Electrosynthesis of electrochromic polymer membranes based on 3,6-di(2-thienyl)carbazole and thiophene derivatives

Five carbazole-containing polymeric membranes (PDTC, P(DTC-co-BTP), P(DTC-co-BTP2), P(DTC-co-TF), and P(DTC-co-TF2)) were electrodeposited on transparent conductive electrodes. P(DTC-co-BTP2) shows a high ∆T (68.4%) at 855 nm. The multichromic properties of P(DTC-co-TF2) membrane range between dark yellow, yellowish-green, gunmetal gray, and dark gray in various reduced and oxidized states. Polymer-based organic electrochromic devices are assembled using 2,2^′-bithiophene-and 2-(2-thienyl)furan-based copolymers as anodic membranes, and poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) (PEDOT-PSS) as the cathodic membrane. P(DTC-co-TF)/PEDOT-PSS electrochromic device (ECD) displays a high transmittance change (∆T%) (43.4%) at 627 nm as well as a rapid switching time (less than 0.6 s) from a colored to a bleached state. Moreover, P(DTC-co-TF2)/PEDOT-PSS ECD shows satisfactory optical memory (the transmittance change is less than 2.9% in the colored state) and high coloration efficiency (512.6 cm² C⁻¹ ) at 627 nm.