A high-performance and easily fabricated Ni/β-Ga₂O₃ Schottky photodiode was developed for ultraviolet solar-blind detection.

Underwater imaging technology plays a pivotal role in marine exploration and reconnaissance, necessitating photodetectors (PDs) with high responsivity, fast response speed, and low preparation costs. This study presents the synergistic optimization of responsivity and response speed in self‐powered photoelectrochemical (PEC)‐type photodetector arrays based on oxygen‐vacancy‐tuned amorphous gallium oxide (a‐Ga₂O₃) thin films, specifically designed for solar‐blind underwater detection. Utilizing a low‐cost one‐step sputtering process with controlled oxygen flow, a‐Ga₂O₃ thin films with varying oxygen vacancy (V_O) concentrations are fabricated. By balancing the trade‐offs among electrocatalytic reactions, charge transfer, carrier recombination, and trapping, both the responsivity and response speed of a‐Ga₂O₃‐based self‐powered PEC‐PDs are simultaneously improved. Consequently, the optimized PEC‐PDs demonstrated exceptional performance, achieving a responsivity of 33.75 mA W⁻¹ and response times of 12.8 ms (rise) and 31.3 ms (decay), outperforming the vast majority of similar devices. Furthermore, a pronounced positive correlation between anomalous transient photocurrent spikes and the concentration of V_O defects is observed, offering compelling evidence for V_O‐mediated indirect recombination. Finally, the proof‐of‐concept solar‐blind underwater imaging system, utilizing an array of self‐powered PEC‐PDs, demonstrated clear imaging capabilities in seawater. This work provides valuable insight into the potential for developing cost‐effective, high‐performance a‐Ga₂O₃ thin‐film‐based PEC‐PDs for advanced underwater imaging technology.

A new type of self-powered solar-blind photoelectrochemical-type photodetector based on 3D a-Ga₂O₃/CFP core–shell structures was obtained. The device is simple, low cost, and has high reproducibility, and extreme stability.