Highly efficient and color stable phosphorescent white light-emitting diodes by using a charge confining emitting layer structure

Quantum efficiency of white phosphorescent organic light-emitting diodes was improved by using a device architecture to confine charges inside an emitting layer. The charge confinement was achieved by stacking two emitting layers with different charge transport properties. An emitting layer with electron transport type host was stacked on an emitting layer with hole transport type host. A maximum quantum efficiency of 18.3% and a current efficiency of 31.5 cd/A were achieved with a color coordinate of (0.38,0.36). In addition, there was little change in the emission spectra from 200 to 10,000 cd/m₂.