学術論文

PAPERS

代表的な論文を赤太字で示し、その概要を記載しています。

2021

49.
Active refractive index control using a stably evaporable perfluororesin for high-outcoupling-efficiency organic light-emitting diodes
J. Mater. Chem. C (in press)
Daisuke Yokoyama, Tatsuki Sasaki, Yasutaka Suzuki, Takefumi Abe, Kaori Tsuruoka, Tatsuya Miyajima, Toshifumi Kakiuchi, Chiho Morita, Masaharu Aoki, Yasuhiro Ouchi, Wataru Aita, Yasuhiro Kuwana, Yutaka Noguchi
Selected as "Journal of Materials Chemistry C Hot Papers"

分解することなく安定に蒸着可能な低コスト・高非晶性のフッ素樹脂を有機EL正孔輸送材料と共蒸着することにより、特異な相分離構造を形成し、電気特性を損なうことなく正孔輸送層の屈折率を能動的に大きく低減させ、有機ELデバイスの光取り出し効率を著しく向上できることを実証した。共蒸着するだけで光取り出し効率を大幅に向上できる新たな手法を提示した。
48.
Molecular orientation anisotropy and hole transport properties of diluted semiconducting films of poly(p-phenylenevinylene) derivative
Org. Electron. 96, 106246 (2021)
Seiya Demura, Tatsuro Endo, Takumi Ishii, Daisuke Yokoyama, Yutaka Noguchi
47.
Effect of the conformer distribution on the properties of amorphous organic semiconductor films for organic light-emitting diodes
Phys. Chem. Chem. Phys. 23, 14242-14251 (2011)
Yoshihito Sukegawa, Kaito Sato, Wataru Fujiwara, Hiroshi Katagiri, Daisuke Yokoyama

これまで非晶質有機薄膜で十分な議論がなされてこなかった「配座異性体」に焦点を当て、類似の構造を持つ3種の構造異性体を対象にしてその多様性・分布を比較し、それらが膜物性に与える影響について考察した。配座異性体分布の評価を通じて、非晶質有機膜の高次構造をより深く理解するための新たな概念と枠組みを提案した。

2020

46.
Significantly sensitized ternary blend polymer solar cells with very small content of narrow-bandgap third component that utilizes optical interference
Macromolecules 53, 10623-10635 (2020)
Masahiko Saito, Yasunari Tamai, Hiroyuki Ichikawa, Hiroyuki Yoshida, Daisuke Yokoyama, Hideo Ohkita, Itaru Osaka
45.
Molecular orientations of delayed fluorescent emitters in a series of carbazole-based host materials
Front. Chem. 8, 427 (2020)
Hisahiro Sasabe, Yuki Chikayasu, Satoru Ohisa, Hiroki Arai, Tatsuya Ohsawa, Ryutaro Komatsu, Yuichiro Watanabe, Daisuke Yokoyama, Junji Kido
44.
Simultaneous realization of high-efficiency, low-drive voltage, and long lifetime TADF OLEDs by multifunctional hole-transporters
J. Mater. Chem. C 8, 7200-7210 (2020)
Takahiro Kamata, Hisahiro Sasabe, Nozomi Ito, Yoshihito Sukegawa, Ayato Arai, Takayuki Chiba, Daisuke Yokoyama, Junji Kido
43.
A terpyridine-modified chrysene derivative as an electron transporter to improve the lifetime in phosphorescent OLEDs
J. Mater. Chem. C 8, 3200-3205 (2020)
Tsukasa Owada, Hisahiro Sasabe, Yoshihito Sukegawa, Taiki Watanabe, Tomohiro Maruyama, Yuichiro Watanabe, Daisuke Yokoyama, Junji Kido

2019

42.
Control of molecular orientation in organic semiconductor films using weak hydrogen bonds
Adv. Mater. 31, 1808300 (2019)
Yuichiro Watanabe, Daisuke Yokoyama, Tomoyuki Koganezawa, Hiroshi Katagiri, Takashi Ito, Satoru Ohisa, Takayuki Chiba, Hisahiro Sasabe, Junji Kido

オリゴピリジン系電子輸送材料群の蒸着膜中の分子凝集状態について分光エリプソメトリーとGIWAXSを組み合わせて系統的な分析を行い、分子間水素結合を利用した分子配向性制御とそのデバイス応用の重要性を示した。

2018

41.
Air-stable and high-performance solution-processed organic light-emitting devices based on hydrophobic polymeric ionic liquid carrier-injection layers
Adv. Mater. 30, 1705915 (2018)
Shugo Sato, Satoru Ohisa, Yukihiro Hayashi, Ryo Sato, Daisuke Yokoyama, Tetsuya Kato, Michinori Suzuki, Takayuki Chiba, Yong-Jin Pu, Junji Kido

2017

40.
Horizontally orientated stick-like emitters: Achieving enhancement of intrinsic out-coupling factor and electroluminescence device performance
Chem. Mater. 29, 8630-8636 (2017)
Ming Liu, Ryutaro Komatsu, Xinyi Cai, Katsuyuki Hotta, Shugo Sato, Kunkun Liu, Dongcheng Chen, Yuki Kato, Hisahiro Sasabe, Satoru Ohisa, Yoshiyuki Suzuri, Daisuke Yokoyama, Shi-Jian Su, Junji Kido
39.
Thermally activated delayed fluorescence OLEDs with fully solution processed organic layers exhibiting nearly 10% external quantum efficiency
Chem. Commun. 53, 2439-2442 (2017)
Ken Albrecht, Kenichi Matsuoka, Daisuke Yokoyama, Yoshiya Sakai, Akira Nakayama, Katsuhiko Fujita, Kimihisa Yamamoto

2016

38.
Fundamental functions of peripheral and core pyridine rings in a series of bis-terpyridine derivatives for high-performance organic light-emitting devices
J. Mater. Chem. C 4, 8980-8988 (2016)
Yuichiro Watanabe, Ryo Yoshioka, Hisahiro Sasabe, Takahiro Kamata, Hiroshi Katagiri, Daisuke Yokoyama, Junji Kido
37.
Syntheses, properties, and OLED characteristics of 2,2'-bipyridine-based electron-transport materials: synergistic effect of molecular shape anisotropy and a weak hydrogen-bonding network on molecular orientation
J. Mater. Chem. C 4, 3699-3704 (2016)
Yuichiro Watanabe, Hisahiro Sasabe, Daisuke Yokoyama, Teruo Beppu, Hiroshi Katagiri, Junji Kido
36.
Excimer emission based on the control of molecular structure and intermolecular interactions
J. Mater. Chem. C 4, 2784-2792 (2016)
Jaehyun Lee, Hyocheol Jung, Hwangyu Shin, Joonghan Kim, Daisuke Yokoyama, Hidetaka Nishimura, Atsushi Wakamiya, Jongwook Park
35.
A series of fluorinated phenylpyridine-based electron-transporters for blue phosphorescent OLEDs
J. Mater. Chem. C 4, 1104-1110 (2016)
Takahiro Kamata, Hisahiro Sasabe, Yuichiro Watanabe, Daisuke Yokoyama, Hiroshi Katagiri, Junji Kido

2015

34.
Photopatterning of indomethacin thin films: a solvent-free vapor-deposited photoresist
ACS Appl. Mater. Interfaces 7, 23398-23401 (2015)
Katherine L. Camera, Jaritza Gomez-Zayas, Daisuke Yokoyama, Mark D. Ediger, Christopher K. Ober
33.
Simple model-free estimation of orientation order parameters of vacuum-deposited and spin-coated amorphous films used in organic light-emitting diodes
Appl. Phys. Express 8, 096601 (2015)
Yoshiya Sakai, Maki Shibata, Daisuke Yokoyama

加熱によって転移させた後に分子配向がランダム化する低分子非晶質薄膜の特性を活かし、複雑な光学モデルを一切用いることなく分光光度計とホットプレートだけを使用して極めて簡潔な式により分子配向度を定量評価する標準的分析手法を新たに提案した。
32.
Advantages and disadvantages of vacuum-deposited and spin-coated amorphous organic semiconductor films for organic light-emitting diodes
J. Mater. Chem. C 3, 11178-11191 (2015) [PDF 3.8MB]
Maki Shibata, Yoshiya Sakai, Daisuke Yokoyama

非晶質有機半導体の蒸着膜と塗布膜を、密度(充填係数)・転移温度(熱安定性)・分子配向性等の観点から成膜条件依存性も含め系統的・網羅的に比較した。膜形成機構・物性の違いの本質を明確化した上で、それぞれの長所・短所をデータとともに整理した。(本文14ページ、Supporting19ページ)
31.
Anisotropic materials in OLEDs for high outcoupling efficiency
Opt. Express 23, 21128-21148 (2015)
Michiel Koen Callens, Daisuke Yokoyama, Kristiaan Neyts
30.
High fill factor and thermal stability of bilayer organic photovoltaic cells with an inverted structure
Appl. Phys. Lett. 106, 053305 (2015)
Zhongqiang Wang, Ziruo Hong, Taojun Zhuang, Guo Chen, Hisahiro Sasabe, Daisuke Yokoyama, Junji Kido
29.
Extended-gate organic field-effect transistor for the detection of histamine in water
Jpn. J. Appl. Phys. 54, 04DK02 (2015)
Tsukuru Minamiki, Tsuyoshi Minami, Daisuke Yokoyama, Kenjiro Fukuda, Daisuke Kumaki, Shizuo Tokito
28.
Simultaneous manipulation of intramolecular and intermolecular hydrogen bonds in n-type organic semiconductor layers: Realization of horizontal orientation in OLEDs
Adv. Opt. Mater. 3 769-773 (2015)
Yuichiro Watanabe, Hisahiro Sasabe, Daisuke Yokoyama, Teruo Beppu, Hiroshi Katagiri, Yong-Jin Pu, Junji Kido

2014

27.
An extended-gate type organic field effect transistor functionalised by phenylboronic acid for saccharide detection in water
Chem. Commun. 50, 15613-15615 (2014)
Tsuyoshi Minami, Tsukuru Minamiki, Yuki Hashima, Daisuke Yokoyama, Tomohito Sekine, Kenjiro Fukuda, Daisuke Kumaki, Shizuo Tokito
26.
Excimer formation in organic emitter films associated with a molecular orientation promoted by steric hindrance
Chem. Commun. 50, 14145-14148 (2014)
Jaehyun Lee, Beomjin Kim, Ji Eon Kwon, Joonghan Kim, Daisuke Yokoyama, Katsuaki Suzuki, Hidetaka Nishimura, Atsushi Wakamiya, Soo Young Park, Jongwook Park
25.
Esterification of indoline-based small-molecule donors for efficient co-evaporated organic photovoltaics
J. Phys. Chem. C 118, 14785-14794 (2014)
Zhongqiang Wang, Xiao-Feng Wang, Daisuke Yokoyama, Hisahiro Sasabe, Junji Kido, Zhaoyang Liu, Wenjing Tian, Osamu Kitao, Toshitaka Ikeuchi, Shin-ichi Sasaki
24.
Quantum yield in blue-emitting anthracene derivatives: vibronic coupling density and transition dipole moment density
Phys. Chem. Chem. Phys. 16, 14244-14256 (2014)
Motoyuki Uejima, Tohru Sato, Daisuke Yokoyama, Kazuyoshi Tanaka, Jongwook Park

2013

23.
Synthesis and electroluminescence properties of highly efficient blue fluorescence emitters using dual core chromophores
J. Mater. Chem. C 1, 432-440 (2013)
Beomjin Kim, Youngil Park, Jaehyun Lee, Daisuke Yokoyama, Ji-Hoon Lee, Junji Kido, Jongwook Park
22.
Highly efficient organic p-i-n photovoltaic cells based on tetraphenyldibenzoperiflanthene and fullerene C70
Energy Environ. Sci. 6, 249-255 (2013)
Zhongqiang Wang, Daisuke Yokoyama, Xiao-Feng Wang, Ziruo Hong, Yang Yang, Junji Kido

2012

21.
Wide-range refractive index control of organic semiconductor films toward advanced optical design of organic optoelectronic devices
Adv. Mater. 24, 6368-6373 (2012)
Daisuke Yokoyama, Ken-ichi Nakayama, Toshiya Otani, Junji Kido
Selected as the back cover Website [PDF 2.5MB]

有機材料の屈折率差と異方性に注目し、精密な光学構造を構築することで、超高反射率の光導電性有機半導体ミラーを実証した(R>98%、有機物として世界最高値)。有機半導体自身による光と電子の同時制御が可能であることを示し、新たな有機光デバイスの創製に向けた技術展開を提示した。
20.
Optical and electrical properties of a squaraine dye in photovoltaic cells
Appl. Phys. Lett. 101, 083904 (2012)
Guo Chen, Daisuke Yokoyama, Hisahiro Sasabe, Ziruo Hong, Yang Yang, Junji Kido
19.
Horizontal orientation of disk-like hole transport molecules and their application for organic light-emitting diodes requiring lower driving voltage
J. Phys. Chem. C 116, 8699-8706 (2012)
Jun-Yun Kim, Daisuke Yokoyama, Chihaya Adachi
18.
Optimizing the charge balance of fluorescent organic light-emitting devices to achieve high external quantum efficiency beyond the conventional upper limit
Adv. Mater. 24, 1765-1770 (2012)
Yong-Jin Pu, Go Nakata, Fumiya Satoh, Hisahiro Sasabe, Daisuke Yokoyama, Junji Kido
17.
High-efficiency simple planar heterojunction organic thin-film photovoltaics with horizontally oriented amorphous donors
Sol. Energy Mater. Sol. Cells 98, 472-475 (2012)
Daisuke Yokoyama, Zhongqiang Wang, Yong-Jin Pu, Kenta Kobayashi, Junji Kido, Ziruo Hong

2011

16.
Molecular orientation in small-molecule organic light-emitting diodes
Feature Article (Invited review)
J. Mater. Chem. 21, 19187-19202 (2011) [PDF 4.0MB]
Daisuke Yokoyama
[ Top 1% highly cited paper ]

非晶性有機半導体薄膜内および有機EL素子内の分子配向に関する数年間の研究を総括した16ページの総説論文。非晶質膜の分子集合状態・物性に関する独自の見方を提示し、これまでの論文4,5,7-13の内容とそれらの研究経緯を概説して、今後の展望も記した。
15.
Dual efficiency enhancement by delayed fluorescence and dipole orientation in high-efficiency fluorescent organic light-emitting diodes
Appl. Phys. Lett. 99, 123303 (2011)
Daisuke Yokoyama, Youngil Park, Beomjin Kim, Sookang Kim, Yong-Jin Pu, Junji Kido, Jongwook Park

過去に報告されている蛍光有機ELデバイスの特異な高効率について、三重項-三重項消滅を経由した遅延蛍光と分子の水平配向の両方を組み合わせて初めて定量的な解釈を行った。
14.
An integrated enzyme-linked immunosorbent assay system with an organic light-emitting diode and a charge-coupled device for fluorescence detection
J. Sep. Sci. 34, 2906-2912 (2011)
Hizuru Nakajima, Yukiko Okuma, Kazuhiro Morioka, Mayo Miyake, Akihide Hemmi, Tatsuya Tobita, Masayuki Yahiro, Daisuke Yokoyama, Chihaya Adachi, Nobuaki Soh, Koji Nakano, Shuhua Xue, Hulie Zeng, Katsumi Uchiyama, Toshihiko Imato
13.
Molecular stacking induced by intermolecular C-H...N hydrogen bonds leading to high carrier mobility in vacuum-deposited organic films
Adv. Funct. Mater. 21, 1375-1382 (2011)
Daisuke Yokoyama, Hisahiro Sasabe, Yukio Furukawa, Chihaya Adachi, Junji Kido

電子輸送材料の分子間水素結合による高次構造形成と電子移動度との相関を追跡した。明確な周期構造を持たない膜を、エリプソメトリー・X線回折・近紫外吸収・赤外吸収・量子化学計算により多角的・複合的に分析した。
12.
Increased light outcoupling efficiency in dye-doped small molecule organic light-emitting diodes with horizontally oriented emitters
Org. Electron. 12, 809-817 (2011)
Jörg Frischeisen, Daisuke Yokoyama, Ayataka Endo, Chihaya Adachi, Wolfgang Brütting

低分子有機ELデバイスにおけるドーパント発光分子の分子配向がデバイスの光取り出し効率に大きな影響を与えていることを示した。(論文5での提案を実験的に初めて実証。)
11.
Influence of substituted pyridine rings on physical properties and electron mobilities of 2-methylpyrimidine skeleton-based electron-transporters
Adv. Funct. Mater. 21, 336-342 (2011)
Hisahiro Sasabe, Daisaku Tanaka, Daisuke Yokoyama, Takayuki Chiba, Yong-Jin Pu, Ken-ichi Nakayama, Masaaki Yokoyama, Junji Kido

2010

10.
In situ real-time spectroscopic ellipsometry measurement for the investigation of molecular orientation in organic amorphous multilayer structures
J. Appl. Phys. 107, 123512 (2010)
Daisuke Yokoyama, Chihaya Adachi
9.
Determination of molecular dipole orientation in doped fluorescent organic thin films by photoluminescence measurements
Appl. Phys. Lett. 96, 073302 (2010)
Jörg Frischeisen, Daisuke Yokoyama, Chihaya Adachi, Wolfgang Brütting
8.
Orientation control of linear-shaped molecules in vacuum-deposited organic amorphous films and its effect on carrier mobilities
Adv. Funct. Mater. 20, 386-391 (2010)
Daisuke Yokoyama, Yousuke Setoguchi, Akio Sakaguchi, Michio Suzuki, Chihaya Adachi

基板温度によって分子配向の制御を行い、非晶性有機半導体薄膜における分子配向が膜の電荷輸送特性に大きな影響を与えていることを示した。(論文5での提案を実験的に初めて実証。)

2009

7.
Enhancement of electron transport by horizontal molecular orientation of oxadiazole planar molecules in organic amorphous films
Appl. Phys. Lett. 95, 243303 (2009)
Daisuke Yokoyama, Akio Sakaguchi, Michio Suzuki, Chihaya Adachi
6.
Thermally activated delayed fluorescence from Sn4+-porphyrin complexes and their application to organic light emitting diodes - a novel mechanism for electroluminescence
Adv. Mater. 21, 4802-4806 (2009)
Ayataka Endo, Mai Ogasawara, Atsushi Takahashi, Daisuke Yokoyama, Yoshimine Kato, Chihaya Adachi
5.
Horizontal orientation of linear-shaped organic molecules having bulky substituents in neat and doped vacuum-deposited amorphous films
Org. Electron. 10, 127-137 (2009)
Daisuke Yokoyama, Akio Sakaguchi, Michio Suzuki, Chihaya Adachi

分光エリプソメトリー分析により非晶性有機半導体薄膜における分子配向の分子構造依存性と一般性(ドープ膜中の配向も含む)を明らかとし、低分子有機ELにおける電荷輸送特性・光取り出し効率の向上に向けた指針を提案した。有機ELにおける分子配向の一般性と汎用性を初めて示した。

2008

4.
Horizontal molecular orientation in vacuum-deposited organic amorphous films of hole and electron transport materials
Appl. Phys. Lett. 93, 173302 (2008)
Daisuke Yokoyama, Akio Sakaguchi, Michio Suzuki, Chihaya Adachi
3.
Spectrally narrow emissions at cutoff wavelength from edges of optically and electrically pumped organic anisotropic films
J. Appl. Phys. 103, 123104 (2008)
J. Appl. Phys. 104, 039909 (2008)
Daisuke Yokoyama, Masato Moriwake, Chihaya Adachi

~2007

2.
Spectrally narrow emission at cutoff wavelength from edge of electrically pumped organic light-emitting diodes
Jpn. J. Appl. Phys. (Express Lett.), 46, L826-L829 (2007)
Daisuke Yokoyama, Hajime Nakanotani, Yousuke Setoguchi, Masato Moriwake, Dai Ohnishi, Masayuki Yahiro, Chihaya Adachi
1.
Three distinct solvated structures of p-nitroaniline in acetonitrile/CCl4 mixed solvents
Bull. Chem. Soc. Jpn. 72, 389-395 (1999)
Kathaperumal Mohanalingam, Daisuke Yokoyama, Chihiro Kato, Hiro-o Hamaguchi