Highly efficient non-doped orange-red phosphorescent organic light-emitting devices based on a novel iridium complex

Abstract

The non-doped orange-red phosphorescent organic light-emitting device (PHOLED) based on a newly synthesized iridium complex, bis[2-(biphenyl-4-yl)benzothiazole-N,C2']iridium(III)(acetylacetonate) [(4Phbt)2Ir(acac)] has been demonstrated. The non-doped device with (4Phbt)2Ir(acac) as the emissive layer achieved ideal turn-on voltage (<4 V) and superior power efficiency (5 lm/W) as well as luminance efficiency (6 cd/A), respectively. Our device performance indicates that (4Phbt)2Ir(acac) possesses excellent self-quenching-resistant property. The potential of this property is originated from the introduction of bulky and twisted aromatic substituents in ligands, which break the molecular planarity and obstruct the molecular packing. Besides, the high electroluminescence efficiency is also attributed to that the energy level alignment between (4Phbt)2Ir(acac) and adjacent charge-transporting materials forms a well-like structure, which confines exciton effectively in emissive layer.