Photo‐Engineered Ionic Conductor Boost Energy‐Saving in Flexible Smart Window

This study presented an in‐situ photopolymerization strategy to fabricate a high‐performance quasi‐solid‐state electrolyte (QSSE) based on polyethylene glycol diacrylate for reversible metal electrodeposition‐based electrochromic reflective devices. The network structure of the electrolyte was optimized by adjusting the polymer content, a grain refinement phenomenon of silver deposition in the QSSE was reported, and the underlying mechanism responsible for the accelerated deposition and relatively slower bleaching behavior is elucidated for the first time. The F‐ERD exhibited a high ionic conductivity of 7.8 × 10 −4 S·cm −1 , featuring a rapid 10 s fast coloration response. It demonstrated excellent optical modulation performance (average solar reflectance of 89.8%, transmittance of 80.6%) across the 300–2500 nm wavelength range and good cycling stability (90% retention of initial modulation range after 1200 cycles). The F‐ERD achieved efficient infrared isolation and photothermal regulation through reflection, and operated stably over a wide temperature range from −40°C to 60°C. Outdoor tests demonstrated that the colored state could reduce the indoor temperature by up to 19°C compared to ordinary glass under solar irradiance of approximately 400 W·m −2 , making it suitable for all‐season applications in both planar and curved smart windows.