ZnO Nanowires for Ultraviolet Detection: Recent Developments, Challenges, and Future Outlook

Zinc oxide (ZnO) nanowires (NWs) are widely investigated for ultraviolet (UV) photodetectors (PDs) due to their wide direct bandgap, high exciton binding energy, and large surface-to-volume ratio enabling efficient light–matter interaction and carrier modulation. This review presents a device-physics-oriented analysis of recent advances in ZnO NW-based UV photodetectors, emphasizing the interplay between nanostructure synthesis, interface engineering, and carrier transport mechanisms. Three main device architectures—photoconductive, Schottky barrier, and metal–semiconductor–metal (MSM)—are compared in terms of operating principles, performance trade-offs, and fundamental limitations. Key enhancement strategies, including doping, surface passivation, plasmonic modification, and hybrid heterostructure integration, are discussed with respect to improvements in responsivity, response speed, and stability. Recent progress in flexible, self-powered, and multifunctional UV photodetectors is also highlighted. Current challenges, including defect control, interface engineering, reproducibility, and scalable fabrication, are critically assessed. By establishing a unified structure–property–device physics framework, this review provides insights into the fundamental limitations of ZnO NW UV photodetectors and design guidelines for next-generation optoelectronic devices.