Research Activities

Solid-state physics and electron transport in organic semiconductors
Development of printed electronics and spintronics

Literature

1. Yu Yamashita, Junto Tsurumi, Tadanori Kurosawa, Kan Ueji, Yukina Tsuneda, Shinya Kohno, Hideto Kempe, Shohei Kumagai, Toshihiro Okamoto, Jun Takeya, and Shun Watanabe*
”Supramolecular cocrystals built through redox-triggered ion intercalation in π-conjugated polymers”
Communications Materials, 2, 45 (2021).
2. Shun Watanabe*, Ryohei Hakamatani, Keita Yaegashi, Yu Yamashita, Han Nozawa, Mari Sasaki, Shohei Kumagai, Toshihiro Okamoto, Cindy G. Tang, Lay‐ Lay Chua, Peter K. H. Ho, and Jun Takeya
”Surface Doping of Organic Single‐ Crystal Semiconductors to Produce Strain‐ Sensitive Conductive Nanosheets”
Advanced Science, 8, 2002065 (2021).
3. Shinya Kohno, Yu Yamashita, Naotaka Kasuya, Tsubasa Mikie, Itaru Osaka, Kazuo Takimiya, Jun Takeya, and Shun Watanabe*
”Controlled steric selectivity in molecular doping towards closest-packed supramolecular conductors”
Communications Materials, 1, 79 (2020).
4. Taiki Sawada, Akifumi Yamamura, Mari Sasaki, Kayo Takahira, Toshihiro Okamoto, Shun Watanabe*, and Jun Takeya*
”Correlation between the static and dynamic responses of organic single-crystal field-effect transistors”
Nature Communications, 11, 4849 (2020).
5. Masato Ito, Yu Yamashita, Yukina Tsuneda, Taizo Mori, Jun Takeya, Shun Watanabe*, and Katsuhiko Ariga*
”100?C?Langmuir?Blodgett Method for Fabricating Highly Oriented, Ultrathin Films of Polymeric Semiconductors”
ACS Applied Materials and Interfaces, 12, 56522 (2020).
6. Shohei Kumagai, Shun Watanabe, Hiroyuki Ishii, Nobuaki Isahaya, Akifumi Yamamura, Takahiro Wakimoto, Hiroyasu Sato, Akihito Yamano, Toshihiro Okamoto, and Jun Takeya
”Coherent Electron Transport in Air‐ Stable, Printed Single‐ Crystal Organic Semiconductor and Application to Megahertz Transistors”
Advanced Materials, 32, 2003245 (2020).
7. Tatsuyuki Makita, Ryohei Nakamura, Mari Sasaki, Shohei Kumagai, Toshihiro Okamoto, Shun Watanabe*, and Jun Takeya*
”Electroless‐ Plated Gold Contacts for High‐ Performance, Low Contact Resistance Organic Thin Film Transistors”
Advanced Functional Materials, 30, 2003977 (2020).
8. Tatsuyuki Makita, Akifumi Yamamura, Junto Tsurumi, Shohei Kumagai, Tadanori Kurosawa, Toshihiro Okamoto, Mari Sasaki, Shun Watanabe*, and Jun Takeya*
”Damage-free Metal Electrode Transfer to Monolayer Organic Single Crystalline Thin Films”
Scientific Reports, 10, 4702 (2020).
9. Akifumi Yamamura, Hiromasa Fujii, Hirohito Ogasawara, Dennis Nordlund, Osamu Takahashi, Yu- taro Kishi, Hiroyuki Ishii, Nobuhiko Kobayashi, Naoyuki Niitsu, Balthasar Blulle, Toshihiro Okamoto, Yusuke Wakabayashi*, Shun Watanabe*, and Jun Takeya*
”Sub-molecular structural relaxation at a physisorbed interface with monolayer organic single-crystal semiconductors”
Communications Physics, 3, 20 (2020).
10. Akifumi Yamamura, Takaaki Sakon, Kayo Takahira, Takahiro Wakimoto, Mari Sasaki, Toshihiro Okamoto, Shun Watanabe*, and Jun Takeya*
”High-Speed Organic Single‐ Crystal Transistor Responding to Very High Frequency Band”
Advanced Functional Materials, 30, 1909501 (2020).
11. Tatsuyuki Makita, Shohei Kumagai, Akihito Kumamoto, Masato Mitani, Junto Tsurumi, Ryohei Hakamatani, Mari Sasaki, Toshihiro Okamoto, Yuichi Ikuhara, Shun Watanabe*, and Jun Takeya*
”High-performance, semiconducting membrane composed of ultrathin, single-crystal organic semiconductors”
Proceedings of the National American of Sciences, 117, 80 (2020).
12. Angela Wittmann, Guillaume Schweicher, Katharina Broch, Jiri Novak, Vincent Lami, David Cornil, Erik R. McNellis, Olga Zadvorna, Deepak Venkateshvaran, Kazuo Takimiya, Yves H. Geerts, Jerome Cornil, Yana Vaynzof, Jairo Sinova, Shun Watanabe, and Henning Sirringhaus
”Tuning spin current injection at ferromagnet-nonmagnet interfaces by molecular design”
Physical Review Letters, 124, 027204 (2020).
13. Xiaozhu Wei, Shohei Kumagai*, Kotaro Tsuzuku, Akifumi Yamamura, Tatsuyuki Makita, Mari Sasaki, Shun Watanabe*, and Jun Takeya
”Solution-processed flexible metal-oxide thin-film transistors operating beyond 20MHz”
Flexible and Printed Electronics, 5, 015003 (2020).
14. Yu Yamashita, Junto Tsurumi, Masahiro Ohno, Ryo Fujimoto, Shohei Kumagai, Tadanori Kurosawa, Toshihiro Okamoto, Jun Takeya, and Shun Watanabe*
”Efficient molecular doping of polymeric semiconductors driven by anion exchange”
Nature, 572, 634 (2019).
15. Shun Watanabe*, Masahiro Ohno, Yu Yamashita, Tsubasa Terashige, Hiroshi Okamoto, and Jun Takeya
”Validity of the Mott formula and the origin of thermopower in π-conjugated semicrystalline polymers”
Physical Review B (Rapid Communications), 100, 241201(R) (2019).
16. Shohei Kumagai*, Akifumi Yamamura, Tatsuyuki Makita, Junto Tsurumi, Ying Ying Lim, Takahiro Wakimoto, Nobuaki Isahaya, Han Nozawa, Kayoko Sato, Masato Mitani, Toshihiro Okamoto, Shun Watanabe*, and Jun Takeya*
”Scalable Fabrication of Organic Single-Crystalline Wafers for Reproducible TFT Arrays”
Scientific Reports, 9, 15897 (2019).
17. Kan Ueji, Masahiro Ohno, Jun Takeya, and Shun Watanabe*
”Correlation between coherent charge transport and crystallinity in doped π-conjugated polymers”
Applied Physics Express, 12, 011004 (2018).
18. Shun Watanabe*, Hirotaka Sugawaram Roger Hausermann, Balthasar Blulle, Akifumi Yamamura, Toshihiro Okamoto, and Jun Takeya*
”Remarkably low flicker noise in solution-processed organic single crystal transistors”
Communications Physics, 1, 37 (2018).
19. Akifumi Yamamura, Shun Watanabe, Mayumi Uno, Masato Mitani, Chikahiko Mitsui, Junto Tsu- rumi, Nobuaki Isahaya, Yusuke Kanaoka, Toshihiro Okamoto, and Jun Takeya
”Wafer-scale, layer-controlled organic single crystals for high-speed circuit operation”
Science Advances, 4, eaao5758 (2018).
20. Katsuhiko Ariga, Shun Watanabe, Taizo Mori, and Jun Takeya
”Soft 2D nanoarchitectonics” (Review article)
NPG Asia Materials, 1, 90 (2018).
21. Ryo Fujimoto, Yu Yamashita, Shohei Kumagai, Junto Tsurumi, Alexander Hinderhofer, Katharina Broch, Frank Schreiber, Shun Watanabe*, and Jun Takeya*
”Molecular doping in organic semiconductors: fully solution-processed, vacuum-free doping with metal?organic complexes in an orthogonal solvent”
Journal of Materials Chemistry C, 5, 12023 (2017).
22. Junto Tsurumi, Hiroyuki Matsui, Takayoshi Kubo, Roger Hausermann, Chikahiko Mitsui, Toshihiro Okamoto, Shun Watanabe*, and Jun Takeya*
”Coexistence of ultra-long spin relaxation time and coherent charge transport in organic single-crystal semiconductors”
Nature Physics, 13, 994 (2017).
23. Ryo Fujimoto, Shun Watanabe*, Yu Yamashita, Junto Tsurumi, Hiroyuki Matsui, Tomokatsu Kushida, Chikahiko Mitsui, Hee Taek Yi, Vitaly Podzorov, and Jun Takeya*
”Control of molecular doping in conjugated polymers by thermal annealing”
Organic Electronics, 47, 139 (2017).
24. Sam Schott, Erik R McNellis, Christian B Nielsen, Hung-Yang Chen, Shun Watanabe, Hisaaki Tanaka, Iain McCulloch, Kazuo Takimiya, Jairo Sinova, and Henning Sirringhaus
”Tuning the effective spin-orbit coupling in molecular semiconductors”
Nature Communications, 8, 15200, (2017).
25. Shohei Kumagai, Hiroko Murakami, Kotaro Tsuzuku, Tatsuyuki Makita, Chikahiko Mitsui, Toshihiro Okamoto, Shun Watanabe*, and Jun Takeya*
”Solution-processed organic?inorganic hybrid CMOS inverter exhibiting a high gain reaching 890”
Organic Electronics, 48, 127, (2017).
26. Josephine Socratous*, Shun Watanabe*, Kulbinder K Banger, Christopher N Warwick, Rita Branquinho, Pedro Barquinha, Rodrigo Martins, Elvira Fortunato, and Henning Sirringhaus
”Energy-dependent relaxation time in quaternary amorphous oxide semiconductors probed by gated Hall effect measurements”
Physical Review B, 95, 622 (2017).
27. Keehoon Kang*, Shun Watanabe*, Katharina Broch, Alessandro Sepe, Adam Brown, Iyad Nasrallah, Mark Nikolka, Zhuping Fei, Martin Heeney, Daisuke Matsumoto, Kazuhiro Marumoto, Hisaaki Tanaka, Shin-ichi Kuroda, and Henning Sirringhaus
”2D coherent charge transport in highly ordered conducting polymers doped by solid state diffusion”
Nature Materials, 15, 896 (2016).
28. Shun Watanabe
”Organic spintronics breaking through”
Asia Pacific News Letter, 3, 6046 (2014).
29. Shun Watanabe*, Kazuya Ando*, Keehoon Kang, Sebastian Mooser, Yana Vaynzof, Hidekazu Kure- bayashi, Eiji Saitoh, and Henning Sirringhaus
”Polaron spin current transport in organic semiconductors”
Nature Physics, 10, 308 (2014).
30. Hisaaki Tanaka, Masataka Hirate, Shun Watanabe, and Shin-ichi Kuroda
”Microscopic signature of metallic state in semicrystalline conjugated polymers doped with fluoroalkylsilane molecules”
Advanced Materials, 26, 2376 (2014).
31. Kazuya Ando*, Shun Watanabe*, Sebastian Mooser, Eiji Saitoh, and Henning Sirringhaus
”Solution-processed organic spin-charge converter”
Nature Materials, 12, 622 (2013).

Other Activities

The Physical Society of Japan
The Japan Society of Applied Physics (JSAP)
Material Researcher Society (MRS)

Future Plan

Based on in-depth understandings of electron transport in molecular solids, we will proceed interdisciplinary researches across the physics, chemistry and engineering towards realization of printed electronics.

Messages to Students

Molecular semiconductors are a soft solid, and have unique properties that deviate from the conventional wisdom of solid-state physics. Understanding the universality and specificity of the standard model based on solid-state physics in molecular solids allows us further advances in materials science. In our laboratory, we are developing electronic devices that can withstand practical usage by combining synthetic chemistry, device engineering, and condensed matter physics. Enjoy researches and development of organic electronics with us!

URL

http://www.organicel.k.u-tokyo.ac.jp/en/