Wave propagation and resonance in four-layer systems for organic light-emitting diodes

Wave propagation and surface plasmon resonance are examined in four-layer optical systems in slab geometry for an OLED (organic light-emitting diode) with an embedded thin metal film. For this purpose, both leaky and bound modes are examined in all ranges of the propagation constant, which determines how surface and volume waves are allowed. Intensive parametric studies are performed on the thicknesses of the two embedded layers, along with the cathode condition and the metal's material dispersion. As a way of interpreting the results, the direction of the depthwise wave propagation is examined in connection with possible excitations arising from light sources within the organic electroluminescence layer. Consequently, several new features are observed on the multiple-wave branches, including exchange of the phase speeds and depthwise standing waves for dissipationless systems. By the insertion of a thin metal film, the light extraction is found to be enhanced through leaky waves from the source layer out toward the viewer's side.