Ultrafast charge-transfer exciton dynamics in C60 thin films

  • The high flexibility of organic molecules offers great potential for designing the optical properties of optically active materials for the next generation of optoelectronic and photonic applications. However, despite successful implementations of molecular materials in today’s display and photovoltaic technology, many fundamental aspects of the light-to-charge conversion in molecular materials have still to be uncovered. Here, we focus on the ultrafast dynamics of optically excited excitons in C60 thin films depending on the molecular coverage and the light polarization of the optical excitation. Using time- and momentum-resolved photoemission with femtosecond extreme ultraviolet (fs-XUV) radiation, we follow the exciton dynamics in the excited states while simultaneously monitoring the signatures of the excitonic charge character in the renormalization of the molecular valence band structure. Optical excitation with visible light results in the instantaneous formation ofThe high flexibility of organic molecules offers great potential for designing the optical properties of optically active materials for the next generation of optoelectronic and photonic applications. However, despite successful implementations of molecular materials in today’s display and photovoltaic technology, many fundamental aspects of the light-to-charge conversion in molecular materials have still to be uncovered. Here, we focus on the ultrafast dynamics of optically excited excitons in C60 thin films depending on the molecular coverage and the light polarization of the optical excitation. Using time- and momentum-resolved photoemission with femtosecond extreme ultraviolet (fs-XUV) radiation, we follow the exciton dynamics in the excited states while simultaneously monitoring the signatures of the excitonic charge character in the renormalization of the molecular valence band structure. Optical excitation with visible light results in the instantaneous formation of charge-transfer (CT) excitons, which transform stepwise into Frenkel-like excitons at lower energies. The number and energetic position of the CT and Frenkel-like excitons within this cascade process are independent of the molecular coverage and the light polarization of the optical excitation. In contrast, the depopulation times of the CT and Frenkel-like excitons depend on the molecular coverage, while the excitation efficiency of CT excitons is determined by the light polarization. Our comprehensive study reveals the crucial role of CT excitons for the excited-state dynamics of homomolecular fullerene materials and thin films.show moreshow less

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Metadaten
Author:Sebastian Emmerich, Sebastian Hedwig, Benito Arnoldi, Johannes Stöckl, Florian Haag, Ralf Hemm, Mirko Cinchetti, Stefan Mathias, Benjamin StadtmüllerGND, Martin Aeschlimann
URN:urn:nbn:de:bvb:384-opus4-1129839
Frontdoor URLhttps://opus.bibliothek.uni-augsburg.de/opus4/112983
ISSN:1932-7447OPAC
ISSN:1932-7455OPAC
Parent Title (English):The Journal of Physical Chemistry C
Publisher:American Chemical Society (ACS)
Type:Article
Language:English
Year of first Publication:2020
Publishing Institution:Universität Augsburg
Release Date:2024/05/14
Volume:124
Issue:43
First Page:23579
Last Page:23587
DOI:https://doi.org/10.1021/acs.jpcc.0c08011
Institutes:Mathematisch-Naturwissenschaftlich-Technische Fakultät
Mathematisch-Naturwissenschaftlich-Technische Fakultät / Institut für Physik
Mathematisch-Naturwissenschaftlich-Technische Fakultät / Institut für Physik / Lehrstuhl für Experimentalphysik II
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Licence (German):CC-BY-NC-ND 4.0: Creative Commons: Namensnennung - Nicht kommerziell - Keine Bearbeitung (mit Print on Demand)