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Highly Efficient Cuprous Complexes with Thermally Activated Delayed Fluorescence for Solution-Processed Organic Light-Emitting Devices

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posted on 13.07.2016, 07:03 by Dong Liang, Xu-Lin Chen, Jian-Zhen Liao, Jin-Yu Hu, Ji-Hui Jia, Can-Zhong Lu
Two mononuclear cuprous complexes [Cu­(PNNA)­(POP)]­BF4 (1) and [Cu­(PNNA)­(Xantphos)]­BF4 (2) (PNNA = 9,9-dimethyl-10-(6-(3-phenyl-1H-pyrazol-1-yl)­pyridin-3-yl)-9,10-dihydroacridine, POP = bis­[2-(dipenylphosphino)­phenyl]­ether, Xantphos =4,5-bis­(diphenylphosphino)-9,9-dimethylxanthene), with intense bluish-green luminescence based on a new diimine ligand were designed and synthesized. Their structural, electrochemical, and photophysical properties were characterized by single-crystal X-ray analysis, cyclic voltammetry, temperature dependence of spectroscopy, time-dependent emission spectroscopy, etc. The complexes exhibit high photoluminescence quantum yields in doped films (up to 74.6%) at room temperature. Thermally activated delayed fluorescence based on intraligand charge transfer was observed by grafting a strong electron-donor moiety, 9,9-dimethylacridan, on the diimine ligand, which is supported by the density functional theory calculations on two complexes. Highly efficient solution-processed OLEDs based on these two complexes were fabricated, among which the electroluminescent device using 2 as dopant shows a peak external quantum efficiency of 7.42%, a peak current efficiency of 20.24 cd/A, and a maximum brightness of 5579 cd/m2.