FY2021 Annual Report

Organic Optoelectronics Unit
Assistant Professor Ryota Kabe



Our laboratory was fully launched in FY2021 and three major grants were also started. The JST FOREST project on understanding organic excitons, the JSPS KAKENHI project on improving the performance of the organic long-persistent luminescence (OLPL), and the OIST PoC project on developing novel applications of OLPL have started. This year, we worked on stabilizing charge-separated states and found the ionic materials to be promising.
Dr. Yemineni joined as PD and Mr. Yoshioka joined as a Ph.D. student from the research internship.

1. Staff

  • Kirill Mitrofanov, Staff Scientist
  • Zesen Lin, Postdoctoral Researcher
  • Hayato Ouchi, Postdoctoral Researcher
  • Sri Lakshmi Venkata Narayana Yemineni, Postdoctoral Researcher
  • Qizheng Zhang, Student
  • Rengo Yoshioka, Student 
  • Emiko Aasato, Administrator

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 Photostimulated luminescence from organic materials

Photostimulated luminescence (PSL) allows energy or data to be stored and released using electromagnetic waves. PSL has attracted considerable interest in the fields of biomedical and information technologies. However, PSL is limited to solid inorganic materials. In this research, we demonstrated photostimulated luminescence from purely organic blend films, composed of electron donor, acceptor, and trap/emitter molecules. By UV photoexcitation, charge carriers are stored as the radical cations of the electron donors and the radical anions of the trap molecules. The stored carriers can be extracted by near-infrared light irradiation. These findings might broadly impact existing applications and provide new prospects for innovative flexible devices.

3.2 Air-stable organic long-persistent luminescence

OLPL materials have practical advantages in applications owing to their flexible design and easy processability. However, the intermediate charge-separated state is unstable and quenched by oxygen. Moreover, OLPL materials usually require ultraviolet photoexcitation. Here we demonstrate that OLPL systems work in air and can be photoexcited by up to 600 nm. By adding cationic photoredox catalysts as electron-accepting dopants in a neutral electron-donor host, stable charge-separated states are generated by hole diffusion in these blends. The addition of hole-trapping molecules extends the photoluminescence durations. By using a p-type host less reactive to oxygen and tuning the donor–acceptor energy gap, our amorphous blends exhibit persistent luminescence stimulated by visible light even in air, expanding the applicability of OLPL materials.

OIST Press releases
AZO Optics

4. Publications

4.1 Journals

[1] Jinnai, K., Kabe, R.*, Lin, Z., Adachi, C.*
Organic long-persistent luminescence stimulated by visible light in p-type systems based on organic photoredox catalyst dopants.
Nat. Mater. 21, 338–344 (2022) DOI:10.1038/s41563-021-01150-9

[2] Paternò, G. M., Chen, Q., Muñoz-Mármol, R., Guizzardi, M., Bonal, V., Kabe, R., Barker, A. J., Boj, P. G., Chatterjee, S., Ie, Y., Villalvilla, J. M., Quintana, J. A., Scotognella, F., Müllen, K., Díaz-García, M. A.*, Narita, A.*, Lanzani, G.*
Excited states engineering enables efficient near-infrared lasing in nanographenes.
Mater. Horizons 9, 393-402 (2022) DOI:10.1039/D1MH00846C

[3] Sakurai, M., Kabe, R.*, Fuki, M., Lin, Z., Jinnai, K., Kobori, Y., Adachi, C., Tachikawa, T.*
Organic photostimulated luminescence associated with persistent spin-correlated radical pairs
Commun. Mater. 2, 74 (2021) DOI:10.1038/s43246-021-00178-3

4.2 Books and other one-time publications

Nothing to report

4.3 Oral and Poster Presentations

[1] (Invited) 嘉部量太, 電荷分離状態を利用した光機能材料, 第23回“光”機到来!Qコロキウム (2021-12-23, online-YouTube Live)

[2] (Invited) R. Kabe, Persistent luminescence from stable charge-separated states, The 6th International TADF Workshop (2021-12-10, online)

[3] (Invited) 嘉部量太, 安定電荷分離状態を利用した光機能材料, 第97回高分子若手研究会(関西) (2021-11-27, online)

[4]  櫻井 学, 嘉部 量太, 婦木 正明, LIN Zesen, 陣内 和哉, 小堀 康博, 安達 千波矢, 立川 貴士, 有機材料を用いた輝尽発光システムの開発, 2021年光化学討論会 (2021-9-14, online)

[5] (Invited) 嘉部量太, 電荷分離を利用した有機蓄光材料, 強光子場科学研究懇談会 2020年度 第2回懇談会 (2021-4-23, Online)

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

Nothing to report

7. Other

Nothing to report