Papers - KADOYA Tomofumi
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High performance ambipolar organic field-effect transistors based on indigo derivatives Reviewed
Oratai Pitayatanakul, Toshiki Higashino, Tomofumi Kadoya, Masaki Tanaka, Hirotaka Kojima, Minoru Ashizawa, Tadashi Kawamoto, Hidetoshi Matsumoto, Ken Ishikawa, Takehiko Mori
JOURNAL OF MATERIALS CHEMISTRY C 2 ( 43 ) 9311 - 9317 2014.11
Publisher：ROYAL SOC CHEMISTRY
A bio-inspired organic semiconductor 5,5'-diphenylindigo shows excellent and well-balanced ambipolar transistor properties; its hole and electron mobilities are 0.56 and 0.95 cm(2) V-1 s(-1), respectively. The enhanced performance is attributed to the extended pi-pi overlap of the phenyl groups as well as the characteristic packing pattern that is a hybrid of the herringbone and brickwork structures. The ambipolar transistor characteristics are analyzed considering its operating regions, where a large unipolar saturated region appears due to the difference of the electron and hole threshold voltages.
DOI： 10.1039/c4tc01563k
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Energy-Level Engineering in Self-Contact Organic Transistors Prepared by Inkjet Printing Reviewed
Tomofumi Kadoya, Sumika Tamura, Takehiko Mori
JOURNAL OF PHYSICAL CHEMISTRY C 118 ( 40 ) 23139 - 23146 2014.10
Publisher：AMER CHEMICAL SOC
Organic field-effect transistors with chemically doped source/drain electrodes are fabricated by selectively transforming the active layer to the conducting material, organic charge-transfer (CT) complex, using inkjet printing. The formation of the CT complex is investigated by X-ray diffraction and Raman spectroscopy, and the resulting CT complex is conducting enough to realize satisfactory transistor performance. The solvent of the ink is a key factor to achieve the optimal chemical doping to form a well-ordered CT complex. In such a manner, we can obtain semiconductor-specific electrodes that significantly reduce the schottky barrier at the electrode/semiconductor interface, because ideal energy-level engineering is automatically attained between the same type of molecules.
DOI： 10.1021/jp5070819
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An Organic Metal Derived from a Selenium Analogue of Benzothienobenzothiophene Reviewed
Toshiki Higashino, Tomofumi Kadoya, Shohei Kumeta, Kohei Kurata, Tadashi Kawamoto, Takehiko Mori
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 24 ( 24 ) 3895 - 3898 2014.8
Publisher：WILEY-V C H VERLAG GMBH
Benzothieno[3,2-b]benzothiophene (BTBT) is an excellent organic transistor material, and its charge-transfer salt (BTBT)(2)PF6 is an organic metal that exhibits conductivity as high as 1500 S cm(-1) at room temperature. Here, we report a charge-transfer salt of the selenium analogue, benzoseleno[3,2-b]benzoselenophene (BSBS). (BSBS)(2)TaF6 is a one-dimensional metal isostructural to (BTBT)(2)PF6. The resistance jump temperature is reduced from 150 to 90 K, and the increase of the low-temperature resistivity is largely diminished. However, the spin susceptibility shows an obvious drop below 50 K, which implies that the low-temperature ground state is essentially a singlet state.
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All-organic self-contact transistors Reviewed
Sumika Tamura, Tomofumi Kadoya, Takehiko Mori
Applied Physics Letters 105 ( 2 ) 023301 - 023301 2014.7
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Self-contact thin-film organic transistors based on tetramethyltetrathiafulvalene Reviewed
Sumika Tamura, Tomofumi Kadoya, Tadashi Kawamoto, Takehiko Mori
APPLIED PHYSICS LETTERS 102 ( 6 ) 063305 - 063308 2013.2
Publisher：AMER INST PHYSICS
Carrier injection from organic contacts to tetramethyltetrathiafulvalene (TMTTF) is investigated in the thin-film transistors. When 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) is patterned on a TMTTF film, the resulting (TMTTF)(TCNQ) works as highly conducting source and drain electrodes. Such self-contact transistors, in which the organic material constructing the active layer is selectively transformed to the contacts, have achieved low contact resistance and high performance. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792704]
DOI： 10.1063/1.4792704
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A highly conducting organic metal derived from an organic-transistor material: benzothienobenzothiophene Reviewed
Tomofumi Kadoya, Minoru Ashizawa, Toshiki Higashino, Tadashi Kawamoto, Shohei Kumeta, Hidetoshi Matsumoto, Takehiko Mori
PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 ( 41 ) 17818 - 17822 2013
Publisher：ROYAL SOC CHEMISTRY
BTBT ([1]benzothieno[3,2-b][1]benzothiophene) is an organic semiconductor that realizes high mobility in organic transistors. Here we report that the charge-transfer (CT) salt, (BTBT)(2)PF6, shows a high room-temperature conductivity of 1500 S cm(-1). This compound exhibits a resistivity jump around 150 K, but when it is covered with Apiezon N grease the resistivity jump is suppressed, and the metallic conductivity is maintained down to 60 K. Owing to the very high conductivity, the ESR signal shows a significantly asymmetric Dysonian lineshape (A/B congruent to 3) even at room temperature. Since most organic conductors are based on strong electron donors, it is remarkable that such a weak electron donor as BTBT realizes a stable and highly conducting organic metal.
DOI： 10.1039/c3cp52881b
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Organic Field-Effect Transistors Based on Small-Molecule Organic Semiconductors Evaporated under Low Vacuum Reviewed
Takuto Takahashi, Sumika Tamura, Yuto Akiyama, Tomofumi Kadoya, Tadashi Kawamoto, Takehiko Mori
APPLIED PHYSICS EXPRESS 5 ( 6 ) 061601 - 061603 2012.6
Publisher：IOP PUBLISHING LTD
Basic small-molecule organic electron acceptors and donors such as dicyanoquinonediimine (DCNQI), tetracyanoquinodimethane (TCNQ), and tetramethyltetrathiafulvalene (TMTTF) do not smoothly form thin films by vacuum evaporation owing to the high vapor pressures. The thin films are, however, fabricated by low-vacuum evaporation, and the resulting organic thin-film transistors have exhibited remarkably improved performance. (C) 2012 The Japan Society of Applied Physics
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Nanoparticles of organic conductors: synthesis and application as electrode material in organic field effect transistors Reviewed
Dominique de Caro, Kane Jacob, Hanan Hahioui, Christophe Faulmann, Lydie Valade, Tomofumi Kadoya, Takehiko Mori, Jordi Fraxedas, Lydie Viau
NEW JOURNAL OF CHEMISTRY 35 ( 6 ) 1315 - 1319 2011
Publisher：ROYAL SOC CHEMISTRY
Stabilization of TTF center dot TCNQ nanoparticles is studied by varying the ionic liquid nature and solvent medium. The best dispersion is obtained in an acetonitrile/acetone mixture and the smaller size by using [BMIM][BF(4)], as a stabilizing ionic liquid. Applications of well-dispersed TTF center dot TCNQ nanoparticles (mean diameter of about 35 nm) as electrode material in organic field-effect transistors are also reported.
DOI： 10.1039/c0nj00858c
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Charge injection from organic charge-transfer salts to organic semiconductors Reviewed
Tomofumi Kadoya, Dominique de Caro, Kane Jacob, Christophe Faulmann, Lydie Valade, Takehiko Mori
JOURNAL OF MATERIALS CHEMISTRY 21 ( 45 ) 18421 - 18424 2011
Publisher：ROYAL SOC CHEMISTRY
Highly conducting films of organic charge-transfer (CT) salts are fabricated by a solution process from the dispersions stabilized by poly(vinylpyrrolidone). This method provides a general way to obtain conducting films of nonvolatile organic cation-and anion-radical salts with inorganic counter ions. Carrier injection from organic CT salts to organic semiconductors is investigated by using these films as electrodes in organic field-effect transistors. Efficient hole injection is observed not only from organic cation-radical salts but also from anion-radical salts to pentacene and sexithiophene. Electron injection is dominant from both types of CT salts to C-60, but hole injection and ambipolar characteristics are observed for cation-radical salts. The Fermi levels of the CT salts are discussed on the basis of these observations.
DOI： 10.1039/c1jm12783g