Theoretical Study of the Mechanism of Aggregation-Caused Quenching in Near-Infrared Thermally Activated Delayed Fluorescence Molecules: Hydrogen-Bond Effect,The Journal of Physical Chemistry C

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Theoretical Study of the Mechanism of Aggregation-Caused Quenching in Near-Infrared Thermally Activated Delayed Fluorescence Molecules: Hydrogen-Bond Effect
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2019-09-27 , DOI: 10.1021/acs.jpcc.9b06388
Kai Zhang ₁ , Jie Liu ₁ , Yuchen Zhang ₁ , Jianzhong Fan ₁ , Chuan-Kui Wang ₁ , Lili Lin ₁

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Aggregation-caused quenching (ACQ) has long been a problem that inhibits the application of organic light-emitting materials in organic light-emitting diodes, especially near-infrared (NIR) materials. Figuring out the reasons that induce ACQ is important for the quantum efficiency enhancement of NIR materials. In this paper, an NIR molecule (TPA-QCN) with thermally activated delayed fluorescence (TADF) is studied based on first-principles calculations and excited-state dynamics investigation in both toluene and in the aggregation state. Our calculation indicates that aggregation can induce a smaller energy gap between the first singlet excited state and the first triplet excited state, which is favorable for TADF. Both the decreased fluorescent rate and the increased nonradiative rate will induce emission quenching in the aggregation state. Based on detailed analyses of the reorganization energy and intermolecular interaction, we find that the hydrogen bond will induce enhanced contribution to the reorganization energy from C–H stretching vibration modes and thus a larger nonradiative rate in the aggregation state than in toluene. A new mechanism of ACQ is proposed, and it could help in the design of new types of NIR-TADF molecules with enhanced fluorescence efficiency.

中文翻译：

近红外热活化延迟荧光分子中聚集引起的猝灭机理的理论研究：氢键效应

长期以来，由于聚集引起的猝灭（ACQ）一直是阻碍有机发光材料特别是近红外（NIR）材料在有机发光二极管中的应用的问题。找出引起ACQ的原因对于提高NIR材料的量子效率很重要。本文基于第一性原理计算以及在甲苯和聚集态的激发态动力学研究，研究了具有热活化延迟荧光（TADF）的NIR分子（TPA-QCN）。我们的计算表明聚集可以在第一单重态激发态和第一三重态激发态之间引起较小的能隙，这对于TADF是有利的。降低的荧光速率和增加的非辐射速率都将在聚集状态下诱导发射猝灭。基于对重组能和分子间相互作用的详细分析，我们发现氢键将引起C–H拉伸振动模式对重组能的增强贡献，因此聚集态的非辐射率比甲苯大。提出了一种新的ACQ机理，它可以帮助设计新型的具有增强荧光效率的NIR-TADF分子。

更新日期：2019-09-28

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