Z‐Scheme Bi ₂ S ₃ /ReS ₂ Heterostructure Enables High‐Responsivity Self‐Powered Photodetector for Underwater Optical Communication

Two‐dimensional Z‐scheme heterostructures exhibit broadband and strong optical absorption, efficient interfacial charge transfer, and robust redox capability. These attributes make them highly promising for constructing broadband, highly sensitive, and stable self‐powered photoelectrochemical (PEC) photodetectors, particularly for underwater optical communication. Despite this promise, how Z‐scheme interface engineering influences photodetection performance remains largely unexplored. In this work, centimeter‐scale Z‐scheme Bi 2 S 3 /ReS 2 heterostructures are synthesized via a two‐step vapor deposition method and employed as photoanodes in a self‐powered PEC photodetector. By virtue of efficient Z‐scheme charge transfer, the device exhibits broadband detection from 300 to 940 nm, a fast response time on the order of several hundred microseconds, and excellent operational stability. To the best of our knowledge, this self‐powered PEC photodetector achieves outstanding photoresponsivity, reaching 30.84 mA/W at 380 nm and a record‐high responsivity of 8.81 mA/W at 850 nm. To explore its practical applicability, we further demonstrate an underwater optical communication system operating at 380 and 850 nm for text data transmission. This work provides an effective strategy for constructing high‐performance self‐powered PEC photodetectors through the rational design of direct Z‐scheme heterostructures.