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

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]PF₆ (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 cm²/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.