Photoelectrochemical properties of nanocrystalline TiO2 electrodes sensitized by porphyrin derivatives with different functional groups

Porous semiconductor TiO₂ electrode was prepared by coating a conducting glass support. The photoelectrochemical properties of the nanocrystalline TiO₂ electrodes sensitized by porphyrin derivatives with different functional groups, e.g., carboxyl, sulfonate and phenyl were investigated. It was found that the all porphyrin derivatives used in this study had sensitization effect. The interaction between the porphyrin and the TiO₂ surface is determined and compared using UV-vis spectra. The adsorption behavior of the porphyrin on the TiO₂ electrode surface was discussed. Furthermore, we examined the photoelectrochemical properties of a free base porphyrin with only one carboxylate group (H₂TC1PP), the result obtained was compared with that of porphyrin with four carboxyl groups (H₂TC4PP). It reveals that the higher photocurrent intensity of H₂TC4PP can be obtained than that of H₂ TC1PP, and the energy conversion efficiency of the solar cell is very dependent on the structure of porphyrin. These results indicate that the binding state between the dye and semiconductor is an important factor affecting the properties of the dye-sensitized solar cell