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题名: Understanding the efficiency drooping of the deep blue organometallic phosphors: a computational study of radiative and non-radiative decay rates for triplets
作者: Peng, Qian1; Shi, Qinghua1; Niu, Yingli1; Yi, Yuanping1; Sun, Shaorui3; Li, Wenqiang2; Shuai, Zhigang2
刊名: JOURNAL OF MATERIALS CHEMISTRY C
发表日期: 2016
卷: 4, 期:28, 页:6829-6838
收录类别: SCI
英文摘要: 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 (k(r)) and non-radiative (k(nr)) decay rates of the lowest triplet state (T-1) 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 (pi -> pi(star)) transition and iridium-to-ligand charge transfer (d -> pi(star)), and the increased pi -> pi(star) and decreased d -> pi(star) 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 pi -> pi(star) 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.
语种: 英语
内容类型: 期刊论文
URI标识: http://ir.iccas.ac.cn/handle/121111/35185
Appears in Collections:有机固体实验室_期刊论文

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作者单位: 1.Chinese Acad Sci, BNLMS, Inst Chem, CAS Key Lab Organ Solids, Beijing 100190, Peoples R China
2.Tsinghua Univ, Dept Chem, Key Lab Organ Optoelect & Mol Engn, Beijing 100084, Peoples R China
3.Beijing Univ Technol, Coll Environm & Energy Engn, Beijing 100124, Peoples R China
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