Optimal design and fabrication of ITO/organic photonic crystals in polymer light-emitting diodes using a focused ion beam

Abstract

This study aims to achieve high directionality and large extraction of light emission from polymer light-emitting diodes via optimizing photonic crystals (PCs). The optimization is achieved through the optical modeling using a 3D finite-difference time-domain (FDTD) method and the intelligent numerical optimization technique, genetic algorithm (GA). In results, the PC period, depth and filling factor can be found. The FDTD method has been proven very effective for modeling complex multilayer PLED devices in which the electron-transporting layer is only a few tens of nanometers away from a metallic layer. On the other hand, GA is a powerful tool to cope with a complicated optimization problem with multiple variables to optimize. The optimized PCs are later fabricated by focused ion beams (FIB) for the PLED. With desired PCs, an increase of the extraction efficiency in excess of 46% is achieved experimentally and the 3D FDTD calculation explains this result faithfully.