The influence of film morphology in high-mobility small-molecule: Polymer blend organic transistors

Jeremy Smith, Richard Hamilton, Yabing Qi, Antoine Kahn, Donal D C Bradley, Martin Heeney, Iain McCulloch, Thomas D. Anthopoulos

Research output: Contribution to journalArticle

100 Scopus citations

Abstract

Organic field-effect transistors (OFETs) based upon blends of small molecular semiconductors and polymers show promise for high performance organic electronics applications. Here the charge transport characteristics of high mobility p-channel orpnic transistors based on 2,8-difluoro-5,11- bis(triethylsilylethynyl) anthradithiophene:poly(triarylamine) blend films are investigated. By simple alteration of the film processing conditions two distinct film microstructures can be obtained: one characterized by small spherulitic grains (SG) and one by large grains (LC). Charge transport measurements reveal thermally activated hole transport in both SC and LG film microstructures with two distinct temperature regimes. For temperatures >115 K, gate voltage dependent activation energies (EA) in the range of 25-60 meV are derived. At temperatures <115 K, the activation energies are smaller and typically in the range 5-30 meV. For both film microstructures hole transport appears to be dominated by trapping at the grain boundaries. Estimates of the trap densities suggests that LG films with fewer grain boundaries are characterized by a reduced number of traps that are less energetically disordered but deeper in energy than for small SG films. The effects of source and drain electrode treatment with self-assembled monolayers (SAMs) on current injection is also investigated. Fluorinated thiol SAMs were found to alter the work function of gold electrodes by up to ∼1 eV leading to a lower contact resistance. However, charge transport analysis suggests that electrode work function is not the only parameter to consider for efficient charge injection.

Original languageEnglish (US)
Pages (from-to)2330-2337
Number of pages8
JournalAdvanced Functional Materials
Volume20
Issue number14
DOIs
StatePublished - Jul 23 2010

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Condensed Matter Physics
  • Electrochemistry

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    Smith, J., Hamilton, R., Qi, Y., Kahn, A., Bradley, D. D. C., Heeney, M., McCulloch, I., & Anthopoulos, T. D. (2010). The influence of film morphology in high-mobility small-molecule: Polymer blend organic transistors. Advanced Functional Materials, 20(14), 2330-2337. https://doi.org/10.1002/adfm.201000427