A Multifunctional Iridium-Carbazolyl Orange Phosphor for High-Performance Two-Element WOLED Exploiting Exciton-Managed Fluorescence/Phosphorescence

Authors

  • Cheuk-Lam Ho,

    1. Department of Chemistry and Centre for Advanced Luminescence, Materials Hong Kong Baptist University, Waterloo Road, Kowloon Tong, Hong Kong (P. R. China)
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  • Wai-Yeung Wong,

    Corresponding author
    1. Department of Chemistry and Centre for Advanced Luminescence, Materials Hong Kong Baptist University, Waterloo Road, Kowloon Tong, Hong Kong (P. R. China)
    • Department of Chemistry and Centre for Advanced Luminescence, Materials Hong Kong Baptist University, Waterloo Road, Kowloon Tong, Hong Kong (P. R. China).
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  • Qi Wang,

    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun 130022 (P. R. China)
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  • Dongge Ma,

    Corresponding author
    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun 130022 (P. R. China)
    • State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun 130022 (P. R. China).
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  • Lixiang Wang,

    1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun 130022 (P. R. China)
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  • Zhenyang Lin

    1. Department of Chemistry, The Hong Kong University of Science and Technology Clearwater Bay, Hong Kong (P. R. China)
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  • This work was supported by a CERG Grant from the Hong Kong Research Grants Council (HKBU 202106) and a Faculty Research Grant from the Hong Kong Baptist University (FRG/04-05/II-59). WOLED: white organic light-emitting diode. Supporting information for this article is available online at Wiley Interscience or from the authors.

Abstract

By attaching a bulky, inductively electron-withdrawing trifluoromethyl (CF3) group on the pyridyl ring of the rigid 2-[3- (N-phenylcarbazolyl)]pyridine cyclometalated ligand, we successfully synthesized a new heteroleptic orange-emitting phosphorescent iridium(III) complex [Ir(L1)2(acac)] 1 (HL1 = 5-trifluoromethyl-2-[3-(N-phenylcarbazolyl)]pyridine, Hacac = acetylacetone) in good yield. The structural and electronic properties of 1 were examined by X-ray crystallography and time-dependent DFT calculations. The influence of CF3 substituents on the optical, electrochemical and electroluminescence (EL) properties of 1 were studied. We note that incorporation of the carbazolyl unit facilitates the hole-transporting ability of the complex, and more importantly, attachment of CF3 group provides an access to a highly efficient electrophosphor for the fabrication of orange phosphorescent organic light-emitting diodes (OLEDs) with outstanding device performance. These orange OLEDs can produce a maximum current efficiency of ∼40 cd A−1, corresponding to an external quantum efficiency of ∼12% ph/el (photons per electron) and a power efficiency of ∼24 lm W−1. Remarkably, high-performance simple two-element white OLEDs (WOLEDs) with excellent color stability can be fabricated using an orange triplet-harvesting emitter 1 in conjunction with a blue singlet-harvesting emitter. By using such a new system where the host singlet is resonant with the blue fluorophore singlet state and the host triplet is resonant with the orange phosphor triplet level, this white light-emitting structure can achieve peak EL efficiencies of 26.6 cd A−1 and 13.5 lm W−1 that are generally superior to other two-element all-fluorophore or all-phosphor OLED counterparts in terms of both color stability and emission efficiency.

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