Dye-injected electron trapping in TiO2 determined by broadband transient infrared spectroscopy

We report the dynamics of electrons injected into TiO2 due to the excitation of Ru-N719 dye at 532 nm. The synchrotron based broadband transient mid-IR spectroscopy revealed that the injected electrons are quickly confined to a trap state with an average energy of ca. 240 meV below the conduction band. The average energy of the trapping states did not change with the increase of the delay time, suggesting a singular electronic identity of the trap states.