Numerical Modelling of Light Emission and Propagation in (Organic) LEDs with the Green's Tensor

摘要

The accepted model for light emission and propagation in organic LEDs (OLED) which consists of several optically thin functional layers deposited on a thick substrate is a classical dipole located in the emitting layer. The propagation of the emitted light is commonly described by a Fourier expansion of the dipole field into plane waves which represent the various radiating and bound modes of the layered structure in k-space. To calculate the electric and magnetic fields inside and outside the LED an integration over the individual plane waves has to be performed. This entails numerical difficulties which can be overcome elegantly with the so-called Green's tensor approach for stratified media recently developed by the second author. In our contribution we demonstrate the applicability of this method to the computation of electromagnetic field distributions in organic LED structures. Visualizations of typical field distributions arising from individual dipoles are presented and discussed thus allowing a more intuitive understanding of effects relating to dipole location and orientation and material absorption. Furthermore it is shown that scattering of bound modes by particle like inhomogeneities of the layer structure can be effectively modelled with the Green's tensor approach. Visualizations are presented and discussed with regard to increased light extraction.