The nature of singlet excitons in oligoacene molecular crystals

H. Yamagata*, J. Norton, E. Hontz, Y. Olivier, D. Beljonne, J. L. Brédas, R. J. Silbey, F. C. Spano

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

215 Scopus citations

Abstract

A theory for polarized absorption in crystalline oligoacenes is presented, which includes Frenkel exciton coupling, the coupling between Frenkel and charge-transfer (CT) excitons, and the coupling of all neutral and ionic excited states to the dominant ring-breathing vibrational mode. For tetracene, spectra calculated using all Frenkel couplings among the five lowest energy molecular singlet states predict a Davydov splitting (DS) of the lowest energy (0-0) vibronic band of only -32cm-1, far smaller than the measured value of 631cm-1 and of the wrong sign-a negative sign indicating that the polarizations of the lower and upper Davydov components are reversed from experiment. Inclusion of Frenkel-CT coupling dramatically improves the agreement with experiment, yielding a 0-0 DS of 601cm-1 and a nearly quantitative reproduction of the relative spectral intensities of the 0-n vibronic components. Our analysis also shows that CT mixing increases with the size of the oligoacenes. We discuss the implications of these results on exciton dissociation and transport. © 2011 American Institute of Physics.
Original languageEnglish (US)
Pages (from-to)204703
JournalThe Journal of Chemical Physics
Volume134
Issue number20
DOIs
StatePublished - May 26 2011
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUSC1-015-21
Acknowledgements: F.C.S. and H.Y. were supported by the National Science Foundation (NSF) under Award DMR-0906464. Work at Georgia Tech was partly supported by the Office of Naval Research (ONR), the STC Program of the National Science Foundation under Award DMR-0120967, and the Center for Advanced Molecular Photovoltaics, Award No KUSC1-015-21, made by King Abdullah University of Science and Technology (KAUST). Research in University of Mons was supported by the Interuniversity Attraction Pole program of the Belgian Federal Science Policy Office (PAI 6/27), Programme d'Excellence de la Region Wallonne (OPTI2MAT project), and FNRS-FRFC; D. B. is an FNRS Research Director. R.J.S. was supported as part of the Center for Excitonics, an Energy Frontier Research Center funded by U.S. Department of Energy and Office of Science, Office of Basic Energy Science (Grant No. DE-SC0001088).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

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