Activity: Talks and presentations › Conference presentations
Abstract: In order to develop and improve new types of organic photovoltaic (OPV) devices and reach higher levels of conversion efficiency of solar energy to electric current, it is essential to have a deep understanding of the photoinduced processes in such devices. We investigate the charge transfer dynamics of a donor-acceptor pair, which is widely used as a building block in low band-gap block copolymers for organic photovoltaics. We simulate dynamics of the benzothiadiazole-thiophene molecule (BT-1T) upon interaction with a vacuum ultraviolet (VUV) pulse and study the potential of probing the subsequent charge dynamics with time-resolved X-ray absorption spectroscopy (TRXAS). TRXAS allows detecting the local geometric structure of the system under study and, at the same time, the underlying electronic structure changes that drive the structural dynamics. The photoinduced dynamics in BT-1T are calculated using on-the-fly non-adiabatic molecular dynamics simulations based on Tully's Fewest Switches Surface Hopping approach via XMOLECULE electronic structure toolkit. For snapshots at various time-delays, the sulphur K-edge absorption lines in the time-resolved X-ray absorption spectrum reflect the ultrafast charge dynamics in the molecule. We show how our simulations demonstrate the perspective for ultrafast time resolved X-ray experiments at X-ray free electron lasers namely in addressing charge transfer dynamics in organic molecules.