The effect of the TiO2/transparent conducting oxide (TCO) interface in a photoelectrode of a dye-sensitized solar cell (DSSC) on its cell performance was investigated using our multiscale simulator, in which we had added a calculation of the voltage loss derived from the Schottky barrier height (SBH) at the TiO2/TCO interface to our previous simulator. We treated the TiO2/TCO interface as a series connection of a Schottky diode of metal/n-type semiconductor. The thermionic-emission theory was applied to describe the electron transfer and the voltage loss at the TiO2/TCO interface. The accuracy of the prediction of the current density-voltage (J-V) characteristics of a DSSC employing the cisdithiocyanato- bis(2,2'-bipyridyl-4, 4'-dicarboxylic acid)-ruthenium(II) (N3 dye) was improved compared with that obtained by our previous simulator. The effects of the SBH on the open circuit voltage (VOC) and the maximum power output (Pmax), as well as the J-V characteristics, of the DSSC were discussed. Our results suggest that a TCO with the SBH ≤ 0:5 is suitable for a DSSC.