Spin Unrestricted Nonradiative Relaxation Dynamics of Cobalt-Doped Anatase Nanowire

5 years ago

Spin Unrestricted Nonradiative Relaxation Dynamics of Cobalt-Doped Anatase Nanowire

Stephanie J. Jensen, Dmitri S. Kilin, Talgat M. Inerbaev, Aisulu U. Abuova

Spin-resolved charge transfer dynamics at the interface of a Co(NH₃)₂-doped (001) anatase TiO₂ nanowire and liquid water calculations based on density functional theory and density matrix formalism are considered. Three models with the same stoichiometry but different electronic structure are explored. While one model had no change to electron count and spin count (neutral model), the other two models were assigned a charge of 2+, one in a doublet and the other a quartet spin configuration. Co²⁺ is the most probable state for dopant in all models and Co acts as an electron acceptor. The optical absorption spectra show a rather unique pattern post 400 nm where the α and β absorptions happen independently at different frequency ranges. Essentially, the relaxation dynamics can be controlled as when an α electron is excited, there is a near zero probability of a β electron also undergoing an excitation and vice versa. The isolated exemption is between 400 and 650 nm in the neutral model. All the models absorb light in the visible range, while the electrons and holes have drastic differences in relaxation rates. The spatial charge separation occurs upon excitation and subsequent trapping, designating the considered system a prospect for electrochemical cell applications. (2+) models trap states more effectively slow down electron relaxation, making the charged models slightly better options for application compared to the neutral model.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b04263

DOI: 10.1021/acs.jpcc.7b04263