Electrochromic characterizations of copolymers based on 4,4′-bis(N-carbazolyl)-1,1′-biphenyl and indole-6-carboxylic acid and their applications in electrochromic devices

151Schematic diagrams of P(BCz1-co-Inc2)/PProDOT-Et2 device. The ECDs were fabricated by arranging the P(BCz1-co-Inc2) anodic polymer film and PProDOT-Et2 cathodic polymer film to face each other, and they were separated by a PMMA-PC-LiClO4 gel electrolyte. At − 1.3 V, P(BCz1-co-Inc2) was transparent in its neutral state and PProDOT-Et2 was transparent in its oxidized state; therefore, the P(BCz1-co-Inc2)/PProDOT-Et2 ECD was transparent. As the applied potential increased from − 1.3 to + 0.7 V, the color of P(BCz1-co-Inc2) and PProDOT-Et2 films became yellowish brown and light blue, respectively. As the applied potential increased further from + 0.7 to + 1.3 V, the color of P(BCz1-co-Inc2) film became greyish black in its highly oxidized state and PProDOT-Et2 layer became dark blue in its neutral state. The color of P(BCz1-co-Inc2)/PProDOT-Et2 ECD was dark blue at 1.3 V.