title: A Solution-Processable Liquid-Crystalline Semiconductor for Low-Temperature-Annealed Air-Stable N-Channel Field-Effect Transistors.
abstract: A new solution-processable and air-stable liquid-crystalline n-channel organic semiconductor (2,2'-(2,8-bis(5-(2-octyldodecyl)thiophen-2-yl)indeno[1,2-b]fluorene-6,12-diylidene)dimalononitrile, α,ω-2OD-TIFDMT) with donor-acceptor-donor (D-A-D) π conjugation has been designed, synthesized, and fully characterized. The new semiconductor exhibits a low LUMO energy (-4.19 eV) and a narrow optical bandgap (1.35 eV). The typical pseudo-focal-conic fan-shaped texture of a hexagonal columnar liquid-crystalline (LC) phase was observed over a wide temperature range. The spin-coated semiconductor thin films show the formation of large (≈0.5-1 μm) and highly crystalline platelike grains with edge-on molecular orientations. Low-temperature-annealed (50 °C) top-contact/bottom-gate OFETs have provided good electron mobility values as high as 0.11 cm2(V s)-1and high Ion/Ioffratios of 107to 108with excellent ambient stability. This indicates an enhancement of two orders of magnitude (100×) when compared with the β-substituted parent semiconductor, β-DD-TIFDMT (2,2'-(2,8-bis(3-dodecylthiophen-2-yl)indeno[1,2-b]fluorene-6,12-diylidene)dimalononitrile). The current rational alkyl-chain engineering route offers great advantages for D-A-D π-core coplanarity in addition to maintaining good solubility in organic solvents, and leads to favorable optoelectronic/physicochemical characteristics. These remarkable findings demonstrate that α,ω-2OD-TIFDMT is a promising semiconductor material for the development of n-channel OFETs on flexible plastic substrates and LC-state annealing of the columnar liquid crystals can lower the electron mobility for transistor-type charge transport.
authors.affiliation: Department of Materials Science and Nanotechnology Engineering, Abdullah Gül University, Kayseri, 38080, Turkey.
authors.forename: Resul
authors.initials: R
authors.lastname: Ozdemir
authors.affiliation: Department of Chemical and Biomolecular Engineering, Sogang University, Mapo-gu, Seoul, 04107, Korea.
authors.forename: Donghee
authors.initials: D
authors.lastname: Choi
authors.affiliation: Department of Materials Science and Nanotechnology Engineering, Abdullah Gül University, Kayseri, 38080, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Ozdemir
authors.affiliation: Department of Chemical and Biomolecular Engineering, Sogang University, Mapo-gu, Seoul, 04107, Korea.
authors.forename: Hyekyoung
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Gebze Technical University, Gebze, Kocaeli, 41400, Turkey.
authors.forename: Sinem Tuncel
authors.initials: ST
authors.lastname: Kostakoğlu
authors.affiliation: Department of Materials Science and Nanotechnology Engineering, Abdullah Gül University, Kayseri, 38080, Turkey.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Erkartal
authors.affiliation: Department of Chemical and Biomolecular Engineering, Sogang University, Mapo-gu, Seoul, 04107, Korea.
authors.forename: Hyungsug
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Chemical and Biomolecular Engineering, Sogang University, Mapo-gu, Seoul, 04107, Korea.
authors.forename: Choongik
authors.initials: C
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Nanotechnology Engineering, Abdullah Gül University, Kayseri, 38080, Turkey.
authors.forename: Hakan
authors.identifier: http://orcid.org/0000-0002-0618-1979
authors.initials: H
authors.lastname: Usta
keywords: charge-carrier mobility; field-effect transistors; liquid crystals; semiconductors; solution processing