Emergent Functional Polymers Research Team

Principal Investigator

PI Name Keisuke Tajima
Degree Ph.D.
Title Team Leader
Brief Resume
2002Ph.D., The University of Tokyo
2002Postdoctoral Researcher, Northwestern University
2004Research Associate, The University of Tokyo
2009Lecturer, The University of Tokyo
2011Associate Professor, The University of Tokyo
2011PRESTO Researcher, Japan Science and Technology Agency (-2017)
2012Team Leader, Emergent Functional Polymers Research Team, RIKEN
2013Team Leader, Emergent Functional Polymers Research Team, Supramolecular Chemistry Division, RIKEN Center for Emergent Matter Science (-present)

Outline

We work on the development of new organic semiconducting polymer materials and their application to organic electronic devices. Specifically, relying on the basic chemistry of the intermolecular interactions during the film forming process from the solutions, we seek the methodology and the molecular design to control the precise structures in molecular- and nano-scale at our will, and try to find breakthroughs to drastically enhance the performance of the organic electronic devices. Targets of our research are not only the conventional organic solar cells and field-effect transistors, but also the organic electronic devices with new functions based on the structure controls.

Research Fields

Chemistry, Engineering, Materials Sciences

Keywords

Organic electronics
Organic solar cells
Polymer synthesis
Self-assembly
Nanostructure control

Results

Control of interfacial structures in organic solar cells

– Elucidating the relationship between junction structures at molecular level and device performances –

Solution-processed organic solar cells draw much attention as a renewable energy source since they have unique features such as light-weight, flexibility, and possibility of low-cost production by using fast coating technologies. This type of devices have molecular junctions of different materials which generates the current by photoirradiation, thus the nature of the organic interfaces affects their performance significantly. However, it is difficult to analyze the interfacial structures in the films prepared by the conventional methodology relying on the mixture of the materials, and there have been no mean to modify the structures at those complicated interfaces. These difficulties hinder pursuing the ideal interfacial structure to improve the performance.    Our team has been studying on the relationship between the junction structures at molecular level and the performance of the solar cells based on a unique methodology: lamination of two organic films. We recently found that either introduction of a thin layer of an insulating material at the interface and doping of the layer with small amount of an organic dye or an energy “cascade” structure at the interface introduced by using surface segregated monolayers could avoid the trade-off relationship between the photocurrent and the photovoltage, resulting in the increase of the performance. These findings could lead to a breakthrough for the further enhancement of the performance in organic solar cells.

Schematic representation of the structures of donor/acceptor interface and the photovoltaic processes in organic solar cells with planar heterojunction.
Reproduced with permission. Copyright 2016, Wiely-VCH. Doi:10.1002/adma.201603269

Members

Keisuke Tajima

Team Leader keisuke.tajima[at]riken.jp R

Kyohei Nakano

Postdoctoral Researcher

Jianming Huang

Postdoctoral Researcher

Soo Won Heo

Postdoctoral Researcher

Chao Wang

Postdoctoral Researcher

Kaori Suzuki

Technical Staff II

Yujiao Chen

Technical Staff II

Articles