Electrodeposited Copolymers Based on 9,9'-(5-Bromo-1,3-phenylene)biscarbazole and Dithiophene Derivatives for High-Performance Electrochromic Devices.

A 1,3-bis(carbazol-9-yl)benzene derivative (BPBC) was synthesized and its related homopolymer (PBPBC) and copolymers (P(BPBC--BT), P(BPBC--CDT), and P(BPBC--CDTK)) were prepared using electrochemical polymerization. Investigations of polymeric spectra showed that PBPBC film was grey, iron-grey, yellowish-grey, and greyish-green from the neutral to the oxidized state. P(BPBC--BT), P(BPBC--CDT), and P(BPBC--CDTK) films showed multicolor transitions from the reduced to the oxidized state. The transmittance change (Δ) of PBPBC, P(BPBC--BT), P(BPBC--CDT), and P(BPBC--CDTK) films were 29.6% at 1040 nm, 44.4% at 1030 nm, 22.3% at 1050 nm, and 41.4% at 1070 nm. The coloration efficiency () of PBPBC and P(BPBC--CDTK) films were evaluated to be 140.3 cm C at 1040 nm and 283.7 cm C at 1070 nm, respectively. A P(BPBC--BT)/PEDOT electrochromic device (ECD) showed a large Δ (36.2% at 625 nm) and a fast response time (less than 0.5 s), whereas a P(BPBC--CDTK)/PEDOT ECD revealed a large (534.4 cm C at 610 nm) and sufficient optical circuit memory.