A zinc(II)-porphyrin dye with four carboxyphenyl moiety of ancillary (ZnTCPP) was studied as a sensitizer in combination with a ruthenium complex (N719) in co-sensitized solar cells. The high molar extinction coefficient (epsilon) of porphyrin dyes leads to high light absorption in the dye-sensitized TiO2 electrode. In spite of the high epsilon of porphyrin dyes, they usually have a narrow absorption band and also to suffer from dye aggregation due to their planar structural nature. This causes lower efficiencies of the DSSCs for the porphyrins than the ruthenium complexes. Co-sensitization of two or more dyes with complementary absorption spectra on TiO2 film is an important method to further enhance the IPCE response and energy conversion efficiency of dye-sensitized solar cells. Interestingly, when the ZnTCPP electrode was used to assemble a co-sensitized solar cell by additional adsorption of N719 dye, the efficiency improved to 6.35% (in comparison to N719 that the efficiency was 4.74%). The results indicated that the co-sensitized device shows enhancements of photovoltaic performance not only in short-circuit current density (J(SC)) but also in open-circuit voltage (V-OC). In the present study we have been shown that co-sensitization of a zinc(II)-porphyrin with N719 dye changes the energy levels of the TiO2 electrode and in result produces further improvement for its device performance. (C) 2013 Elsevier Ltd. All rights reserved.