Preparation and characterization of spray deposited n-type WO3 thin films for electrochromic devices

The n-type tungsten oxide (WO3) polycrystalline thin films have been prepared at an optimized substrate temperature of 250 °C by spray pyrolysis technique. Precursor solution of ammonium tungstate ((NH4)2WO4) was sprayed onto the well cleaned, pre-heated fluorine doped tin oxide coated (FTO) and glass substrates with a spray rate of 15 ml/min. The structural, surface morphological and optical properties of the as-deposited WO3 thin films were studied. Mott–Schottky (M–S) studies of WO3/FTO electrodes were conducted in Na2SO4 solution to identify their nature and extract semiconductor parameters. The electrochromic properties of the as-deposited and lithiated WO3/FTO thin films were analyzed by employing them as working electrodes in three electrode electrochemical cell using an electrolyte containing LiClO4 in propylene carbonate (PC) solution.