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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Conjugation-Induced Thermally Activated Delayed Fluorescence: Photophysics of a Carbazole-Benzophenone Monomer-to-Tetramer Molecular Series
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Conjugation-Induced Thermally Activated Delayed Fluorescence: Photophysics of a Carbazole-Benzophenone Monomer-to-Tetramer Molecular Series

机译：缀合诱导的热活化延迟荧光：咔唑-二苯甲酮单体对四聚体系列的光学药物

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摘要

Materials exhibiting thermally activated delayed fluorescence (TADF) have been extensively explored in the last decade. These emitters have great potential of being used in organic light-emitting diodes because they allow for high quantum efficiencies by utilizing triplet states via reverse intersystem crossing. In small molecules, this is done by spatially separating the highest occupied molecular orbital from the lowest unoccupied molecular orbital, forming an intramolecular charge-transfer (iCT) state and leading to a small energy difference between lowest excited singlet and triplet states (ΔE _(ST)). However, in polymer emitters, this is harder to achieve, and typical strategies usually include adding known TADF units as sidechains onto a polymer backbone. In a previous work, we proposed an alternative way to achieve a TADF polymer by repeating a non-TADF unit, polymerizing it via electron-donating carbazole moieties. The extended conjugation on the backbone reduced the ΔE _(ST) and allowed for an efficient TADF polymer. In this work, we present a more in-depth study of the shift from a non-TADF monomer to TADF oligomers. The monomer shows non-TADF emission, and we find the delayed emission to be of triplet–triplet annihilation origin. An iCT state is formed already in the dimer, leading to a much more efficient TADF emission. This is confirmed by an almost two-fold increase of photoluminescence quantum yield, a decrease in the delayed luminescence lifetime, and the respective spectral lineshapes of the molecules.
机译：显示热激活延迟荧光（TADF）的材料在过去十年中得到了广泛的探索。这些发光体在有机发光二极管中具有巨大的应用潜力，因为它们通过反向系统间交叉利用三重态来实现高量子效率。在小分子中，这是通过在空间上将最高被占分子轨道与最低未被占分子轨道分离，形成分子内电荷转移（iCT）状态，并导致最低激发单线态和三线态之间的能量差很小（ΔE ST））。然而，在聚合物发射器中，这很难实现，典型的策略通常包括在聚合物主链上添加已知的TADF单元作为侧链。在之前的工作中，我们提出了一种替代方法，通过重复非TADF单元，通过给电子咔唑部分使其聚合，来实现TADF聚合物。主链上的延伸共轭降低了ΔE_ST（ST），并允许形成有效的TADF聚合物。在这项工作中，我们对从非TADF单体到TADF低聚物的转变进行了更深入的研究。单体显示非TADF发射，我们发现延迟发射是三重态-三重态湮灭起源。二聚体中已经形成iCT状态，导致更有效的TADF排放。光致发光量子产率几乎增加了两倍，延迟发光寿命减少，分子的光谱线型也证实了这一点。

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    Qiang Wei; Paulius Imbrasas; Enrique Caldera-Cruz; Liang Cao; Nanan Fei; Heidi Thomas; Reinhard Scholz; Simone Lenk; Brigitte Voit; Sebastian Reineke; Ziyi Ge;

  • 作者单位

    Ningbo Institute of Materials Technology &

    Engineering Chinese Academy Sciences;

    Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics Technische Universit?t Dresden;

    Leibniz-Institut für Polymerforschung Dresden e.V. Hohe Stra?e;

    Ningbo Institute of Materials Technology &

    Engineering Chinese Academy Sciences;

    Ningbo Institute of Materials Technology &

    Engineering Chinese Academy Sciences;

    Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics Technische Universit?t Dresden;

    Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics Technische Universit?t Dresden;

    Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics Technische Universit?t Dresden;

    Leibniz-Institut für Polymerforschung Dresden e.V. Hohe Stra?e;

    Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics Technische Universit?t Dresden;

    Ningbo Institute of Materials Technology &

    Engineering Chinese Academy Sciences;

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  • 正文语种 eng
  • 中图分类 物理化学（理论化学）、化学物理学;
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