Monte Carlo modeling of the light transport in polymer light-emitting devices on plastic substrates

A Monte Carlo method for modeling the light transport phenomena in organic polymer light-emitting devices (PLEDs) has been reported previously (Badano and Kanicki, 2001). The advantage of this simulation method is its ability to model bulk absorption, thin-film coatings, and uneven or irregular surfaces by tracking the photon polarization in realistic device structures. We have applied this method to analyze the PLEDs spectral outputs and out-coupling efficiencies. We have established that the calculated out-coupling efficiencies are approximately the same (η_coup∼0.2) for the red and green PLEDs. Using a description of uneven surfaces with Fresnel analysis, we showed that the nonsmooth interfaces (as modeled by the algorithm for uneven surfaces) between light-emitting polymer and hole transporting layer increase the probabilities of out-coupling and wave-guiding of the internally generated light. In this paper, we use this method to calculate the angular distribution of the PLED light-emission. We found that the Monte Carlo simulated PLED light-emission angular distribution shows better agreement with the experimental data than previously used models relying on standard refraction theory at one interface.