To investigate the mechanisms of the improvement on separation efficiency of photogenerated carriers, a Fe2O3/SrTiO3 heterojunction semiconductor with an improved separation efficiency was successfully prepared. The heterojunction semiconductor was characterized with X-ray diffraction (XRD), UV-vis absorption spectrum, scanning electron microscope (SEM) and surface photovoltage (SPV) spectroscopy. The energy band diagrams of Fe2O3 and SrTiO3 were determined with X-ray photoelectron spectroscopy (XPS), based on which the conduction band offset (CBO) between Fe2O3 and SrTiO3 was quantified to be 1.26 +/- 0.03 eV. The recombination of photogenerated carriers was investigated with photoluminescence (PL) spectrum, which indicates that the formation of Fe2O3/SrTiO3 decreases the recombination. Thus the improved separation efficiency is mainly due to the energy difference between the conduction band edges of Fe2O3 and SrTiO3, and the decreased electron-hole recombination for Fe2O3/SrTiO3. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.