We report on the characteristics of a TiO2 passivating layer grown by radio frequency (RF) magnetron sputtering on F-doped SnO2 (FTO) electrodes as a function of its thickness. The optical transparency, surface roughness and passivation properties of the TiO2 layer passivating the FTO electrode depend on the thickness of the TiO2 passivating layer. In addition, it was found that the power conversion efficiency of the dye-sensitized solar cells (DSSCs) is critically dependent on the thickness of RF sputtered TiO2 layer inserted between FTO electrode and nanoporous TiO2 layer. The DSSC fabricated on 50 nm thick TiO2 passivating FTO electrode showed the maximum power conversion efficiency of 4.42% due to effective prevention of the electron transfer to electrolyte. This indicates that the thickness optimization of the TiO2 passivating layer is one of the important parameter to obtain high performance DSSCs. (c) 2010 Published by Elsevier B.V.