It is known that surface passivation plays a significant role in upgrading solar cell performance. In this study, silicon thin films deposited by LPCVD (low pressure chemical vapor deposition) are used to passivate the surface of solar-grade p-type crystalline silicon solar cells for the first time. Intrinsic amorphous silicon films and poly-silicon films were obtained on the front and rear surfaces of solar wafers at the deposition temperatures of 560 °C and 620 °C, respectively. Both kinds of silicon films proved to be effective in improving the open-circuit voltage owing to surface passivation for crystalline silicon solar cells. Optical spectral responses in the short and long wavelength ranges (e.g. the range 300–600 nm and the range 850–1100 nm, respectively) also showed an improvement in photogenerated current resulting from reduced surface recombination rates on the front and back surface.