Pentacene-based organic phototransistor with high sensitivity to weak light and wide dynamic range

In this letter, the channel length effect, combined with the photoelectric field effect of organic phototransistors, has been investigated for the first time. Reducing the channel length and applying a positive gate bias during illumination enhance electron trapping effectively and hence improve the photoresponsivity of a pentacene-based phototransistor. The sensing dynamic range and the photosensitivity to very weak light (in the range of microwatts per square centimeter) are also discussed through the interaction between deep trapped states, interface energy-band bending, and photoexcited electrons.