Injection Kinetics and Electronic Structure at the N719/TiO 2 Interface Studied by Means of Ultrafast XUV Photoemission Spectroscopy

The method of transient XUV photoemission spectroscopy is developed to investigate the ultrafast dynamics of heterogeneous electron transfer at the interface between the N719 ruthenium dye complex and TiO2 nanoparticles. XUV light from high-order harmonic generation is used to probe the electron density distribution among the ground and excited states at the interface after its exposure to a pump laser pulse of 530 nm wavelength. A spectral decomposition of the transient emission signal is used to follow the population and decay dynamics of the involved transient states individually. By comparing results obtained for the N719/TiO2 and N719/FTO interfaces, we can unambiguously reveal the kinetics of electrons injected to TiO2 from the singlet metal-to-ligand charge-transfer (MLCT) excited state of the dye. With the developed approach, we characterize both the kinetic constants and the absolute binding energies of the singlet and triplet MLCT states of the dye and the state of electrons injected to the cond...