Characteristics of blue organic electroluminescent devices with distyryl arylene derivatives

Abstract
We have studied organic electroluminescence (EL) characteristics for a multilayer thin film cell with distyryl arylene derivatives (DSA) as emitting materials. We found that it is very important for an emitting layer not to form exciplex or charge transfer complex (ECT) with the hole transporting layer (diamine derivatives) in addition to an ability to form a good thin film. In this paper, we report a new series of DSA not to form the ECT with the hole transporting layer owing to the molecular conformation. We substituted two hydrogen atoms for two phenyl rings and designed some new DSA which are not planar. These DSA are intense blue fluorescent materials and have good film-forming ability. A cell with ITO/hole transporting layer/emitting layer/Mg:Ag was fabricated by vacuum evaporation technique. We obtained bright emission more than 1000 cd/m2 with dc voltage of less than 12 V and high luminous efficiency about 0.6 lm/W at 1000 cd/m2 for several kinds of DSA as emitting materials. In these cells we successfully avoid ECT formation at the interface between the hole transporting layer and the emitting layer.