Model spectroscopic study of cobalt phthalocyanine thin film interfaces with inorganic substrates

Model experiments concerning the interface formation between Cobalt Phthalocyanine (CoPc) ultra thin films and inorganic substrates (ITO and Au) were carried out by using X-ray and Ultra-Violet photoelectron spectroscopies (XPS, UPS). Organic films of controlled thickness were deposited under ultrahigh vacuum conditions. From valence band measurements on the growing films, the CoPc Highest Occupied Molecular Orbital (HOMO) cut-off was determined similar to 0.80 eV from the analyser Fermi level, whereas the work function of the CoPc film was found to be 4.40 +/- 0.10 eV on both substrates. The experimental results show that CoPc forms non-reactive inter-faces with Au and ITO. The interfacial energy level alignment of CoPc/ITO and CoPc/Au was derived from the photoemission spectroscopic results and a hole injection barrier of similar to 0.80 eV was obtained for both interfaces.