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.