Effects of 4-tert-Butylpyridine and Li Ions on Photoinduced Electron Injection Efficiency in Black-Dye-Sensitized Nanocrystalline TiO2 Films

Using transient absorption spectroscopy, we investigated the effects of 4-tert-butylpyridine (tBP) and Li ions on photoinduced electron injection efficiency in nancrystalline TiO2 films sensitized by black dye. The efficiency increased with the addition of Li ions but decreased with the addition of tBP molecules. These results indicate that a conduction band shift was induced by the solvation effect of the additives. Using recombination kinetic measurements, we examined that such a solvation effect was induced by the intercalation of Li ions into TiO2 particles and by the adsorption of tBP on the TiO2 surface. When both additives were used simultaneously, the efficiency was Suppressed more than when only tBP was added. This difference in efficiency suggests that the local concentration of tBP near the TiO2 surface increased with the addition of Li ions. This cooperative effect may have been caused by the formation of a complex between tBP and Li in Solution.