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 highest mobilities, 2) new semiconducting polymers and their OPVs showing high efficiencies, and 3) stable ambipolar polymer that can afford CMOS-like like inverter with monolithic semiconducting layer.

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 major carriers in ambipolar polymer semiconductor by self-assembled monolayers

Ambipolar organic semiconductors (AOSs) that can transport both hole and electron have been attractive materials, which enables simple fabrication of logic circuits, such as CMOS, with single semiconducting material. However, AOSs so far reported have several drawbacks, e.g., lack of air-stability, ill-balanced hole and electron mobility. Furthermore, CMOS devices with AOSs usually show large leakage current owing to non-complete off state during the operation, which has been regarded as fatal drawback of ambipolar-based devices. To overcome these issues, we have developed new ambipolar polymers based on original electron deficient building blocks, which ensure air stability and balanced high mobilities both of hole and electron. In addition, we found that self-assembled monolayer (SAM) deposited on the substrate surface can make the device unipolar, either p- or n-type, depending on the nature of SAM molecules. Furthermore, by patterning different SAMs on a substrate and simply depositing AOS on top of it, high-performance CMOS-like inverter with ideal switching characteristics can be easily fabricated.

Control of major carriers in ambipolar polymer semiconductor by self-assembled monolayers.


Kazuo Takimiya

Team Leader takimiya[at]riken.jp R

Masahiro Nakano

Special Postdoctoral Researcher

Naoya Suzuki

Special Postdoctoral Researcher

Chengyuan Wang

Postdoctoral Researcher

Takuya Ogaki

Postdoctoral Researcher

Maitisidike Rukeyamu

Special Postdoctoral Researcher

Johan Jean-Claude Maurice Hamonnet

Technical Staff I

Nobuhiko Ohtsuka

Junior Research Associate

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