The (WO3)(1-x)-(Fe2O3)(x) (0 <= x <= 1) nano-particle thin films with various compositions have been deposited onto the fluorine thin oxide (FTO) coated glass substrate using sol-gel, spin-coating technique. An electrode/electrolyte interface has been formed between an n-type (WO3)(1-x)-(Fe2O3)(x) composite semiconductor and a 0.5 mol L-1 Na2SO4 aqueous solution. The photo-catalytic activity of the films has been investigated through the photocurrent-voltage. UV-visible spectroscopy, SEM and XRD have been used to characterize solar absorption, surface morphology and the crystallinity of samples, respectively. The photoelectrochemical (PEC) experiments were performed under solar irradiation to evaluate the amount of electron-hole generation in different samples. All the composite nanoparticles indicated higher efficiency compared to pristine iron and tungsten oxides. A clear relationship was also confirmed between band gap energy and photo-catalytic activity of thin films. The band-gap energy of mixed thin films decreased linearly with the increasing Fe2O3 content in the film samples. The maximum photocurrent density of 2.34 mA cm(-2) has been obtained for sample with x = 0.25 at 1.4 V vs. RHE. The result revealed that the sample also has the highest photon-to-current efficiency (0.87%), and solar absorption. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.