Polycarbazole Electropolymerization Materials with Excellent Electrochromic Performance Based on Phenothiazine/Phenoxazine Group

Abstract Electrochromic small molecules suffer from the difficult film processibility and serious dissolvability at their oxidation state, which greatly limit their applications in electrochromic areas. Here, well‐defined electrochemical polymer structures, pCZ‐FSQ and pCZ‐FEQ, are obtained by taking advantage of the unique electrochemical dimerization of carbazole, and low redox‐potential phenothiazine and phenoxazine groups are introduced as an electrochromic color‐changing unit with the interruption of conjugation between them via an alkyl chain linkage. The obtained polymer films pCZ‐FSQ and pCZ‐FEQ are composed of the independent dimeric carbazole and organic small molecule units. Finally, they exhibit outstanding electrochromic properties with optical contrast of more than 50%, switching time of less than 1 s, excellent stability (over 500 cycles of optical stability), and ultrahigh coloration efficiency (276 cm 2 C −1 for pCZ‐FSQ , 384 cm 2 C −1 for pCZ‐FEQ). This is thought to be greatly attributed to the well‐defined electrochemical polymer structures with dual electrochromic color‐changing properties of both phenothiazine/phenoxazine and dimeric carbazole. This can also provide some implications for the future in‐depth study of small molecule electrochromism and the solution to the problem of difficult processing of small molecules.