A novel molecular descriptor for highly efficient (ϕTADF > 90%) transition metal TADF Au(III) complexes,Journal of Materials Chemistry A

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A novel molecular descriptor for highly efficient (ϕTADF > 90%) transition metal TADF Au(III) complexes
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020-08-26 , DOI: 10.1039/d0ta07149h
Yu Wang _{1,

2,

3,

4,

5} , Qian Peng _{6,

7,

8,

9,

10} , Qi Ou _{1,

2,

3,

4,

5} , Shiyun Lin _{1,

2,

3,

4,

5} , Zhigang Shuai _{1,

2,

3,

4,

5}

Affiliation

It is generally perceived that a fast reverse intersystem crossing rate of T₁ → S₁ (k_risc) is crucial for efficient organic thermally activated delayed fluorescence (TADF) emitters. Herein, we demonstrate the non-radiative decay rate of T₁ → S₀ (k^T_nr) for transition metal complexes that is even more important. We calculated the interconversion rates among S₀, S₁ and T₁ states for two Au(III)–TADF complexes with triphenylamine (TPA) as a donor moiety but with quite different quantum efficiencies: one with a moderate efficiency of 79% and the other with a high efficiency of 94%, and we found that the former has a much larger k_risc (∼10¹⁰ s⁻¹) than the latter (∼10⁷ s⁻¹). Such contradictions with the conventional picture are attributed to the relatively large k^T_nr (∼10⁶ s⁻¹) for the former, leading to an overall lower quantum efficiency. Thus, we propose a novel molecular design descriptor (the triplet non-radiative decay rate k^T_nr) for highly efficient transition metal TADF emitters. Further, we find that tetradentate ligand scaffolds with 5-5-6 membered chelate rings could reduce k^T_nr to <10⁵ s⁻¹ for Au(III)–TADF complexes, thereby achieving quantum efficiencies above 90%. Based on this theoretical guideline, we have proposed nine newly designed Au(III) complexes and predicted their high TADF efficiency.

中文翻译：

高效（ϕTADF> 90％）过渡金属TADF Au（III）配合物的新型分子描述符

通常认为，T ₁ →S ₁（k _risc）的快速反向系统间交叉速率对于有效的有机热激活延迟荧光（TADF）发射器至关重要。在这里，我们证明了过渡金属配合物的T ₁ →S ₀（k ^T_nr）的非辐射衰减速率更为重要。我们计算了两个Au（III）在S ₀，S ₁和T ₁状态之间的互转换率）–以三苯胺（TPA）作为供体部分的TADF络合物，但量子效率却大不相同：一种具有中等效率79％，另一种具有94％的高效率，我们发现前者的k大得多_risc（〜10 ¹⁰ s ^-1）高于后者（〜10 ⁷ s ^-1）。与传统图像的这种矛盾归因于前者的相对较大的k ^T_nr（〜10 ⁶ s ^-1），从而导致总体上较低的量子效率。因此，我们提出了一种新颖的分子设计描述符（三重态非辐射衰变率k ^T_nr）用于高效过渡金属TADF发射器。此外，我们发现具有5-5-6元螯合环的四齿配体支架可以将Au（III）-TADF络合物的k ^T_nr降低至<10 ⁵ s ^-1，从而实现90％以上的量子效率。根据这一理论指导，我们提出了九种新设计的Au（III）配合物，并预测了它们的高TADF效率。

更新日期：2020-09-22

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