High-mobility organic thin-film transistors based on a small-molecule semiconductor deposited in vacuum and by solution shearing

Robert Hofmockel, Ute Zschieschang, Ulrike Kraft, Reinhold Rödel, Nis Hauke Hansen, Matthias Stolte, Frank Würthner, Kazuo Takimiya, Klaus Kern, Jens Pflaum, Hagen Klauk

Research output: Contribution to journalArticle

73 Citations (Scopus)

Abstract

The small-molecule organic semiconductor 2,9-di-decyl-dinaphtho-[2,3-b: 2′,3′-f]-thieno-[3,2-b]-thiophene (C10-DNTT) was used to fabricate bottom-gate, top-contact thin-film transistors (TFTs) in which the semiconductor layer was prepared either by vacuum deposition or by solution shearing. The maximum effective charge-carrier mobility of TFTs with vacuum-deposited C10-DNTT is 8.5 cm2/V s for a nominal semiconductor thickness of 10 nm and a substrate temperature during the semiconductor deposition of 80 C. Scanning electron microscopy analysis reveals the growth of small, isolated islands that begin to coalesce into a flat conducting layer when the nominal thickness exceeds 4 nm. The morphology of the vacuum-deposited semiconductor layers is dominated by tall lamellae that are formed during the deposition, except at very high substrate temperatures. Atomic force microscopy and X-ray diffraction measurements indicate that the C 10-DNTT molecules stand approximately upright with respect to the substrate surface, both in the flat conducting layer near the surface and within the lamellae. Using the transmission line method on TFTs with channel lengths ranging from 10 to 100 μm, a relatively small contact resistance of 0.33 kΩ cm was determined. TFTs with the C10-DNTT layer prepared by solution shearing exhibit a pronounced anisotropy of the electrical performance: TFTs with the channel oriented parallel to the shearing direction have an average carrier mobility of (2.8 ± 0.3) cm2/V s, while TFTs with the channel oriented perpendicular to the shearing direction have a somewhat smaller average mobility of (1.3 ± 0.1) cm2/V s.

Original languageEnglish
Pages (from-to)3213-3221
Number of pages9
JournalOrganic Electronics
Volume14
Issue number12
DOIs
Publication statusPublished - 2013 Jan 1
Externally publishedYes

Keywords

  • Contact resistance
  • Organic thin-film transistors
  • Solution shearing
  • Thin-film morphology

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering

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