A fast-response self-powered UV–Vis–NIR broadband photodetector based on a AgIn₅Se₈/t-Se heterojunction

Abstract

Type II p-n heterojunction could improve the photodetecting performance of a photodetector due to the excellent ability of carrier separation. N-type AgIn5Se8 (AIS) exhibits a large optical absorption coefficient, high optical conductivity and suitable bandgap, which shows potential application in broadband photodetecting. Even though our previous study on AgIn5Se8/FePSe3 exhibited a good response speed, it still gave low responsivity due to the poor quality of p-type FePSe3 thin-film. Se with a direct bandgap (around 1.7 eV), p-type conductivity, high electron mobility and high carrier density is likely to form a low dimensional structure, which leads to the increase of effective contact area of the heterojunction and further improves the photodetector performance. In this work, continuous and dense t-Se thin-film was prepared by electrochemical deposition. The self-powered AgIn5Se8/t-Se heterojunction photodetector exhibited a broadband detecting range from 365 to 1200 nm. The responsivity and detectivity of the heterojunction photodetector are 32 mA/W and 1.8×109 Jones, respectively, which show around 9 and 4 times higher than the AgIn5Se8/FePSe3 heterojunction photodetector. The main reason is due to the good quality of the t-Se thin-film and the formation of the low dimensional t-Se nanoribbons, which optimized the transport pathway of carriers. The results indicate that AgIn5Se8/t-Se heterojunction proves to be an excellent candidate for broadband and self-powered photoelectronic devices.