High‐Visibility Underwater Imaging Enabled by Schottky Barrier Engineering in Multilayer WS ₂ Based Self‐Powered Blue‐Light Photodetector

Self‐powered blue‐light photodetectors, operating without an external power source, are highly desirable for low‐latency and interference‐resistant underwater wireless optical communication (UWOC). However, a key challenge persists in designing device architecture that provides a sufficiently strong built‐in electric field, limiting progress toward high‐performance self‐powered operation. Here, we address this challenge through Schottky barrier engineering at the interfaces, combined with multilayer WS 2 as the photosensitive layer that leverages high‐energy excitons for strong blue‐light absorption. The resulting PdSe 2 /WS 2 /graphene heterojunction photodetector exhibits a significantly enhanced built‐in electric field, yielding an ultrahigh responsivity of 214 mA/W and a high specific detectivity of 3 × 10 12 Jones. When integrated into a single‐pixel imaging system, the photodetector enables high‐visibility underwater imaging in both clear and turbid water environments, with the peak signal‐to‐noise ratio consistently maintained above 22 dB. This work introduces a new paradigm for self‐powered optoelectronic devices through Schottky barrier engineering and provides a foundation for next‐generation UWOC and real‐time underwater imaging systems.