Photo-Excited Electron and Hole Dynamics in Semiconductor Quantum Dots: Phonon-Induced Relaxation, Multiple Excito Generation and Recombination

Abstract

Phonon-induced relaxation, multiple exciton generation and recombination (MEG and MER) govern optical properties and photo-excited dynamics in QDs. We simulated such photo-excited dynamics of electron and hole in semiconductor quantum dots (QD) by combining time-dependent ab initio density functional theory and non-adiabatic molecular dynamics. Our approach is based on atomictic simulations accounting for QD size, shape, defects, core–shell distribution, surface ligands, and charge trapping, which significantly influence the properties of photo-excited QDs. The calculated data were obtained as real-time photo-induced processes and described as various dynamics owing to the non-perturbative treatment of quantum transition dynamics. The simulations provide direct evidence that the high-frequency ligand modes on the QD surface play a key role in all of the electron–phonon relaxation, MEG and MER. The insights reported here suggest novel routes for controlling the photo-induced processes in semiconductor QDs and lead to new design principles for increasing efficiencies of photovoltaic devices.