White light emitting electrophosphorescent devices with solution processed emission layer

Abstract

White light emitting diodes with high efficiency and brightness have been fabricated using phosphorescent materials by spin coating an emission layer. The emission layer consisted of sky blue and orange light emitting materials based on iridium complexes, which were dissolved in toluene solvent with 4,4'-bis#carbazoyl-9-yl#biphenyI #CBP# as a host and polystyrene as a binder. The introduction of polystyrene binder resulted in not only good film forming properties but also better device performance than that of poly#vinyl carbazole# conventionally used as a host material. The device structure was ITO/ PEDT: PS S /emission layer/BAlq/LiF/Al. The color of the devices varied according to the composition of light emitting materials and the device having the closest to white emission showed CIE coordinates of #0.33,0.39# with an external quantum efficiency and a current efficiency of 6.1% and 13 cd/A, respectively, at 100 cd/m#2#.