New Mixed-C^N Ligand Tris-cyclometalated Ir(III) Complexes for Highly-Efficient Green Organic Light-Emitting Diodes with Low Efficiency Roll-off

This article reports new tris‐cyclometalated Ir complexes containing mixed‐C^N ligands, (C^N1)2Ir(C^N2), which are a rarely explored class of Ir(III) complexes. Two new mixed 2‐phenylpyridine (ppy) / 4‐methyl‐2,5‐diphenylpyridine (mdp) complexes (ppy)2Ir(mdp) and (ppy)Ir(mdp)2 have been synthesized and their optoelectronic properties have been systematically characterized. Photoluminescence quantum yield values are 0.76‐0.85; excited state lifetimes are 0.07‐0.11 μs. Phosphorescent organic light emitting devices (PhOLEDs) based on these emissive complexes in a very simple device architecture reproducibly showed slightly higher external quantum efficiency (EQE) and power efficiency (PE) values compared with devices using the analogous conventional homoleptic Ir complexes Ir(ppy)3 and Ir(mdp)3, and the heteroleptic complexes (ppy)2Ir(acac) and (mdp)2Ir(acac). The new complexes (ppy)2Ir(mdp) 3 and (ppy)Ir(mdp)2 4 give PhOLEDs with EQEmax and PEmax values of 26.7 and 26.0% / 94.7 and 94.1 lm W−1, respectively, and very high values are retained at the practical luminances of 100 and 1000 cd m−2. The values for (ppy)2Ir(mdp) are 26.3% and 73.6 lm W−1 (at 100 cd m−2) and 24.6% and 53.5 lm W−1 (at 1000 cd m−2). These efficiencies are comparable with the highest reported values of PhOLEDs using conventional Ir(III) emitters in more complicated device structures. Mixed C^N ligand systems are, therefore, a viable strategy for developing new efficient phosphorescent emitters

mer-Bis[3,5-difluoro-2-(2-pyrid­yl)phenyl-κ2 C 1,N]{5-(2-pyridyl-κN)-3-[3-(4-vinyl­benz­yloxy)phen­yl]-1,2,4-triazol-1-ido}iridium(III) methanol solvate

In the title compound, [Ir(C11H6F2N)2(C22H17N4O)]·CH3OH, the coordination at iridium is essentially octa­hedral, but with distortions associated with the bite angles of the ligands [76.25 (9)–80.71 (12)°] and the differing trans influences of C and N ligands [Ir—N = 2.04 Å (average) trans to N but 2.14 Å trans to C]. All three bidentate ligands have coordinating ring systems that are almost coplanar [inter­planar angles = 1.7 (1)–3.8 (2)°]. The vinyl­benzyl group is disordered over two positions with occupations of 0.653 (4) and 0.347 (4). The methanol solvent mol­ecule is involved in a classical O—H⋯N hydrogen bond to a triazole N atom

Phosphorescent Organic Light-Emitting Devices: Working Principle and Iridium Based Emitter Materials

Even though organic light-emitting device (OLED) technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs), further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting special focus on the general working principle of single and multilayer OLEDs, fluorescent and phosphorescent emitter materials as well as transfer processes in host materials doped with phosphorescent dyes. Moreover, as a prototypical example of phosphorescent emitter materials, a brief discussion of homo- and heteroleptic iridium(III) complexes is enclosed concentrating on their synthesis, photophysical properties and approaches for realizing iridium based phosphorescent polymers

New oxazoline- and thiazoline-containing heteroleptic iridium(III) complexes for highly-efficient phosphorescent organic light-emitting devices (PhOLEDs) : colour tuning by varying the electroluminescence bandwidth.

Two new homologous phosphorescent iridium complexes, bis-(2-phenylpyridine)(2-(2′-hydroxyphenyl)-2-oxazoline)iridium(III) [(ppy)2Ir(oz)] (1) and bis-(2-phenylpyridine)(2-(2′-hydroxyphenyl)-2-thiazoline)iridium(III) [(ppy)2Ir(thoz)] (2), have been obtained in good yields and characterized by single-crystal X-ray diffraction, cyclic voltammetry, photoluminescence and electroluminescence studies, and by time-dependent density functional theory (TD-DFT) calculations. Using the two complexes, which differ only by the heteroatom (O or S) substitution at the same site in the ancillary ligand, as the emitter, doped in a 4,4′-bis(N-carbazolyl)biphenyl (CBP) host, gave phosphorescent organic light-emitting diodes (PhOLEDs) with very efficient green and yellow emission, respectively. The turn-on voltages for both devices are low (3.5–3.7 V). The green-emitting (ppy)2Ir(oz) – based device has a maximum brightness of 61560 cd m−2 (at 16 V); maximum luminance efficiency of 66.2 cd A−1, 17.1% external quantum efficiency, 54 lm W−1 power efficiency and CIE coordinates of (0.35, 0.61) at a brightness of 10000 cd m−2. For the yellow-emitting (ppy)2Ir(thoz)-based device with a wide full spectral width at half maximum (FWHM) of 110 nm, the corresponding values are 21350 cd m−2 (at 14.5 V); 27.0 cd A−1, 8.5%, 18.0 lm W−1 and CIE coordinates of (0.46, 0.50). Colour tuning is primarily a consequence of the significantly wider emission bandwidth of complex 2 compared to complex 1