A new way towards high-efficiency thermally activated delayed fluorescence devices via external heavy-atom effect.
A new way towards high-efficiency thermally activated delayed fluorescence devices via external heavy-atom effect.
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通过外部重原子效应，一种新的高效热激活延迟荧光装置的方法。
DOI：
10.1038/srep30178
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发表时间：
2016-07-21
影响因子：
4.6
通讯作者：
Wang L
中科院分区：
文献类型：
--
作者：
Zhang W;Jin J;Huang Z;Zhuang S;Wang L
热激活延迟荧光（TADF）机制是一种重要的方法，可以捕获三重态和单重态激子用于发射。然而，迄今为止，大多数研究工作都集中在单重态-三重态分裂（ΔEST）与荧光效率的关系上，而忽略了自旋轨道耦合（SOC）的重要性。在这方面的贡献，开发了一种新的方法来实现高效率的TADF为基础的设备，通过简单的设备结构优化。通过以所需的方式插入一个外重原子（EHA）微扰层，它提供了一种有用的手段，加速TADF分子中的T1 → S1反向系间穿越（RISC），而不会严重影响相应的S1 → T1过程。此外，该策略还促进了主体→客体能量转移过程中通过Förster机制对主体三重态的利用，从而摆脱了对Dexter机制的单一依赖.基于这种策略，我们成功地将基于4CzPN的器件的外量子效率（EQE）与对照器件相比提高了近38%。这些发现为EHA在基于TADF的器件中所起的作用提供了敏锐的见解，为利用某些具有高辐射跃迁率但相对低效RISC的TADF染料提供了有价值的指导。
Thermally activated delayed fluorescence (TADF) mechanism is a significant method that enables the harvesting of both triplet and singlet excitons for emission. However, up to now most efforts have been devoted to dealing with the relation between singlet-triplet splitting (ΔEST) and fluorescence efficiency, while the significance of spin-orbit coupling (SOC) is usually ignored. In this contribution, a new method is developed to realize high-efficiency TADF-based devices through simple device-structure optimizations. By inserting an ultrathin external heavy-atom (EHA) perturber layer in a desired manner, it provides useful means of accelerating the T1 → S1 reverse intersystem crossing (RISC) in TADF molecules without affecting the corresponding S1 → T1 process heavily. Furthermore, this strategy also promotes the utilization of host triplets through Förster mechanism during host → guest energy transfer (ET) processes, which helps to get rid of the solely dependence upon Dexter mechanism. Based on this strategy, we have successfully raised the external quantum efficiency (EQE) in 4CzPN-based devices by nearly 38% in comparison to control devices. These findings provide keen insights into the role of EHA played in TADF-based devices, offering valuable guidelines for utilizing certain TADF dyes which possess high radiative transition rate but relatively inefficient RISC.