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Hydrogen-Bonding-Facilitated Layer-by-Layer Growth of Ultrathin Organic Semiconducting Films

Jeong, Sang-Mi, Kim, Taek-Gyoung, Jung, Eunyoung, Park, Ji-Woong
ACS Applied Materials & Interfaces 2013 v.5 no.15 pp. 6837-6842
crystals, films (materials), hydrogen bonding, organic compounds
We demonstrated that the layer-by-layer growth of thin film crystals of conjugated organic molecules is facilitated by their hydrogen-bonding capabilities. We synthesized bis(3-hydroxypropyl)-sexithiophene (bHP6T), which includes two hydroxyalkyl groups that promote interlayer and intermolecular molecular interactions during the crystal growth process. Under the optimal deposition conditions, the crystals grew in a nearly perfect layer-by-layer mode on the solid substrate surfaces, enabling the formation of uniform charge transporting films as thin as a few monolayers. A thin film transistor device prepared from a bHP6T film only 9 nm thick exhibited a charge carrier mobility well above 1 × 10–² cm²/(V s) and an on/off ratio exceeding 1 × 10⁴. These properties are better than the properties of other sexithiophene-based devices yet reported. The devices exhibited enhanced stability under atmospheric conditions, and they functioned properly, even after storage for more than 2 months.