First principles study of the hot electron relaxation dynamics in rutile TiO2

In the process of solar energy conversion, the dynamics of excited hot carriers are crucial in determining the efficiency energy transfer. We investigated hot electron relaxation in rutile TiO2 using the non-adiabatic molecular dynamics momentum space (NAMD_k) method. In this study, we choose hot electrons with two different initial energies 0.64 eV and Eini= 2.75 eV), each with momentum located at the Gamma point, to study their relaxation dynamics. The show that the hot electron relaxation process mainly involves two stages: (1) First, the hot electrons are scattered iso-energy surface within the first Brillouin zone, forming the hot electron ensemble, which can be understood momentum relaxation process. For Eini= 0.64 eV and Eini= 2.75 eV, the momentum relaxation ranges from 15 to (2) Subsequently, the hot electron ensemble as a whole gradually relaxes to the conduction band minimum which understood as the energy relaxation process. Here, the energy relaxation time of Eini= 0.64 eV and Eini= 2.75 eV and 97 fs, respectively. During the hot electron relaxation, energy is transferred to the TiO2 lattice through electron phonon coupling. As an ionic crystal, Fr & ouml;hlich type electron-phonon coupling plays a key role in the hot electron relaxation, causing most of the energy of the hot electrons to be transferred to the A1g phonons, which corresponds Ti-O stretching longitudinal optical phonon. Our study provides new physical insights for understanding the hot electron relaxation and energy conversion processes in rutile TiO2.