Eliminating Surface Plasmon Polariton Modes in Thin Film Light-Emitting Diodes through Planar Metamaterials

Thin film light-emitting diodes (LEDs) traditionally employ metal mirrors as electrodes to inject carriers into active layers and efficiently redirect photons. However, undesired surface plasmon polaritons (SPPs) excited by emitters on the surface of metal mirrors induce energy dissipation and limit the optical outcoupling efficiency. An artificial optical metamaterial between the metal mirror and the emitting layer can manipulate the equifrequency surface of electromagnetic waves. Theoretical calculation predicts that the existence of SPP modes can be disrupted when metamaterials possess highly anisotropic type I hyperbolic or effective dielectric dispersion. The metamaterials can be realized through metal-dielectric multilayers, whose fabrication only needs a common coating process. The prism coupling experiment confirmed the elimination of SPP modes on the metal mirror surface after the introduction of the metamaterial. Moreover, the metallic components within the metamaterials can seamlessly substitute traditional metal mirrors as electrodes without compromising the electrical characteristics of the devices. Consequently, metamaterials have the potential to enhance the outcoupling efficiency, making them promising candidates for implementation in solid-state LEDs.