Enhancement of Electroluminescent Green Emission by Far-Field Coupling of Au Nanoparticles in Organic Light Emitting Diodes

Far-field surface plasmon enhanced green electroluminescence in organic light-emitting devices (OLEDs) is harvested by tuning the gold nanoparticles (Au NPs) density at the interface of the anode:hole transport layer (HTL) in OLEDs using Ir­(DMSPI)₂(acac) as emissive layer. Au NPs increases the hole injection with 35/μm² density at the indium tin oxide (ITO):N,N′-di-1-naphthyl-N,N′-diphenylbenzidine (NPB) interface and leads to enhanced emission intensity as a result of increased radiative rate (k_r). The Au NPs modified anode in OLEDs injects holes effectively into the NPB layer and stabilizes its energy level which results in an increase of current density. The reduced hole injection barrier (HIB) was analyzed by using the Richardson–Schottky equation. The far-field plasmonic coupling with hole injection ability of Au NPs at the ITO:HTL interface enhanced the device efficiencies at low turn-on voltage in this work. However, the anode with 6.0/μm² density of Au NPs shows poor hole injection ability into the HTL due to trapping of holes at the interface.