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arXiv · 2110.00373

Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN:PFP Co-Crystalline Films: Limits of Non-Periodic Modelling

Darius Günder·Ana M. Valencia·Michele Guerrini·Tobias Breuer·Caterina Cocchi·Gregor Witte
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Abstract

Charge-transfer excitons (CTX) at organic donor/acceptor interfaces are considered important intermediates for charge separation in photovoltaic devices. Crystalline model systems provide microscopic insights into the nature of such states as they enable microscopic structure-property investigations. Here, we use angular-resolved UV/Vis absorption spectroscopy to characterize the CTX of crystalline pentacene:perfluoro-pentacene (PEN:PFP) films allowing to determine the polarization of this state. This analysis is complemented by first-principles many-body calculations, performed on the three-dimensional PEN:PFP co-crystal, which confirm that the lowest-energy excitation is a CTX. Analogous simulations performed on bimolecular clusters are unable to reproduce this state. We ascribe this failure to the lack of long-range interactions and wave-function periodicity in these cluster calculations, which appear to remain a valid tool for modelling properties of organic materials ruled by local intermolecular couplings.

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Darius Günder, Ana M. Valencia, Michele Guerrini, Tobias Breuer, Caterina Cocchi, Gregor Witte. 2021-10-01. Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN:PFP Co-Crystalline Films: Limits of Non-Periodic Modelling. https://doi.org/10.1021/acs.jpclett.1c02761

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