The syntheses, structures, photophysical, and electroluminescent properties of three green emitting heteroleptic cyclometalated iridium(III) complexes, (ptfmppy)
2Ir(pic) (Ir1), (dfptfmppy)
2Ir(pic) (Ir2), and (tfptfmppy)
2Ir(pic) (Ir3) [ptfmppy = 5‐(trifluoromethyl)‐2‐(phenyl)pyridine, dfptfmppy = 5‐(trifluoromethyl)‐2‐(2,4‐difluorophenyl) pyridine, tfptfmppy = 5‐(trifluoromethyl)‐2‐(2,3,4‐difluorophenyl)pyridine, and picH = picolinic acid] and the results of an investigation on their suitabilities for phosphorescent organic light‐emitting diodes (phOLEDs) applications are reported. X‐ray single crystal structures showed that iridium(III) cations in Ir1 and Ir2 adopted six‐coordinated geometries involving two C and two N atoms from substituted‐ppy, and one N and one O atom from pic, which produced a distorted octahedral geometry. Photoluminescence (PL) spectra revealed that the synthesized iridium(III) complexes exhibited emissions at 497 ~ 534 nm in dichloromethane with high photoluminescence quantum yield (PLQY) ranging from 60 to 67%, and TGA experiments showed that they had good thermal stabilities. In Ir3, the conjugation effect rather than the electronic effect of the 3‐positioned fluorine atom on phenyl ring of ppy increased the HOMO energy level causing bathochromic shifts. Electroluminescent devices of ITO(110 nm)/PEDOT:PSS (40 nm)/PVK:TCTA:OXD‐7:Ir (80 nm)/TmPyPB (20 nm)/Al (100 nm) were fabricated using the iridium(III) complexes as phosphors in an emitting layer, and their electroluminescent performances were investigated.
New orange–yellow phosphorescent cyclometalated iridium(III) complex, (bt)2Ir(btz), where btH = 2‐phenylbenzothiazole and btzH = 2‐(2‐hydroxyphenyl)benzothiazole, was synthesized, and its structural, photophysical and electroluminescence properties were investigated to apply for organic light‐emitting diodes (OLEDs) applications. The coordination geometry around iridium metal ion was distorted octahedral, exhibiting cis‐C, C′ and trans‐N, N′ chelate dispositions with narrow ligand bite angles ranging from 79.7° (2) to 84.5° (1). The optical properties revealed that the π‐conjugated nature of bt ligand caused a bathochromic shift in emission and btz ligand played a role in fine color tuning. The synthesized (bt)2Ir(btz) was soluble in common organic solvents and the emitting layer was readily spin‐coated in chlorobenzene solution onto substrate. The OLED fabricated with the configuration of ITO/PEDOT:PSS/PVK:TCTA:OXD‐7: (bt)2Ir(btz) (32:32:28:8)/Bphen/LiF/Al exhibited a maximum external quantum efficiency (EQE) of 4.67% and a maximum luminance efficient (LE) of 8.61 cd/A with CIE (x, y) coordinates of (0.54,0.45).
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