Uniaxial alignment of liquid-crystalline conjugated polymers by nanoconfinement

Zijian Zheng, Keng Hoong Yim, Mohammad S.M. Saifullah, Mark E. Welland, Richard H. Friend, Ji Seon Kim, Wilhelm T.S. Huck

Research output: Journal article publicationJournal articleAcademic researchpeer-review

161 Citations (Scopus)

Abstract

We demonstrate the uniaxial alignment of a liquid-crystalline conjugated polymer, poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) by means of nanoconfinement during nanoimprinting. The orientation of the conjugated backbones was parallel to the nanolines imprinted into the polymer film. Polarized UV-vis absorption and photoluminescence spectra were measured to quantify the degree of alignment, showing that the polarization ratio and uniaxial molecular order parameter were as high as 66 and 0.97, respectively. The aligned F8BT film was used as the active layer in a PLED, which resulted in polarized electroluminescence with a polarization ratio of 11. Ambipolar PFET in a top-gate configuration with aligned F8BT as the active semiconducting layer showed mobility enhancement when the chains were aligned parallel to the transport direction. Mobility anisotropies for hole and electron transport were 10-15 and 5-7, respectively, for current flow parallel and perpendicular to the alignment direction.
Original languageEnglish
Pages (from-to)987-992
Number of pages6
JournalNano Letters
Volume7
Issue number4
DOIs
Publication statusPublished - 1 Apr 2007
Externally publishedYes

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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