Ultrafast, Self-Driven, and Air-Stable Photodetectors Based on Multilayer PtSe₂/Perovskite Heterojunctions

We report on the large-scale synthesis of polycrystalline multilayer PtSe₂ film with typical semimetallic characteristics. With the availability of the large-area film, we constructed a heterojunction composed of multilayer PtSe₂ and Cs-doped FAPbI₃, which can function as a self-driven photodetector in a broadband wavelength from the ultraviolet to the near-infrared region. Further photoresponse analysis revealed that the heterojunction device showed outstanding photosensitive characteristics with a large I_light/I_dark ratio of 5.7 × 10³, high responsivity of 117.7 mA W^-1, and decent specific detectivity of 2.91 × 10¹² Jones at zero bias. More importantly, the rise/fall times were estimated to be 78/60 ns, rendering our device the fastest device among perovskite-2D photodetectors reported to date. In addition, it was also observed that the PtSe₂/perovskite photodetector can almost retain its photoresponse properties after storage in ambient conditions for 3 weeks. This study suggests the potential of the present PtSe₂/perovskite heterojunction for future air-stable ultrafast photodetecting applications.