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The Ultrafast Dynamics of Electronic Excitations in Pentacene Thin Films

Published online by Cambridge University Press:  01 February 2011

Henning Marciniak ,
Bert Nickel  and
Stefan Lochbrunner
Henning Marciniak
Affiliation:
[email protected], Universität Rostock, Institut für Physik, Rostock, Germany
Bert Nickel
Affiliation:
[email protected], CeNS, Munich, Germany
Stefan Lochbrunner
Affiliation:
[email protected], Universität Rostock, Institut für Physik, Rostock, Germany
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Abstract

Pentacene films which are model systems for organic electronics exhibit contrary to the pentacene monomer extremely little photoluminescence. This points to an ultrafast relaxation mechanism. We apply pump-probe absorption spectroscopy with a time resolution of 30 fs to microcrystalline pentacene films. It is found that the primarily excited Frenkel excitons decay within 70 fs to a non fluorescing singlet species. Contrary to expectations fission into triplets is only a minor channel. We propose that the ultrafast relaxation of the photoexcited excitons leads to a species very similar to excimers. The radiative transition of the excimer to the ground state is electric dipole forbidden due to symmetry reasons. The excimer formation provides therefore an efficient mechanism to turn off the emission.

Keywords

absorptionorganicsemiconducting
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1270: Symposia GG/HH/II – Organic Photovoltaics and Related Electronics-From Excitons to Devices , 2010 , 1270-II09-53
Copyright
Copyright © Materials Research Society 2010

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References

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