A freestanding electrochromic copolymer for multicolor smart window

Abstract Electrochromic devices with low-cost, energy-saving advantages, and controllable color switching have gained widely attention. Yet, electrochromic materials are limited for smart window due to challenges such as difficulty freestanding, monotonous color change, slow switching capability, and low optical contrast. In this work, a freestanding copolymer based on Poly(N-vinylcarbazole) (PVK) and 3, 4-ethoxylenedioxythiophene (EDOT) are designed. The copolymer synthesized by the good secondary film-forming of PVK not only contains the self-standing property of PVK, but also possesses excellent electrical and electrochemical properties of EDOT. The freestanding copolymer is used to create the multicolor: brown, dark brown, purple, blue. A high optical contrast of up to 39.1% and a color efficiency of up to 107.00 cm 2 C-1 prove a significant coloration and bleaching effect, which is satisfactory for the application of electrochromic devices. Further, an electrochromic device based on P(PVK-co-EDOT) as coloring materials is constructed. This work contributes new ideas into the design of electrochromic smart materials.