Organic Light-Emitting Diodes with Carrier Balance Structures

Organic light-emitting diodes (OLEDs) with high luminance efficiency were successfully fabricated using the LiF/N,N'-bis(1-naphyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) carrier balance structures. It was found that the insertion of the LiF/NPB carrier balance structures can balance the charge injection and transport, which is helpful in enhancing the performance of OLEDs. It was also found that we can achieve the best performance from the OLED with three pairs of LiF/NPB (0.3 nm/15 nm) structures. The luminance and transport efficiency were both enhanced with the increase in the numbers of pairs of LiF/NPB carrier balance structures. We can attribute the improvement to the better carrier balance at the device interface. (C) 2011 The Japan Society of Applied Physics