The electrical characteristics of hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs), in the dark or under front-side illumination, were investigated at different temperatures. Temperatures ranging from 100 K to 300 K were applied in this study, and experimental results showed the degradation of on-state current, mobility, and threshold voltage at lower temperatures. Furthermore, different photo-leakage-current trends were found in this work. Accordingly, we provide the indirect recombination rate and the parasitic resistance (R-p) to explain the photo-leakage-current of a-Si:H TFTs under varied temperature operations. (C) 2009 Elsevier Ltd. All rights reserved.