Using Molecular Design to Increase Hole Transport: Backbone Fluorination in the Benchmark Material Poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]-thiophene (pBTTT)

Pierre Boufflet, Yang Han, Zhuping Fei, Neil D. Treat, Ruipeng Li, Detlef M. Smilgies, Natalie Stingelin, Thomas Anthopoulos, Martin Heeney*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

The synthesis of a novel 3,3′-difluoro-4,4′-dihexadecyl-2,2′-bithiophene monomer and its copolymerization with thieno[3,2-b]thiophene to afford the fluorinated analogue of the well-known poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]-thiophene) (PBTTT) polymer is reported. Fluorination is found to have a significant influence on the physical properties of the polymer, enhancing aggregation in solution and increasing melting point by over 100 C compared to nonfluorinated polymer. On the basis of DFT calculations these observations are attributed to inter and intramolecular S...F interactions. As a consequence, the fluorinated polymer PFBTTT exhibits a fourfold increase in charge carrier mobility compared to the nonfluorinated polymer and excellent ambient stability for a nonencapsulated transistor device. Backbone fluorination of the benchmark liquid crystalline polymer poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]-thiophene) is shown to significantly influence its physical properties, substantially increasing the melting point and promoting aggregation. Density functional theory calculations suggest that this is related to a more coplanar backbone for the fluorinated polymer. Field effect transistor measurements show a fourfold increase in mobility upon fluorination.

Original languageEnglish (US)
Pages (from-to)7038-7048
Number of pages11
JournalAdvanced Functional Materials
Volume25
Issue number45
DOIs
StatePublished - Dec 2 2015

Keywords

  • PBTTT
  • S-F interactions
  • fluorination
  • organic field-effect transistors
  • planarity

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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