Analysis of spatial coherence of organic light-emitting devices through investigation of interference effects observed in top-emitting devices

Interference effects in top-emitting organic light-emitting diodes (OLEDs) containing an air gap of 15 mu m are studied over a range of angles in order to obtain information about the spatial coherence properties. The devices display effects similar to a Fabry-Perot Etalon illuminated by a source with a broad spectral range, but the interference effects diminish rapidly with angle, which is inexplicable with simple thin film optics. The results suggest that this effect is due to the spatial coherence of the OLED. From an analysis of the interference pattern a number of device parameters can also be determined. (c) 2007 American Institute of Physics.