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Theoretical investigation on reverse intersystem crossing from upper triplet to lowest singlet: A “hot exciton” path for blue fluorescent OLEDs
International Journal of Quantum Chemistry ( IF 2.3 ) Pub Date : 2020-08-25 , DOI: 10.1002/qua.26399
Yidan Liu 1 , Yizhong Yuan 1 , Xiaohui Tian 1 , Jinyu Sun 1
Affiliation  

Nowadays, blue fluorescent organic light‐emitting diodes (FOLEDs) have attracted considerable attention from both academia and industry. According to spin statistics, electrical excitation results in the formation of ∼25% singlet excitons and ∼75% triplet excitons (signifying ~75% energy loss), which triggered wide‐ranging efforts to harvest as many triplet excitons as possible. The materials that can convert triplet excitons into singlet excitons from the high‐lying excited triplet states (referred as “hot exciton” channel) to realize high efficiency were reported, which can also efficaciously avoid the accumulation of triplet excitons in T1 state. In this study, by means of density functional theory (DFT) and time‐dependent DFT, we have theoretically investigated the electronic and photophysical properties of 16 newly designed molecules with donor‐bridge‐acceptor framework to search for the blue FOLED materials exploiting the “hot exciton” path. Important properties, such as singlet‐triplet energy gaps, absorption and emission parameters, and reverse intersystem crossing rates (kRISC), of five target molecules were studied. The calculated results demonstrate that thiophene‐diphenylamine (kRISC up to 1.03 × 108 seconds−1) may have promising potential as blue FOLED materials by virtue of the “hot exciton” effect.

中文翻译:

从上三重态到最低单重态的反向系统间交叉的理论研究:蓝色荧光OLED的“热激子”路径

如今,蓝色荧光有机发光二极管(FOLED)引起了学术界和工业界的极大关注。根据自旋统计,电激发导致约25%的单重态激子和约75%的三重态激子形成(表示约75%的能量损失),从而引发了广泛的努力,以尽可能多地收获三重态激子。据报道,可以将三重态激子从高激发态的三重态转变为单重态激子(称为“热激子”通道)以实现高效率的材料,还可以有效避免三重态激子在T 1中的积累。州。在这项研究中,我们通过密度泛函理论(DFT)和随时间变化的DFT,从理论上研究了16种带有供体桥受体骨架的新设计分子的电子和光物理性质,以探索蓝色FOLED材料。热激子”路径。研究了五个靶分子的重要特性,例如单重态-三重态能隙,吸收和发射参数以及反向系统间交叉速率(k RISC)。计算结果表明,噻吩二苯胺(k RISC高达1.03×10 8 秒-1)由于“热激子”效应而具有作为蓝色FOLED材料的潜力。
更新日期:2020-10-30
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