Enhancing NIR Electrochromism with Twisted Copolymer Films of Corannulene-Carbazole and 3,4-Ethylenedioxythiophene

The copolymer films of corannulene-carbazole (CCZ) and 3,4-ethylenedioxythiophene (EDOT) were developed and applied to near-infrared (NIR) electrochromic window in this study. Two strategies were designed to improve the NIR electrochromic performance, including using a twisted structure and copolymerization. CCZ was selected as a twisted center due to its twisted polymer network after electropolymerization, which exhibited better NIR electrochromic performance, including faster response and higher stability, compared to planar carbazole-based materials. The electrochemical impedance analysis demonstrated the enhancing NIR electrochromism with the twisted structure originating from increasing ion transportation. In addition, EDOT, a monomer of a conjugated polymer, was employed to improve the optical contrast in the NIR region. The copolymer films were prepared in different feeding ratios of CCZ and EDOT, and the electrochemical properties and chemical composition of these copolymers were investigated. Finally, the copolymer films can exhibit the highest optical contrast (45% in 1000 nm) when a suitable ratio of EDOT to CCZ was used, indicating that introducing copolymerization with EDOT could further enhance the NIR electrochromism. This study gave critical insight into the molecular design of corannulene-based materials for electrochromic applications.