Harunobu Koike
Tokyo University of Science
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Publication
Featured researches published by Harunobu Koike.
ACS Applied Materials & Interfaces | 2016
Chi Li; Jian Wei; Mikio Sato; Harunobu Koike; Zhong-Zhi Xie; Yan-Qing Li; Kaname Kanai; Satoshi Kera; Nobuo Ueno; Jian-Xin Tang
Solution-processed perovskite solar cells are attracting increasing interest due to their potential in next-generation hybrid photovoltaic devices. Despite the morphological control over the perovskite films, quantitative information on electronic structures and interface energetics is of paramount importance to the optimal photovoltaic performance. Here, direct and inverse photoemission spectroscopies are used to determine the electronic structures and chemical compositions of various methylammonium lead halide perovskite films (MAPbX3, X = Cl, Br, and I), revealing the strong influence of halide substitution on the electronic properties of perovskite films. Precise control over halide compositions in MAPbX3 films causes the manipulation of the electronic properties, with a qualitatively blue shift along the I → Br → Cl series and showing the increase in ionization potentials from 5.96 to 7.04 eV and the change of transport band gaps in the range from 1.70 to 3.09 eV. The resulting light absorption of MAPbX3 films can cover the entire visible region from 420 to 800 nm. The results presented here provide a quantitative guide for the analysis of perovskite-based solar cell performance and the selection of optimal carrier-extraction materials for photogenerated electrons and holes.
Applied Physics Letters | 2013
Harunobu Koike; Takashi Kubo; Kazuyuki Uchida; Masayuki Chikamatsu; Reiko Azumi; Kazuhiko Mase; Kaname Kanai
We directly observed development of an energy band in a one-dimensional biradical molecular chain, which is constructed by exploiting the covalency between organic biradical molecules of a diphenyl derivative of s-indacenodiphenalene (Ph2-IDPL). The morphology and crystallinity of the Ph2-IDPL films were controlled by varying film growth conditions. Ultraviolet photoemission spectroscopy revealed the process of energy band development in the biradical molecular chain, clearly showing that the dispersion width of the π-band was extremely broad, exceeding 1 eV.
Japanese Journal of Applied Physics | 2016
Wataru Yamane; Harunobu Koike; Masayuki Chikamatsu; Takashi Kubo; Tomohiko Nishiuchi; Kaname Kanai
We have improved the properties of ambipolar organic field-effect transistors by chemically treating the source and drain electrodes with a vacuum-deposited biradicaloid film. Biradicaloid was a diphenyl derivative of s-indacenodiphenalene (Ph2-IDPL). An alkane thiol self-assembled monolayer (SAM) was used as an insulator buffer layer at the Ph2-IDPL/electrode interface to prevent off-current. We confirmed the transport level alignment at the Ph2-IDPL/SAM/electrode interface by ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy. Although Ph2-IDPL transistors containing the SAM showed a higher on/off ratio or mobility than a previously reported device without the buffer layer, there was a trade-off between on/off ratio and mobility. Our results suggest that biradical molecules are promising candidates for use in low-power inverters.
Advanced Functional Materials | 2016
Harunobu Koike; Masayuki Chikamatsu; Reiko Azumi; Jun’ya Tsutsumi; Kazumichi Ogawa; Wataru Yamane; Tomohiko Nishiuchi; Takashi Kubo; Tatsuo Hasegawa; Kaname Kanai
Physical Review B | 2016
Ao Yang; Antoni Franco-Cañellas; Mikio Sato; Bin Wang; Rongbin Wang; Harunobu Koike; Ingo Salzmann; P. Thakur; Tien-Lin Lee; Lijia Liu; Satoshi Kera; Alexander Gerlach; Kaname Kanai; Jian Fan; Frank Schreiber; Steffen Duhm
Organic Electronics | 2016
Harunobu Koike; Jun’ya Tsutsumi; Satoshi Matsuoka; Kazuma Sato; Tatsuo Hasegawa; Kaname Kanai
Journal of The Vacuum Society of Japan | 2013
Kaname Kanai; Harunobu Koike; Rie Suizu; Kunio Awaga; Kazuhiko Mase; Takashi Kubo
The Japan Society of Applied Physics | 2017
Hirotaka Mizushima; Harunobu Koike; Kenta Kuroda; Y. Ishida; M. Nakayama; Kazuhiko Mase; Takeshi Kondo; Shik Shin; Kaname Kanai
The Japan Society of Applied Physics | 2017
Hirotaka Mizushima; Harunobu Koike; Kazuhiko Mase; Kaname Kanai
Physical Chemistry Chemical Physics | 2017
Hirotaka Mizushima; Harunobu Koike; Kenta Kuroda; Y. Ishida; M. Nakayama; Kazuhiko Mase; Takeshi Kondo; Shik Shin; Kaname Kanai
Collaboration
Dive into the Harunobu Koike's collaboration.
National Institute of Advanced Industrial Science and Technology
View shared research outputsNational Institute of Advanced Industrial Science and Technology
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