Characteristics of Photo Leakage Currents of a-Si:H TFT Caused by the Illuminations from CCFL and White LED Backlight

The photo leakage currents of a conventional hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) were investigated and compared when the a-Si:H layer was exposed to the illumination from cold cathode fluorescent lamp (CCFL) backlight and white light emitting diode (LED) backlight. The photo leakage characteristics showed the difference in the leakage level and in the on/off current ratio in spite of the similar luminance. From the spectral analysis of backlight systems, the leakage level is expected to be related to the absorption of photons at lower wavelength, the generation of electron–hole pairs in a-Si layer.