Enhanced ultraviolet photo-detecting by constructing TiO2/KNbO3 heterojunction

Abstract

The demands of the ultraviolet (UV) radiation monitoring is rising in fields of human health and survival surroundings. Among many types of UV detectors, the photoelectrochemical (PEC) type UV detectors based on solar sensitized cells have gained a lot attention because of their fast response, low cost, simple manufacturing process, self-powered and so on. The heterojunction can accelerate the separation and migration of photogenerated carriers and then improve the photoresponse of UV detectors. In this work, the nanostructure KNbO3 (KNO) films were modified by chemical bath deposition to form a TiO2/KNO heterojunction. Compared with the UV detectors based on pure KNO and TiO2, the responsivity of the developed PEC UV photodetectors based on TiO2/KNO reached 11.99 mA W−1 under UV illumination of 35 mW cm−2 @ 365 nm, which is higher than that of the pure KNO UV detector (1.26 mA W−1) and the TiO2 UV detector (3.96 mA W−1). Besides, the lifetime of photogenerated carrier, response time and recovery time of the detector are all promoted. The results can be attributed to the formation of a TiO2/KNO heterojunction, in which the generated built-in electric field can promote the separation of photogenerated carriers and hinder the recombination of photogenerated electron–hole pairs, thus improving the detection performance of the UV detectors.