Sky‐blue and blue‐emitting, carbazolyl functionalized, bis‐tridentate Ir(III) phosphors Cz‐1–Cz‐3 with bright emission and short radiative lifetime are successfully synthesized in a one‐pot manner. They exhibit very high photostability against UV–vis irradiation in degassed toluene, versus both green and true‐blue‐emitting reference compounds, i.e., fac‐[Ir(ppy)3] and mer‐[Ir(pmp)3]. Organic light‐emitting diodes (OLEDs) based on Cz‐2 exhibit maximum external quantum efficiency (EQE) of 21.6%, EQE of 15.1% at 100 cd m−2, and with CIEx , y coordinates of (0.17, 0.25). This study provides a conceptual solution to the exceedingly stable and efficient blue phosphor. It is promising that long lifespan blue OLED based on these emitters can be attained with further engineering of devices suitable for commercial application.

There is growing interest in the bis-tridentate Ir(III) emitters as they are expected to display both improved emission efficiency and improved photostability. Herein, we turned to the new emitters m2h-1−3 and m6h-1−3, bearing a pincer carbene ancillary and a chromophoric chelate derived from judiciously selected phenyl-pyrimidine-pyrazole entities (pzm2h F )H 2 and (pzm6h F )H 2 , which differ in terms of the location of phenyl and pyrazole substituents on the central pyrimidine. Density functional theory calculations revealed a notable change in the spin density distribution from the pyrimidine-pyrazolate entity in m2h to the pyrimidine-phenyl fragment in m6h. As a consequence, the m6h emitters exhibited both shortened emission lifetimes and improved stabilities during extensive photolysis in solution, while corresponding organic light-emitting diodes (OLEDs) doped with green-emitting m6h-1 and sky-blue-emitting m6h-2 and m6h-3 exhibited external quantum efficiencies of 17.6, 15.9, and 17.6%, respectively, superior to those of all of their m2h counterparts at a practical luminance of 10 3 cd/m 2 . This finding suggests a new methodology for fine-tuning the electronic transition that is important to high-performance and durable phosphorescent OLEDs. 49 increase of the emitting excited state energy, which is needed 50 to achieve blue emission, also reduces the energy separation 51 between this emitting excited state and the upper-lying metal-52 centered (MC) dd states. These quenching states are capable 53 of fostering a fast nonradiative decay, giving an unsatisfactory 54 efficiency. 19−21 Notably, one method for blocking this 55 nonradiative process is to employ metal phosphors with a 56 bis-tridentate architecture, 22−24 for which the imposed higher 57 rigidity and multiple metal−chelate coordination bonding are 58 expected to offer higher ligand-field strength and, hence, a 59 much destabilized MC dd excited state and more efficient blue 60 emission.

This review is aimed at the current research progression of a unique class of Pt(II) metal complexes bearing at least one azolate‐containing bidentate chelate. The azole fragment can link to a neutral heteroaromatic entity or another azole and form bidentate chelates, such as monoanionic 3‐pyridyl‐1H‐pyrazole and derivatives, dianionic 3,3′‐bi‐1H‐pyrazole, 3,3′‐(1‐methylethylidene)‐bis‐1H‐pyrazole, and their analogs. These azole‐containing chelates readily react with a variety of Pt(II) reagents to afford the corresponding bis‐bidentate Pt(II) complexes. Most of them were highly emissive in solution, doped polymer matrix, thin film, and even as crystal or powder, due to the high ligand field strength exerted by these chelates and their high propensity in forming the singular square‐planar architecture and intermolecular aggregates with substantially strengthened Pt⋯Pt interaction, according to their structural design. Therefore, they hold bright prospects in academic research and future optoelectronic applications such as organic light‐emitting diodes.