Efficient Electrochromic Materials Based on PEDOT/WO3 Composites Synthesized in Ionic Liquid Media

A series of ionic liquids such as 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMIMTFSI), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPTFSI) were used as both electrochemical growth media and electrolytes for the synthesis of poly(3,4-ethylenedioxythiophene)/tungsten oxide (PEDOT/WO3) composite films for electrochromic device applications. The surface and electrochromic properties of the composites changed depending on characteristic of ionic liquids. The maximum transmittance window 41.3% was obtained at 620 nm with the operating potentials between +2 and -2 V, for the BMPTFSI synthesis medium. Optical transmittance spectra results of EC devices indicated that optical modulations values were 32.8% and 22.3% at 620 nm for the PEDOT/WO3 composites synthesized in the presence of BMIMPF6 and BMIMTFSI, respectively.