Photoelectrochemical properties of TiO2 thin films via co-catalyst sol-gel reaction for dye-sensitized solar cells (DSSCs) were investigated. Three different types of nanocrystalline TiO2 thin films were fabricated from the hydrolysis of Ti isopropoxide with various proportions of an acid/base co-catalyst. The acid/base co-catalyst with a lower proportion of base catalyst reduces particle size of the TiO2 and increases its cluster size including pore volume, which enhance short-circuit current density and open-circuit voltage of the DSSCs device by reducing charge transfer loss across the TiO2/redox electrolyte interface. (C) 2013 Elsevier Ltd. All rights reserved.