The n-type tungsten oxide (WO3) polycrystalline thin films have been prepared at an optimized substrate temperature of 250 degreesC by spray pyrolysis technique. Precursor solution of ammonium tungstate ((NH4)(2)WO4) 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. (C) 2004 Elsevier Ltd. All rights reserved.