Time-domain ab initio modeling of charge and exciton dynamics in nanomaterials

Abstract

Nonequilibrium dynamical processes in nanoscale materials involving electrons, excitons, and vibrations are under active experimental investigation. Corresponding theoretical studies, however, are much scarcer. This chapter starts with the basics of time-dependent density functional theory, recent developments in nonadiabatic molecular dynamics methods, and the fusion of the two techniques. Ab initio simulations of this kind allow us to directly mimic a great variety of time-resolved experiments performed with pump-probe laser spectroscopies. We systematically investigate two important building blocks of modern nanotechnology, namely, quantum dots (QDs) and titanium dioxide (TiO2). The focus is on the ultrafast photoinduced charge and exciton dynamics at interfaces formed by two complementary materials, including QD-TiO2 hybrids, organic-QD and organic-TiO2 interfaces, and all organic systems. These interfaces involve bulk semiconductors, metallic and semiconducting nanoclusters, graphene, carbon nanotubes, fullerenes, polymers, molecules and molecular crystals. The detailed atomistic insights available from time-domain ab initio studies provide a unique description and a comprehensive understanding of the competition between various dynamical processes (e.g., electron transfer, thermal relaxation, energy transfer, and charge recombination). These advances now make it possible to directly guide the development of organic and hybrid solar cells, as well as photocatalytic, electronic, spintronic, and other devices relying on complex interfacial dynamics.