A cold cathode fluorescent lamp (CCFL) and various color spectrum filters were used in the investigation of photoelectric characteristics of hydrogenated amorphous silicon thin film transistor(a-Si:H TFT). From the photo leakage currents of a-Si:H TFT for the transmitted backlights through the various color spectrum filters, it was possible to conclude the photo leakage currents are not directly related to the luminance of the transmitted backlights. The photoelectric characteristics were well described in terms of photon energy spectrums calculated from the photon energy and the energy transmittance of backlight through the color spectrum filters.