The mechanism and control of spin flips in thermally activated delayed fluorescence emitters

2021 Fiscal Year Final Research Report

• Project/Area Number: 18H03902
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 32:Physical chemistry, functional solid state chemistry, and related fields
• Research Institution: Osaka Prefecture University
• Principal Investigator: Kobayashi Takashi 大阪府立大学, 工学(系)研究科(研究院), 准教授 (10342784)
• Co-Investigator(Kenkyū-buntansha): 細貝 拓也 国立研究開発法人産業技術総合研究所, 計量標準総合センター, 主任研究員 (90613513)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 熱活性化遅延蛍光材料 / 高次三重項励起状態 / スピン反転 / 逆項間交差 / 有機EL

Outline of Final Research Achievements

The fast spin-flip realized in some thermally activated delayed fluorescence emitters is considered to be due to a higher-order triplet excited state (Tn). The aim of this project was to collect experimental evidences of Tn, in order to gain a deeper understanding of its role in the fast spin-flip process. As the main experimental techniques, transient photoluminescence (PL) and time-resolved PL spectrum measurements were utilized. In this project, we first developed the necessary analytic methods of the experimental results and then found experimental conditions where singlet-triplet and triplet-triplet annihilation processes is negligible. In addition, the influences of long-lived PL components due to charge recombination and dimers (or aggregates) in solid-state samples were clarified. Finally, we demonstrated that the energy level of Tn is determined and its characters were revealed by means of transient PL and time-resolved PL spectrum measurements.

Free Research Field

有機エレクトロニクス

Academic Significance and Societal Importance of the Research Achievements

TADF材料は低コストで高効率な有機EL素子を実現する発光材料として現在でも精力的に研究開発が進められている。また燐光発光材料に比べて材料設計の自由度が高いこともその魅力の一つとなっている。その自由度の高さを最大限に生かすためにも、高効率TADF材料の合理的な設計指針が不可欠であり、その鍵がTnに他ならない。本研究で構築した解析法や得られた知見に加え、Tnに関する実験的証拠はこれらに大きく貢献するものと期待できる。