A π-Stacking Terthiophene-Based Quinodimethane Is an n-Channel Conductor in a Thin Film Transistor

A terthiophene-based quinodimethane, 3‘,4‘-dibutyl-5,5‘ ‘-bis(dicyanomethylene)-5,5‘ ‘-dihydro-2,2‘:5‘,2‘ ‘-terthiophene (1) was synthesized and crystallized. Compound 1 has a planar quinoid geometry that is stabilized by dicyanomethylene groups at each end of the molecule. In the crystal each molec...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2002-04, Vol.124 (16), p.4184-4185
Main Authors: Pappenfus, Ted M, Chesterfield, Reid J, Frisbie, C. Daniel, Mann, Kent R, Casado, Juan, Raff, Jonathan D, Miller, Larry L
Format: Article
Language:English
Subjects:
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Conductivity of specific materials
Electronic transport in condensed matter
Exact sciences and technology
Physics
Polymers
organic compounds (including organic semiconductors)
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Summary:A terthiophene-based quinodimethane, 3‘,4‘-dibutyl-5,5‘ ‘-bis(dicyanomethylene)-5,5‘ ‘-dihydro-2,2‘:5‘,2‘ ‘-terthiophene (1) was synthesized and crystallized. Compound 1 has a planar quinoid geometry that is stabilized by dicyanomethylene groups at each end of the molecule. In the crystal each molecule is part of a dimerized face-to-face π-stack, with intermolecular spacings of 3.47 and 3.63 Å, respectively. Cyclic voltammetry showed that 1 could be reversibly reduced and oxidized in methylene chloride solution. Thin film transistors (TFTs) were prepared by vacuum evaporation of 1 onto SiO2(300 nm)/Si substrates, followed by evaporation of Ag source and drain contacts. The doped Si substrate served as the gate electrode. X-ray diffraction and atomic force microscopy indicate the films are polycrystalline, with the long axes of the molecules approximately perpendicular to the substrate. The TFT measurements revealed n-channel conduction in films of 1, with room-temperature electron field effect mobilities as high as 0.005 cm2/Vs. The butyl side chains give 1 appreciable solubility in a range of common solvents, and preliminary TFT results on films cast from chlorobenzene show electron mobility as high as 0.002 cm2/Vs. These results indicate that π-stacked quinoidal thiophene oligomers are a promising new class of soluble n-channel organic semiconductors.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja025553j