Approaching disorder-free transport in high mobility conjugated polymers
Kronemeijer, Auke Jisk
Nature Publishing Group
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Venkateshvaran, D., Nikolka, M., Sadhanala, A., Lemaur, V., Zelazny, M., Kepa, M., Hurhangee, M., et al. (2014). Approaching disorder-free transport in high mobility conjugated polymers. Nature, 515 348-388. https://doi.org/10.1038/nature13854
Conjugated polymers are enabling flexible semiconductor devices that can be processed from solution at low temperatures. Over the last 25 years, devices’ performances have improved greatly as a wide variety of molecular structures have been studied . However, one major limitation has not been overcome; transport properties in polymer films are still limited by pervasive conformational and energetic disorder [2-5]. This not only limits the rational design of materials with higher performance, but also prevents study of physical phenomena associated with an extended -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 near amorphous microstructure , the charge transport properties are approaching intrinsic disorder-free limits in 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 important molecular-design guidelines for “disorder-free” conjugated polymers.
We gratefully acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) through a programme grant (EP/G060738/1) and the Technology Strategy Board (TSB) (PORSCHED project). D. Venkateshvaran acknowledges financial support from the Cambridge Commonwealth Trust through a Cambridge International Scholarship. K. Broch acknowledges post-doctoral fellowship support from the German Research Foundation (DFG). Mateusz Zelazny acknowledges funding from the NanoDTC in Cambridge. The work in Mons was supported by the European Commission / Région Wallonne (FEDER – Smartfilm RF project), the Interuniversity Attraction Pole program 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.
External DOI: https://doi.org/10.1038/nature13854
This record's URL: https://www.repository.cam.ac.uk/handle/1810/246380