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

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 alpha-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 mu s) 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/alpha-In2Se3 p-n heterojunction photodetector is demonstrated, which is promising for next-generation high-performance and low-power detection applications.