Exciton migration in β-phase poly(9,9-dioctylfluorene)

M. Ariu, M. Sims, M. D. Rahn, J. Hill, A. M. Fox, D. G. Lidzey, M. Oda, J. Cabanillas-Gonzalez, and D. D. C. Bradley
Phys. Rev. B 67, 195333 – Published 30 May 2003
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Abstract

We have studied the dynamics of optically generated excitations in spin-coated glassy films of poly(9,9-dioctylfluorene) (PFO) and in β-phase PFO films using picosecond time resolved photoluminescence (PL) spectroscopy, performed both at room temperature (RT) and at 5 K. We also present measurements of the PL emission of PFO and β-phase PFO at RT and 5 K following continuous wave (cw) excitation. We show that the cw emission from β-phase PFO at 5 K is very highly resolved, permitting us to make an assignment of the different vibrational modes of the molecule that couple to the S1S0 transition. Via time-dependent spectroscopy measurements performed at 5 K, we are able to follow exciton diffusion and relaxation through an energetically broadened density of states to polymer chains having a longer conjugation length and lower energy gap. By comparing the relative emission intensity of the different vibronic transitions as a function of time, we are able to directly demonstrate that the lower energy emissive states are associated with longer conjugation length polymeric chains that have enhanced rigidity. At room temperature, we find that these relaxation processes occur faster than the resolution of our detector due to thermally assisted energy migration.

  • Received 21 November 2002

DOI:https://doi.org/10.1103/PhysRevB.67.195333

©2003 American Physical Society

Authors & Affiliations

M. Ariu*, M. Sims*, M. D. Rahn, J. Hill, A. M. Fox, and D. G. Lidzey

  • Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom

M. Oda

  • University of Potsdam, Institute of Physics, Am Neuen Palais 10, 14469 Potsdam, Germany

J. Cabanillas-Gonzalez and D. D. C. Bradley

  • The Blackett Laboratory, Imperial College London, Prince Consort Road, SW7 2BZ London, United Kingdom

  • *Present address: The Blackett Laboratory, Imperial College London, Prince Consort Road, SW7 2BZ, London, UK.
  • Corresponding authors. Electronic address: d.g.lidzey@ sheffield.ac.uk Electronic address: d.bradley@ic.ac.uk
  • Present address: Sony Corporation, Fusion Domain Laboratory, R&D Group Haneda Tec. 5-21-15 Higashikojiya Ota-ku, 144-0033 Tokyo, Japan.

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Issue

Vol. 67, Iss. 19 — 15 May 2003

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