External coupling efficiency in planar organic light-emitting devices

The external coupling efficiency in planar organic light-emitting devices is modeled based on a quantum mechanical microvavity theory and measured by examining both the far-field emission pattern and the edge emission of light trapped in the glass substrate. The external coupling efficiency is dependent upon the thickness of the indium-tin-oxide layer and the refractive index of the substrate. The coupling efficiency ranges from similar to 24% to similar to 52%, but in general it is much larger than the 18.9% expected from classical ray optics. (C) 2001 American Institute of Physics.