Enhanced Green Electrophosphorescence from Oxadiazole-Functionalized Iridium Complex-Doped Devices Using Poly(9,9-Dioctylfluorene) Instead of Poly(N-Vinylcarbazole) as a Host Matrix

Optoelectronic properties of the oxadiazole-functionalized iridium complex-doped polymer light-emitting devices (PLEDs) are demonstrated with two different polymeric host matrices at the dopant concentrations 1--8%. The devices using a blend of poly(9,9-dioctylfluorene)(PFO) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) as a host matrix exhibited a maximum luminance efficiency of 11.3cd/A at 17.6mA/cm². In contrast, the devices using a blend of poly(N-vinylcarbazole) (PVK) and PBD as a host matrix reveal only a peak luminance efficiency of 6.5cd/A at 4.1mA/cm². The
significantly enhanced electrophosphorescent emissions are observed in the devices with the PFO-PBD blend as a host matrix. This indicates that choice of polymers in the host matrices is crucial to achieve highly efficient phosphorescent dye-doped PLEDs.