Investigation of interfacial interactions of solid-state benzene with low work function metals by Raman spectroscopy and mass spectrometry

Extensive previous studies have been performed to fully understand and optimize charge injection across metal-organic interfaces in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs). However, the interpretation of these studies is complicated at best. Therefore, in order to fully understand the chemistry at these junctions, it is essential to understand the fundamental solid state interactions between simple "model" organic molecules and common electrode metals. Many of the common organic molecules that are presently being used in these devices are comprised of aryl-containing moieties, leading to the selection of benzene as the "model" molecule in the current research. Thin solid benzene films were deposited under ultrahigh vacuum conditions and reacted with increasing amounts of Al, Ca, Mg, and Ag. Raman spectroscopy was used to investigate vibrational modes of products formed, while mass spectrometry was used to determine the stoichiometry and thermal stability of metal-organic complexes. Implications of these results for low work function metal-organic interfaces in devices will be discussed.