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Highly Efficient Electroluminescence from Green-Light-Emitting Electrochemical Cells Based on CuI Complexes

Authors

  • Q. Zhang,

    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Graduate School of the Chinese Academy of Sciences, Changchun 130022, P.R. China
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  • Q. Zhou,

    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Graduate School of the Chinese Academy of Sciences, Changchun 130022, P.R. China
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  • Y. Cheng,

    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Graduate School of the Chinese Academy of Sciences, Changchun 130022, P.R. China
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  • L. Wang,

    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Graduate School of the Chinese Academy of Sciences, Changchun 130022, P.R. China
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  • D. Ma,

    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Graduate School of the Chinese Academy of Sciences, Changchun 130022, P.R. China
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  • X. Jing,

    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Graduate School of the Chinese Academy of Sciences, Changchun 130022, P.R. China
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  • F. Wang

    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Graduate School of the Chinese Academy of Sciences, Changchun 130022, P.R. China
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  • This work was supported by the National Natural Science Foundation of China (No. 20474062) and 973 Project (2002CB613401).

Abstract

The complexes [Cu(dnbp)(DPEphos)]+(X) (dnbp and DPEphos are 2,9-di-n-butyl-1,10-phenanthroline and bis[2-(diphenylphosphino)phenyl]ether, respectively, and X is BF4, ClO4, or PF6) can form high-quality films with photoluminescence quantum yields of up to 71 ± 7 %. Their electroluminescent properties are studied using the device structure indium tin oxide (ITO)/complex/metal cathode. The devices emit green light efficiently, with an emission maximum of 523 nm, and work in the mode of light-emitting electrochemical cells. The response time of the devices greatly depends on the driving voltage, the counterions, and the thickness of the complex film. After pre-biasing at 25 V for 40 s, the devices turn on instantly, with a turn-on voltage of ca. 2.9 V. A current efficiency of 56 cd A–1 and an external quantum efficiency of 16 % are realized with Al as the cathode. Using a low-work-function metal as the cathode can significantly enhance the brightness of the device almost without affecting the turn-on voltage and current efficiency. With a Ca cathode, a brightness of 150 cd m–2 at 6 V and 4100 cd m–2 at 25 V is demonstrated. The electroluminescent performance of these types of complexes is among the best so far for transition metal complexes with counterions.

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