A multifunctional smart window: Detecting ultraviolet radiation and regulating the spectrum automatically

Excessive ultraviolet (UV) radiation is known to cause several skin diseases, and hence smart electronics with the capacity to measure and control UV radiation have attracted substantial attention. In this work, a dual-functional smart window that can detect outdoor UV intensity in real time and then respond by automatically adjusting its color to control UV transmission has been developed for the first time by integrating a TiO₂ based photodetector with a viologen hydrogel based electrochromic device. Excellent photodetector properties, including high transparency of 90% at 585 nm, great photoresponsivity of 67.15 mA W^-1 and an outstanding photo-dark current ratio of 1.48 × 10⁴ have been demonstrated. Meanwhile, the viologen hydrogel based electrochromic device possesses a significant color change with modulation of transmittance up to 60% in the visible range and can efficiently block almost 94% radiation in the UV-A range. This work demonstrates the ability of real time monitoring and regulating the UV radiation via integration of TiO₂ films with electrochromic hydrogels, which may guide the development of next generation multifunctional smart windows.