Electrodeposited Copolymers Based on 9,9′-(5-Bromo-1,3-Phenylene)Biscarbazole and Dithiophene Derivatives for High-Performance Electrochromic Devices

• Main Authors: Chung-Wen Kuo, Jui-Cheng Chang, Jeng-Kuei Chang, Sheng-Wei Huang, Pei-Ying Lee, Tzi-Yi Wu
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Polymers
• Subjects: electrodeposition; absorption spectra; transmittance; electrochromic device; redox stability
• Online Access: https://www.mdpi.com/2073-4360/13/7/1136
• ISSN: 2073-4360

A 1,3-bis(carbazol-9-yl)benzene derivative (BPBC) was synthesized and its related homopolymer (PBPBC) and copolymers (P(BPBC-<i>co</i>-BT), P(BPBC-<i>co</i>-CDT), and P(BPBC-<i>co</i>-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-<i>co</i>-BT), P(BPBC-<i>co</i>-CDT), and P(BPBC-<i>co</i>-CDTK) films showed multicolor transitions from the reduced to the oxidized state. The transmittance change (D<i>T</i>) of PBPBC, P(BPBC-<i>co</i>-BT), P(BPBC-<i>co</i>-CDT), and P(BPBC-<i>co</i>-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 (<i>η</i>) of PBPBC and P(BPBC-<i>co</i>-CDTK) films were evaluated to be 140.3 cm² C⁻¹ at 1040 nm and 283.7 cm² C⁻¹ at 1070 nm, respectively. A P(BPBC-<i>co</i>-BT)/PEDOT electrochromic device (ECD) showed a large D<i>T</i> (36.2% at 625 nm) and a fast response time (less than 0.5 s), whereas a P(BPBC-<i>co</i>-CDTK)/PEDOT ECD revealed a large <i>η</i> (534.4 cm² C^–1 at 610 nm) and sufficient optical circuit memory.