High-Performance, Self-Powered Photodetector Based on a NbOI 2 /WS 2 van der Waals Heterojunction with Type-II Band Alignment

Abstract The design of superior van der Waals (vdW) heterojunctions is a pivotal objective in condensed matter physics, aiming to achieve strong interlayer coupling and tailored charge transfer, thereby enabling functionalities that transcend the capabilities of individual constituent layers. Herein, we demonstrate a high-performance photodetector based on NbOI 2 /WS 2 heterojunction, which exhibits a pronounced photoresponse across the visible light region, achieving a peak responsivity of 380 mA/W and a specific detectivity of 1.20×10 12 Jones at 405 nm. Notably, the device operates in a self-powered mode at zero bias with a high on/off ratio of 2.48×10 4 and exhibits fast response with rising/falling times of ~ 32/34 ms. Spectral and computational analyses confirm a type-II band alignment for this heterojunction, which generates a strong built-in electric field at the heterointerface. This field is identified as the key factor for the efficient separation of photogenerated carriers, underpinning the superior device performance.