Ti₃C₂T_<i>x</i> MXene-Mediated Synthesis of a Prussian Blue Nanocomposite Film for a Flexible Large-Area Electrochromic Device

Smart window applications are highly promising for tuning the sunlight intensity in buildings and vehicles. Large-area flexible smart windows are easily integrated with any curved surface compared to the conventional rigid devices yet are challenging due to the difficulty in fabricating large-area homogeneous electrochromic films. Herein, we demonstrate a MXene mediated Prussian blue <i>in situ</i> synthesis strategy to fabricate a large-area MXene@Prussian blue composite film (MPB) on rigid (up to 900 cm²) and flexible ITO substrates with high homogeneity and adjustable thickness. The MPB composite films exhibit remarkable electrochromic performance, including faster optical modulation response (3/5 s for coloring/bleaching), higher coloration efficiency (194.5 cm² C^-1), and enhanced electrochromic stability compared to pure Prussian blue films. The assembled MPB/Zn electrochromic device demonstrates energy storage ability, achieving multifunction as a smart power source with capacity visualization. Notably, the MPB composite based flexible device maintains stable electrochromic cycling with no obvious optical modulation degradation after rigorous mechanical bending. The present method will provide a fresh impetus for the development of flexible large-area electrochromic devices toward practical applications.