Obvious Efficiency Enhancement Of Organic Light-Emitting Diodes By Parylene-N Buffer Layer

A parylene-N (PPXN) buffer layer inserted between anode and organic layers in typical organic light-emitting diodes (OLEDs) based on N, N'-bis(naphthalene-1-yl)-N, N'-bis(phenyl) benzidine (NPB) and tris (8-hydroxyquinolato) aluminum (Alq(3)) results in significant enhancement of the current efficiency. The enhancement can be 1.7 times higher compared to that of the buffer-free structure. Analyzing indicates that the buffer plays a role of blocking both the hole and electron current. Whether hole injection can be enhanced depends on electron accumulation at the buffer-organic interface. Inserting the PPXN buffer modifies carrier balance in the device, leading to the observed efficiency enhancement. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704365]