Design and Synthesis of Pyrimidine-Based Iridium(III) Complexes with Horizontal Orientation for Orange and White Phosphorescent OLEDs.

Two phosphorescent Ir(III) complexes Ir(ppm)2(acac) and Ir(dmppm)2(acac) were synthesized and characterized with emission ranged at 584/600 nm and high photoluminescence quantum yields (PLQYs) of 0.90/0.92, respectively. The angle-dependent PL spectra analysis reveals that the two orange iridium(III) complexes embodied horizontal orientation property. The high photoluminescence quantum yield and high horizontal dipoles ratio determine their excellent device performance. The devices based on Ir(ppm)2(acac) and Ir(dmppm)2(acac) achieved efficiencies of 26.8% and 28.2%, respectively, which can be comparable to the best orange phosphorescent devices reported in the literature. Furthermore, with the introduction of FIrpic as sky-blue emitter, phosphorescent two-element white organic light-emitting devices (OLEDs) have been realized with external quantum efficiencies (EQEs) as high as 25%, which are the highest values among the reported two-element white OLEDs.