Design of microcavity organic light emitting diodes with optimized electrical and optical performance.

A multivariable and multiobjective organic light emitting diode (OLED) design and optimization procedure is presented that produces a microcavity OLED with optimal optical and electrical characteristics. We propose here a design procedure that splits the design process into two design stages where each stage can be optimized independently. In the first stage we design the OLED with optimal electrical and optical performance, where the mirrors are specified by their optimal spectral reflectivity, transmissivity, absorptance, and the phase shift on reflection. In the second stage we synthesize the top and the bottom multilayer mirrors with a minimal number of layers that satisfy the required optimal spectral dependencies determined in the first part of the design process. As a case study we present an optimized design for a top-emitting OLED with a simple bilayered cavity consisting of N, N'-di(naphthalene-1-yl)-N, N'-diphenylbenzidine (NPB) as the hole transport layer and tris(8-hydroxyquinoline)aluminium (Alq3) as the electron transport layer. Conventional devices with an ITO-LiF/Al electrode pair and a Ag?Ag electrode pair are used as reference devices to benchmark the performance of our design. Electrical simulations using the drift-diffusion model and optical simulations employing the integrated dipole antenna approach are implemented to test the performance of the devices. The optimized device shows improved optical and electrical performance when compared with the reference devices.