Organic light-emitting devices have been prepared with multilayer Al–Li–Al cathodes in an ultrahigh vacuum molecular beam deposition system. The optimum device characteristics are obtained when there is a single Al layer separating the Li layer from the organic materials.Ab initiomolecular dynamics calculations of the Al–Li interaction clarify the role of Al as a blocking layer to Li diffusion into the organic films as well as the behavior of the device when the thickness of this Al interfacial layer is changed. ©1997 American Institute of Physics.