Superior-performance InSe/CdS van der Waals heterojunction photodetector for self-powered imaging

Abstract

Van der Waals heterojunction (vdWH) photodetectors and self-powered photodetectors hold considerable promise for modern technology, though it remains challenging to achieve high performance. In this work, we employ band engineering to construct an InSe/CdS vdWH photodetector. Benefiting from a type-II band alignment with conduction band matching, a high potential barrier in the valence band, and a robust built-in electric field, the device demonstrates exceptional optoelectronic performance. Under an applied bias, it delivers a responsivity of 2.16 × 10³ A W⁻¹, an ultrahigh on/off ratio of 3.71 × 10⁷, a fast response speed of 45 µs, and a specific detectivity approaching the theoretical limit of 2.94 × 10¹³ Jones. In self-powered mode (zero bias), the device achieves a photocurrent of 3.33 nA, a responsivity of 58.23 mA W⁻¹, and a rapid response speed of 69 µs. The DFT theoretical results revealed that the carrier concentration of the heterojunction is larger than that of either single CdS or InSe, which explains the photoelectronic enhancement mechanism of the device. Remarkably, the InSe/CdS vdWH photodetector also exhibits excellent high-resolution and high-contrast imaging capabilities under zero bias. These results highlight its significant potential for low-power applications and point to a novel, innovative device solution for this field.