In this study, a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/n-Si hybrid solar cell is fabricated via spin coating and treatment with HNO3 vapor. It is found that after the HNO3 treatment, the hybrid solar cell shows much better performance with an open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and power conversion efficiency (η) of 555.34 mV, 23.61 mA/cm2, 0.54, and 8.81%, respectively. The conversion efficiency is nearly two times larger than that before HNO3 treatment. The possible reason is that HNO3 could significantly reduce the resistivity of the spin-coated PEDOT:PSS. The effect of HNO3 treatment time on the PEDOT:PSS/n-Si HSC's performance is also investigated.