Tailoring the hole-injection layer in organic light-emitting devices by introducing Au@SiO₂ nanoparticles

A simple and efficient method to improve the internal and external quantum efficiency of phosphorescent organic light-emitting devices (PhOLEDs) is demonstrated, i.e., combining the localized surface plasmon (LSP) and optical scattering effects by introducing gold nanoparticles (NPs) coated by SiO₂ (named as Au@SiO₂). The effects of LSP and optical scattering on PhOLEDs are studied. The lifetime of the triplet exciton in the device is modified by surface plasmon coupling induced by Au@SiO₂ NPs, which results in increased internal quantum efficiency of the NP-containing devices. The optical scattering effect induced by Au@SiO₂ NPs enhances the light outcoupling efficiency of the PhOLEDs and is demonstrated by measuring the angularly resolved photoluminescence. As a result, a PhOLED with 101% improved efficiency and 21% reduced efficiency roll-off is achieved using the composite HTL.