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Hole dynamics in a photovoltaic donor-acceptor couple revealed by simulated time-resolved X-ray absorption spectroscopy

Authors :
Khadijeh Khalili
Ludger Inhester
Caroline Arnold
Ralph Welsch
Jens Wenzel Andreasen
Robin Santra
Source :
Structural Dynamics, Vol 6, Iss 4, Pp 044102-044102-8 (2019)
Publication Year :
2019
Publisher :
AIP Publishing LLC and ACA, 2019.

Abstract

Theoretical and experimental methodologies that can characterize electronic and nuclear dynamics, and the coupling between the two, are needed to understand photoinduced charge transfer in molecular building blocks used in organic photovoltaics. Ongoing developments in ultrafast pump-probe techniques such as time-resolved X-ray absorption spectroscopy, using an X-ray free electron laser in combination with an ultraviolet femtosecond laser, present desirable probes of coupled electronic and nuclear dynamics. In this work, we investigate the charge transfer dynamics of a donor-acceptor pair, which is widely used as a building block in low bandgap block copolymers for organic photovoltaics. We simulate the dynamics of the benzothiadiazole-thiophene molecule upon photoionization with a vacuum ultraviolet (VUV) pulse and study the potential of probing the subsequent charge dynamics using time-resolved X-ray absorption spectroscopy. The photoinduced dynamics are calculated using on-the-fly nonadiabatic molecular dynamics simulations based on Tully's Fewest Switches Surface Hopping approach. We calculate the X-ray absorption spectrum as a function of time after ionization at the Hartree-Fock level. The changes in the time-resolved X-ray absorption spectrum at the sulfur K-edge reveal the ultrafast charge carrier dynamics in the molecule occurring on a femtosecond time scale. These theoretical findings anticipate that ultrafast time-resolved X-ray absorption spectroscopy using an X-ray probe in combination with a VUV pump offers a new approach to investigate the detailed dynamics of organic photovoltaic materials.

Subjects

Subjects :
Crystallography
QD901-999

Details

Language :
English
ISSN :
23297778
Volume :
6
Issue :
4
Database :
Directory of Open Access Journals
Journal :
Structural Dynamics
Publication Type :
Academic Journal
Accession number :
edsdoj.0ef5f3fb3a6e43ecaa161aa246ee2e35
Document Type :
article
Full Text :
https://doi.org/10.1063/1.5097653