The interfacial structure plays a critical role in modern optoelectronics.
Currently multilayer electrodes are used to optimize the injection and lifetime
properties. The choice of interlayer is not universal, with different effects
for the same material with different capping metals. Using a novel in-situ
characterization method with X-ray photoelectron spectroscopy, the
organic/inorganic interface in OLEDs was examined for two common cathode metals
with a LiF interlayer. The impact of the interfacial layer on the performance
of devices can be attributed to the bulk lattice matching of the interfacial
layer and of the by-products of interfacial oxidation, and the metallic
cathode.