Mechanism of dark spot formation of organic light-emitting devices

Using chemically sensitive x-ray photoelectron microscopy, we investigate the mechanism of dark-spot formation and degradation of organic light-emitting devices. The morphological and chemical evolution of the Al cathode surface under operation conditions reveals the formation of "domelike" structures, followed by local disruptions of the cathode, exposing microareas of the underlying indium tin oxide anode. The chemical maps and microspot spectra identify a release of volatile In-, Sn-, and C-containing species, including metallic In, which is clear evidence that the degradation is driven by local decomposition of the anode/organic interface. (C) 2005 American Institute of Physics.