New iridium complexes bearing C^N=N ligand for high efficiency OLEDs

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• 作者：BaoXiu Mi^a ; ^{iambxmi@njupt.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Chao Zhong^a ; Jie Sang^a ; Zhangjin Liao^b ; Hongjiao Wang^b ; ZhiQiang Gao^b ; ^{iamzqgao@njupt.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 刊名：Journal of Luminescence
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：180
• 期：Complete
• 页码：51-57
• 全文大小：2165 K

文摘

Three iridium complexes, with 3-methyl-6-(2,4-difluoro-phenyl)pyridazine (mdfppya, C^N=N type ligand) as cyclometalated ligands, and picolinate (pic) or acetylacetonate (acac) as ancillary ligand, were synthesized and structurally characterized. Among these complexes,the homoleptic one, which contains two fluorine atoms on the cyclometalated phenyl moiety to lower the LUMO and a methyl group at the cyclometalated pyridazine part to raise the HOMO, possesses the shortest emission wavelength with peak of 506 nm. Importing ancillary ligands of picolinate (pic) and acetylacetonate (acac) yielded iridium complexes with emission of longer wavelength. The investigation of photophysical, electrochemical properties, as well as quantum chemistry calculation revealed optoelectrical property differences among them, corresponding principles were discussed. Photophysical, electrochemical features, quantum chemistry simulation and electroluminescence properties were systematically investigated. All complexes were applied to organic light-emitting diodes (OLEDs) as dopant emitters and the influence of ancillary ligands on device performance is significant. Based on pic-complex, maximum device efficiencies of 41.0 cd A⁻¹ , 33.9 lm W⁻¹ and 11.62% were achieved. Additionally, this device exhibits extremely small efficiency roll-off. The reason for this good performance is mainly attributed to the high photoluminescence quantum yield and fast radiative decay rate of the phosphor, as wells rather matched energy levels in device.