Energy Barrier Reduction and Exciton Confinement Using an Intermediate Blocking Layer in Organic Light-Emitting Diodes

The intermediate blocking layer (IBL) was investigated for the development of highly efficient and bright organic light-emitting diodes (OLEDs). The insertion of an IBL between a hole transport layer and an emitting layer (EML) has resulted in the development of highly efficient and bright OLEDs. The quantum efficiency and electrical durability at high voltage were highly dependent on the thickness of the IBL. The maximum external quantum efficiency of the devices with a 1.5-nm-thick IBL was increased by 28% compared with the reference. The enhanced performance of the OLEDs appears to be due to the improvement of carrier balance and exciton confinement.