RIKEN Center for Emergent Matter Science Emergent Functional Polymers Research Team

Team Director: Keisuke Tajima (Ph.D.)

Japanese Page

Research Summary

We work on the development of new organic semiconducting polymer materials and their application to organic electronic devices. Specifically, 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.

Main Research Fields

Chemistry

Related Research Fields

Engineering

Keywords

Organic solar cells
Semiconducting organic polymers
Thin films
Nanostructures
Interfacial science

Selected Publications

1. Nakano, K., Kaji, Y., and Tajima, K.:
"A Single-Device Approach for Simultaneous Measurement of Exciton Diffusion Length and Charge Generation Yield in Organic Semiconductors"
Commun. Mater., 7, 52 (2026).
2. Yokoyama, T., and Tajima, K.:
"Quantifying Anisotropic Mobility Enhancement in Uniaxially Aligned Polythiophene Films via Ion-Exchange Doping"
J. Mater. Chem. C, 14, 243-251 (2026).
3. Jung, H., Nakano, K., and Tajima, K.:
"One-Pot Stille Coupling Homopolymerization Toward Bithiophene–Quinoxaline Copolymers with Reduced Sequence Defects"
ACS Appl. Mater. Interfaces, 17, 66980–66987 (2025).
4. Suzuki, R., Nakano, K., Miyasaka, M., and Tajima, K.:
"Vertical Component Distributions in Organic Solar Cells Controlled by Photocrosslinking and Layer-by-Layer Deposition"
Small, 22, 2411988 (2025).
5. Nakano, K., Kaji, Y., Suzuki, R., and Tajima, K.:
"Quantifying Unit Ratios in Semiconducting Copolymers and Effect of Structural Deviations on Photovoltaic Performance"
Commun. Mater., 6, 37 (2025).
6. Nakano, K., and Tajima, K.:
"Insights from Planar Heterojunctions: Understanding Charge Carrier Generation in Organic Photovoltaics"
ACS Appl. Mater. Interfaces, 17, 8 (2025).
7. Yokoyama, T., and Tajima, K.:
"Fluoroalkylated Non-fullerene Acceptor as Surface Segregated Monolayer for Controlling Molecular Orientation of Acceptor Layer in Organic Photovoltaics"
ACS Appl. Mater. Interfaces, 17, 8107-8116 (2025).
8. Lin, J.-W., Busireddy, M. R., Chen, J.-T., Tajima, K., and Hsu, C.-S.:
"Phenothiazine-Based Solid Additives for Optimizing Film Morphologies in High-Performance Organic Photovoltaics"
ACS Appl. Eneryg Mater., 8, 2506-2515 (2025).
9. Yokoyama, T., and Tajima, K.:
"Surface Segregated Monolayers of Fluoroalkylated Rod-like Molecule for Asymmetric Charge Transport at Organic Semiconductor Interfaces"
ACS Appl. Electron. Mater., 6, 4570-4577 (2024).
10. Ono, S., Mikie, T., Nakano, K., Tajima, K., and Osaka, I.:
"Two Isomeric Benzo[d]imidazole-Based Nonfullerene Acceptors for Organic Photovoltaics"
ACS Appl. Energy. Mater., 7, 2946-2954 (2024).