The interest in organic electronics has been growing tremendously in the recent decade. The idea of printing flexible electronic devices has inspired scientists and engineers to develop new applications, e.g. displays, lighting and solar cells on flexible plastic foils. The development and tailoring of new devices and materials for organic electronics require a detailed understanding of the fundamental properties of organic thin films.
It will be demonstrated that photoelectron spectroscopy (PES) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy are very valuable for the investigation of the electronic structure of organic thin films, surfaces and interfaces. The use of a soft x-ray synchrotron light source allows the recording of high resolution core level spectra with high surface sensitivity. As an example the energy level alignment of well defined organic/metal interfaces will be discussed, in particular tin-phthalocyanine (SnPc) thin films deposited on either a clean or a PTCDA terminated Ag(111) surface, respectively. A systematic and comparative PES investigation indicates that the energy level alignment can be altered considerably by the first adsorbate monolayer (ML). Moreover, a coverage dependent rigid level shift is observed, which can be related to the formation of an interface dipole.
Furthermore, a study will be briefly summarized which aims at a detailed understanding of the core level spectra of strongly coupled adsorbates on metal surfaces. In this context some general trends in the high-resolution core level spectra of a systematic series of adsorbate ML films on Ag(111) will be discussed with respect to adsorbate-substrate charge transfer on the time scale of the core hole life time.