Inhomogeneous luminance in organic light emitting diodes related to electrode resistivity

In organic light emitting diodes (OLEDs) with transparent electrodes, the luminance usually becomes inhomogeneous if the size of the pixel increases above 10 mm. A theoretical model for inhomogeneous voltage and luminance in OLEDs is provided together with an approximate analytical solution for the problem in case of cylindrical symmetry. Experimental observations of inhomogeneous luminance are compared with numerical simulations based on the theoretical model, proving the applicability of the approximations made in the theoretical model. (c) 2006 American Institute of Physics.