Zhang Kai, Yang Fei, Zhang Yuchen, Ma Yuying, Fan Jianzhong, Fan Jian, Wang Chuan-Kui, Lin Lili
Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, Jinan 250014, China.
Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu 215123, China.
J Phys Chem Lett. 2021 Feb 25;12(7):1893-1903. doi: 10.1021/acs.jpclett.0c03805. Epub 2021 Feb 15.
Near-infrared (NIR) thermally activated delayed fluorescence (TADF) materials have shown great application potential in organic light-emitting diodes, photovoltaics, sensors, and biomedicine. However, their fluorescence efficiency (Φ) is still highly inferior to those of conventional NIR fluorescent dyes, seriously hindering their applications. This study aims to provide theoretical guidance and experimental verification for highly efficient NIR-TADF molecular design. First, the light-emitting mechanism of two deep-red TADF molecules is revealed using first-principles calculation and the thermal vibration correlation function (TVCF) method. Then several acceptors are theoretically designed by changing the position of the cyano group or by introducing the phenanthroline into CNBPz, and 44 molecules are designed and studied theoretically. The photophysical properties of DA-3 in toluene and the amorphous state are simulated using a multiscale method combined with the TVCF method. The NIR-TADF property for DA-3 is predicted both in toluene and in the amorphous state. Experimental measurement further confirms that the TADF emission wavelength of DA-3 is 730 nm and Φ is as high as 20%. It is the highest fluorescence efficiency reported for TADF molecules with emission wavelengths larger than 700 nm in toluene. Our work provides an effective molecular design strategy, and a good candidate for highly efficient NIR-TADF emitters is also predicted.
近红外（NIR）热激活延迟荧光（TADF）材料在有机发光二极管、光伏、传感器和生物医学领域展现出了巨大的应用潜力。然而，它们的荧光效率（Φ）仍远低于传统近红外荧光染料，严重阻碍了其应用。本研究旨在为高效近红外TADF分子设计提供理论指导和实验验证。首先，利用第一性原理计算和热振动相关函数（TVCF）方法揭示了两种深红色TADF分子的发光机制。然后，通过改变氰基位置或在CNBPz中引入菲咯啉，从理论上设计了几种受体，并对44个分子进行了理论设计和研究。采用多尺度方法结合TVCF方法模拟了DA - 3在甲苯和非晶态下的光物理性质。预测了DA - 3在甲苯和非晶态下的近红外TADF性质。实验测量进一步证实，DA - 3的TADF发射波长为730 nm，Φ高达20%。这是甲苯中发射波长大于700 nm的TADF分子报道的最高荧光效率。我们的工作提供了一种有效的分子设计策略，并且还预测了一种高效近红外TADF发射体的良好候选物。
