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

摘要

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)-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-Si devices also confirmed the existence of the built-in electric field. Such Fe:TiO₂-Si heterojunction photodetectors might be potentially useful for relative applications with weak-signal fast detection in the UV-visible band.