Excited states of emissive organic molecules undergo various kinds of quenching phenomena such as vibration-coupled quenching depending on their environmental conditions. Because bright singlet excitons in purely organic molecules exhibiting thermally activated delayed fluorescence (TADF) can access dark triplet excited states, photogenerated singlet excitons can decay nonradiatively through both singlet and triplet excited states. Here, we investigated nonradiative decay behavior, including internal and external exciton quenching processes, of various types of TADF materials in solution. Under air-saturated conditions, both the lowest singlet and triplet excited states of almost all of the TADF materials showed oxygen quenching. We considered the effect of oxygen quenching for both spin states to develop a method for determination of the triplet contribution to the total photoluminescence quantum yield from the transient photoluminescence profiles. Furthermore, we observed a clear energy gap law for the internal nonradiative processes.

中文翻译：

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从溶液中热活化延迟荧光发射体的单重态和三重态的非辐射失活行为观察。

发光有机分子的激发态根据其环境条件会经历各种猝灭现象，例如振动耦合猝灭。由于纯有机分子中表现出热激活延迟荧光（TADF）的明亮单线态激子可以进入暗三线态激发态，因此光生单线态激子可以通过单线态和三线态激发态进行非辐射衰减。在这里，我们研究了溶液中各种类型TADF材料的非辐射衰减行为，包括内部和外部激子猝灭过程。在空气饱和条件下，几乎所有TADF材料的最低单重态和三重态激发态都显示出氧猝灭。我们考虑了氧对两个自旋态的猝灭效应，以开发一种确定瞬态光致发光图谱中三线态对总光致发光量子产率的贡献的方法。此外，我们观察到内部非辐射过程的清晰的能隙定律。