Efficiency improvement of blue phosphorescent organic light emitting diodes by using a stacked emitting structure

Quantum efficiency of blue phosphorescent organic light emitting diodes (PHOLEDs) was improved by using a stacked emitting structure which can balance holes and electrons in light emitting layer. N,N′-dicarbazolyl-3,5-benzene (mCP) doped with iridium(III) bis(4,6-(di-fluorophenyl)-pyridinato-N,C2′) picolinate (FIrpic) was used as an emitting layer with good hole injection properties near hole transport layer and 1,3-bis(triphenylsilyl)-benzene (TSB) doped with FIrpic was used as an emitting layer with good electron injection properties near electron transport layer. High quantum efficiency of 10.2% was obtained at 500 cd/m2 compared with 7.5% and 7.6% of mCP and TSB reference devices.