FY2022 Annual Report

Organic Optoelectronics Unit
Assistant Professor Ryota Kabe


In FY2022, we focused on the realization and control of stable charge-separated states of organic materials. Dr. Liliia Moshniaha joined our group as an organic synthesis specialist. We accepted three rotation students, Mr. Saurav Raj, Mr. Amal Jose, and Mr. Harley Suchiang, and two intern students, Mr. Abhijeet Choudhury and Ms. Yeuk Lam Sui.

1. Staff

  • Kirill Mitrofanov, Staff Scientist
  • Zesen Lin, Postdoctoral Researcher
  • Sri Lakshmi Venkata Narayana Yemineni, Postdoctoral Researcher
  • Liliia Moshniaha, Postdoctoral Researcher
  • Rengo Yoshioka, Student 
  • Emiko Aasato, Administrator
  • Saurav Raj, Rotation student
  • Amal Jose, Rotation student
  • Harley Suchiang, Rotation student
  • Abhijeet Choudhury, Intern student
  • Yeuk Lam Sui, Intern student

2. Collaborations

2.1 Development of organic long persistent luminescence systems

  • Type of collaboration: Joint research
  • Researchers:
    • Professor Chihaya Adachi, Kyushu University

2.2 Analysis of organic long persistent luminescence systems

  • Type of collaboration: Joint research
  • Researchers:
    • Professor Takashi Tachikawa, Kobe University

3. Activities and Findings

3.1 Development of persistent luminescence polymers

Organic long-persistent luminescence (OLPL) systems utilize charge separation at the electron-donor and electron-acceptor interfaces to achieve long-lasting luminescence. Conventional OLPL systems are mixtures of small molecule donor and acceptor materials. While they are easy to design, synthesize, and purify, they lack physical properties such as flexibility and compatibility in the bulk state. In particular, phase separation can quickly occur when ionic materials are used.
In this project, we developed OLPL polymers made of electron donor units and acceptor units. Monomers with electron donor and acceptor units were synthesized and randomly copolymerized in different mixing ratios. The resulting copolymers exhibit OLPL in the solid state. Similar to the OLPL systems using small molecules, the LPL duration was changed depending on the mixing ratio of electron donors and acceptors. Compared to small-molecule-based LPL systems, OLPL polymers have improved processability and stability.

3.2 Charge separation mechanism of OLPL

Understanding the charge separation process in OLPL systems is essential for the development of efficient OLPL systems. Charge separation in OLPL systems containing electron donors and acceptors is a complex process involving singlet excited states, triplet excited states, charge transfer excited states, and charge-separated states of each material. Transient absorption measurements are carried out over a wide time range from femtoseconds to several hundred milliseconds, to elucidate the complete picture of the charge separation process.

Transient absorption spectrum of m-MTDATA in toluene.

4. Publications

4.1 Journals

[1] Zhang, C.; Mariotti, S.; K. Ono, L.; Ding, C.; Mitrofanov, K.; Zhang, C.; Yuan, S.; Ji, P.; Zhang, J.; Wu, T.; Kabe, R.; Qi, Y.*
A Hole Injection Monolayer Enables Cost-Effective Perovskite Light-Emitting Diodes.
Journal of Materials Chemistry C https://doi.org/10.1039/D2TC05491D.

[2] Xu, X.; Serra, G.; Villa, A.; Muñoz-Mármol, R.; Vasylevskyi, S.; Gadea, M.; Lucotti, A.; Lin, Z.; G. Boj, P.; Kabe, R.; Tommasini, M.; Á. Díaz-García, M.; Scotognella, F.; Maria Paternò, G.*; Narita. A.*
Synthesis of Zigzag- and Fjord-Edged Nanographene with Dual Amplified Spontaneous Emission.
Chemical Science, 13, 13040–13045 (2022). https://doi.org/10.1039/D2SC04208H.

[3] Wu, T.; K. Ono, L.; Yoshioka, R.; Ding, C.; Zhang, C.; Mariotti, S.; Zhang, J.; Mitrofanov, K.; Liu, X.; Segawa, H.; Kabe, R.; Han, L.; Qi, Y.*
Elimination of Light-Induced Degradation at the Nickel Oxide-Perovskite Heterojunction by Aprotic Sulfonium Layers towards Long-Term Operationally Stable Inverted Perovskite Solar Cells.
Energy & Environmental Science 15, 4612–4624 (2022). https://doi.org/10.1039/D2EE01801B

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

[1] (Invited) 嘉部量太, 固体有機材料における電荷蓄積とその光機能,  第70回 応用物理学会 春季学術講演会 (2023-3-17)

[2] R. Kabe, Organic afterglow caused by stable charge carriers, OIST-KEIO SHOWCASE TALK Series 4 (2023-3-13)

[3]  Z. Lin, M. Li, R. Kabe, Near-infrared organic long-persistent luminescence from p-type co-polymer, 7th TADF workshop (2022-12-1, online)

[4] (Invited) 嘉部量太, 有機材料の安定電荷分離状態とその光機能, 応用物理学会フォトニクス分科会・フォトニクスワークショップ 第7回フォトニクス, ワークショップ「遍く拡がる光科学の可能性!」(2022-11-25)

[5] (Invited) 嘉部量太, 有機材料中の電荷蓄積とその光機能, 第13回動的エキシトン若手セミナー (2022-10-19)

[6] R. Kabe, 3rd Japanese-American-German Frontiers of Science (JAGFOS) Symposium (2022-9-15)

[7] (Invited) 嘉部量太, 安定電荷分離状態からの刺激応答発光, 第71回高分子討論会 (2022-9-5)  

[8] (Invited) 嘉部量太, 有機材料における電荷蓄積とその光機能, 分子研物質分子科学研究領域研究会「物質分子科学の研究展望」(2022-8-30, online)

[9] (Invited) R. Kabe, Long-persistent luminescence from an exciplex-based organic light-emitting diode, SPIE Optics + Photonics (2022-8-21)

[10] Z. Lin, M. Li, R. Kabe, Near-infrared p-type organic long-persistent luminescence copolymer, The 5 th International Symposium on Aggregation- Induced Emission, (2022-8-13)

[11] (Invited) R. Kabe, Unique optoelectronic properties of stable organic radical ion pairs, The 5th International Union of Materials Research Societies International Conference of Young Researchers on Advanced Materials (IUMRS-ICYRAM2022), (2022-8-4)      

[12] (Invited) 嘉部量太, 電荷分離を利用した有機光機能材料, 錯体化学若手の会夏の学校2022 (2022-8-2)      

[13] (Invited) 嘉部量太, 電荷分離を利用した機能性発光材料, 高分子学会 22-1有機エレクトロニクス研究会 (2022-5-12) 

[14] (Invited) R. Kabe, Persistent luminescence from stable photoinduced charge-separated state, SPIE Photonics Europe 2022 (2022-4-6, online)   


5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

6.1 Seminar "Organic Semiconductor Optoelectronics: Emerging Applications in Medicine and Communications"

  • Date: March 10, 2023
  • Venue: OIST Campus Lab4
  • Speaker: Prof. Ifor Samuel (University of St Andrews, St Andrews)

7. Other

Nothing to report.