AB INITIO ELECTRONIC STRUCTURE AND MOLECULAR DYNAMICS SIMULATIONS OF THE ULTRAFAST ELECTRON INJECTION IN DYE SENSITIZED TiO_2

摘要

Ab initio electronic structure calculations elucidate the dramatic differences observed in the electronic spectra of the catechol and alizarin molecules upon binding to titanium. By examining the details of the calculations, we can rationalize the spectral differences in the catechol and alizarin systems by the positioning of the catechol and alizarin 7r molecular orbitals relative to the conduction band of TiCV A real-time atomistic simulation of the photoinduced electron transfer (ET) from the alizarin chrornophore to the T1O2 semiconductor at ambient temperature is reported, including both electron and nuclear dynamics. The Bimulation reproduces the experimentally observed sub-10 femtosecond ET, establishes the reaction mechanism, and provides a detailed picture of the ET process. The electronic structure of the chrornophore-semiconductor system and the electron-nuclear dynamics are simulated by ab initio density functional theory, including non-adiabatic transitions between electronic states. The simulation indicates that vibrationatly driven adiabatic transfer is the dominant ET mechanism.