title: Syntheses, photophysics, and application of iridium(III) phosphorescent emitters for highly efficient, long-life organic light-emitting diodes.
abstract: 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)=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 PPh2 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. % of 3 doped in CBP and with BCP as hole blocking material, give bright electroluminescence with lambda(max)=628 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 cd A(-1) and 4.5 lm W(-1) at 20 mA cm(-2). The maximum efficiency reaches 14.7 cd A(-1)and 6.8 lm W(-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 36,000 h at an initial luminance of 500 cd m(-2).
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan.
authors.forename: Tsang-Chi
authors.initials: TC
authors.lastname: Lee
authors.forename: Chiung-Fang
authors.initials: CF
authors.lastname: Chang
authors.forename: Yuan-Chieh
authors.initials: YC
authors.lastname: Chiu
authors.forename: Yun
authors.initials: Y
authors.lastname: Chi
authors.forename: Tzu-Ying
authors.initials: TY
authors.lastname: Chan
authors.forename: Yi-Ming
authors.initials: YM
authors.lastname: Cheng
authors.forename: Chin-Hung
authors.initials: CH
authors.lastname: Lai
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Chen-Han
authors.initials: CH
authors.lastname: Chien
authors.forename: Ching-Fong
authors.initials: CF
authors.lastname: Shu
authors.forename: Jens
authors.initials: J
authors.lastname: Leonhardt