Broadband Visible−Near Infrared Two‐Dimensional WSe₂/In₂Se₃ Photodetector for Underwater Optical Communications

Abstract P–n junctions based on 2D materials can be achieved using a selective doping technique, while such a method is challenged by the complex fabrication process. Here, a facile van der Waals (vdWs) structured p–n heterojunction is demonstrated by simply transferring an n‐type multilayer α‐In₂Se₃ (direct bandgap) on a p‐type ultra‐thin WSe₂ nanosheet. The vdWs stacked photodetector with an improved type‐II band alignment not only realizes a broadband spectral response from visible to near infrared (405–905 nm), but also operates well with a diode‐like behavior. This behavior is further confirmed by the high‐resolution scanning photocurrent mapping. As a result, the as‐fabricated device exhibits a short response time (<120 µs) and a high responsivity of 1.84 A W⁻¹ under 520 nm laser illumination. Accordingly, an underwater optical communication system based on the WSe₂/α‐In₂Se₃ p‐n heterojunction photodetector is demonstrated, which is promising for next‐generation high‐performance and low‐power detection applications.