High-performance tandem organic light-emitting diodes based on a buffer-modified p-type planar organic heterojunction as charge generation layer

摘要

High-performance tandem organic light-emitting diodes (TOLEDs) were realized using a buffer-modified p-type planar organic heterojunction (OHJ) as charge generation layer (CGL) consisting of common organic materials,and the configuration of this p-type CGL was "LiF/N,N'-diphenyl-N,N'-bis(1-napthyl)-1,1 '-biphenyl-4,4'-diamine (NPB)/4,7-diphenyl-l,10-phenanthroline (Bphen)/ molybdenum oxide (MoO_x)".The optimized TOLED exhibited a maximum current efficiency of 77.6 cd/A without any out-coupling techniques,and the efficiency roll-off was greatly improved compared to the single-unit OLED.The working mechanism of the p-type CGL was discussed in detail.It is found that the NPB/Bphen heterojunction generated enough charges under a forward applied voltage and the carrier extraction was a tunneling process.These results could provide a new method to fabricate high-performance TOLEDs.