Effects of confinement on microstructure and charge transport in high performance semicrystalline polymer semiconductors

Scott Himmelberger*, Javier Dacuña, Jonathan Rivnay, Leslie H. Jimison, Thomas McCarthy-Ward, Martin Heeney, Iain McCulloch, Michael F. Toney, Alberto Salleo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

The film thickness of one of the most crystalline and highest performing polymer semiconductors, poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b] thiophene) (PBTTT), is varied in order to determine the effects of interfaces and confinement on the microstructure and performance in organic field effect transistors (OFETs). Crystalline texture and overall film crystallinity are found to depend strongly on film thickness and thermal processing. The angular distribution of crystallites narrows upon both a decrease in film thickness and thermal annealing. These changes in the film microstructure are paired with thin-film transistor characterization and shown to be directly correlated with variations in charge carrier mobility. Charge transport is shown to be governed by film crystallinity in films below 20 nm and by crystalline orientation for thicker films. An optimal thickness is found for PBTTT at which the mobility is maximized in unannealed films and where mobility reaches a plateau at its highest value for annealed films. The effects of confinement on the morphology and charge transport properties of poly(2,5-bis(3-tetradecylthiophen-2-yl) thieno[3,2-b]thiophene) (PBTTT) are studied using quantitative X-ray diffraction and field-effect transistor measurements. Polymer crystallinity is found to limit charge transport in the thinnest films while crystalline texture and intergrain connectivity modulate carrier mobility in thicker films.

Original languageEnglish (US)
Pages (from-to)2091-2098
Number of pages8
JournalAdvanced Functional Materials
Volume23
Issue number16
DOIs
StatePublished - Apr 25 2013

Keywords

  • charge transport
  • crystallinity
  • organic electronics
  • organic field-effect transistors
  • thin films

ASJC Scopus subject areas

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

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