Studies of interfacial recombination in the dyed TiO2 electrode using Raman spectra and electrochemical techniques

In this work, the effect of benzimidazole on the interface recombination in dye-sensitized solar cells was investigated in detail using Raman spectroscopy and electrochemical impedance spectroscopy (EIS). A strong Raman peak at 143 cm−1 (TiO2) indicated that the electrolyte additive benzimidazole suppressed the recombination reaction at the TiO2 photoelectrode/electrolyte interface. The enhanced electron lifetime for dye-sensitized solar cells with benzimidazole could be attributed to the negative shift in the conduction band edge of the semiconductor. The results from EIS for DSC at different negative potentials indicated that addition of benzimidazole could obviously reduce the rate constant (ket) for the back electron transfer from the conduction band of TiO2 to I3- ions and also retain no influence on the trap distribution in energy below the conduction band. The devices with benzimidazole showed nearly constant in the open-circuit voltage (Voc) after 1000 h at 60 °C in the dark, keeping the dyed TiO2/electrolyte interface stable.