Spatial separation of two blue triplet emitters for improved lifetime in blue phosphorescent organic light-emitting diodes by confining excitons at the interface between two emitting layers

A device architecture to improve the lifetime of blue phosphorescent organic light-emitting diodes was developed using a double emitting layer structure with different blue triplet emitters in each emitting layer. The two emitters were chosen to have a similar light-emission spectrum, but different carrier trapping properties. An electron trapping type blue triplet emitter was doped in the first emitting layer and a hole trapping type blue triplet emitter was doped in the second emitting layer to control the emission zone of the blue phosphorescent organic light-emitting diodes. The device engineering using the spatially separated two emitters resulted in the lifetime improvement by more than 6 times compared to that of a single emitting layer device.