High-Performance UV-Crosslinked PMMA-Based Solid Polymer Electrolyte for Flexible Electrochromic Devices

Abstract

Electrochromic devices (ECDs) hold significant promise for applications in smart windows and flexible displays due to their tunable optical properties and low energy consumption. The electrolyte, serving as the critical ionic transport medium between the working and counter electrodes, fundamentally governs device stability, response kinetics, and operational lifetime. Herein, we report novel UV-crosslinked solid-state poly(methyl methacrylate) (PMMA) electrolytes. The amorphous structure of PMMA enables the electrolyte to achieve relatively high ionic conductivity and excellent optical transparency, which, when combined with the mechanically robust three-dimensional network of PEGDA, further amplifies PMMA's advantages. This rationally designed electrolyte architecture achieves a remarkable combination of high ionic conductivity (0.045 mS cm-1), wide electrochemical stability window (2 V), exceptional optical transparency (transmittance >90%), and superior mechanical flexibility, and effectively addresses the film-forming challenges and interfacial instability issues associated with conventional polymer electrolytes. The fabricated ECDs (2 × 2 cm2) exhibit high optical contrast (ΔT = 39%), rapid response times (coloring/bleaching times of 0.5 s/0.6 s), high coloration efficiency (2200 cm2 C-1), and exceptional cycling stability (After 10,000 cycles, the ΔT decreased by only 6%, and the switching time remained approximately 1 s.), and excellent temperature stability. CYM trichromatic ECDs enable full-color display. Furthermore, the flexible devices maintain over 90% of their initial ΔT after 2000 bending cycles at a radius of 15 mm. They also demonstrate good compatibility with inkjet printing processes, and large-area devices (10 × 10 cm2) fabricated using this method exhibit excellent electrochromic performance. This work provides a viable pathway toward the practical realization of large-area, patterned, and flexible ECDs.