Redox Dependent Color Modulating Copper(I) Complex for Flexible Electrochromic Device

Abstract Pursuing the development of eco‐friendly, cost‐effective and flexible materials that offer high‐color contrast and low power consumption is a promising approach for advancing the next‐generation optoelectronic devices. Herein, we report the synthesis of a heteroleptic copper(I) complex [Xantphos‐Cu‐cmdf]PF 6 ( C1 ), in high yield, using Xantphos and cmdf ligands. The complex has high thermal stability and displays low‐energy absorption between 360 and 470 nm due to the metal‐to‐ligand charge transfer (MLCT) transition. The electrochemical analysis confirmed the electrochromic properties of C1 . A bilayer electrochromic device (ECD) incorporating P3HT and C1 demonstrated excellent color modulation (45 %) and rapid switching times (less than one second). Furthermore, the flexible ECD utilizing C1 showed superior performance compared to its solid‐state counterpart, with high efficiency (~200 cm 2 /C), color modulation (69 %) and sub‐second switching times. The high coloration efficiency and fast switching time of the ECDs developed from stable and cost‐effective Cu(I) complex, C1 , make it a promising candidate for real‐world electrochromic applications.