SnSe/MoS ₂ Van der Waals Heterojunction for Ultrasensitive and Broadband Photodetection

Abstract Broadband photodetectors capable of detecting light from ultraviolet (UV) to near‐infrared (NIR) wavelengths are crucial for advanced optoelectronic applications. Here, the fabrication and characterization of a SnSe/MoS 2 van der Waals heterojunction photodetector with exceptional broadband sensitivity and ultrahigh responsivity are reported. Theoretical calculations and experimental analyses reveal a type‐II band alignment in the heterojunction, enabling efficient charge separation and transport. The photodetector demonstrates a high current on/off ratio (≈10 3 ) and outstanding responsivity, achieving 518 A W −1 at 380 nm, 540 A W −1 at 600 nm, and 25 A W −1 at 900 nm under a 1 V bias. Furthermore, the device exhibits a specific detectivity of up to 1.93 × 10 12 cm Hz 1/2 ·W −1 and an external quantum efficiency exceeding 195 000%. Raman spectroscopy and atomic force microscopy confirm the high quality of the SnSe and MoS 2 films and the successful formation of the heterojunction. Time‐dependent photoresponse and power‐dependent measurements demonstrate stable, repeatable performance across the UV, visible, and NIR spectra. This work highlights the SnSe/MoS 2 heterojunction as a promising platform for broadband, energy‐efficient photodetection, offering significant potential for applications in optical communication, imaging, and sensing technologies.