High color rendering white organic light-emitting diodes fabricated using a broad-bandwidth red phosphorescent emitter for lighting applications

High color rendering white organic light-emitting devices (WOLEDs) were developed using a broad-bandwidth red phosphorescent iridium complex, bis[2-(1-naphthyl)benzothiazolato-N,C²′]iridium(III) acetylacetonate [Ir(absn)₂(acac)]. The red phosphorescent emitter Ir(absn)₂(acac) was used to fabricate blue-red and blue-green-red WOLEDs by combining blue-emitting bis[2-(4,6-difluorophenyl)pyridinato-N,C ²′]iridium(III) picolinate (FIrpic) and green-emitting tris-fac-(2-cyclohexenylpyridine) iridium (III) [Ir(chpy)₃] in multiple-emissive layers. Mixed host emissive layers were employed using a hole-transport-type host 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA) and an electron-transport-type host 2,6-bis[3-(carbazol-9-yl)phenyl] pyridine (DCzPPy) for efficient charge carrier injection. Di-[4-(N,N-ditolyl- amino)-phenyl]cyclohexane (TAPC) and 1,3-bis(3,5-dipyrid-3-yl-phenyl)benzene (BmPyPB) were used as the hole and electron transporting layers, respectively. The effects of the emissive layer thickness and the doping ratios of different color dopants on WOLED performances were investigated. The WOLED based on ITO/TAPC/TCTA:FIrpic (10%):Ir(absn)₂(acac) (4%)/TCTA:Ir(chpy) ₃ (9%, 6 nm)/DCzPPy:FIrpic (13%):Ir(absn)₂(acac) (4%)/BmPyPB/LiF/Al exhibited an external quantum efficiency of 10.7%, a power efficiency of 23.0 lm/W, a very high color rendering index (CRI) of 88.1, and a correlated color temperature (CCT) of 2629 K at 1000 cd/m².