Molecular-weight dependence of interchain polaron delocalization and exciton bandwidth in high-mobility conjugated polymers

J.F. Chang, J. Clark, N. Zhao, H. Sirringhaus, Dag Werner Breiby, Jens Wenzel Andreasen, Martin Meedom Nielsen, M. Giles, M. Heeney, I. McCulloch

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Interchain interactions have a profound effect on the optical as well as charge transport properties of conjugated polymer thin films. In contrast to oligomeric model systems in solution-deposited polymer thin films the study of such effects is complicated by the complex microstructure. We present here a detailed study of interchain interaction effects on both charged polarons as well as neutral excitons in highly crystalline, high-mobility poly-3-hexylthiophene (P3HT) as a function of molecular weight. We find experimental evidence for reduced exciton bandwidth and increased polaron delocalization with increasing conjugation length and crystalline quality. From comparative studies of field-effect transistor characteristics, film morphology, and optical properties our study provides a microscopic understanding of the factors which limit the charge transport in P3HT to field-effect mobilities around 0.1 cm(2)/V s, and which will need to be addressed to improve mobility further.
Original languageEnglish
JournalPhysical Review B Condensed Matter
Issue number11
Pages (from-to)115318
Number of pages12
Publication statusPublished - 2006

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