicon layer thickness, and polysilicon doping concentration. Our observations indicated that the roles of polysilicon are contact, in-diffusion barrier action, field effect, gettering, and light absorption. Based on the observations, a iV(OC) of 741 mV was obtained. Finally, to increase J(SC) with high V(OC), the polysilicon was etched after hydrogenation to reduce light absorption with high passivation quality. iV(OC) was not affected by etching; moreover, by etching the polysilicon from 300 nm to 60 nm, the cell efficiency increased from 20.48% to 20.59% with increasing J(SC), constant V(OC), and fill factor.