High Symmetry Metal-Dielectric Photonic Crystal Organic Light Emitting Diodes With Single-Cavity Unit Cells

Vertically-stacked organic light emitting diode (OLED) microcavities form 1D metal-dielectric photonic crystals (MDPC) with many degrees of freedom for engineering complex emission profiles. The photonic band structure of the MDPC OLED is determined by the underlying unit cell and is particularly sensitive to the properties of the metallic electrodes. The electronic requirements of microcavity OLED fabrication often necessitate dissimilar metallic electrodes to achieve good performance. This can profoundly impact the photonic properties of a MDPC by doubling the unit cell length. This work presents a MDPC OLED formed with single-cavity unit cells by employing optically similar Ag alloys as the semi-transparent electrode materials. The crystal is found to display a single photonic band without a band gap up to eight stacked cavities. The states within the band are evenly-spaced and clearly resolved, which is critical for applications seeking to utilize specific photonic states. Design considerations are presented for optimizing the photonic behavior of MDPC OLEDs through selective control of the optical properties of metallic alloys.