Electrochromic property of a copolymer based on 5-cyanoindole and 3,4-ethylenedioxythiophene and its application in electrochromic devices

The spectroelectrochemical and electrochromic properties of a novel copolymer (P(CNIn-co-EDOT)) obtained from 3,4-ethylenedioxythiophene (EDOT) and 5-cyanoindole (CNIn) were discussed. P(CNIn-co-EDOT) can change between purple in the reduced state and blue in the oxidized state. Electrochromic devices (ECDs) based on P(CNIn-co-EDOT) and poly(3,4-ethylenedioxythiophene) (PEDOT) were also fabricated. This as-prepared ECD showed good optical contrast (48% at 630 nm), high coloration efficiency (680 cm2 C−1), fast response time (0.8 s at 630 nm), good optical memory and long-term stability. Clear change of ECD from brown (reduced state) to dark blue color (oxidized state) was demonstrated with robust cycle life.