This manuscript reports the modification of the interface between the mesoporous TiO(2) work electrode and electrolyte of dye-sensitized solar cells (DSCs) with oxide layers deposited by the thermal evaporation of metals and subsequent oxidation with UV ozone. Both Al(2)O(3) and MgO can be deposited on mesoporous TiO(2) by this method, and their thickness can be precisely controlled. A thin layer of Al(2)O(3) or MgO on the TiO(2) work electrode can improve the photovoltaic efficiency. The optimal thicknesses are 14.1 and 4.9 angstrom for Al(2)O(3) and MgO, respectively. The oxide effect has been investigated by the electrochemical impedance spectroscopy, cyclic voltammetry and UV-Vis-NIR absorption spectroscopy. The improvement in the photovoltaic efficiency by an oxide layer is attributed to the upward shift of the conduction band of TiO(2), the passivation of the TiO(2) surface, and the retardation of the charge recombination through the interface between TiO(2) and electrolyte. (C) 2011 Elsevier B.V. All rights reserved.