α-C:H films produced on various substrate materials by using radio frequency plasma vapor deposition method have been analysed by Raman spectroscopy, indicating both diamond-like and diamond phases appear in these films. After analysing the transmittance and the refractive index of the films in the visible range, we suggest that the deposited film on silicon solar cell can be used as antireflective coating. The spectrum response value of the solar cell can be improved obviously over a wide range of wavelength from 0.55 to 1.0 μm and the short-circuit cxurent(lsc) of the solar cell is increased by 38% over the uncoated ones.