Self-powered UV-visible photodetector with fast response and high photosensitivity employing an Fe:TiO2/n-Si heterojunction

An ultrasensitive, fast response and self-powered photodetector would be preferable in practical applications. In this paper, we report fast response, high photosensitivity and self-powered Fe doped TiO2 (Fe:TiO2)/n-Si UV-visible detectors via a facile solution process. As-fabricated devices exhibited excellent photoresponse properties, including high responsivity of 46 mA W−1 (350 nm) and 60 mA W−1 (600 nm) with 0.5 mW cm−2 light irradiation under zero bias, as well as an ultrasensitive (on/off ratio up to 103), fast (rise/decay time of <10/15 ms), and broad-band (UV-visible) photodetection with no or low external energy supply. Furthermore, the quantum efficiency of the heterojunction rose up beyond 100% with a broad wavelength range at a small reverse bias of −0.5 V. The self-power originated from the existence of a built-in electric field between Fe:TiO2 and Si that helps facilitate the separation of photogenerated electron–hole pairs and regulate the electron transport. Capacitance–voltage (C–V) measurements of Fe:TiO2/n-Si devices also confirmed the existence of the built-in electric field. Such Fe:TiO2/n-Si heterojunction photodetectors might be potentially useful for relative applications with weak-signal fast detection in the UV-visible band.