High-Performance Self-Powered Photodetectors Based on the MnS/MoS2 Heterojunction with Smooth Interfacial Band Bending

Self-powered photodetectors operate without external power sources, offering potential as critical components in next-generation smart systems that function independently, wirelessly, and sustainably. Enhancing the photoresponse of self-driven devices to light is crucial. In this work, a type-II heterojunction of MnS/MoS2 is rationally designed and fabricated without interfacial abrupt band bending using nonlayered MnS and layered MoS2. The discrepancy in the Fermi level between MnS and MoS2 flakes, revealed by Kelvin probe force microscope and first-principles calculations, is as small as 30 and 60.6 meV, respectively, forming smooth band bending at the heterojunction interface and facilitating the separation of photoinduced electron-hole pairs. As a result, the MnS/MoS2 heterojunction exhibits exceptional performance as a self-powered photodetector, with a photoresponsivity of 1.31 A W-1 and an external quantum efficiency of 316% at zero bias under 532 nm laser irradiation. Additionally, the photodetectors demonstrate broadband detection in the visible range with a maximal photoresponsivity of 11.58 A W-1 and a response time of 20/30 ms, outperforming the component materials MoS2 and MnS. The strategy of band engineering demonstrated in this work may provide a useful guideline for designing high-performance self-powered photodetectors.