Effect of Charge-transporting Molecules on Electrophosphorescence in a Device Fabricated Using Third-generation Dendrimer Encapsulated Tris[2-benzo[b]thiophen-2-ylpyridyl]iridium Complex

Abstract

We have synthesized a new deep-red light-emitting phosphorescent third-generation dendrimer with hole-transporting carbazole dendrons. The new dendrimer is highly efficient when used as a solution-processable emitting material and when used in an electrophosphorescent light-emitting diode system. We selected 4,4'-bis(9-carbazolyl)-1,1'-biphenyl (CBP) and 2-(1,1'biphenyl-4-yl)-5-(4-tert-butylphenyl)- 1,3,4-oxadiazole (PBD) as guest molecules in order to manipulate the carrier transport and carrier confinement in the emissive layer. We fabricated a dendrimer light-emitting diode (DLED) whose configuration is represented as ITO/PEDOT:PSS (40 nm)/dendrimer containing guest molecules (55 nm)/BCP (2,9-dimethyl-4,7-diphenylphenanthroline) (10 nm)/Alq(3) (40 nm)/LiF (1 nm)/Al (100 nm) and investigated the device performance. The luminance of the multilayered devices fabricated using the PBD-containing dendrimer was 381 cd/m(2) at 52.42 mA/cm(2) (20 V) for the dendrimer hearing PBD, which was slightly better than that of a device fabricated using dendrimer alone.