Highly efficient all phosphorescent white organic light-emitting diodes for solid state lighting applications

•Highly efficient all phosphorescent white OLEDs were developed.•Effective charges and exciton confinements were achieved by stacking two EMLs.•White OLEDs with an EQE and PE of 24.3% and 45.9 lm/W at 1000 nits were obtained.

We report highly efficient all phosphorescent white organic light-emitting diodes (OLEDs) with an exciton-confinement structure. By stacking two emissive layers (EMLs) with different charge transporting properties, effective charges as well as exciton confinements were achieved. Accordingly, efficient blue OLEDs with a peak external quantum efficiency (EQE) over 22% and power efficacy (PE) over 50 lm/W were developed by using iridium(III) bis(4,6-(difluorophenyl) pyridinato-N,C2′)picolinate (FIrpic) as an electro-phosphorescent dopant. When the optimized orange and red EMLs were sandwiched between the stacked two blue EMLs, white OLEDs with an EQE and PE of 24.3% and 45.9 lm/W at a luminance of 1000 cd/m2 were obtained without the use of any out-coupling techniques. In addition, these white OLEDs exhibit a color rendering index (CRI) value of 84 with high efficacy.