Li Ping, Lv Qixin, Sun Chengxi, Zhang Peng, Wang Xianjie, Yin Chao, Pan Yuyu, Chen Runfeng
State Key Laboratory of Organic Electronics and Information Displays, Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, P. R. China.
School of Petrochemical Engineering, Shenyang University of Technology, 30 Guanghua Street, Liaoyang 111003, P. R. China.
J Phys Chem Lett. 2024 Sep 26;15(38):9787-9794. doi: 10.1021/acs.jpclett.4c02282. Epub 2024 Sep 18.
Organic materials with thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) dual emission have attracted great attention in recent years, but the regulation mechanism via internal and external heavy atoms is not clear enough. Here, we carry out a systematic theoretical investigation on the photophysical properties of the materials by introducing aliphatic or aromatic bromine atoms. The molecule with aromatic bromine atoms exhibits obvious TADF owing to the effective reverse intersystem crossing (RISC) with matchable energy levels and enhanced spin orbit couplings, the molecule with aliphatic bromine atoms shows a long RTP lifetime because of the reduced nonradiative transition of triplet excitons, and the molecule with both aliphatic and aromatic bromine atoms presents balanced TADF and RTP emissions thanks to the synergy internal and external heavy-atom effects. Besides, the internal and external heavy atoms induce multisite intermolecular interactions, effectively suppressing the nonradiative process in the solid phase. The efficient RISC process and the suppressed nonradiative process of triplet excitons should be key to regulating the dual emission property. These findings and insights are of great importance for revealing the structure-performance relationship, providing theoretical guidance for the design of TADF and RTP dual emission molecules via internal and external heavy-atom effects.
近年来，具有热激活延迟荧光（TADF）和室温磷光（RTP）双发射的有机材料备受关注，但通过内部和外部重原子的调控机制尚不够清晰。在此，我们通过引入脂肪族或芳香族溴原子，对材料的光物理性质进行了系统的理论研究。具有芳香族溴原子的分子由于能级匹配的有效反向系间窜越（RISC）和增强的自旋轨道耦合而表现出明显的TADF，具有脂肪族溴原子的分子由于三重态激子的非辐射跃迁减少而具有较长的RTP寿命，而同时具有脂肪族和芳香族溴原子的分子由于内部和外部重原子效应的协同作用而呈现出平衡的TADF和RTP发射。此外，内部和外部重原子诱导多位点分子间相互作用，有效抑制了固相中的非辐射过程。高效的RISC过程和三重态激子的非辐射过程抑制应是调节双发射性质的关键。这些发现和见解对于揭示结构-性能关系、为通过内部和外部重原子效应设计TADF和RTP双发射分子提供理论指导具有重要意义。
