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Origin of the different transport properties of electron and hole polarons in an ambipolar polyselenophene-based conjugated polymer

Zhuoying Chen, Matthew Bird, Vincent Lemaur, Guillaume Radtke, Jérôme Cornil, Martin Heeney, Iain McCulloch, and Henning Sirringhaus
Phys. Rev. B 84, 115211 – Published 27 September 2011

Abstract

Understanding the mechanisms limiting ambipolar transport in conjugated polymer field-effect transistors (FETs) is of both fundamental and practical interest. Here, we present a systematic study comparing hole and electron charge transport in an ambipolar conjugated polymer, semicrystalline poly(3,3-di-n-decylterselenophene) (PSSS). Starting from a detailed analysis of the device characteristics and temperature/charge-density dependence of the mobility, we interpret the difference between hole and electron transport through both the Vissenberg-Matters and the mobility-edge model. To obtain microscopic insight into the quantum mechanical wave function of the charges at a molecular level, we combine charge modulation spectroscopy (CMS) measuring the charge-induced absorption signatures from positive and negative polarons in these ambipolar FETs with corresponding density functional theory (DFT) calculations. We observe a significantly higher switch-on voltage for electrons than for holes due to deep electron trap states, but also a higher activation energy of the mobility for mobile electrons. The CMS spectra reveal that the electrons that remain mobile and contribute to the FET current have a wave function that is more localized onto a single polymer chain than that of holes, which is extended over several polymer chains. We interpret this as evidence that the transport properties of the mobile electrons in PSSS are still affected by the presence of deep electron traps. The more localized electron state could be due to the mobile electrons interacting with shallow trap states in the vicinity of a chemical, potentially water-related, impurity that might precede the capture of the electron into a deeply trapped state.

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  • Received 5 July 2011

DOI:https://doi.org/10.1103/PhysRevB.84.115211

©2011 American Physical Society

Authors & Affiliations

Zhuoying Chen1,2,*, Matthew Bird1,3, Vincent Lemaur4, Guillaume Radtke2, Jérôme Cornil4, Martin Heeney5, Iain McCulloch5, and Henning Sirringhaus1,†

  • 1Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
  • 2Institut Matériaux Microélectronique Nanosciences de Provence, UMR CNRS 6242, Faculté des Sciences St Jérôme, Université Aix-Marseille III, 13397 Marseille cedex 20, France
  • 3Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
  • 4Laboratory for Chemistry of Novel Materials, University of Mons, B-7000 Mons, Belgium
  • 5Department of Chemistry, Imperial College, London, SW7 2AZ, United Kingdom

  • *zhuoying.chen@im2np.fr
  • hs220@cam.ac.uk

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Issue

Vol. 84, Iss. 11 — 15 September 2011

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