Photonic Quasi-crystal enhanced Organic Light Emitting Diodes

In this paper we discuss theoretical modelling methods for design of photonic crystal and photonic quasi-crystal (PQC) Organic –Light Emitting Diodes, and apply them to the analysis of the extraction enhancement performance, and extraction beam shaping profile of bottom emitting organic LED structures incorporating photonic crystal structures within the layer stack. We first discuss trapping mechanisms within an OLED stack and investigate the effect of position of the patterning within the OLED layer structure, to derive the optimal position for maximum extraction efficiency and ease of fabrication. We investigate performance improvement associated with top and rear side patterning of the glass cover slip, effect of refractive index contrast for the backfill material and effect of lattice pitch. In addition, we examine the physical mechanisms giving rise to performance improvement in each case, examining the interplay and relative contributions to performance improvement such as effective index reduction effects which alter conditions for total internal reflection at the device air interface, and photonic crystal scattering effects which give rise to radically improved extraction performance.