Effect of Dipole Position and Orientation on Light Extraction for Red OLEDs on Periodically Corrugated Substrate - FEM Simulations Study

Abstract

One of the main efficiency-limiting factors for organic light-emitting diodes (OLEDs) is poor light extraction, which typically reaches only 20% (in best cases up to 30%) in flat standard devices. Optical modeling and simulations play an important role in improving light extraction and optimizing outcoupling efficiency. Using FEM modeling approach, the effect of dipole positions and orientations for red OLEDs on periodically corrugated substrate is evaluated and used to enhance the outcoupling efficiency. It is shown that with only 3 carefully selected dipole positions, the outcoupling efficiency over the whole area can be predicted with very reasonable accuracy, which greatly reduces the number of simulations required. The presented modelling approach is used for optimization of the sine texture as a substrate corrugation structure. OLEDs with optimized simulated texture show a relative improvement of light outcoupling from the thin film stack to the substrate by more than 25% compared to the flat plane devices.