The effect of TiCl4-treated TiO2 compact layer on the performance of dye-sensitized solar cell

In order to prevent the charge recombination at the interface between the transparent-conducting oxide (TCO) substrate and electrolyte, a TiO2 compact layer was deposited on the substrate by hydrolysis of TiCl4 aqueous solution. Optimum thickness of the compact layer was found to be ∼25 nm, which showed ∼24% increase in the power-conversion efficiency compared with the bare cell. Impedance spectra indicated that the interfacial charge-transfer resistance of TCO/electrolyte interface was increased by more than a factor of three with the TiO2 compact layer at 0.4 V. Moreover, the electron-carrier lifetime of the 25 nm-deposited cell was improved by a factor of five compared with the bare cell.