Leakage-free flexible and stretchable electrochromic devices enabled by acrylate viologens and perfluorinated CNT-modified transparent electrodes

Abstract

Electrolyte leakage and electrode fragility have been persistent obstacles in advancing flexible electrochromic devices (ECDs). Though efficient for ion transfer, liquid electrolytes are prone to leakage under mechanical stress, while gel electrolytes face mechanical constraints. Conventional indium tin oxide (ITO) electrodes are rigid and susceptible to cracking when subjected to deformation, restricting their flexibility. To resolve these challenges, this study seamlessly integrates leakage-free electrolyte films formed by incorporating acrylate viologen into a photocurable polymer matrix, with perfluorinated carbon nanotubes (FCNTs) synthesized through a direct arylation reaction. The fluorinated nanotube surface preserves CNTs' intrinsic properties while enhancing dispersion and preventing aggregation of CNT bundles. By integrating acrylate viologen-based electrolyte films with FCNT-modified electrodes, the flexible ECDs achieve high transmittance contrast, mechanical flexibility, and operational stability. The prepared devices maintain durability beyond 12,000 s, and rigorous bending tests confirm their robustness. Furthermore, when combined with PDMS substrates, stretchable ECDs are successfully fabricated. Notably, the ion gel electrolyte functions efficiently under stretched without any leakage concerns, demonstrating the durability of the electrode and the active electrochromic layers. The current work addresses key challenges in electrolyte leakage and electrode fragility, paving the way for next-generation ECDs and highly flexible and stretchable wearable technologies.