Black electrochromic devices based on a highly conductive n-type polymer and a bilayer structure

Abstract

Organic electrochromic materials are particularly distinguished by their adjustable coloration and solution processability, showing significant potential in the domains of smart windows and automotive applications. Conductive polymer-based electrochromic devices can achieve color-rich and high-performance devices by altering the material structure. However, traditional electrochromic devices face challenges such as non-black coloration, cumbersome preparation process and electrode corrosion problems. To address these issues, this study applies a novel n-type conducting polymer poly(benzodifurandione) (PBFDO) as one electrochromic layer and introduces a ferrocene-based redox couple into the ion-transporting electrolyte film. The resulting bilayer black devices achieve complete electrochromic cycles via PBFDO reduction and redox couple oxidation. High-quality PBFDO films with controllable thickness, neutral gray-black color, and robust adhesion to ITO substrates were confirmed. The devices exhibit broad-spectrum modulation, good electrochromic performance, excellent cyclic stability (50 000 cycles), and superior heat insulation performance. This innovative approach streamlines the fabrication process on a large scale and offers substantial support for their practical deployment.