Understanding of ultralong-lifetime phosphorescence in organic crystals of chiral molecules and development in material chemistry

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05207
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 35030:Organic functional materials-related
• Research Institution: Chiba University
• Principal Investigator: Karatsu Takashi 千葉大学, 大学院工学研究院, 教授 (70214575)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 超長寿命りん光 / 有機結晶 / 固体発光 / キラル結晶 / ラセミ結晶 / 分子間相互作用 / π-π相互作用 / 水素結合

Outline of Final Research Achievements

Regarding the new phosphorescence phenomenon observed in solid phases of organic crystal, which appears extremely long lifetimes on the order of seconds and at low energy positions, we are conducting material chemistry by elucidating the principles and searching for useful molecular groups. By examining the classification of compounds that emit phosphorescence, the correlation with molecular and crystal structures based on single crystal X-ray structural analysis, the correlation with solid phase fabrication methods including single crystals and vapor-deposited films. We inductively investigated the generality of the molecular structure that exhibits phosphorescence using organic synthesis methods. We found that hydrogen bonds that act strongly from the initial stage of association contribute to the orientation of molecules, and that weak π-π interactions are delocalized by excited electrons. It was clarified that it affects the luminescence efficiency.

Free Research Field

光化学

Academic Significance and Societal Importance of the Research Achievements

近年、有機エレクトロニクスは飛躍的な進歩を遂げている。特に有機エレクトロルミネッセンス、有機トランジスタ―や有機太陽電池では工業的にも展開され産業界にも大きな変革をもたらしており，日本企業の国際的競争力にも直結する重要な課題である。中でも有機物の固体状態、結晶状態の性質はある程度理解が進んでいると考えられていたが、本研究課題では室温超長寿命りん光など新規な現象が発現することが解明されており、物質資源、エネルギー問題などに資すると考えられる。本研究の成果は発光材料に新たな視点を与えるのみならず有機結晶・固体材料の未解明な学理や用途を切り開く一助となった。