Zhao Chen, Liu Songsong, Gao Yang, Lin Lili, Wang Chuan-Kui, Song Yuzhi, Fan Jianzhong
Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Institute of Materials and Clean Energy, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China.
Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, Institute of Materials and Clean Energy, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2026 Jan 5;344(Pt 1):126710. doi: 10.1016/j.saa.2025.126710. Epub 2025 Jul 18.
Circularly polarized thermally activated delayed fluorescence (CP-TADF) organic light-emitting diodes (OLEDs) have emerged as promising optoelectronic devices due to their high exciton utilization efficiency and simplified device architecture, demonstrating broad application prospects in 3D displays, quantum computing, and information storage. However, the inherent trade-off between luminescent efficiency and luminescent dissymmetry factor (g) has significantly limited the diversity of high-performance CP-TADF materials. In this study, we systematically investigated the luminescent mechanism of a reported thermally activated delayed fluorescence molecule QAO using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods coupled with the thermal vibration correlation function (TVCF) approach. Through calculations of intersystem crossing rates, reverse intersystem crossing rates, radiative decay rates, and non-radiative decay rates, we confirmed the TADF characteristics of QAO. Moreover, the evaluation of electronic circular dichroism (ECD) spectrum and g values (1.92 × 10) confirmed the circularly polarized luminescent (CPL) feature. Furthermore, based on these findings, two strategies (introducing chiral unit and extending the acceptor unit) were proposed to enhanced the CPL and TADF properties, and two new efficient CP-TADF molecules (QAO-Cz and QAO-CzNCF) were constructed. Results indicate that the g values of QAO-Cz (4.06 × 10) and QAO-CzNCF (4.46 × 10) were largely improved compared with that of initial QAO with decreased electric transition dipole moment (|μ|) and magnetic transition dipole moment (|m|) of the molecules. Compared to |m| (0.723 × 10 erg·G, 0.474 × 10 erg·G, 0.349 × 10 erg·G), |μ| (3.885 × 10 esu·cm, 1.242 × 10 esu·cm, 0.786 × 10 esu·cm) exhibits a greater degree of reduction, leading to an enhancement in |m|/|μ| and g values and further improving the CPL performance. Meanwhile, the energy gap of the molecules QAO-Cz (0.03 eV) and QAO-CzNCF (0.05 eV) are significantly reduced compared to QAO (0.14 eV), while the spin-orbit coupling values are remarkably increased, ensuring the excellent TADF properties of these molecules. Thus, the fundamental structure-property relationship is revealed and inner luminescent mechanism is illustrated. Wise strategy for designing CP-TADF molecules is proposed, and both designed CP-TADF molecules successfully achieve synergistic optimization of CPL and TADF properties, this work provides new insights for developing high-performance CP-TADF emitters.
圆偏振热激活延迟荧光（CP-TADF）有机发光二极管（OLED）因其高激子利用效率和简化的器件结构而成为有前途的光电器件，在3D显示、量子计算和信息存储等方面展现出广阔的应用前景。然而，发光效率与发光不对称因子（g）之间固有的权衡显著限制了高性能CP-TADF材料的多样性。在本研究中，我们使用密度泛函理论（DFT）和含时DFT（TD-DFT）方法，并结合热振动相关函数（TVCF）方法，系统地研究了已报道的热激活延迟荧光分子QAO的发光机制。通过计算系间窜越速率、反向系间窜越速率、辐射衰减速率和非辐射衰减速率，我们证实了QAO的TADF特性。此外，对电子圆二色性（ECD）光谱和g值（1.92×10）的评估证实了圆偏振发光（CPL）特性。此外，基于这些发现，我们提出了两种策略（引入手性单元和扩展受体单元）来增强CPL和TADF性能，并构建了两种新型高效的CP-TADF分子（QAO-Cz和QAO-CzNCF）。结果表明，与初始QAO相比，QAO-Cz（4.06×10）和QAO-CzNCF（4.46×10）的g值有了很大提高，分子的电跃迁偶极矩（|μ|）和磁跃迁偶极矩（|m|）减小。与|m|（0.723×10尔格·高斯、0.474×10尔格·高斯、0.349×10尔格·高斯）相比，|μ|（3.885×10静电单位·厘米、1.242×10静电单位·厘米、0.786×10静电单位·厘米）的降低程度更大，导致|m|/|μ|和g值增加，进一步提高了CPL性能。同时，与QAO（0.14电子伏特）相比，分子QAO-Cz（0.03电子伏特）和QAO-CzNCF（0.05电子伏特）的能隙显著减小，而自旋轨道耦合值显著增加，确保了这些分子具有优异的TADF性能。因此，揭示了基本的结构-性能关系并阐明了内部发光机制。提出了设计CP-TADF分子的明智策略，并且所设计的CP-TADF分子均成功实现了CPL和TADF性能的协同优化，这项工作为开发高性能CP-TADF发光体提供了新的见解。
