posted on 2021-02-25, 17:34authored byMoon 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.