Emergent Molecular Function Research Team

Principal Investigator

PI Name Kazuo Takimiya
Degree D.Eng.
Title Team Leader
Brief Resume
1994Ph.D., Hiroshima University
1994Research Associate, Hiroshima University
1997Visiting Researcher, Odense University, Denmark
2003Associate Professor, Hiroshima University
2007Professor, Hiroshima University
2012Team Leader, Emergent Molecular Function Research Team, RIKEN
2013Group Director, Emergent Molecular Function Research Group, Supramolecular Chemistry Division, RIKEN Center for Emergent Matter Science
2017Professor, Tohoku University (-present)
2018Team Leader, Emergent Molecular Function Research Team, Supramolecular Chemistry Division, RIKEN Center for Emergent Matter Science (-present)


Our research activity is based upon organic synthesis that can afford new organic materials utilized in optoelectronic devices, such as organic field-effect transistors (OFETs), organic solar cells (organic photovoltaics, OPVs), and organic thermoelectric devices (OTE). To this end, our group develops new organic materials, which can be designed and synthesized in order to have appropriate molecular and electronic structures for target functionalities. Our recent achievements are: 1) high-performance molecular semiconductors applicable to OFETs with the high mobilities, 2) new non-fullerene acceptors and their OPVs showing high power conversion efficiencies, and 3) new molecular design strategies to control packing structures of organic semiconductors.

Research Fields

Chemistry, Engineering, Materials Sciences


Organic semiconductor
Pi-conjugated compound
Organic Synthesis
Organic field-effect transistor
Organic solar cells
Organic thermoelectric materials


Control of packing structures of thienoacene-based organic semiconductors

Solid-state properties of organic semiconductors, e.g., carrier mobility, are largely dependent not only on the molecular structure but also packing structure and molecular orientation in the solid state. The packing structures of representative organic semiconductors, e.g. acenes and thienoacenes, are classified into a herringbone packing, which is characterized with a “T-shaped” edge-to-face structural motif. On the other hand, one of the most promising materials in the organic field-effect transistor realizing the highest mobility is rubrene, which affords another characteristic packing motif, so-called “pitched π-stack”, where the long-molecular axis are inclined so as to form partial π-stacking with end-to-face intermolecular interaction. Although control and prediction of the solid state structures from the molecular level are regarded as formidable task, we recently found that simple methylthionation on a series of thienoacenes selectively induces the rubrene-like “pitched π-stack” in the solid state. These results suggest that a proper molecular modification can pave the way to “artificial rubrene”, i.e., packing structure control of thienoacenes for high-performance organic semiconductors.

Control of packing structures of thienoacene-based organic semiconductors


Kazuo Takimiya

Team Leader takimiya[at]riken.jp R

Naoyuki Shibayama

Postdoctoral Researcher

Masanori Sawamoto

Postdoctoral Researcher

Kirill Bulgarevich

Postdoctoral Researcher

Yang Wang

Visiting Researcher

Kohsuke Kawabata

Visiting Scientist


  • Dec 22, 2017 RIKEN RESEARCH Washable solar cells
    A new stretchy and washable organic solar cell has opened up the possibility of textile-integrated solar power
  • Mar 24, 2017 RIKEN RESEARCH Plugging leaks in printable logic
    Self-assembling thin films make it possible to produce flexible electronic devices using a single plastic transistor
  • Sep 30, 2016 RIKEN RESEARCH Fluorine offers solar power boost
    Tweaking the chemical composition of polymer solar cells improves efficiency and voltage


2-1 Hirosawa, Wako, Saitama 351-0198 Japan