Improving the efficiency of organic electroluminescent devices by introducing an electron-accepting and thermally stable polymer

A new hole-transporting material for multi-layer organic electroluminescent devices (OELDs) was prepared by the copolymerization of a hole-transporting material (9-vinyl carbazole) and an electron-retarding material (bis-4-vinyl-benzyl-4,4'-dipyridinium chloride). The resulting polymer has good thermal stability and electron-retarding property, due to its chemical structure and the 4,4'-dipyridyl groups, respectively. The OELDs were fabricated with a multi-layer structure of an anode/new polymeric hole-transporting layer (HTL)/emitter/cathode. It was found that the electroluminescence efficiency was improved by using an electron-retarding material in a HTL.