Dependence of regioregular poly(3-hexylthiophene) film morphology and field-effect mobility on molecular weight

R. Joseph Kline, Michael D. McGehee*, Ekaterina N. Kadnikova, Jinsong Liu, Jean M.J. Fréchet, Michael F. Toney

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

904 Scopus citations

Abstract

Morphological characterization has been used to explain the previously observed strong correlation between charge carrier mobility measured with thin-film transistors and the number-average molecular weight (MW) of the conjugated polymer regioregular poly(3-hexylthiophene). Atomic force microscopy and X-ray diffraction show that the low-mobility, low-MW films have a highly ordered structure composed of nanorods and the high-mobility, high-MW films have a less ordered, isotropic nodule structure. Modifying the morphology for a constant MW by changing the casting conditions or annealing the samples strongly affects the charge transport and morphology in the low-mobility, low-MW films, but has little effect on the high-MW films. In-plane grazing incidence X-ray scattering shows the in-plane π-stacking peak increases when the mobility increases for a constant MW. When the MW is changed, this correlation breaks down, confirming that in-plane π-stacking does not cause the mobility - MW relationship. We believe a combination of disordered domain boundaries and inherent effects of chain length on the electronic structure cause the mobility - MW relationship.

Original languageEnglish (US)
Pages (from-to)3312-3319
Number of pages8
JournalMacromolecules
Volume38
Issue number8
DOIs
StatePublished - Apr 19 2005

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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