Abstract
Highly efficient and stable phosphorescent organic-light emitting diodes (PHOLEDs) were demonstrated in view of optimization of emitting and/or carrier transporting materials. The device characteristics of the red PHOLED was improved by selecting a host material, which surrounds the phosphorescent dopant. The host/dopant combination was found to be a crucial factor in obtaining high efficiency and stability in the PHOLEDs. On the other hand, the novel hole-transporting materials were synthesized to improve the efficiency and operational stability of green PHOLEDs. The optimized red and green OLEDs exhibit a maximum external quantum efficiency of about 20% and an expected half lifetime of over 10,000 h with an initial luminance of 1,000 cd/m2.
