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

doi:10.1063/1.3590871

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 journal › Article › peer-review

241 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.

Original language	English (US)
Article number	204703
Journal	JOURNAL OF CHEMICAL PHYSICS
Volume	134
Issue number	20
DOIs	https://doi.org/10.1063/1.3590871
State	Published - May 28 2011
Externally published	Yes

Bibliographical note

Funding Information:
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 Région 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).

ASJC Scopus subject areas

General Physics and Astronomy
Physical and Theoretical Chemistry

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title = "The nature of singlet excitons in oligoacene molecular crystals",

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.",

author = "H. Yamagata and J. Norton and E. Hontz and Y. Olivier and D. Beljonne and Br{\'e}das, {J. L.} and Silbey, {R. J.} and Spano, {F. C.}",

note = "Funding Information: 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{\textquoteright}Excellence de la R{\'e}gion 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).",

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AU - Norton, J.

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AU - Olivier, Y.

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AU - Brédas, J. L.

AU - Silbey, R. J.

AU - Spano, F. C.

N1 - Funding Information: 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 Région 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).

PY - 2011/5/28

Y1 - 2011/5/28

N2 - 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.

AB - 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.

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The nature of singlet excitons in oligoacene molecular crystals

Abstract

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