Abstract

Conjugated polymers enable the production of flexible semiconductor devices that can be processed from solution at low temperatures. Over the past 25 years, device performance has improved greatly as a wide variety of molecular structures have been studied1. However, one major limitation has not been overcome; transport properties in polymer films are still limited by pervasive conformational and energetic disorder2,3,4,5. This not only limits the rational design of materials with higher performance, but also prevents the study of physical phenomena associated with an extended π-electron delocalization along the polymer backbone. Here we report a comparative transport study of several high-mobility conjugated polymers by field-effect-modulated Seebeck, transistor and sub-bandgap optical absorption measurements. We show that in several of these polymers, most notably in a recently reported, indacenodithiophene-based donor–acceptor copolymer with a near-amorphous microstructure6, the charge transport properties approach intrinsic disorder-free limits at which all molecular sites are thermally accessible. Molecular dynamics simulations identify the origin of this long sought-after regime as a planar, torsion-free backbone conformation that is surprisingly resilient to side-chain disorder. Our results provide molecular-design guidelines for ‘disorder-free’ conjugated polymers.

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Acknowledgements

We gratefully acknowledge financial support from the Engineering and Physical Sciences Research Council through a programme grant (EP/G060738/1) and the Technology Strategy Board (PORSCHED project). D.V. acknowledges financial support from the Cambridge Commonwealth Trust through a Cambridge International Scholarship. K.B. acknowledges post-doctoral fellowship support from the German Research Foundation. M.Z. acknowledges funding from NanoDTC in Cambridge. The work in Mons was supported by the European Commission/Région Wallonne (FEDER – Smartfilm RF project), the Interuniversity Attraction Pole programme of the Belgian Federal Science Policy Office (PAI 7/05), Programme d’Excellence de la Région Wallonne (OPTI2MAT project) and FNRS-FRFC. D.B. and J.C. are FNRS Research Fellows.

Author information

Author notes

    • Deepak Venkateshvaran
    •  & Mark Nikolka

    These authors contributed equally to this work.

Affiliations

  1. Optoelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK

    • Deepak Venkateshvaran
    • , Mark Nikolka
    • , Aditya Sadhanala
    • , Mateusz Zelazny
    • , Auke Jisk Kronemeijer
    • , Vincenzo Pecunia
    • , Iyad Nasrallah
    • , Igor Romanov
    • , Katharina Broch
    •  & Henning Sirringhaus
  2. Laboratory for Chemistry of Novel Materials, Université de Mons, 20 Place du Parc, 7000 Mons, Belgium

    • Vincent Lemaur
    • , Yoann Olivier
    • , Jerome Cornil
    •  & David Beljonne
  3. Centre for Science at Extreme Conditions, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, UK

    • Michal Kepa
  4. Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, UK

    • Michael Hurhangee
    •  & Iain McCulloch
  5. Department of Physics and Astronomy, University of New Mexico, 1919 Lomas Boulevard Northeast, Albuquerque, New Mexico 87131, USA

    • David Emin

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Contributions

D.V. designed and fabricated the devices and performed field-effect modulated Seebeck measurements on them. M.N. and A.J.K. optimized the fabrication of IDTBT-based organic FETs and performed transistor measurements. A.S. and M.N. performed photothermal deflection spectroscopy measurements. V.P. optimized the patterning procedure for organic devices. V.L., M.Z., Y.O., J.C. and D.B. performed quantum chemical and molecular dynamic simulations. M.Z. and M.K. acquired the high-pressure induced Raman spectra. K.B. performed measurements on DPPTTT-based devices. I.N. and I.R. performed charge accumulation spectroscopy measurements (Supplementary Information). I.M. and M.H. synthesized IDTBT. D.E. explained the Seebeck measurements on the basis of a narrow-band model. H.S. directed and coordinated the research. D.V., M.N., V.L., Y.O., J.C., D.B., D.E. and H.S. wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Henning Sirringhaus.

Supplementary information

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    Supplementary Information

    This file contains Supplementary Text and Data, Supplementary Figures 1-20, Supplementary Tables 1-2 and Supplementary references.

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DOI

https://doi.org/10.1038/nature13854

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