Metal-Dielectric Photonic Crystal Organic Light Emitting Diodes

A periodic array of stacked microcavity organic light emitting diodes (OLEDs) creates a photonic crystal comprising alternating metal and dielectric layers, a metal-dielectric photonic crystal (MDPC). In these MDPC-OLEDs, the semitransparent metals layers serve dual function as both mirrors and either the anode or cathode in the OLED device enabling simultaneous electroluminescence from each unit cell. The angle-resolved electroluminescence spectra of the MDPC-OLED reflects the photonic dispersion of the crystal with rich, energy, momentum, and polarization dependent behavior depending on the physical geometry of the crystal and the optical properties of the constituent materials. The number of states in the band, the bandwidth, and mid-band Peierls distortion can be controlled by varying the physical dimensions of the crystal through additive manufacturing. Linewidths of the photonic states are reduced by improving the optical symmetry of the unit cell. Crystal defects can be included to introduce mid-gap photonic states. These properties are modeled using a computational transfer matrix simulation and experimentally verified. Lastly, we develop an analytical model based on coupled mode theory and quasi-normal mode theory to determine the relationship between optical constants (index of refraction and extinction coefficient) of the metal and organic layers to the resulting photonic band structure.