Organic electroluminescent devices with improved stability

Highly stable organic electroluminescent devices based on vapor-deposited Alq thin films have been achieved. The improvement in stability is derived from several factors including: (1) a multilayer thin-film structure with a CuPc stabilized hole-injection contact, (2) a hole-transport diamine layer using a naphthyl-substituted benzidine derivative, and (3) an ac drive wave form. These emissive devices have shown an operational half-lifetime of about 4000 h from an initial luminance of 510 cd/m2.