Anomalous Energy Transfer Dynamics due to Torsional Relaxation in a Conjugated Polymer

Sebastian Westenhoff, Wichard J. D. Beenken, Richard H. Friend, Neil C. Greenham, Arkady Yartsev, and Villy Sundström
Phys. Rev. Lett. 97, 166804 – Published 18 October 2006

Abstract

In isolated conjugated polymers two explanations are in discussion for the redshift of the emission on a picosecond time scale—exciton energy transfer (EET) between conjugated segments along the chains and conformational changes of these segments themselves, i.e., torsional relaxation. In order to resolve this question we perform femtosecond time-resolved transient absorption measurements of the energy relaxation of poly[3-(2,5-dioctylphenyl)thiophene] in toluene solution. We show that torsional relaxation can be distinguished from EET by site-selectively exciting low-energy conjugated segments. We present a unified model that integrates EET and torsional dynamics. In particular, comparison to ultrafast depolarization measurements shows that torsional dynamics cannot be neglected when analyzing EET dynamics and furthermore reveals that the exciton extends itself by about 2 monomer units during torsional relaxation.

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  • Received 8 May 2006

DOI:https://doi.org/10.1103/PhysRevLett.97.166804

©2006 American Physical Society

Authors & Affiliations

Sebastian Westenhoff1,*, Wichard J. D. Beenken2, Richard H. Friend1, Neil C. Greenham1, Arkady Yartsev3, and Villy Sundström3

  • 1Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CH3 0HE, United Kingdom
  • 2Department of Physics, Technische Universität Ilmenau, 98684 Ilmenau, Germany
  • 3Department of Chemical Physics, Lund University, Box 124, S-221 00 Lund, Sweden

  • *Electronic address: sw372@cam.ac.uk

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Vol. 97, Iss. 16 — 20 October 2006

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