Defect-Driven Negative Photoresponse in Flexible Self-Powered Porous β-Ga2O3 Deep-UV Photoelectrochemical Photodetector

Abstract Monoclinic gallium oxide (β-Ga2O3) is a promising wide-bandgap oxide semiconductor material with intrinsic solar-blind spectral selectivity that renders it well suited for advanced next-generation deep-ultraviolet (DUV) photodetector applications in the fields of aquatic surveillance and undersea imaging. Herein, we have demonstrated a β-Ga2O3 based flexible, self-powered photoelectrochemical (PEC) DUV photodetector using a simple and cost-effective electrophoretic deposition (EPD) technique. Notably, this work reports the successful realization of β-Ga2O3 films on a flexible conducting aluminum substrate for PEC photodetection. It was found that the prevalence of oxygen vacancy derived surface-defect states in conjunction with significantly large film thickness (>3 μm) and film porosity dictated the dominant photogenerated charge transport mechanisms and response kinetics. This synergistic effect suppressed the drift-driven photogenerated electron extraction to the back electrode and facilitated diffusion-controlled electron transfer across the semiconductor/electrolyte interface, resulting in a stable and robust negative photoresponse under DUV illumination. The photoresponse characteristic analysis of the β-Ga2O3 films exhibited a maximum responsivity of 1.17 mA/W, a detectivity of 3.22 × 109 Jones, along with a fast dynamic response with rise and decay times of 18 and 95 ms, respectively. Moreover, the devices exhibit stable photodetection performance under various bending angles and after repeated bending cycles of up to 200 times, demonstrating excellent mechanical flexibility and structural robustness for reliable operation in dynamic underwater environments. These findings highlighted a scalable, solution-processed strategy for realizing ultrafast, flexible, self-powered β-Ga2O3-based PEC DUV photodetectors, for underwater-based optoelectronic applications.