Integration of high surface-energy electrochromic polymer with in-situ polymerized quasi-solid electrolyte for efficient electrochromism

Abstract

All solid electrochromic devices (ECDs) owing to their high safety, easy assembly, and good flexibility have attracted considerable attention for smart windows, simple displays, etc., while their practical applications are always impeded by poor interface affinity between electrochromic material and solid electrolyte. To address this issue, we herein synthesized a high surface-energy electrochromic polymer by incorporation of oligo(ethylene glycol) (OEG) unit into the 3,4-propylenedioxythiophene (Prodot) polymer side chain, and at the same time, prepared a quasi-solid electrolyte in situ by direct thermal polymerization of ionic liquid-containing electrolyte in porous Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane. The combination of molecular design of electrochromic polymer and in situ polymerization of electrolyte render the assembled ECDs with significantly reduced interface resistance, improved ion diffusion coefficient, and excellent electrochromic performance. ECDs based on Prodot-OEG and composite electrolyte exhibit high transmittance contrast (56% at 544 nm), fast switching response (2 s and 2 s for bleaching and coloring process, respectively), and high coloration efficiency (918 cm2/C at 544 nm).