Three-coordinated Cu(I) complexes for electrochromic devices with high coloration efficiency

The development of efficient electrochromic materials is critical for advancing energy-efficient smart windows and next-generation display systems. In this study, three-coordinated heteroleptic Cu(I) complexes [Cu(Sphos)(cmdf)]PF6 (1) and [Cu(Xphos)(cmdf)]PF6 (2), incorporating bulky phosphine ligands, have been synthesized to design energy-efficient electrochromic smart devices. Complex 1 exhibits the structural robustness along with reversible and stable redox performance, making it suitable for device integration. Both rigid and flexible devices constructed using 1 demonstrate excellent electrochromic performance. Complex 1 delivers reproducible and high-contrast switching, demonstrating a color contrast as high as 42% and a coloration efficiency of 690 cm2/C. These results highlight the potential of Cu(I) complexes as viable alternatives to traditional electrochromic materials.