Vacancy Engineering Optimizing Solid/Liquid Interfacial Properties for Boosting Self‐Powered Solar‐Blind Photodetection

Abstract Due to the nature of the aqueous operation characteristics of photoelectrochemical‐type (PEC) optoelectronic devices, it is vital to manipulate the semiconductor/electrolyte interfacial properties to synergistically regulate the photogenerated carrier separation, charge transport in semiconductors, and interfacial charge transfer. In this work, it is demonstrated that sulfur vacancy effectively manipulates the band structure of ZnS and works as electrochemical reaction active sites synchronously. ZnS with more sulfur vacancy forms a larger built‐in electric field at the ZnS/electrolyte interface, simultaneously boosting photogenerated charge separation efficiency and promoting charge transport in ZnS. The sulfur vacancy also functions as the interfacial electrochemical reaction active sites, thereby accelerating the interfacial electrochemical reaction kinetics and reducing photo‐oxidation behavior. Hence, the corresponding ZnS PEC photodetectors exhibit excellent self‐powered solar‐blind ultraviolet detection capability with ultrahigh responsivity of 241.71 mA W^⁻1, fast rise/decay time of 15/15 ms, high detectivity of 8.9 × 10¹¹ Jones, outstanding wavelength selectivity of 1343, and excellent stability (92.6% after 8‐month storage), which is one of state‐of‐the‐art PEC UV photodetectors. Furthermore, the prototype of an underwater wireless optical communication device is demonstrated using ZnS PEC photodetectors as the light signal receiver. This work endows new sight for ZnS applications in underwater optoelectronic devices.