Science of zero oscillator strength for circularly polarized luminescence and their application for light emitting diodes

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K19152
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Polymer, Organic materials, and related fields
• Research Institution: The University of Electro-Communications
• Principal Investigator: Hirata Shuzo 電気通信大学, 大学院情報理工学研究科, 助教 (20552227)
• Project Period (FY): 2017-06-30 – 2019-03-31
• Keywords: 円偏光発光 / 遅延蛍光 / 振動子強度 / ダビドブ分裂 / 凝集誘起発光

Outline of Final Research Achievements

Novel chiral conjugated molecules with significant small oscillator strength for fluorescence (F) were synthesized. The chiral molecules that a chiral carbon is located between the highest occupied molecular orbital and the lowest unoccupied molecular orbital showed circularly polarized luminescence with absolute value of dissymmetry factor (|g|) of 10-3 when they were doped in solutions or solid films. On the other hand, |g| of the molecules largely increased up to 5×10-2 in their crystalline thin films. Emission yield (ΦPL) of the molecules did not decrease between doped condition and aggregated crystalline state because of no large Davydov splitting due to the significant small F value. One of the chiral molecules showed large ΦPL as well as large |g| in crystalline state.

Free Research Field

光化学

Academic Significance and Societal Importance of the Research Achievements

蛍光の遷移双極子が著しく小さい光学活性分子においても、凝集に伴う円偏光発光の二色性の大きな増加が観測されたことは、凝集時の円二色性や円偏光発光の増幅機構に関する新しい知見を与える可能性がある。さらに蛍光の遷移双極子が著しく小さい光学活性分子の凝集状態の形成が、ディスプレイで必要とされる高速の発光、大きな発光収率、大きな円偏光発光二色性の全てを持ち合わせる材料を得るための一つの指針になることが確認された。