Applying a Nanoantenna Array on Metal To Improve the Efficiency of Phosphorescent OLEDs at High Luminance

Abstract

Phosphorescent organic light-emitting diodes (OLEDs) are suitable for display and lighting applications due to their superior luminance and efficiency. However, the strong efficiency roll-off severely hinders their potential applications in transparent displays, virtual reality, and other high-luminance-demanding fields, which is mainly attributed to severe triplet–triplet annihilation (TTA) and triplet-polaron quenching (TPQ). In this study, by employing a thin Ag anode close to the phosphorescent emitter, a Purcell factor over 5 has been achieved, nearly triple that of a conventional indium tin oxide (ITO)-based device. This enhancement significantly accelerates the exciton decay rate and reduces exciton concentration, thereby considerably lowering the incidence of TTA and TPQ. Meanwhile, such devices are capable of nearly eliminating waveguide modes, with over 77% of the energy being coupled into a surface plasmon polariton (SPP). A nanoantenna array on metal (NAoM), situated on the exterior surface of the thin Ag anode, efficiently extracts the SPP when the plasmonic antenna modes resonate with the gap modes within the NAoM. This configuration yields an efficiency enhancement of 100% at 40,000 cd/m² compared to conventional phosphorescent devices with similar structures, providing a promising avenue for high-luminance phosphorescent OLED.