The light sensing of the a-Si:H
pinphotodiode with respect to the wavelength and power intensity of the illumination light has been investigated. With the decrease of the wavelength, the diodes external quantum efficiency is dependent on the competition of electron-hole pairs generation from the light absorption and recombination from defects in the structure. Both the series resistance and the shunt resistance decreased with the increase of the light intensity following the power law, which are contributed by the combination of changes of photocurrent and leakage current. The light sensing is a complicated function of the incident light and the film properties.