In dye-sensitized solar cell, the introduction of coadsorbents are supposed to suppress the dye-aggregation and improve the performance of the cell. In the study, the surface modification of nanocrystalline TiO₂ electrode by coadsorbents with one carboxylate acid as adsorption group have been studied by the methods such as spectroelectrochemistry, linear sweep voltammetry and electrical impedance spectrum (EIS). The results demonstrate that the flat-band potential of TiO₂ film shifts negatively and the recombination of the TiO₂ conduction band electrons with the electron acceptors in the electrolyte has been retarded by using the coadsorbents, in which the cholic acid derivatives display the better performance for retarding. The open-circuit voltage, fill factor and photoelectric conversion efficiency could be improved by introducing chenodeoxycholic acid of proper concentration in N719 sensitized solar cells.

Key words: coadsorbent, solar cell, surface modification, dye-sensitized, spectroelectrochemistry