Nickel Doping in Tin Disulfide Enables Visible Photodetectors with Extended Detection Range and High Responsivity

Visible photodetectors based on two-dimensional tin disulfide (SnS₂) have attracted interest for applications in optical communication, information capture, and military reconnaissance owing to their high absorption efficiency, atomic-scale thickness, and nontoxicity. However, their intrinsic bandgap limits their spectral detection range, hindering further practical applications. Herein, we introduce VIII B-nickel (Ni) with a similar ionic radius to Sn to form Ni-doped SnS₂ few-layers via micromechanical exfoliation. As the Ni-doping concentration increases, the bandgap decreases from 2.14 (SnS₂) to 1.95 eV (Sn_0.9Ni_0.1S₂). Subsequently, Ni-doped SnS₂-based photodetectors are fabricated and characterized. These devices exhibit an extended spectral detection range and excellent performance, with a maximum responsivity of 2009 A W^-1 and high normalized detectivity of 2.47 × 10¹² cm Hz^1/2 W^-1. Furthermore, to suppress dark current and noise, SnS₂/Ni-doped SnS₂ homostructures and their corresponding photodetectors are fabricated. The built-in electrical field of the homostructure effectively reduces the dark current of the homostructure photodetector to 110 nA. Consequently, the responsivity is enhanced to 3350 A W^-1 and the response time is reduced to 3.5 ms, outperforming most other 2D material-based and commercial photodetectors. And Ni-SnS₂ VPDs show an application potential in imaging and visible-light communication systems. Thus, this study presents an effective approach to extend the detection spectrum of SnS₂-based photodetectors and pave the way for their future applications.