Zhang Kai, Cai Lei, Fan Jianzhong, Song Yuzhi, Lin Lili, Wang Chuan-Kui
Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China.
Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu 215123, China.
Phys Chem Chem Phys. 2022 Nov 9;24(43):26764-26775. doi: 10.1039/d2cp03697e.
Thermally activated delayed fluorescence (TADF) molecules with deep-red (DR) and near-infrared (NIR) luminescence show great potential in biomedical sensing/imaging and telecommunications. However, developing efficient DR- and NIR-TADF molecules remains a powerful challenge, and new design strategies are highly desired. Based on 2,3-bis(4-(diphenylamino)phenyl)quinoxaline-5,8-dicarbonitrile (CNQ-TPA), two novel TADF molecules CNQ-b-TPA and CNQ-f-TPA are theoretically constructed through the design strategy of molecular bonding and molecular fusion. The photophysical properties and luminescence mechanisms of the three molecules in toluene and the crystal state are revealed with first-principles calculations and the thermal vibration correlation function (TVCF) method. Compared with CNQ-TPA, CNQ-b-TPA and CNQ-f-TPA can achieve an effective red-shift of intrinsic emission and efficient DR and NIR emission. Remarkably, molecular bonding and molecular fusion not only greatly increase the oscillator strength, but also effectively reduce the energy gap between the first singlet excited state (S) and the first triplet excited state (T), resulting in their high radiative and reverse intersystem crossing rate. Moreover, the charge transport properties are studied based on kinetic Monte Carlo simulations. Molecular bonding to balance charge transport is found, enabling ambipolar transport properties. Our work provides a feasible solution to overcome the design limitations of previous DR- and NIR-TADF materials and predicts good candidates for both DR- and NIR-TADF emitters.
具有深红色（DR）和近红外（NIR）发光的热激活延迟荧光（TADF）分子在生物医学传感/成像和电信领域显示出巨大潜力。然而，开发高效的DR和NIR-TADF分子仍然是一个巨大的挑战，因此迫切需要新的设计策略。基于2,3-双（4-（二苯基氨基）苯基）喹喔啉-5,8-二腈（CNQ-TPA），通过分子键合和分子融合的设计策略从理论上构建了两种新型TADF分子CNQ-b-TPA和CNQ-f-TPA。利用第一性原理计算和热振动相关函数（TVCF）方法揭示了这三种分子在甲苯和晶体状态下的光物理性质和发光机制。与CNQ-TPA相比，CNQ-b-TPA和CNQ-f-TPA可以实现本征发射的有效红移以及高效的DR和NIR发射。值得注意的是，分子键合和分子融合不仅大大增加了振子强度，而且有效地减小了第一单重激发态（S）和第一三重激发态（T）之间的能隙，从而导致它们具有高辐射和反向系间窜越速率。此外，基于动力学蒙特卡罗模拟研究了电荷传输性质。发现分子键合可平衡电荷传输，实现双极性传输性质。我们的工作为克服先前DR和NIR-TADF材料的设计局限性提供了一种可行的解决方案，并预测了DR和NIR-TADF发射体的良好候选材料。
