Molecular engineering of cross-linked polymers based on camphor substituted quinoxaline and 2,5-dithiophen-2-yl-pyrrole for efficient electrochromic energy storage devices

In this work, two donor-acceptor monomers SNSCQH and SNSCQF consisting of two 2,5-dithiophen-2-yl-pyrrole units and camphor substituted quinoxaline-based linkers were developed for electrochromic and energy storage applications. The cross-linked conjugated polymer thin films PSNSCQH and PSNSCQF were successfully prepared through electrochemical polymerization of the corresponding monomers and deposited on ITO substrates, which exhibited remarkable electrochromic performance, involving large optical contrast over 50 %, short response time less than 1.5 s, and high coloration efficiency over 220 cm2/C. Moreover, both PSNSCQH and PSNSCQF demonstrated large areal specific capacitance, with values of 9.27 mF/cm2 and 10.13 mF/cm2 at a current density of 0.1 mA/cm2, respectively. Additionally, electrochromic energy storage devices based on PSNSCQH and PSNSCQF thin films in a sandwich configuration were fabricated, enabling visualization of the energy storage state through color changes. This study provided valuable insights into the behavior of crosslinked two-dimensional conjugated polymers with intermolecular interactions between layers for electrochemical devices.