Interchain effects in the ultrafast photophysics of a semiconducting polymer: THz time-domain spectroscopy of thin films and isolated chains in solution

E. Hendry, M. Koeberg, J. M. Schins, H. K. Nienhuys, V. Sundström, L. D. A. Siebbeles, and M. Bonn
Phys. Rev. B 71, 125201 – Published 2 March 2005

Abstract

We compare the generation and decay dynamics of charges and excitons in a model polymer semiconductor (MEH-PPV) in solution and drop-cast thin films, by recording the sub-ps transient complex conductivity using THz time-domain spectroscopy. The results show that the quantum efficiency of charge generation is two orders of magnitude smaller in solution (105) than in the solid film (103). The proximity of neighboring chains in the films apparently facilitates (hot) exciton dissociation, presumably by allowing the electron and hole to separate on different polymer strands. For both samples, photoexcitation leads to the predominant formation of bound charge pairs (excitons) that can be detected through their polarizability. Surprisingly, the polarizability per absorbed photon is a factor of 3 larger in solution than in the film, suggesting that interchain interactions in the film do not result in a substantial delocalization of the exciton wave function.

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  • Received 20 August 2004

DOI:https://doi.org/10.1103/PhysRevB.71.125201

©2005 American Physical Society

Authors & Affiliations

E. Hendry1,2,*, M. Koeberg1,2, J. M. Schins3, H. K. Nienhuys4, V. Sundström4, L. D. A. Siebbeles3, and M. Bonn1,2

  • 1Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
  • 2FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ, Amsterdam, The Netherlands
  • 3Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands
  • 4Department of Chemical Physics, Chemical Center, Lund University, Getingevägen 60, 222 41 Lund, Sweden

  • *FAX: +31-71-5274451. Electronic address: e.hendry@chem.leidenuniv.nl

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Vol. 71, Iss. 12 — 15 March 2005

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