Papers - KADOYA Tomofumi
-
Semiconductor Properties of π‐Extended 2‐(Thiopyran‐4‐ylidene)‐1,3‐benzodithiole (TP‐BT) Analogs
Hiroshi Nishimoto, Tomofumi Kadoya, Takeshi Kawase, Jun‐ichi Nishida
Asian Journal of Organic Chemistry 12 ( 12 ) 2023.12
Publisher：Wiley
Abstract
Despite having an asymmetric structure, 2‐(thiopyran‐4‐ylidene)‐1,3‐benzodithiole (TP‐BT) is a good p‐type semiconductor containing isotropic three‐dimensional (3D) intermolecular interactions. Moreover, its π‐extended analogs can potentially work as organic electronic materials. Herein, a fused‐type π‐extended analog containing an extra benzene ring on the benzodithiole unit, i. e., 2‐(thiopyran‐4‐ylidene)‐1,3‐naphtho[2,3‐d]dithiole (TP‐NT), and three σ‐bonded‐type π‐extended analogs, i. e., phenyl‐, naphthyl‐, and anthryl‐substituted analogs (Ph‐TP‐BT, Nap‐TP‐BT, and Ant‐TP‐BT, respectively), were prepared and their molecular arrangements and organic field‐effect transistor (OFET) properties were investigated. TP‐NT formed a herringbone arrangement with 3D intermolecular interactions similar to that of the parent TP‐BT. Meanwhile, Ant‐TP‐BT formed a bilayer‐type layered herringbone arrangement. Since the highest occupied molecular orbital and the lowest unoccupied molecular orbital are located on the TP‐BT and anthracene units, respectively, a unique donor–acceptor separated network was formed. In OFETs prepared via a vapor deposition method using the σ‐bonded‐type analogs, slightly lower mobilities (0.1 to 8×10<sup>−3</sup> cm<sup>2</sup>/Vs) than that of TP‐NT (0.1 cm<sup>2</sup>/Vs) were observed. Upon photo‐irradiation, the OFET of Ant‐TP‐BT exhibited a larger threshold voltage shift and an increase in the off current compared with TP‐NT. The σ‐bonded‐type analogs showed a larger photo‐response effect than TP‐NT derived from the donor–acceptor molecular structure. -
Measurement of electron injection barriers in OS/Au (OS=phthalocyanine and pentacene) using accumulated charge measurement Reviewed
Takeshi Oda, Koji Yamaguchi, Tomofumi Kadoya, Hiroyuki Tajima
Organic Electronics 120 106827 - 106827 2023.9
-
Hiroyuki Tajima, Takeshi Oda, Tomofumi Kadoya
Magnetochemistry 2023.7
-
Sonomi Arata, Yuna Kim, Norihisa Hoshino, Keishiro Tahara, Kiyonori Takahashi, Tomofumi Kadoya, Tomonori Inoue, Takayoshi Nakamura, Tomoyuki Akutagawa, Jun‐ichi Yamada, Kazuya Kubo
European Journal of Inorganic Chemistry 2023.2
Publisher：Wiley
Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ejic.202300017
-
Boundary research between organic conductors and transistors: new trends for functional molecular crystals Reviewed
Tomofumi Kadoya, Toshiki Higashino
CrystEngComm 2023
-
Tomofumi Kadoya, Masaharu Shishido, Shiori Sugiura, Toshiki Higashino, Keishiro Tahara, Kazuya Kubo, Takahiko Sasaki, Jun-ichi Yamada
Chemistry Letters 51 ( 7 ) 683 - 686 2022.7
Authorship：Lead author, Corresponding author Publisher：The Chemical Society of Japan
DOI： 10.1246/cl.220148
-
Hiroshi Nishimoto, Tomofumi Kadoya, Rikyu Miyake, Takeshi Oda, Jun-ichi Nishida, Kazuya Kubo, Hiroyuki Tajima, Takeshi Kawase, Jun-ichi Yamada
CrystEngComm 2022
Authorship：Corresponding author Publisher：Royal Society of Chemistry (RSC)
We report the synthesis of P-BT and TP-BT and their OTFT properties based on electronic dimensionality and access resistance (R<sub>acc</sub>). TP-BT can suppress R<sub>acc</sub> due to its 3D electronic structure.
DOI： 10.1039/d2ce00644h
-
Toby J. Blundell, Alexander L. Morritt, Elizabeth K. Rusbridge, Luke Quibell, Jakob Oakes, Hiroki Akutsu, Yasuhiro Nakazawa, Shusaku Imajo, Tomofumi Kadoya, Jun-ichi Yamada, Simon J. Coles, Jeppe Christensen, Lee Martin
Materials Advances 3 ( 11 ) 4724 - 4735 2022
Publisher：Royal Society of Chemistry (RSC)
Six new BEDT-TTF salts with tris(oxalato)gallate or -iridate anions including two new superconductors β′′-(BEDT-TTF)<sub>4</sub>[(H<sub>3</sub>O)Ga(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>]·guest (bromobenzene or iodobenzene) and a novel 5 : 1 metal–insulator β′′-(BEDT-TTF)<sub>5</sub>Ir(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub> ethanol.
DOI： 10.1039/d2ma00384h
-
Synthesis and electron-transport properties of N-trifluoromethylphenyl-phthalimides containing selenophene substituents Reviewed
Jun-ichi Nishida, Yoshiki Morikawa, Akito Hashimoto, Yasuyuki Kita, Hiroshi Nishimoto, Tomofumi Kadoya, Hiroyasu Sato, Takeshi Kawase
Materials Advances 2 7861 - 7868 2021.10
-
Thermal and non-thermal equilibrium processes of charge extraction in accumulated charge measurement (ACM) Reviewed
Hiroyuki Tajima, Tomofumi Kadoya, Koji Yamaguchi, Yuichi Omura, Takeshi Oda, Akinari Ogino
Journal of Applied Physics 130 ( 19 ) 195501 2021.10
-
Kazuya Kubo, Mamoru Sadahiro, Sonomi Arata, Norihisa Hoshino, Tomofumi Kadoya, Tomoyuki Akutagawa, Reizo Kato, Jun-ichi Yamada
Crystals 11 ( 10 ) 1154 - 1154 2021.9
Publisher：MDPI AG
The effects of substituents on the arrangement of metal–dithiolene complexes based on π-conjugated systems, which are extensively used to synthesize various functional materials, have not been studied adequately. New donor-type nickel–dithiolene complexes fused with bulky cycloalkane substituents [Ni(Cn-dddt)2] (C5-dddt = 4a,5,6,6a-pentahydro-1,4-benzodithiin-2,3-dithiolate; C6-dddt = 4a,5,6,7,8,8a-hexahydro-1,4-benzodithiin-2,3-dithiolate; C7-dddt = 4a,5,6,7,8,9,9a-heptahydro-1,4-benzodithiin-2,3-dithiolate; and C8-dddt = 4a,5,6,7,8,9,10,10a-octahydro-1,4-benzodithiin-2,3-dithiolate) were synthesized in this study. All the complexes were crystallized in cis-[Ni(cis-Cn-dddt)2] conformations with cis-oriented (R,S) conformations around the cycloalkylene groups in the neutral state. Unique molecular arrangements with a three-dimensional network, a one-dimensional column, and a helical molecular arrangement were formed in the crystals owing to the flexible cycloalkane moieties. New 2:1 cation radical crystals of [Ni(C5-dddt)2]2(X) (X = ClO4− or PF6−), obtained by electrochemical crystallization, exhibited semiconducting behaviors (ρrt = 0.8 Ω cm, Ea = 0.09 eV for the ClO4− crystal; 4.0 Ω cm, 0.13 eV for the PF6− crystal) under ambient pressure due to spin-singlet states between the dimers of the donor, which were in accordance with the conducting behaviors under hydrostatic pressure (ρrt = 0.2 Ω cm, Ea = 0.07 eV for the ClO4− crystal; 1.0 Ω cm, 0.12 eV for the PF6− crystal at 2.0 GPa).
-
Dihedral-Angle Dependence of Intermolecular Transfer Integrals in BEDT-BDT-Based Radical-Cation Salts with θ-Type Molecular Arrangements Invited Reviewed
Tomofumi Kadoya, Shiori Sugiura, Toshiki Higashino, Keishiro Tahara, Kazuya Kubo, Takahiko Sasaki, Kazuo Takimiya, Jun-ichi Yamada
Crystals 11 ( 8 ) 868 - 868 2021.7
Authorship：Lead author, Corresponding author Publisher：MDPI AG
We report the structural and physical properties of a new organic Mott insulator (BEDT-BDT)AsF6 (BEDT-BDT: benzo[1,2-g:4,5-g′]bis(thieno[2,3-b][1,4dithiin). This AsF6 salt has the same structure as the PF6 salt. Although the anions are disordered, the donor molecules form a θ-type arrangement. The temperature dependence of the resistivity exhibits semiconducting behavior. The static magnetic susceptibility follows Curie–Weiss law over a wide temperature range; however, below 25 K, the magnetic susceptibility is in agreement with a one-dimensional chain model with the exchange coupling J = 7.4 K. No structural phase transition was observed down to 93 K. At 270 K, the Fermi surface calculated by the tight-binding approximation is a two-dimensional cylinder; however, it is significantly distorted at 93 K. This is because the dihedral angles between the BEDT-BDT molecules become larger due to lattice shrinkage at low temperatures, which results in a smaller transfer integral (t1) along the stack direction. This slight change in the dihedral angle gives rise to a significant change in the electronic structure of the AsF6 salt. Radical-cation salts using BEDT-BDT, in which the highest occupied molecular orbital does not have a dominant sign throughout the molecule, are sensitive to slight differences in the overlap between the molecules, and their electronic structures are more variable than those of conventional θ-type conductors.
-
Aoi Hori, Yuna Kim, Keishiro Tahara, Tomofumi Kadoya, Jun‐ichi Yamada, Kazuya Kubo
European Journal of Inorganic Chemistry 2021 ( 11 ) 1023 - 1027 2021.3
Publisher：Wiley
Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ejic.202001014
-
Aoi Hori, Yuna Kim, Keishiro Tahara, Tomofumi Kadoya, Jun‐ichi Yamada, Kazuya Kubo
European Journal of Inorganic Chemistry 2021 ( 11 ) 1014 - 1014 2021.3
Publisher：Wiley
Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ejic.202100134
-
Sunao Shimomoto, Tomofumi Kadoya, Toshiaki Tanimura, Kazusuke Maenaka, Tokuji Yokomatsu, Takeshi Komino, Hiroyuki Tajima
The Journal of Physical Chemistry C 125 ( 3 ) 1990 - 1998 2021.1
Authorship：Corresponding author Publisher：American Chemical Society (ACS)
This study investigates the charge injection barrier at the phthalocyanine (H2Pc)/Pd using accumulated charge measurement (ACM). Because the hole injection barrier is relatively small, the voltage oscillation method in ACM is achieved at the highest occupied molecular orbital/Pd interface, and the hole injection barrier was determined to be 0.26 eV. A negative offset voltage was applied to determine the electron injection barrier at the lowest unoccupied molecular orbital (LUMO)/Pd interface. However, when the electron injection barrier was significantly large, the charge-injected thermal equilibrium state (CITES) could not be achieved at the interface, and an accurate injection barrier could not be determined. Surprisingly, by applying a positive offset voltage, a CITES of electrons was obtained at the LUMO/Pd interface, and the band gap was determined to be 2.75 eV. Furthermore, the electron injection barrier was found to be 2.49 eV. By applying a positive offset voltage, band bending occurred at the H2Pc/Pd interface, thereby reducing the depletion layer in the LUMO and enabling the determination of the band gap and electron injection barrier.
-
Toby J. Blundell, Michael Brannan, Hiroshi Nishimoto, Tomofumi Kadoya, Jun-ichi Yamada, Hiroki Akutsu, Yasuhiro Nakazawa, Lee Martin
Chemical Communications 57 ( 44 ) 5406 - 5409 2021
Publisher：Royal Society of Chemistry (RSC)
<p>Synthesis of a chiral molecular metal which shows metallic behaviour down to at least 4.2 K.</p>
DOI： 10.1039/d1cc01441b
-
Keishiro Tahara, Yuya Ashihara, Takashi Ikeda, Tomofumi Kadoya, Jun-ichi Fujisawa, Yoshiki Ozawa, Hiroyuki Tajima, Noriaki Toyoda, Yuichi Haruyama, Masaaki Abe
Inorganic Chemistry 59 ( 24 ) 17945 - 17957 2020.12
Publisher：American Chemical Society (ACS)
Chemical modification of insulating material surfaces is an important methodology to improve the performance of organic field-effect transistors (OFETs). However, few redox-active self-assembled monolayers (SAMs) have been constructed on gate insulator film surfaces, in contrast to the numerous SAMs formed on many types of conducting electrodes. In this study, we report a new approach to introduce a pi-conjugated organic fragment in close proximity to an insulating material surface via a transition metal center acting as a one-atom anchor. On the basis of the reported coordination chemistry of a catecholato complex of Pt(II) in solution, we demonstrate that ligand exchange can occur on an insulating material surface, affording SAMs on the SiO2 surface derived from a newly synthesized Pt(II) complex containing a benzothienobenzothiophene (BTBT) framework in the catecholato ligand. The resultant SAMs were characterized in detail by water contact angle measurements, X-ray photoelectron spectroscopy, atomic force microscopy, and cyclic voltammetry. The SAMs served as good scaffolds of 7c-conjugated pillars for forming thin films of a well-known organic semiconductor C8-BTBT (2,7- dioctyl[1]benzothieno[3,2-b][1]benzothiophene), accompanied by the engagements of the C8-BTBT molecules with the SAMs containing the common BTBT framework at the first layer on SiO2. OFETs containing the SAMs displayed improved performance in terms of hole mobility and onset voltage, presumably because of the unique interfacial structure between the organic semiconducting and inorganic insulating layers. These findings provide important insight into creating new elaborate interfaces through installing coordination chemistry in solution to solid surfaces, as well as OFET design by considering the compatibility between SAMs and organic semiconductors.
-
Ferrocene on Insulator: Silane Coupling to a SiO2 Surface and Influence on Electrical Transport at a Buried Interface with an Organic Semiconductor Layer Reviewed International journal
Takashi Ikeda, Keishiro Tahara, Tomofumi Kadoya, Hiroyuki Tajima, Noriaki Toyoda, Satoshi Yasuno, Yoshiki Ozawa, Masaaki Abe
Langmuir 36 ( 21 ) 5809 - 5819 2020.6
Publisher：American Chemical Society (ACS)
A silane coupling-based procedure for decoration of an insulator surface containing abundant hydroxy groups by constructing redox-active self-assembled monolayers (SAMs) is described. A newly synthesized ferrocene (Fc) derivative containing a triethoxysilyl group designated FcSi was immobilized on SiO2/Si by a simple operation that involved immersing the substrate in a toluene solution of the Fc silane coupling reagent and then rinsing the resulting substrate. X-ray photoelectron spectroscopy (XPS) measurements confirmed that the Fc group was immobilized on SiO2/Si in the Fe(II) state. Cyclic voltammetry measurements showed that the Fc groups were electrically insulated from the Si electrode by the SiO2 layer. The FcSi on SiO2/Si structures were found to serve as a good scaffold for formation of organic semiconductor thin films by vacuum thermal evaporation of C8-BTBT (2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene), which is well-known as an organic field-effect transistor (OFET) material. The X-ray diffraction profile indicated that the conventional standing-up conformation of the C8-BTBT molecules perpendicular to the substrates was maintained in the thin films formed on FcSi@SiO2/Si. Further vacuum thermal evaporation of Au provided an FcSi-based OFET structure with good transfer characteristics. The FcSi-based OFET showed pronounced source-drain current hysteresis between the forward and backward scans. The degree of this hysteresis was varied reversibly via gate bias manipulation, which was presumably accompanied by trapping and detrapping of hole carriers at the Fc-decorated SiO2 surface. These findings provide new insights into application of redox-active SAMs to nonvolatile OFET memories while also creating new interfaces through junctions with functional thin films, in which the underlying redox-active SAMs play supporting roles.
-
Steric effect of halogen substitution in an unsymmetrical benzothienobenzothiophene organic semiconductor Reviewed
Tomofumi Kadoya, Shotaro Mano, Aoi Hori, Keishiro Tahara, Kunihisa Sugimoto, Kazuya Kubo, Masaaki Abe, Hiroyuki Tajima, Jun-ichi Yamada
Organic Electronics 78 105570 - 105570 2020.3
Authorship：Lead author, Corresponding author Publisher：Elsevier BV
We report a crystal structure analysis of an unsymmetrical organic semiconductor 2-bromo-7-butyl[1]benzothieno[3,2-b][1]benzothiophene (Br-BTBT-C ) and its transistor characteristics. Unlike the parent compound 2-butyl-[1]benzothieno[3,2-b][1]benzothiophene (BTBT-C ) forming a bilayer-type structure composed of head-to-head herringbone packings, Br-BTBT-C forms a dense head-to-tail herringbone packing arranged so as to avoid the steric hindrance between bromine atoms. The intermolecular transfer integrals in Br-BTBT-C suggest its advantage for carrier transport; however, the transistor characteristics of Br-BTBT-C and BTBT-C were found to be almost the same. This is because BTBT-C has a higher crystallinity than Br-BTBT-C in vacuum deposited thin films. 4 4 4 4 4 4 4 4
-
Tomofumi Kadoya, Shiori Sugiura, Keishiro Tahara, Toshiki Higashino, Kazuya Kubo, Takahiko Sasaki, Kazuo Takimiya, Jun-ichi Yamada
CrystEngComm 22 ( 36 ) 5949 - 5953 2020
Authorship：Lead author, Corresponding author Publisher：Royal Society of Chemistry (RSC)
<p>We have succeeded in developing a two-dimensional radical–cationic Mott insulator that does not contain a 1,3-dithiol-2-ylidene moiety.</p>
DOI： 10.1039/d0ce00878h