Monte Carlo modeling of organic polymer light-emitting devices on flexible plastic substrates

A Monte Carlo method for modeling the light transport phenomena in organic polymer light-emitting devices (PLEDs) is reported. In this simulation we assumed a point light source having photon emission spectrum represented by the photoluminescence (PL) spectrum of the organic polymers. This method describes the fate of photons through multiple scattering events determined by the wavelength-dependent material optical properties in a 3-D Cartesian geometry, thus considering the effects of refraction at different interfaces, back-reflection from the cathode, interference effect in the ITO thin film, and absorption within the polymer layers. We apply this method to analyze the wavelength output distribution and extraction efficiency. We found that the simulated light emission spectra of the green and red light-emitting devices are very similar to the measured PL spectra, suggesting that the light transport phenomena do not change the energy distribution significantly. We also established that the calculated extraction efficiency for the red ( ext η =19.5%) and green ( ext η =19.9%) PLEDs are approximately the same. We further investigated the light emission angular distribution of the PLEDs, and found that the simulated angular distribution shows better agreement with the experimental data than previously used models that rely on standard refraction theory at one interface.