MRS Proceedings

Table of Contents - Volume  1270  - Symposia GG/HH/II – Organic Photovoltaics and Related Electronics-From Excitons to Devices  

Editors : V.R. Bommisetty, N.S. Sariciftci, K. Narayan, G. Rumbles, P. Peumans, J. van de Lagemaat, G. Dennler, S.E. Shaheen

Articles

The Ultrafast Dynamics of Electronic Excitations in Pentacene Thin Films

2010 MRS Spring Meeting.

Henning Marciniaka1, Bert Nickela2 and Stefan Lochbrunnera3

a1 henning.marciniak@uni-rostock.de, Universität Rostock, Institut für Physik, Rostock, Germany

a2 nickel@lmu.de, CeNS, Munich, Germany

a3 stefan.lochbrunner@uni-rostock.de, Universität Rostock, Institut für Physik, Rostock, Germany

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.

(Received March 26 2010)

(Accepted September 29 2010)

Key Words:

  • absorption;
  • organic;
  • semiconducting
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