Extended molecular design concept of molecular materials for electroluminescence: sublimed–dye films, molecularly doped polymers and polymers with chromophores

Abstract
Electroluminescent (EL) devices with multilayer structures which are composed of two or three vacuum–sublimed dye films have been shown to exhibit high device performances. The working mechanism for charge–injection–type EL devices is reviewed and then the design of dye molecules used for hole transport, electron transport and emissive layers for multilayer EL devices are summarized. It is also demonstrated that the molecular design concept of dye films is applicable for the cases of polymer–dispersed dye systems. The possibility of extension of the molecular design concept to polymers with chromophores in skeletons is discussed. In addition, the importance of the adoption of multilayer structures for obtaining high EL efficiency is discussed.