Semi-solid-state electrochromic devices based on poly(3-hexylthiophene) thin films and commercial UV-curable resins for low-power applications

Abstract

Electrochromic devices (ECDs) that combine low power consumption with fast, reversible optical modulation are critical for advancing smart window and display technologies. Here, we report semi-solid-state ECDs based on regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) thin films integrated with commercially available UV-curable epoxy resins as gel electrolyte matrices. Spin-coated P3HT films on indium tin oxide (ITO)-coated glass exhibited high optical transparency (> 60% transmittance at 550 nm) and Raman signatures consistent with an ordered, pristine polymer microstructure. Devices employing a lithium perchlorate-propylene carbonate (LiClO₄-PC) electrolyte embedded within a UV-cured epoxy network demonstrated fully reversible switching between a colored (purple-pink) and bleached (transparent) state under ± 2 V bias. Cyclic voltammetry (CV) confirmed stable and reproducible redox behavior across multiple scan rates; scan-rate-dependent anodic peak shifts were attributed to charge-transfer kinetics within the viscous gel matrix. Optical transmission measurements revealed a modulation depth exceeding 30% at 550 nm, and time-resolved transmission studies yielded a rapid 90 − 10% response time of approximately 60 ms. These findings demonstrate that integrating P3HT electroactive films with UV-curable gel matrices enables high-contrast, low-power, and scalable polymer-based ECDs from commercially available components.