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 x 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.