Near-infrared electrochromic modulation of quinoxaline and cyclopenta[2,1-b;3,4-b']dithiophene-based polymer

Modulation of near-infrared (NIR) radiation transmittance can be achieved through the electrochromic phenomenon. Polymer films deposited using different techniques often exhibit distinct electrochemical behavior and associated optical properties. To investigate these effects, this study examines three fabrication methods used to obtain polymer films based on cyclopenta[2,1-b;3,4-b']dithiophene, and 2,3-bis(3-(octyloxy)phenyl)quinoxaline monomers. We found that the resulting polymer shows only minor changes in visible-range transmittance, while its NIR transmittance varies strongly depending on the applied voltage. The material proved especially sensitive to the deposition procedure, yielding electrochromic layers with markedly different ratios of visible to NIR modulation. A comprehensive optoelectronic characterization was performed, including cyclic voltammetry, UV–Vis–NIR spectroscopy, spectroelectrochemical measurements, and kinetic analyses.