Ultrafast Charge Separation and Recombination across a Molecule/CsPbBr3 Quantum Dot Interface from First-Principles Nonadiabatic Molecular Dynamics Simulation

Abstract

All-inorganic perovskite quantum dots (QDs) hold great promise in photovoltaic solar cells. However, the reduced dimensionality of QDs confines the photoexcited electron–hole pairs, suppresses charge separation, and accelerates charge recombination (CR), limiting the photon-to-electron conversion efficiency of a solar cell. Molecule passivation can overcome this shortcoming via efficiently extracting charge carriers from QDs. Using a combination of time-domain density functional theory and nonadiabatic (NA) molecular dynamics, we demonstrate that low-frequency vibrations promoted both charge separation and recombination. The photoexcited excitons on a CsPbBr3 QD can efficiently dissociate into free charge carriers via rapid interfacial electron transfer (ET) and hole transfer (HT) to a binding benzoquinone (BQ) and a phenothiazine (PTZ) molecule on similar sub-100 ps time scales, respectively. This is manifested by the fact that the QD-BQ system holds smaller energy gap and NA coupling between the donor a...