Fast-switching all-solid state electrochromic device having main-chain 1,2,3-triazolium-based polyelectrolyte with extended oxyethylene spacer obtained via click chemistry

A fast-switching all-solid state symmetrical electrochromic device was successfully fabricated using poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as electrode and a poly(ionic liquid) based on 1,2,3-triazole with oxyethylene spacer as solid electrolyte. PEDOT:PSS solution was spincoated on ITO glass and annealed to obtain the electrode layers. Two different types of electrolyte were synthesized via copper-catalyzed alkyne-azide cycloaddition (CuAAC) using novel azide/alkyne-terminal monomers. These newly developed main-chain 1,2,3-triazole-based poly(ionic liquid)s having variable spacer length underwent quaternization using methyl iodide and subsequently allowed to make anion exchange with lithium bis(trifluoromethane)sulfonimide salt to obtain PILs with remarkable properties. The PIL bearing [-(CH2CH2O)6-] spacer showed a conductivity of 1.20 × 10−4 S cm−1 which is at par with best side-chain PILs in literature and it efficiently switches an electrochromic device (ECD) with 22% optical contrast from its transparent state to a colored state in 2.5 s and 3.2 s to return to its bleached state. Likewise, it exhibits excellent thermal and mechanical stability that is ideal for practical applications.