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Hopping transport and the Hall effect near the insulator–metal transition in electrochemically gated poly(3-hexylthiophene) transistors

Nature Communications volume 3, Article number: 1210 (2012) | Download Citation

Abstract

Despite 35 years of investigation, much remains to be understood regarding charge transport in semiconducting polymers, including the ultimate limits on their conductivity. Recently developed ion gel gating techniques provide a unique opportunity to study such issues at very high charge carrier density. Here we have probed the benchmark polymer semiconductor poly(3-hexylthiophene) at electrochemically induced three-dimensional hole densities approaching 1021 cm−3 (up to 0.2 holes per monomer). Analysis of the hopping conduction reveals a remarkable phenomenon where wavefunction delocalization and Coulomb gap collapse are disrupted by doping-induced disorder, suppressing the insulator–metal transition, even at these extreme charge densities. Nevertheless, at the highest dopings, we observe, for the first time in a polymer transistor, a clear Hall effect with the expected field, temperature and gate voltage dependencies. The data indicate that at such mobilities (~0.8 cm2V−1 s−1), despite the extensive disorder, these polymers lie close to a regime of truly diffusive band-like transport.

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Acknowledgements

This work was supported primarily by the MRSEC programme of the NSF under DMR-0819885. C.D.F. also acknowledges support from DOE BES, under DESC0004200. B. Shklovskii is acknowledged for useful discussions.

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Affiliations

  1. Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA

    • Shun Wang
    • , Mingjing Ha
    • , Michael Manno
    • , C Daniel Frisbie
    •  & C Leighton

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Contributions

C.D.F. and C.L. conceived the project. S.W., M.H. and M.M. synthesized the samples, performed the experiments and analysed the data, under the supervision of C.L. and C.D.F. C.L., S.W. and C.D.F. wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to C Leighton.

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https://doi.org/10.1038/ncomms2213

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