Robust Tris-Cyclometalated Iridium(III) Phosphors with Ligands for Effective Charge Carrier Injection/Transport: Synthesis, Redox, Photophysical, and Electrophosphorescent Behavior

With the target to design and develop new functionalized green triplet light emitters that possess distinctive electronic properties for robust and highly efficient phosphorescent organic light-emitting diodes (PHOLEDs), a series of bluish-green to yellow-green phosphorescent tris-cyclometalated homoleptic iridium(III) complexes [Ir(ppy-X)(3)] (X=SiPh3, GePh3, NPh2, POPh2, OPh, SPh, SO2Ph, Hppy=2-phenylpyridine) have been synthesized and fully characterized by spectroscopic, redox, and photophysical methods. By chemically manipulating the lowest triplet-state character of Ir(ppy)(3) with some functional main-group 14-16 moieties on the phenyl ring of ppy, a new family of metallophosphors with high-emission quantum yields, short triplet-state lifetimes, and good hole-injection/hole-transporting or electron-injection/electron-transporting properties can be obtained. Remarkably, all of these Ir-III complexes show outstanding electrophosphorescent performance in multi-layer doped devices that surpass that of the state-of-the-art green-emitting dopant Ir(ppy)(3). The devices described herein can reach the maximum external quantum efficiency (eta(ext)) of 12.3\%, luminance efficiency (eta(L)) of 50.8 cd A(-1), power efficiency (eta(p)) of 36.9 Lm W-1 for [Ir(ppy-SiPh3)(3)], 13.9\%, 60.8 cd A(-1), 49.1 Lm W-1 for [Ir(ppy-NPh2)(3)], and 10.1\%, 37.6 cd A(-1), 26.1 Lm W-1 for [Ir(ppy-SO2Ph)(3)]. These results provide a completely new and effective strategy for carrier injection into the electrophosphor to afford high-performance PHOLEDs suitable for various display applications

Metallophosphors of platinum with distinct main-group elements: a versatile approach towards color tuning and white-light emission with superior efficiency/color quality/brightness trade-offs

A new series of phosphorescent platinum(II) cyclometalated complexes with distinct electronic structures has been developed by simple tailoring of the phenyl ring of ppy (Hppy = 2-phenylpyridine) with various main-group moieties in [Pt(ppy-X)(acac)] (X = B(Mes)(2), SiPh3, GePh3, NPh2, POPh2, OPh, SPh, SO2Ph substituted at the para position). Their distinctive electronic characters, resulting in improved hole-injection/hole-transporting or electron-injection/electron-transporting features, have confined/consumed the electrons in the emission layer of organic light-emitting diodes (OLEDs) to achieve good color purity and high efficiency of the devices. The maximum external quantum efficiency of 9.52\%, luminance efficiency of 30.00 cd A(-1) and power efficiency of 8.36 lm W-1 for the OLEDs with Pt-B (X = B(Mes)(2)) as the emitter, 8.50\%, 29.74 cd A(-1) and 19.73 lm W-1 for the device with Pt-N (X NPh2), 7.92\%, 22.06 cd A(-1) and 13.64 lm W-1 for the device with Pt-PO (X POPh2) as well as 8.35\%, 19.59 cd A(-1) and 7.83 lm W-1 for the device with Pt-SO2 (X = SO2Ph) can be obtained. By taking advantage of the unique electronic structures of the Pt-Ge (X = GePh3) and Pt-O (X = OPh) green emitters and the intrinsic property of blue-emitting hole-transport layer of 4,4'-bis[N-(1-naphthyl)- N-phenylamino] biphenyl (NPB), single-dopant white OLEDs (WOLEDs) can be developed. These simple WOLEDs emit white light of very high quality (CIE at (0.354, 0.360), CRI of ca. 97 and CCT at 4719 K) even at high brightness (>15000 cd m(-2)) and the present work represents significant progress to address the bottle-neck problem of WOLEDs for the efficiency/color quality/brightness trade-off optimization that is necessary for pure white light of great commercial value