Thermally activated delayed fluorescence emitters with dual conformations for white organic light-emitting diodes: mechanism and molecular design.
Thermally activated delayed fluorescence emitters with dual conformations for white organic light-emitting diodes: mechanism and molecular design.
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DOI：
10.1039/c9cp05552e
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发表时间：
2019-12
期刊：
影响因子：
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通讯作者：
Feiyan Li;G. Jiang;Muzhen Li;Jianzhong Fan;Yuzhi Song;Chuan-kui Wang;Lili Lin
中科院分区：
文献类型：
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作者：
Feiyan Li;G. Jiang;Muzhen Li;Jianzhong Fan;Yuzhi Song;Chuan-kui Wang;Lili Lin
热激活延迟荧光（TADF）分子具有双重发光特性，在白色有机电致发光器件（WOLED）中具有很大的应用潜力。本文系统地研究了具有蓝橙双发光的PTZ-TTR和PTZ-Ph-TTR的发光机理。近平面和近正交构象分别负责蓝色和橙子发射。对于PTZ-TTR，近正交构象只能通过近平面构象的转化产生，而PTZ-Ph-TTR的近正交构象可以通过激发和转化两种方式产生。这导致PTZ-Ph-TTR中相对强的橙子发射。此外，TADF机制进行了研究，并揭示了两个分子的上转换途径。通过对PTZ-TTR在甲苯中的物理性质和聚集态的物理性质的比较，发现聚集态可以使PTZ-TTR的第一单重激发态和第一三重激发态之间的能隙变小。此外，还研究了施主的取代效应对发光性能的影响，提出了具有双构象和补偿发射的发光体的设计原则。我们的理论研究结果将有助于理解发光机理，以及设计新型的WOLED TADF发射器。
Thermally activated delayed fluorescence (TADF) molecules with dual emission have great potential for use as single emitters in white organic light-emitting diodes (WOLEDs). In this paper, the light-emitting mechanisms of PTZ-TTR and PTZ-Ph-TTR with blue-orange dual emission are studied systematically. The near-planar and near-orthogonal conformations are responsible for the blue and orange emission, respectively. For PTZ-TTR, the near-orthogonal conformation is only generated by the transformation from the near-planar conformation, while the near-orthogonal conformation of PTZ-Ph-TTR can be generated by both excitation and transformation. This results in relatively strong orange emission in PTZ-Ph-TTR. In addition, the TADF mechanism is investigated, and two up-conversion pathways are revealed for both molecules. Based on the comparison of the photophysical properties of PTZ-TTR in toluene and the aggregation state, we find that aggregation could induce a smaller energy gap between the first singlet excited state and the first triplet excited state. Besides, the substitution effect of donors on light-emitting properties is studied, and the design rules for emitters with dual conformations and compensatory emission are proposed. Our theoretical results would favor the understanding of the light-emitting mechanism as well as the design of new-type TADF emitters for WOLEDs.