Response Speed‐Tunable Photodetectors Based on Hybrid Ternary FePSe3 Nanoflakes

Abstract 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 FePSe 3 , a high‐performance FePSe 3 photodetector, which shows tunable response speed in the range of ultraviolet (UV) to near‐infrared (NIR), is designed. The FePSe 3 photodetector exhibits a high photoresponsivity of 236.18 A·W −1 under 532 nm laser illumination (laser power density P = 1 mW cm −2 ). The properties of FePSe 3 can be modulated by oxygen plasma treatment, which transfer to oxygen‐doped FePSe 3 (FePSe 3 ‐O). Moreover, the speed of the FePSe 3 ‐O photodetector can be improved more than 240 times compared to the intrinsic FePSe 3 photodetector under NIR illumination ( λ = 808 nm). In addition, the FePSe 3 ‐graphene heterojunction can significantly improve the photoresponsivity and simultaneously prolong the response time of the device due to the FePSe 3 /graphene interfacial barrier. These results suggest that intrinsic, doped FePSe 3 and its heterojunction can be used as multifunctional photodetectors with tunable response speeds.