Electroluminescent mechanism of organic multilayer thin film devices

High performance organic electroluminescent (EL) devices which are composed of organic thin multilayer films are described. The EL devices were classified into three categories and the optimization of EL cell structures was performed from the viewpoint of the electronic properties of emitter layers. The position of the emission sites in three different types of EL cells was determined by a doping method, and two important aspects in the EL mechanism for high luminance were pointed out. We concluded that high luminance was derived from the confinement of charge carriers and molecular excitons inside emitter layers. Moreover, effective confinement of charge carriers and molecular excitons within a molecular-size area was achieved in the case of double hetero structures.