Theoretical study on a series of iridium complexes with low efficiency roll-off property

• A series of Ir (III) complexes were investigated by DFT and TD-DFT method.
• The Ir complexes appeared here have an advantage of low efficiency roll-off property.
• The materials appeared here are practical for OLED industrialization.

A series of heteroleptic cyclometalated Ir (III) complexes for OLEDs application have been investigated theoretically to explore their electronic structures and spectroscopic properties. The geometries, electronic structures, and the lowest-lying singlet absorptions and triplet emissions of (piq)2Ir(acac) (labeled 1) and theoretically designed models (piq)2Ir(dpis) (labeled 2), (4Fpiq)2Ir(dpis) (labeled 3), (4F5M-piq)2Ir(dpis) (labeled 4), (4,5-2F-piq)2Ir(dpis) (labeled 5) and (5-F-piq)2Ir(dpis) (labeled 6) were investigated with density functional theory (DFT)-based approaches, where, piq = 1-phenylisoquinolato, acac = acetylacetonate and dpis = diphenylimidodisilicate. Their structures in the ground and excited states have been optimized at the DFT/B3LYP/LANL2DZ and TDDFT/B3LYP/LANL2DZ levels, and the lowest absorptions and emissions were evaluated at B3LYP and M062X level of theory, respectively. Furthermore, the energy-transfer mechanism of these complexes also be analyzed here, and the result shown that the complexes 1–6 are having the low efficiency roll-off property. Except that, the oscillator strength analyze shown that the complexes 2–6, which were designed by theory, are suitable for OLED since their high oscillator strength property.

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