Spatial resolution of methods for measuring the light-emission profile in organic light-emitting diodes

An analysis is presented of the resolution limits of two alternative methods for deducing the light-emission profile in organic light-emitting diodes (OLEDs) from the angular and polarization dependent emission spectra. The comparison includes the "fit-profile" (FP) method, within which the known physics of the recombination process is employed to describe the shape of the profile using a strongly reduced number of degrees of freedom, and the Tikhonov method, which provides a more general solution. First, the cases of a delta-function shaped emission profile and a broad single-peak emission profile are investigated. It is demonstrated that for these cases a ~1¿nm resolution of the peak position may be obtained, provided that the peak is positioned optimally in the OLED microcavity. Subsequently, an analysis is given for a double-peak emission profile and for a rectangular profile, as may be obtained in multilayer OLEDs, revealing a resolution of ~10¿nm for the cases studied. It is suggested that, in general, an optimal analysis should be based on a combined Tikhonov-FP approach.