Organic phototransistor based on poly(3-hexylthiophene)/$TiO2$ nanoparticle composite

Light sensitive phototransistor based on the composite of poly(3-hexylthiophene) and $TiO2$ nanoparticles has been developed. The device shows a quick change in channel current under light exposure, which can be attributed to a positive shift of the threshold voltage, while no change in the field effect mobility and off current can be observed. The shift of the threshold voltage is induced by accumulated electrons trapped by the $TiO2$ nanoparticles in the channel. The photosensitivity of the device has been found to be dependent on the concentration of $TiO2$ nanoparticles, the incident wavelength and the voltage between the source and drain.