系统间交叉
单重态
材料科学
有机发光二极管
激发态
三重态
密度泛函理论
基态
化学物理
原子物理学
光化学
接受者
纳米技术
化学
物理
计算化学
凝聚态物理
图层(电子)
作者
Wei Li,Mengke Li,Wenqi Li,Zhengming Xu,Lin Gan,Kunkun Liu,Nan Zheng,Chengyun Ning,Dongcheng Chen,Yuan‐Chun Wu,Shi‐Jian Su
标识
DOI:10.1021/acsami.0c19302
摘要
Thermally activated delayed fluorescence (TADF) emitters with a spiral donor show tremendous potential toward high-level efficient blue organic light-emitting diodes (OLEDs). However, the underlying design strategy of the spiral donor used for blue TADF emitters remains unclear. As a consequence, researchers often do “try and error” work in the development of new functional spiral donor fragments, making it slow and inefficient. Herein, we demonstrate that the energy level relationships between the spiral donor and the luminophore lead to a significant effect on the photoluminescent quantum yields (PLQYs) of the target materials. In addition, a method involving quantum chemistry simulations that can accurately predict the aforementioned energy level relationships by simulating the spin density distributions of the triplet excited states of the spiral donor and corresponding TADF emitters and the triplet excited natural transition orbitals of the TADF emitters is established. Moreover, it also revealed that the steric hindrance in this series of molecules can form a nearly unchanged singlet (S1) state geometry, leading to a reduced nonradiative decay and high PLQY, while a moderated donor–acceptor (D-A) torsion in the triplet (T1) state can induce a strong vibronic coupling between the charge-transfer triplet (3CT) state and the local triplet (3LE) state, achieving an effective reverse intersystem crossing (RISC) process. Furthermore, an electric–magnetic coupling is formed between the high-lying 3LE state and the charge-transfer singlet (1CT) state, which may open another RISC channel. Remarkably, in company with the optimized molecular structure and energy alignment, the pivotal TADF emitter DspiroS-TRZ achieved 99.9% PLQY, an external quantum efficiency (EQE) of 38.4%, which is the highest among all blue TADF emitters reported to date.
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