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Highly efficient green electroluminescence of iridium(III) complexes based on (1H-pyrazol-5-yl)pyridine derivatives ancillary ligands with low efficiency roll-off

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Abstract

Four iridium(III) complexes, namely Ir-me, Ir-cf3, Ir-py, and Ir-ph, were synthesized, in which 2-(4-trifluoromethyl)phenylpyridine (tfmppy) was used as the main ligand and 2-(3-methyl-1H-pyrazol-5-yl)pyridine (mepzpy), 2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridine (cf3pzpy), 2,2′-(1H-pyrazole-3,5-diyl)dipyridine (pypzpy), and 2-(3-phenyl-1H-pyrazol-5-yl)pyridine (phpzpy) were applied as ancillary ligands, respectively. All complexes showed similar green light peaking at 494–499 nm with high phosphorescence quantum efficiency (0.76–0.82). The organic light-emitting diodes (OLEDs) with the structure of ITO/HATCN (hexaazatriphenylenehexacabonitrile) (5 nm)/TAPC (bis[4-(N,N-ditolylamino)-phenyl]cyclohexane, 50 nm)/Ir complexes (8 wt%): TCTA (4,4′,4′′-tri(9-carbazoyl)triphenylamine, 20 nm)/TmPyPB (1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene, 40 nm)/LiF (1 nm)/Al (100 nm) displayed high current efficiency with low efficiency roll-off. Moreover, the device based on the Ir-me complex exhibited the best performances with a maximum luminance of 38 155 cd m−2, maximum current efficiency of 92 cd A−1, and a maximum external quantum efficiency of 28.90%. These results suggested that green Ir(III) complexes were obtained by modification of the ppy ligand and rational introduction of (1H-pyrazol-5-yl)pyridine derivatives as the ancillary ligands for high efficient OLEDs.

Graphical abstract: Highly efficient green electroluminescence of iridium(iii) complexes based on (1H-pyrazol-5-yl)pyridine derivatives ancillary ligands with low efficiency roll-off

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Publication details

The article was received on 10 Mar 2018, accepted on 09 May 2018 and first published on 11 May 2018


Article type: Paper
DOI: 10.1039/C8TC01182F
Citation: J. Mater. Chem. C, 2018, Advance Article
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    Highly efficient green electroluminescence of iridium(III) complexes based on (1H-pyrazol-5-yl)pyridine derivatives ancillary ligands with low efficiency roll-off

    N. Su, G. Lu and Y. Zheng, J. Mater. Chem. C, 2018, Advance Article , DOI: 10.1039/C8TC01182F

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