Type-I isotype MoS₂/InSe heterostructure enabling self-powered broadband photodetection with high responsivity and detectivity

We report the development of a self-powered broadband photodetector based on a vertically stacked type-I isotype MoS₂/InSe heterojunction, fabricated by transferring chemical vapor deposition-grown monolayer MoS₂ onto exfoliated InSe. The resulting n − n heterostructure forms a unilateral depletion region and establishes a favorable type-I band alignment that enables efficient charge carrier separation and suppresses dark current. Benefiting from the synergistic integration of broadband optical absorption and efficient carrier dynamics at the interface, the MoS₂/InSe heterojunction photodetector demonstrates excellent performance across a broad spectral range from ultraviolet to near-infrared. Under 365 nm illumination at a reverse bias of –5 V, the device achieves a responsivity of 936.8 A/W, a specific detectivity of 9.67 × 10 ¹ ² Jones, and an external quantum efficiency (EQE) of 3186.8 %, along with excellent stability and reproducibility. Particularly, under zero bias, the device supports self-powered operation, achieving a responsivity of 26.8 A/W, a detectivity of 2.63 × 10¹¹ Jones, and an EQE of 91.4 %. Spatially resolved photocurrent mapping reveals a localized photoresponse within the junction region, highlighting the influence of the built-in electric field induced by the type-I isotype band alignment. These findings underscore that the potential of the MoS₂/InSe heterostructure as a promising platform for next-generation broadband photodetectors with high sensitivity and wide spectral response.