American Chemical Society
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Molecular Orientation Control of Liquid Crystal Organic Semiconductor for High-Performance Organic Field-Effect Transistors

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journal contribution
posted on 2021-02-25, 17:34 authored by Moon Jong Han, Don-Wook Lee, Eun Kyung Lee, Joo-Young Kim, Ji Young Jung, Hyunbum Kang, Hyungju Ahn, Tae Joo Shin, Dong Ki Yoon, Jeong-Il Park
The control of molecular orientation and ordering of liquid crystal (LC) organic semiconductor (OSC) for high-performance and thermally stable organic thin-film transistors is investigated. A liquid crystalline molecule, 2-(4-dodecyl thiophenyl)[1]­dibenzothiopheno­[6,5-b:6′,5′-f]-thieno­[3,2-b]­thiophene (C12-Th-DBTTT) is synthesized, showing the highly ordered smectic X (SmX) phase, demonstrating molecular reorganization via thermal annealing. The resulting thermally evaporated polycrystalline film and solution-sheared thin film show high charge carrier mobilities of 9.08 and 27.34 cm2 V–1 s–1, respectively. Atomic force microscopy and grazing-incidence X-ray diffraction analyses prove that the random SmA1-like structure (smectic monolayer) is reorganized to the highly ordered SmA2-like structure (smectic bilayer) of C12-Ph-DBTTT at the crystal-SmX transition temperature region. Because of the strong intermolecular interactions between rigid DBTTT cores, the thin film devices of C12-Th-DBTTT show excellent thermal stability up to 300 °C, indicating that LC characterization of conventional OSC materials can obtain high electrical performance as well as superior thermal durability.