Successful preparation of tungsten oxide thin films on paper substrate, using a novel room temperature deposition method involving the connection of tungsten oxide nanoparticles by UV-irradiation, is reported. WO3 thin films, prepared from synthesized monoclinic WO3 powder as compared to commercial ones, show higher electrochemical activity and good cycling stability in 0.3 M trifluoromethanesulfonimide (HTFSI) in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI) ionic liquid electrolyte versus Pt as counter electrode. Electrochromic performances of complete devices using Prussian Blue (PB) as complementary counter electrode and 0.3 M Lithium Bis(Trifluoromethanesulfonyl)Imide LiTFSI in BMITFSI plastified with polymethylmetacrylate (PMMA) membrane electrolyte are associated with a contrast in reflectance of 13%, from a yellow to a blue color. (C) 2014 Elsevier Ltd. All rights reserved.