Temporal Fluctuations in Excimer-Like Interactions between π-Conjugated Chromophores

Stangl, Thomas; Wilhelm, Philipp; Schmitz, Daniela; Remmerssen, Klaas; Henzel, Sebastian; Jester, Stefan‐S.; Höger, Sigurd; Vogelsang, Jan; Lupton, John M.

doi:10.1021/acs.jpclett.5b00328

Cited by 24 publications

(63 citation statements)

References 54 publications

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“…The regime of exciton transport (coherent or incoherent) is determined by the relative strength of the excitonic coupling and the exciton-phonon coupling. [35][36][37] Furthermore, short range interactions at finite temperature cause strong fluctuations in the excitonic coupling 3,13,36 which in some instances can influence or limit the energy transfer dynamics. [37][38][39] In photosynthesis, light absorption and efficient transport of the excitation energy is achieved by clusters of chromophores in proteins commonly called light harvesting complexes (LHCs).…”

Section:   a B A Bmentioning

confidence: 99%

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Importance and Nature of Short-Range Excitonic Interactions in Light Harvesting Complexes and Organic Semiconductors

Fornari

Rowe

Padula

et al. 2017

J. Chem. Theory Comput.

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Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:"This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Chemical Theory and Computation. copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work http://pubs.acs.org/page/policy/articlesonrequest/index.html ." A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL above for details on accessing the published version and note that access may require a subscription. AbstractThe singlet excitonic coupling between many pairs of chromophores is evaluated in three different Light Harvesting Complexes (LHCs) and two organic semiconductors (amorphous and crystalline). This large database of structures is used to assess the relative importance of short-range (exchange, overlap, orbital) and long-range (Coulombic) excitonic coupling. We find that Mulliken atomic transition charges can introduce systematic errors in the Coulombic coupling and that the dipole-dipole interaction fails to capture the true Coulombic coupling even at intermolecular distances of up to 50 Å. The non-Coulombic short range contribution to the excitonic coupling is found to represent up to ~70% of the total value for molecules in close contact, while, as expected, it is found to be negligible for dimers not in close contact. For the face-to-face dimers considered here, the sign of the short range interaction is found to correlate with the sign of the Coulombic coupling, i.e. reinforcing it when it is already strong. We conclude that for molecules in van der Waals contact the inclusion of short range effects is essential for a quantitative description of the exciton dynamics.

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Section:   a B A Bmentioning

confidence: 99%

“…3,4 For the study of the quantum mechanical evolution of excited states it has become commonplace to evaluate the excitonic coupling for a large number of structures, e.g. those deriving from a molecular dynamics simulation [5][6][7][8][9][10][11][12][13] or representing the interaction between chromophores in an amorphous system.…”

Section: Introductionmentioning

confidence: 99%

Importance and Nature of Short-Range Excitonic Interactions in Light Harvesting Complexes and Organic Semiconductors

Fornari

Rowe

Padula

et al. 2017

J. Chem. Theory Comput.

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“…The authors therefore suggested that the dynamic heterogeneity in strong interchromophore couplings must be accounted for to gain insights into the flow of excitation energy in bulk optoelectronic systems. [15] The description of the exciton transport in organic molecular crystals is particularly simple in two limiting transport regimes (coherent and incoherent). [2] In the coherent regime, the excitonic coupling is much larger than the local exciton-phonon coupling (reorganization energy) and the exciton wavefunction is delocalized over the aggregate.…”

Section: Introductionmentioning

confidence: 99%

“…not dependent on time or, equivalently, on the nuclear displacement (Condon approximation). Nevertheless, it is now clear [14,15] that the thermal fluctuation of the excitonic couplings in molecular crystals or aggregates is an effect that should become 4 part of any quantitative exciton transport theory. The formulation of such a theory depends on the characteristic timescale of the excitonic coupling fluctuations and their strength.…”

Section: Introductionmentioning

confidence: 99%

Regimes of Exciton Transport in Molecular Crystals in the Presence of Dynamic Disorder

Aragó

Troisi

2015

Adv Funct Materials

133

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Thermal motions in molecular crystals cause substantial fluctuation of the excitonic coupling between neighboring molecules (dynamic disorder). We explore the effect of such fluctuation on the exciton dynamics in two limiting cases, exemplified by the crystals of anthracene and a heteropentacene derivative. When the excitonic coupling is small in comparison with the electron phonon coupling, the exciton diffusion is incoherent and the inclusion of excitonic coupling fluctuation does not alter the exciton physics but can improve the agreement between computed and experimental diffusion coefficients. For large excitonic couplings, when the transport becomes coherent, the thermal motions determine the diffusivity of the exciton, which can be several orders of magnitude larger than in the incoherent case. The coherent regime is less frequent but potentially of great technological importance.2

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“…Since oscillator strength is lost from the lowest-energy transition, an increase in fluorescence lifetime is observed -provided, however, that there is no incoherent EET (i.e. FRET) to molecular quenching sites which induce non-radiative decay (13,14).…”

Section: Introductionmentioning

confidence: 99%

Mesoscopic quantum emitters from deterministic aggregates of conjugated polymers

Stangl

Wilhelm

Remmerssen

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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An appealing definition of the term "molecule" arises from consideration of the nature of fluorescence, with discrete molecular entities emitting a stream of single photons. We address the question of how large a molecular object may become by growing deterministic aggregates from single conjugated polymer chains. Even particles containing dozens of individual chains still behave as single quantum emitters due to efficient excitation energy transfer, whereas the brightness is raised due to the increased absorption cross-section of the suprastructure. Excitation energy can delocalize between individual polymer chromophores in these aggregates by both coherent and incoherent coupling, which are differentiated by their distinct spectroscopic fingerprints. Coherent coupling is identified by a 10-fold increase in excited-state lifetime and a corresponding spectral red shift. Exciton quenching due to incoherent FRET becomes more significant as aggregate size increases, resulting in singleaggregate emission characterized by strong blinking. This mesoscale approach allows us to identify intermolecular interactions which do not exist in isolated chains and are inaccessible in bulk films where they are present but masked by disorder.photophysics | single-molecule spectroscopy | interchromophoric coupling | structure-property relations | organic electronics A molecule, as the smallest entity of a material, is a deterministic discrete object. A simple optical technique can be devised to test this discreteness of molecules: photon antibunching, the deterministic fluorescence emission of a stream of individual photons, one at a time (1-3). By dissolving a molecular material and diluting it to ever smaller concentrations, recording the fluorescence with a microscope objective, and passing the light through a beam splitter onto two different photodetectors, photon coincidence rates on the two detectors are measured. Because a single photon cannot be at two places at once, discrete emission of single photons is easily observed in a drop of the coincidence rate at zero delay time between the two detector channels. This test of molecular discreteness begs a simple question: how large can a molecular object become for it to still behave as a perfect quantum emitter? Recently, antibunching has been demonstrated from large π-conjugated macrocycles (4) over 6 nm in diameter, and from comparably sized natural lightharvesting complexes (5). Less-pronounced antibunching has also been observed from some multichromophoric conjugated polymers of comparable molecular weight (6). Because the ease of deterministic synthesis of ultralarge π-conjugated complexes deteriorates rapidly with size, one may consider instead growing molecule-like objects by van der Waals bonding to small aggregates--the "molecular mesoscopic" approach. Such aggregates can be grown in a controlled way by single-molecule solvent vapor annealing (7), raising the question of what the fundamental size scale is for which a transition from molecular to bulk behavior occurs.Fl...

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Temporal Fluctuations in Excimer-Like Interactions between π-Conjugated Chromophores

Cited by 24 publications

References 54 publications

Importance and Nature of Short-Range Excitonic Interactions in Light Harvesting Complexes and Organic Semiconductors

Importance and Nature of Short-Range Excitonic Interactions in Light Harvesting Complexes and Organic Semiconductors

Regimes of Exciton Transport in Molecular Crystals in the Presence of Dynamic Disorder

Mesoscopic quantum emitters from deterministic aggregates of conjugated polymers

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