Pyrazine-EDOT D-A-D type Hybrid Polymer for Patterned Flexible Electrochromic Devices

Abstract

Two donor-acceptor type pyrazine-EDOT hybrid polymers are developed as high performance electrochromic materials and employed to fabricate flexible electrochromic devices via electropolymerization patterning. By coupling EDOT with pyrazine at 2,5-positions, the resultant precursor 2,5-BEP can facilely electropolymerize to yield high quality pyrazine-EDOT hybrid polymer films with excellent electrochemical stability. Spectroelectrochemistry and kinetic studies demonstrate that as-formed pyrazine-EDOT hybrid polymer exhibits reversible color-changing nature from purple to gray with high coloration efficiency (134 cm2 C−1), fast response time (0.2 s) and high optical contrast (> 55%) over a wide wavelength range of 800–2200 nm in near-infrared (NIR) region. To harness its excellent electrochromic performance as well as the ease of electropolymerization patterning, we fabricate patterned flexible electrochromic devices (ECDs) via facile electropolymerization and such ECDs display reversible color changes with decent optical stability (25% reduction in optical contrast upon 1000 cycling) and excellent mechanical stability (9.6% reduction in optical contrast upon bending 5000 cycles). The excellent electrochromic performance and stability of pyrazine-EDOT hybrid polymers as well as their-based ECDs make them good candidates towards near infrared electrochromic applications.