Charge and Exciton Transport in Molecular Materials and Biomolecules
by
B228
ΘΕΕ02
Abstract: The transport of charge carriers and electronic excitations in systems that are subject to strong thermal fluctuations is essential for many energy conversion processes in Nature and Technology. A molecular understanding of these processes is challenging because one needs to go beyond the Born-Oppenheimer approximation and suitably account for the electronic structure and the finite-temperature motion of the atomistic structure.
Our group has contributed to this objective by developing a novel non-adiabatic molecular dynamics simulation tool in recent years. In our approach, the wavefunction of charge carriers (electrons or holes) or electronic excitations is propagated in nanoscale molecular assemblies or materials (10-100 nm) on the 10-100 ps timescale by solving the time-dependent electronic Schrödinger equation coupled to the finite temperature motion of the nuclei. The method thus includes not only the effect of thermal nuclear motion on the electronic evolution but also the important feedback from the electronic to the nuclear degrees of freedom that leads, e.g., to polaron formation from delocalized states. The method has resulted in a paradigmatic shift of our mechanistic understanding of charge and exciton transport processes in ordered (high mobility) organic semiconductors, transient quantum delocalization.
In my talk I will present several applications of our non-adiabatic dynamics simulation methodology to charge transport[1,2], thermoelectric current generation[3], exciton transport[4] and exciton dissociation[5] in organic molecular materials, which have helped us rationalize and explain experimental measurements and observations. I will also review some of the design principles for high performance organic materials that have resulted from our mechanistic insight drawn from atomistic simulations. Finally I will give a brief survey of our simulations aimed at understanding charge transport in biological systems including multi-heme cytochromes and molecular models of highly conductive cable bacteria fibrils.
References:
[1] S. Giannini and J. Blumberger, “Charge transport in organic semiconductors: the perspective from non-adiabatic molecular dynamics,” Acc. Chem. Res., vol. 55, p. 819–830, 2022.
[2] S. Giannini, L. Di Virgilio, M. Bardini, J. Hausch, J. Geuchies, W. Zheng, M. Volpi, J. Elsner, K. Broch, Y. H. Geerts, F. Schreiber, G. Schweicher, H. Wang, J. Blumberger, M. Bonn, and D. and Beljonne, “Transiently delocalized states enhance hole mobility in organic molecular semiconductors,” Nat. Mater., vol. 22, pp. 1361-1369, 2023.
[3] J. Elsner, Y. Xu, E. D. Goldberg, F. Ivanovic, A. Dines, S. Giannini, H. Sirringhaus, and J. Blumberger, “Thermoelectric transport in molecular crystals driven by gradients of thermal electronic disorder,” Sci. Adv., vol. 10, p. eadr1758, 2024.
[4] S. Giannini, W. -T. Peng, L. Cupellini, D. Padula, A. Carof, and J. Blumberger, “Exciton transport in molecular organic semiconductors boosted by transient quantum delocalization,” Nat. Commun., vol. 13, p. 2755, 2022.
[5] F. Ivanovic, W.-T. Peng, S. Giannini, J. Blumberger, Transiently Delocalised Hybrid Quantum States are the Gateways for Efficient Exciton Dissociation at Organic Donor-Acceptor Interfaces", under review (2025)
Speaker: Prof. Jochen Blumberger obtained his PhD degree from the University of Cambridge in 2005, where he worked on density functional based molecular dynamics simulation of redox reactions, under the supervision of Prof. Michiel Sprik. Subsequently, he has held post-doctoral researcher positions at the University of Pennsylvania and the University of Cambridge. In 2009, Prof Blumberger moved to University College London (UCL), Department of Physics and Astronomy, where he was appointed University Lecturer (2009), Reader (2013), Professor of Chemical Physics (2015), Head of Condensed Matter and Materials Physics (2022) and Co-Director of the Thomas Young Centre London (2020). His research interests focus on the development and application of atomistic computer simulation methods to study diverse physical and chemical processes in biological systems, materials, and most recently also at solid/liquid interfaces.