Influence of alkyl chain length on charge transport in symmetrically substituted poly(2,5-dialkoxy-p-phenylenevinylene) polymers

Sachetan M. Tuladhar, Marc Sims, James Kirkpatrick, Robert C. Maher, Amanda J. Chatten, Donal D. C. Bradley, Jenny Nelson, Pablo G. Etchegoin, Christian B. Nielsen, Philippe Massiot, Wayne N. George, and Joachim H. G. Steinke
Phys. Rev. B 79, 035201 – Published 8 January 2009
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Abstract

We report on the hole transport characteristics, as measured by time of flight, of a family of symmetrically substituted dialkoxy poly(p-phenylenevinylene) polymers with different side-chain length. As side-chain length is decreased, the magnitude of the hole mobility μh increases while the field dependence of μh becomes more positive and the temperature dependence of μh becomes stronger. For the shortest side-chain derivative studied, μh exceeds 104cm2V1s1 at electric fields greater than 105Vcm1. The trend in magnitude of μh with side-chain length is consistent with the expected increase in electronic wave-function overlap as interchain separation decreases, while the trends in electric-field and temperature dependences of μh are consistent with increasing site energy disorder. We show that the electrostatic contribution to the site energy difference for pairs of oligomers follows the observed trend as a function of interchain separation, although the pairwise contribution is too small to explain the data quantitatively. Nonresonant Raman spectroscopy is used to characterize the microstructure of our films. We construct spatial maps of the Raman ratio I1280/I1581 and confirm an expected decrease in average film density with side-chain extension. The structural heterogeneity in the maps is analyzed but no clear correlation is observed with transport properties, suggesting that the structural variations relevant for charge transport occur on a length scale finer than the resolution of 1μm.

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  • Received 25 June 2008

DOI:https://doi.org/10.1103/PhysRevB.79.035201

©2009 American Physical Society

Authors & Affiliations

Sachetan M. Tuladhar, Marc Sims, James Kirkpatrick, Robert C. Maher, Amanda J. Chatten, Donal D. C. Bradley, and Jenny Nelson

  • Department of Physics, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom

Pablo G. Etchegoin

  • The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand

Christian B. Nielsen, Philippe Massiot, Wayne N. George, and Joachim H. G. Steinke

  • Department of Chemistry, Imperial College London, Prince Consort Road, London SW7 2AY, United Kingdom

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Issue

Vol. 79, Iss. 3 — 15 January 2009

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