Visualized UV Photodetectors Based on Prussian Blue/TiO₂ for Smart Irradiation Monitoring Application

The growing needs in monitoring health and environmental risks call for the development of smart ultraviolet (UV) photodetectors with special or multiple functions. Herein, a photoelectrochemical cell based self‐powered and wearable UV photodetector system with high stability, high speed, and an interesting visualization feature is successfully developed. TiO 2 nanotubes on flexible Ti foil and Prussian blue on flexible polyethylene terephthalate/indium‐tin oxide are selected as the photoanode and electrochromic counter electrode, respectively. The integrated flexible UV photodetectors can not only function stably for many bending cycles but also exhibit visualized indication of UV exposure by recyclable color change without external power. Moreover, the as‐fabricated visible‐blind photodetectors show excellent UV responsivity (78.3 mA W −1 ), ultralow UV light detection limit (<10 µW cm −2 ), and fast response with a rise time and a decay time of 0.04 and 0.06 s, respectively. Our all‐in‐one smart photodetector has demonstrated great application potential in self‐powered smart sensors and wearable healthcare electronics.