Unlocking the potential of p-doped hole transport layers in inverted organic light emitting diodes

摘要

The MoO_3 doped N,N'-bis-(l-naphthyl)-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB:MoO_3 in 2:1 mass ratio) and 4,4'-N,N'-dicarbazole-biphenyl (CBP:MoO_3 in 2:1 mass ratio) as p-doped hole transport layers have been used in inverted organic light emitting diodes (IOLEDs). Compared to the NPB/20 nm NPB: MoO_3 structure, the NPB/10 nm CBP:MoO_3/10 nm NPB:MoO_3 structure showed increased device performance, mostly because the hole transport barrier from CBP:MoO_3 to NPB was smaller than that from NPB:MoO_3 to NPB; it also presented improved device performance than the NPB/20 nm CBP:MoO_3 structure, ascribed to the higher conductivity of NPB:MoO_3 than that of CBP:MoO_3. We provide a manageable way to unlock the merits of p-doped hole transport layers for markedly increasing the performance of IOLEDs.