Heteroacene-Based Polymer with Fast-Switching Visible-Near Infrared Electrochromic Behavior

The electrochromic properties and application of electronically conducting polymers (ECPs) (PTRPZ-EDOT) consisting of a 3,4-ethylenedioxythiophene (EDOT) and the heteroacene-based molecular scaffold, 6H-pyrrolo[3,2-b:4,5-b'] bis [1,4] benzothiazine (TRPZ), are reported. Known for its high electron mobility and conducting properties, the novel TRPZ scaffold was synthesized to possess two EDOT molecules termini affording TRPZ-EDOT. Electropolymerization of TRPZ-EDOT resulted in remarkable spectroscopic and conductive properties suitable for electrochromic device fabrication. Using atomic force microscopy (AFM), the average surface roughness and surface topography of PTRPZ-EDOT polymer thin films were determined. Spectroelectrochemical data showed that the polymer achieved switching times of 4.07 (coloration) and 0.47 s (bleaching) at 539 nm. The PTRPZ-EDOT film exhibits an optical contrast of 36-44% at 539 nm between its neutral and colored states, respectively. The NIR region from 1000 to 1700 nm shows the appearance of charge carrier bands with a 0-1 V potential range. An electrochromic device was successfully fabricated from PTRPZ-EDOT, showcasing the potential and applicability of the polymer material for advanced technologies such as smart windows, flexible electrochromic screens, and energy storage devices.