Centers & Labs

RIKEN Center for Emergent Matter Science

Emergent Molecular Function Research Group

Group Director: Kazuo Takimiya (D.Eng.)
Kazuo  Takimiya(D.Eng.)

The Research Team engages in the development and application of new functional organic molecules. Organic molecules can be designed and synthesized as they should have appropriate molecular and electronic structures for certain functionalities, and such functional molecules are utilized in fabricating optoelectronic devices such as organic field-effect transistors (OFETs) and organic solar cells (organic photovoltaics, OPVs). Recent our achievements are 1) development of high-performance molecular semiconductors applicable to OFETs with the highest mobilities, and 2) development of versatile semiconducting polymers that can be utilized to high performance solution-processed OTFTs and OPVs.

Main Research Field


Related Research Fields

Engineering / Materials Sciences

Research Subjects

  • Development of new organic semiconductors
  • Control of electronic structure of organic semiconductors
  • Application of organic semiconductors to electronic devices

Selected Publications

  1. Vohra, V., Kawashima, K., Kakara, T., Koganezawa, T., Osaka, I., Takimiya, K., Murata, H.:
    “Efficient inverted polymer solar cells employing favourable molecular orientation”
    Nat. Photon. 9, 403–408 (2015).
  2. Kawashima, K., Tamai, Y., Ohkita, H., Osaka, I., Takimiya, K.:
    “High-efficiency polymer solar cells with small photon energy loss”
    Nat. Commun. 6, 10085 (2015).
  3. Nakano, M., Osaka, I., Hashizume, D., Takimiya, K.:
    “α-Modified Naphthodithiophene Diimides-Molecular Design Strategy for Air-Stable n-Channel Organic Semiconductors”
    Chem. Mater. 27, 6418–6425 (2015).
  4. Saito, M., Osaka, I., Suzuki, Y., Takimiya, K., Okabe, T., Ikeda, S., Asano, T.:
    “Highly Efficient and Stable Solar Cells Based on Thiazolothiazole and Naphthobisthiadiazole Copolymers”
    Sci. Rep. 5, 14202 (2015).
  5. Nakano, M., Osaka, I., and Takimiya, K.:
    " Thermally, Operationally, and Environmentally Stable Organic Thin-Film Transistors Based on Bis[1]benzothieno[2,3-d:2’,3’-d’]naphtho[2,3-b:6,7-b’]dithiophene Derivatives: Effective Synthesis, Electronic Structures, and Structure–Property Relationship "
    Chem. Mater. 27, 5049–5057 (2015).
  6. Kawashima, K., Osaka, I., Takimiya, K.:
    “Effect of Chalcogen Atom on the Properties of Naphthobischalcogenadiazole-Based pi-Conjugated Polymers”
    Chem. Mater. 27, 6558–6570 (2015).
  7. Osaka, I., Saito, M., Koganezawa, T., and Takimiya, K.:
    "Thiophene-Thiazolothiazole Copolymers: Significant Impact of Side Chain Composition on Polymer Orientation and Solar Cell Performances"
    Adv. Mater. 26, 331–338 (2014).
  8. Takimiya, K., Osaka, I., Mori, T., and Nakano, M.:
    "Organic Semiconductors Based on [1]Benzothieno[3,2-b][1]benzothiophene Substructure"
    Acc. Chem. Res., 47, 1493–1502 (2014).
  9. Osaka, I., Kakara, T., Takemura, N., Koganezawa, T., and Takimiya, K.:
    "Naphthodithiophene–Naphthobisthiadiazole Copolymers for Solar Cells: Alkylation Drives the Polymer Backbone Flat and Promotes Efficiency"
    J. Am. Chem. Soc., 135, 8834–8837 (2013).
  10. Fukutomi, Y., Nakano, M., Hu, J.-Y., Osaka, I. and Takimiya, K.:
    "Naphthodithiophenediimide (NDTI): Synthesis, Structure, and Applications"
    J. Am .Chem. Soc., 135, 11445–11448 (2013)

Lab Members

Principal Investigator

Kazuo Takimiya
Group Director

Core Members

Itaru Osaka
Senior Scientist
Masahiro Nakano
Postdoctoral Researcher
Masahiko Saito
Postdoctoral Researcher
Hiroyoshi Sugino
Postdoctoral Researcher
Chengyuan Wang
Postdoctoral Researcher
Tsubasa Mikie
Postdoctoral Researcher
Ji-Hoon Kim
Postdoctoral Researcher
Masanori Sawamoto
Junior Research Associate
Yasuhito Suzuki
Technical Staff II

Contact information

504 Main Research Building,
2-1 Hirosawa,
Wako, Saitama
351-0198, Japan

Email: takimiya [at]

Related links

Recent research results

March 24, 2017: RIKEN RESEARCH
Plugging leaks in printable logic
September 30, 2016: RIKEN RESEARCH
Fluorine offers solar power boost
December 3, 2015: Press Release
New plastic solar cell minimizes loss of photon energy
May 26, 2015: Press Release
Fine-tuned molecular orientation is key to more efficient solar cells