The near-infrared responsivity of a silicon photodetector employing the impurity photovoltaic(IPV) effect is investigated with a numerical method. The improvement of the responsivity can reach 0.358 A/W at a wavelength of about1200 nm, and its corresponding quantum efficiency is 41.1%. The origin of the enhanced responsivity is attributed to the absorption of sub-bandgap photons, which results in the carrier transition from the impurity energy level to the conduction band. The results indicate that the IPV effect may provide a general approach to enhancing the responsivity of photodetectors. The improvement of the responsivity can reach 0.358 A / W at a wavelength of about 1200 nm, and its corresponding quantum efficiency is 41.1%. The near-infrared responsivity of a silicon photodetector employing the impurity photovoltaic (IPV) effect is investigated with a numerical method. The origin of the enhanced responsivity is attributed to the absorption of sub-bandgap photons, which results in the carrier transition from the impurity energy level to the conduction band. The results that that the IPV effect may provide a general approach to enhance the responsivity of photodetectors.