Polymer-Passivated ZnO Microcluster Arrays for High-Responsivity, Low-Voltage UV Photodetection

Metal-oxide UV photodetectors typically require elevated bias to achieve high sensitivity, limiting their suitability for low-power and portable applications. Here, we demonstrate poly(methyl methacrylate) (PMMA)-engineered zinc oxide (ZnO) nano-microcluster arrays (NMCAs) that deliver outstanding UV photodetection performance at a low operating voltage of 0.1 V. The optimized device exhibited a high responsivity of 376 mA W-1, representing an ∼8.5-fold enhancement over pristine NMCA-structured ZnO under identical testing conditions, while maintaining excellent cycling stability. Controlled PMMA infiltration progressively modulates surface defects and interparticle charge-transport pathways in these mechanically robust, liquid-sintered NMCAs, with the performance enhancement primarily arising from defect passivation rather than optical absorption changes. Structural and spectroscopic analyses suggest that controlled PMMA infiltration modifies the polymer-oxide interface without altering the intrinsic wurtzite ZnO crystal structure, with the enhanced response primarily attributed to PMMA-assisted defect passivation and improved carrier lifetime. A clear responsivity-speed trade-off emerges with increasing polymer loading, whereby intermediate PMMA content yields effective defect passivation and maximum responsivity, while excessive infiltration introduces transport bottlenecks. The relatively slow rise and decay times indicate that these devices are better suited to static or quasi-static UV monitoring rather than high-speed photodetection. Moreover, by enhancing UV photoresponse at a very low operating voltage of 0.1 V through rational polymer-oxide interfacial engineering, this scalable approach provides a promising strategy for battery-compatible UV monitoring and porous metal-oxide optoelectronic systems.