“…A large variety of deposition techniques like thermal evaporation [10], sputtering [11], chemical vapor deposition [12], solution thermolysis [13], electrochemical [14], and spray pyrolysis [15][16][17][18] have been utilized to obtain WO 3 thin films with different morphologies, crystalline state and compositions. To enhance the electrochromic efficiency through transitions between two kinds of metal sites, efforts have also been made to fabricate thin films of selective mixed oxide semiconductors, based on their electrochromic performance [19][20][21].…”