Nonradiative Transition Beyond Energy-Gap Law in Fused-Ring pi-Conjugated Molecules

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K19062
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 35:Polymers, organic materials, and related fields
• Research Institution: Kyoto University
• Principal Investigator: Ohkita Hideo 京都大学, 工学研究科, 教授 (50301239)
• Co-Investigator(Kenkyū-buntansha): KIM HYUNGDO 京都大学, 工学研究科, 助教 (80837899)
• Project Period (FY): 2022-06-30 – 2024-03-31
• Keywords: 縮環系共役分子 / 輻射遷移 / 無輻射遷移 / エネルギーギャップ則 / 再配向エネルギー / 振電相互作用 / 分子軌道 / 凝集状態

Outline of Final Research Achievements

We systematically studied the radiative transition, which is a luminescent process, and the nonradiative transition, which is a nonluminescent process, for various fused-ring π-conjugated molecules. As a result, we found that while the radiative transition rate can be roughly evaluated by the conventional model equation, the energy-gap law of the conventional model does not simply describe the nonradiative transition rate of these fused-ring π-conjugated molecules, suggesting that the nonradiative transition would be limited by other factors such as reorganization energy, orbital spatial distribution, and aggregation state dominate rather than bandgap energy. The results suggest that it is possible to design molecules with suppressed nonradiative transition by appropriately controlling these limiting factors.

Free Research Field

高分子光物理・光化学

Academic Significance and Societal Importance of the Research Achievements

本研究成果は、縮環系π共役分子の発光特性を利用した有機オプトエレクトロニクスにおける分子設計指針を与えるものである。特に、発光量子収率が一般に低く性能を十分に発揮することができていないエネルギーギャップの小さな近赤外域の縮環系π共役分子に対して、再配向エネルギーや分子軌道の広がりや凝集状態などを制御することによって、無輻射遷移速度を抑制するとともに発光量子収率を向上することができると期待される。