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Sky-blue phosphorescence from bis- and tris-cyclometalated iridium(III) complexes bearing carbazole-based dendrons: fabrication of non-doped multilayer organic light-emitting diodes by solution processing

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Abstract

Novel phosphorescent bis- and tris-cyclometalated iridium(III) complexes bearing carbazole-appended dendrons were successfully synthesized, and fabrication of non-doped multilayer OLEDs by solution processing was demonstrated by using these complexes as emitting materials. The complexes exhibited sky-blue photoluminescence (PL) at 460–464 nm with excellent PL quantum yields of ca. 0.8, and their neat films also emitted sky-blue photoluminescence: the dendrons effectively suppressed aggregation between the luminescent cores, although referential core complexes, bearing no dendrons, exhibited aggregate-based green PL even when the core complexes were doped into a model host material of the dendron in the same core–dendron molar ratios as the present dendritic bis- and tris-cyclometalated iridium(III) complexes. As hydrophobic tert-butyl groups are placed on the periphery, the dendritic complexes exhibit good solubility in cyclohexane and poor solubility in 2-propanol. Such special properties allow for fabrication of solution-processed non-doped multilayer OLEDs consisting of a stack of the hole-transporting layer (HTL)/emitting layer (the dendritic complex)/electron-transporting layer (ETL). The devices showed sky-blue electroluminescence with excellent electron–hole charge balance factors (γ) of ca. 0.9, which were much higher than those of simple non-doped devices without HTL and ETL (γ; ca. 0.1).

Graphical abstract: Sky-blue phosphorescence from bis- and tris-cyclometalated iridium(iii) complexes bearing carbazole-based dendrons: fabrication of non-doped multilayer organic light-emitting diodes by solution processing

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Publication details

The article was received on 22 Jun 2017, accepted on 29 Jul 2017 and first published on 31 Jul 2017


Article type: Paper
DOI: 10.1039/C7NJ02240A
Citation: New J. Chem., 2017, Advance Article
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    Sky-blue phosphorescence from bis- and tris-cyclometalated iridium(III) complexes bearing carbazole-based dendrons: fabrication of non-doped multilayer organic light-emitting diodes by solution processing

    N. Okamura, T. Maeda and S. Yagi, New J. Chem., 2017, Advance Article , DOI: 10.1039/C7NJ02240A

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