Response Speed-Tunable Photodetectors Based on Hybrid Ternary FePSe₃ Nanoflakes

The layered metal phosphorus trichalcogenides (MPTs) are a newly emerging van der Waals material family with bandgaps ranging from 1.3 to 3.5 eV, which are promising candidates for optoelectronic devices. By using the excited multiple energy levels of FePSe3, a high-performance FePSe3 photodetector, which shows tunable response speed in the range of ultraviolet (UV) to near-infrared (NIR), is designed. The FePSe3 photodetector exhibits a high photoresponsivity of 236.18 A center dot W-1 under 532 nm laser illumination (laser power density P = 1 mW cm(-2)). The properties of FePSe3 can be modulated by oxygen plasma treatment, which transfer to oxygen-doped FePSe3 (FePSe3-O). Moreover, the speed of the FePSe3-O photodetector can be improved more than 240 times compared to the intrinsic FePSe3 photodetector under NIR illumination (lambda = 808 nm). In addition, the FePSe3-graphene heterojunction can significantly improve the photoresponsivity and simultaneously prolong the response time of the device due to the FePSe3/graphene interfacial barrier. These results suggest that intrinsic, doped FePSe3 and its heterojunction can be used as multifunctional photodetectors with tunable response speeds.