Photonic Properties of Metal-Dielectric Photonic Crystal OLEDs

Metal-dielectric photonic crystals (MDPCs) represent a unique class of photonic structures realized through vertically-stacked metallic OLED microcavities. The coupling of multiple microcavities results in hybridization of the cavity modes to form a band of narrow linewidth, tunable emission peaks, expressed directly though the electroluminescence spectrum of the OLEDs. The properties of the photonic band depend sensitively on the resonance states of the underlying unit cells and lie outside the effective medium regime. We discuss the photonic band structure observed in binary (two-cavity) and mono-cell MDPCs and explore the role of the metallic layers in determining the device performance. We examine trends in the state positioning, modal quality factor, and spontaneous emission enhancement as functions of the number of cavities, unit cell geometry, and material properties. The analysis is extended outside the light cone using transfer matrix simulations to discern the waveguided mode structure.