Syntheses, Photophysics, and Application of Iridium(III) Phosphorescent Emitters for Highly Efficient, Long-Life Organic Light-Emitting Diodes

摘要

Rational design and synthesis of Ir~(III) complexes (1-3) bearing two cyclometalated ligands (C^N) and one 2-(diphenylphosphino)phenolate chelate (P^O) as well as the corresponding Ir~(III) derivatives (4-6) with only one (C^N) ligand and two P^O chelates are reported, where (C^NH)(velence)phenylpyridine (ppyH), 1-phenylisoquinoline (piqH), and 4-phenylquinazoline (nazoH). Single crystal X-ray diffraction studies of 3 reveal a distorted octahedral coordination geometry, in which two nazo ligands adopt an eclipsed configuration, with the third P^O ligand located trans to the phenyl group of both nazo ligands, confirming the general skeletal pattern for 1-3. In sharp contrast, complex 4 reveals a trans-disposition for the PPh_(2) groups, along with the phenolate groups residing opposite the unique cyclometalated ppy ligand, which is the representative structure for 4-6. These Ir~(III) complexes exhibit green-to-red photoluminescence with moderate to high quantum efficiencies in the degassed fluid state and bright emission in the solid state. For 1-6, the resolved emission spectroscopy and relaxation dynamics are well rationalized by the computational approach. OLEDs fabricated using 12 wt.percent of 3 doped in CBP and with BCP as hole blocking material, give bright electroluminescence with (lambda)_(max)velence628 nm and CIE_(xy) coordinates (0.65, 0.34). The turn-on voltage is 3.2 V, while the current efficiency and the power efficiency reach 11.2 cdA~(-1) and 4.5 lm W~(-1) at 20 mA cm~(-2). The maximum efficiency reaches 14.7 cd A~(-1) and 6.8 lmW~(-1) upon switching to TPBI as hole blocking material. For evaluating device lifespan, the tested device incorporating CuPc as a passivation layer, 3 doped in CTP as an emitting layer, and BAlq as hole blocking material, shows a remarkably long lifetime up to 36000 h at an initial luminance of 500 cd m~(-2).