Understanding the efficiency drooping of the deep blue organometallic phosphors: a computational study of radiative and non-radiative decay rates for triplets
Understanding the efficiency drooping of the deep blue organometallic phosphors: a computational study of radiative and non-radiative decay rates for triplets
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了解深蓝色有机金属荧光粉的效率下降：三重态辐射和非辐射衰减率的计算研究
DOI：
10.1039/c6tc00858e
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发表时间：
2016-07
影响因子：
6.4
通讯作者：
Shuai Zhigang
中科院分区：
文献类型：
--
作者：
Peng Qian;Shi Qinghua;Niu Yingli;Yi Yuanping;Sun Shaorui;Li Wenqiang;Shuai Zhigang
高效的深蓝有机金属荧光粉是有机发光器件必不可少的材料。虽然绿色铱配合物通常具有较高的发光效率，但当发射变为深蓝色时，发光量子效率总是急剧下降。在这项工作中，从详细的计算研究中阐明了这种急剧下降的微观机制。以苯吡啶基、苯吡唑基、联吡啶、嘧啶吡啶基和嘧啶吡唑基配体为基础，计算了5种具有代表性的环金属化铱（III）配合物的最低三重态（T1）的辐射（kr）和非辐射（knr）衰变速率。所有化合物的T1态都具有配体内混合（π→π*）跃迁和铱-配体电荷转移（d→π*）的特征，并且π→π*部分的增加和d→π*部分的减少导致了1 < 2 < 4 < 5 < 3的蓝移发射。引人注目的是，我们发现由π→π*跃迁引起的严重配体内部振动弛豫引起的knr的急剧增加是导致磷光量子效率下降的主要原因，这与以往许多研究报道的热激活转变为暗金属中心配体场激发态提供了不同的失活机制。与已有研究的化合物1-3相比，新设计的化合物4和5在高效率和大能隙之间取得了很好的平衡，是很有前途的深蓝色荧光粉。这些发现将有助于高效蓝色有机金属荧光粉的合理设计，特别是在配体方面。
High-efficiency deep blue organometallic phosphors are imperative to organic luminescence devices. While green iridium complexes commonly exhibit high luminescence efficiencies, the luminescence quantum efficiency always drops sharply when emission becomes deep blue. In this work, the microscopic mechanism of such a drastic decrease is elucidated from detailed computational investigation. Both radiative (kr) and non-radiative (knr) decay rates of the lowest triplet state (T1) are calculated for five representative cyclometalated iridium(III) complexes with emission color ranging from green to deep blue, based on phenylpyridyl, phenylpyrazolyl, bipyridinato, pyrimidinpyridyl, and pyrimidinprazolyl ligands. For all compounds, the T1 states are characteristic of mixed intraligand (π → π*) transition and iridium-to-ligand charge transfer (d → π*), and the increased π → π* and decreased d → π* portions lead to the blue-shifted emission of 1 < 2 < 4 < 5 < 3. Strikingly, it is found that the drastic increase of knr arising from severe intra-ligand vibration relaxations induced by the enhanced π → π* transition is mainly responsible for the droop of the phosphorescence quantum efficiency, which provides a different deactivation mechanism from the thermally-activated transformation into a dark metal-centred ligand field excited state reported in many previous studies. Compared with the well-studied compounds 1–3, the newly designed compounds 4 and 5 achieve a good balance between high efficiency and a large energy gap and are very promising as deep blue phosphors. These findings are expected to be helpful for the rational design of high-efficiency blue organometallic phosphors, especially in terms of ligands.
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影响因子：
8.4
作者：
Escudero D
通讯作者：
Escudero D
影响因子：
3
作者：
Tao Liu;B. Xia;Qingchuan Zheng;Xin Zhou;Qingjiang Pan;Hong-Xing Zhang
通讯作者：
Tao Liu;B. Xia;Qingchuan Zheng;Xin Zhou;Qingjiang Pan;Hong-Xing Zhang
具有高功函数的氯化氧化铟锡电极，可实现有机器件兼容性
影响因子：
56.9
作者：
Helander, M. G.;Wang, Z. B.;Lu, Z. H.
通讯作者：
Lu, Z. H.
分子荧光量子效率的定量预测：杜钦斯基旋转的作用
影响因子：
15
作者：
Peng, Qian;Yi, Yuanping;Shao, Jiushu
通讯作者：
Shao, Jiushu
影响因子：
4.4
作者：
Geng, Hua;Niu, Yingli;Bredas, Jean-Luc
通讯作者：
Bredas, Jean-Luc