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Theoretical studies on full-color thermally activated delayed fluorescence molecules
Journal of Materials Chemistry C ( IF 5.7 ) Pub Date : 2020-03-17 , DOI: 10.1039/d0tc00279h Lei Liu 1, 2, 3, 4, 5 , Qi Wei 1, 2, 3, 4, 5 , Yajuan Cheng 3, 4, 6, 7, 8 , Huili Ma 5, 9, 10, 11 , Shiyun Xiong 1, 2, 3, 4, 5 , Xiaohong Zhang 1, 2, 3, 4, 5
Journal of Materials Chemistry C ( IF 5.7 ) Pub Date : 2020-03-17 , DOI: 10.1039/d0tc00279h Lei Liu 1, 2, 3, 4, 5 , Qi Wei 1, 2, 3, 4, 5 , Yajuan Cheng 3, 4, 6, 7, 8 , Huili Ma 5, 9, 10, 11 , Shiyun Xiong 1, 2, 3, 4, 5 , Xiaohong Zhang 1, 2, 3, 4, 5
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Thermally activated delayed fluorescence (TADF) materials have attracted wide attention due to the full utilization of triplet and singlet excitons. Beyond the typical donor–acceptor (D–A) TADF compounds, D–π–A–π–D TADF emitters were reported recently. In this paper, we study the dynamic nature of excited states of four D–π–A–π–D TADF molecules with full color emission at the first principles level. It shows that MAC-PN has good TADF efficiency benefiting from the large reverse intersystem crossing (RISC, krisc) and radiative decay (kr) rates. PX-PN and MCZ-DPPN molecules have a reduced TADF efficiency, owing to the largely increased non-radiative decay rate (knr) by two orders of magnitude and decreased krisc, respectively, while PX-CNP shows the worst TADF performance, because knr is five orders of magnitude larger than kr. Moreover, reorganization energy analysis reveals that the RISC process is largely manipulated by the torsional vibration of the dihedral angle, while the non-radiative process mainly happens through the channels of bond stretching vibration. These calculations agree well with the experimental efficiency trend among the four TADF molecules and uncover the intrinsic TADF mechanisms, providing the possibility of further engineering the molecules with improved TADF efficiency.
中文翻译：
全色热活化延迟荧光分子的理论研究
由于充分利用了三重态和单重态激子，热活化延迟荧光（TADF）材料引起了广泛的关注。除了典型的供体-受体（DA）TADF化合物以外，最近还报道了D-π-A-π-DTADF发射体。在本文中，我们研究了在第一个原理水平上具有全色发射的四个D–π–A–π–D TADF分子的激发态的动力学性质。结果表明，MAC-PN具有良好的TADF效率，这得益于较大的反向系统间交叉（RISC，k risc）和辐射衰减（k r）速率。PX-PN和MCZ-DPPN分子的非辐射衰变率（knr）分别降低两个数量级并降低k risc，而PX-CNP显示最差的TADF性能，因为k nr比k r大五个数量级。此外，重组能量分析表明，RISC过程在很大程度上受到二面角扭转振动的控制，而非辐射过程主要通过键拉伸振动的通道发生。这些计算与四个TADF分子之间的实验效率趋势非常吻合，并揭示了固有的TADF机理，从而为进一步设计具有提高的TADF效率的分子提供了可能性。
更新日期：2020-03-17
中文翻译：
全色热活化延迟荧光分子的理论研究
由于充分利用了三重态和单重态激子，热活化延迟荧光（TADF）材料引起了广泛的关注。除了典型的供体-受体（DA）TADF化合物以外，最近还报道了D-π-A-π-DTADF发射体。在本文中，我们研究了在第一个原理水平上具有全色发射的四个D–π–A–π–D TADF分子的激发态的动力学性质。结果表明，MAC-PN具有良好的TADF效率，这得益于较大的反向系统间交叉（RISC，k risc）和辐射衰减（k r）速率。PX-PN和MCZ-DPPN分子的非辐射衰变率（knr）分别降低两个数量级并降低k risc，而PX-CNP显示最差的TADF性能，因为k nr比k r大五个数量级。此外，重组能量分析表明，RISC过程在很大程度上受到二面角扭转振动的控制，而非辐射过程主要通过键拉伸振动的通道发生。这些计算与四个TADF分子之间的实验效率趋势非常吻合，并揭示了固有的TADF机理，从而为进一步设计具有提高的TADF效率的分子提供了可能性。
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