Highly simplified phosphorescent organic light emitting diode with >20% external quantum efficiency at >10,000 cd/m2

A simplified trilayer green phosphorescent organic light emitting diode with high efficiency and an ultralow efficiency roll-off has been demonstrated. In particular, the external quantum efficiency drops <1% from 100 to 5,000 cd/m(2) and remains as high as similar to 21.9% at 10,000 cd/m(2). The power efficiency is also significantly improved, reaching 78.0 lm/W at 100 cd/m(2), 50.5 lm/W at 5,000 cd/m(2), and 42.8 lm/W at 10,000 cd/m(2). The working mechanism of this simple device structure with an unprecedented high efficiency is also discussed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3532844]