Dye-sensitized solar cell (DSC) consists of a TiO2 nano film of the photo electrode, dye molecules on the surface of the TiO2 film, an electrolyte layer and a counter electrode. Among these, the nano porous TiO2 film plays an important role as the photo electrode in DSC because it adsorbs a large number of the dye molecules which provide electrons. Therefore, the condition of the TiO2 film affects the cell performance such as current density (J(sc)), open circuit voltage (V-oc) and fill factor (FF). The thickness of TiO2 film is one of these conditions. Its variation influences on the internal impedances of DSC related to the electron transport. In this study, we analyzed the characteristics of DSC with the different thicknesses of TiO2 film by using electrochemical impedance spectroscopy (EIS) in details. As a result, it was demonstrated that the variation of the TiO2 thickness has an effect on the electron transport in the DSC. Finally, the TiO2 thickness is optimized for the best performance of DSC. Crown Copyright (C) 2009 Published by Elsevier B. V. All rights reserved.