Enhanced photovoltaic performance of dye-sensitized solar cells by the adsorption of Zn-porphyrin dye molecule on TiO2 surfaces

Abstract The electronic structure, optical absorption and charge transfer performances of Zn-porphyrin (ZnPP) dye molecule adsorbed on anatase (101) and rutile (110) TiO 2 surfaces have been investigated systematically using spin-polarized density functional theory calculations. The calculated results indicate that the strong interactions of ZnPP dye molecule and TiO 2 surfaces cause an obvious variation of the conduction band minimum and valence band maximum for ZnPP dye molecule adsorbed on TiO 2 surfaces, and the valence band of adsorption systems has a large bandwidth compared with that of the TiO 2 bulk and surfaces, which induces a red-shift of the optical absorption edge and improves greatly the optical absorption of adsorption systems in the ultraviolet and visible light regions. Moreover, the change of charge density indicates that the photoelectrons transfer from the ZnPP dye molecule to TiO 2 across the interface, and a built-in electric field is formed at the interface, which effectively enhances the separation of photogenerated electron-hole pairs. These results suggest that the sensitized actions of ZnPP dye molecule on TiO 2 surfaces can generate an excellent photovoltaic performance of TiO 2 photoanode in DSSCs.