A new electrochromic material from an indole derivative and its application in high-quality electrochromic devices

A novel electrochromic material, poly(indole-6-carboxylic acid) (PIn), and its application in electrochromic devices (ECDs) are discussed. PIn was switched between yellow in the reduced state and green in the oxidized state. Electrochromic switching of PIn film shows that it has fast switching time and high optical contrast. ECD based on PIn and poly(3,4-ethylenedioxythiophene) (PEDOT) was also fabricated and characterized. The response time of this device was found to be 1.0 s and the optical contrast was 45%. The coloration efficiency (CE) was calculated to be 510 cm2 C−1. Clear change from green (neutral) to blue-violet color (oxidized) of ECD is demonstrated with robust cycle life. These results provide an avenue for applications of polyindole family in electrochromic devices.