Synthesis of New Heteroleptic Iridium(III) Complex Consisting of 2-Phenylquinoline and 2-[4-(Trimethylsilyl) phenyl]Pyridine for Red and White Organic Light-Emitting Diodes

A novel red iridium(III) complex, (PQ)₂Ir(TMSppy), containing 2-phenylquinoline (PQ) as the main cyclometalated ligand and 2-[4-(trimethylsilyl)phenyl]pyridine (TMSppy) as the ancillary ligand, was synthesized for use in phosphorescent organic light-emitting diodes (OLEDs). (PQ)₂Ir(TMSppy) had a red emission with a maximum emission wavelength (λ_max) at 603 nm. To investigate the (PQ)₂Ir(TMSppy) as a red emitter in OLEDs, we fabricated a device with a multi-layer architecture. The (PQ)₂Ir(TMSppy) device showed an electroluminescence (EL) maximum emission peak at 612 nm and showed a maximum quantum efficiency (EQE_max) of 15.5% at a 10% doping concentration. In addition, white OLEDs, having three primary color components, made from (PQ)₂ Ir(TMSppy) with bis(4,6-difluorophenylpyridine)picolinate (Flrpic) and tris(2-phenylpyridinato-C²,N)iridium(III) (Ir(ppy)₃) gave the best performances, with an EQE_max of 18.1%, maximum power efficiency (PE_max) of 22.8 lm/w, and maximum current efficiency (CE_max) of 36.5 cd/A with Commission Internationale de LEclairage coordinates of (0.39,0.42) at a luminance of 1,000 cd/m².