Polycrystallization phenomena of organic alloy and multilayer structures on naphthyl-substituted diamine-based hole transport layer for organic light-emitting diode

We demonstrated the poycrystallization process of N,N'-di(1-naphthyl)-N,N'-diphinyl-1,1'-diphenyl-1,4'-diamine (NPD) and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-dipheyl-4,4'-diamine (TDP), which is well known as a hole transport material, and the availablility of the organic alloy method fabricated by co-evaporation method. We fabricated multi-layer structure of NPD and TPD: especially bilayer as a basic and typical structure. One is TPD layer on NPD layer (T/N specimen) and the kkother is NPD layer on TPD layer (N/T specimen). The polycrystallization of bilayer structure specimens is suppressed as compared with organic NPE:TPD-1:1 alloy specimen. Especially the T/N specimen is found to be stable in an amorphous region. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.