The influence of the hole blocking layers on the electroluminescence stability of phosphorescent organic light emitting devices

Delayed electroluminescence (EL) measurements are used to investigate electroluminescence stability in phosphorescent organic light emitting devices (PHOLEDs) containing typical hole blocking layers (HBLs). The results show a strong correlation between the extent of hole blockage capacity of the HBL and the rate of deterioration in device EL efficiency, pointing to the major role that the build-up of hole space charges in the emitting layer (EML) plays in EL degradation. In this regard, the use of a strongly blocking material significantly increases the build-up of holes in the EML, and accelerates EL degradation.

Figure optionsDownload as PowerPoint slideHighlights
► Operational lifetimes of devices with various HBLs are studied.
► The results show a strong correlation between hole blockage capacity and the rate of deterioration in EL efficiency.
► Build-up of hole space charges in the emitting layer plays a major role in EL degradation.
► Use of a strongly blocking material (e.g. BCP) significantly accelerates EL degradation.