Interface electronic structure of organic semiconductors with controlled doping levels

We investigate the properties of inorganic - organic interfaces by ultraviolet and X-ray photoemission spectroscopy (UPS and XPS) and transport experiments. In particular, we study the interface between inorganic conductive substrates and organic layers that are intentionally p-type doped by co-evaporation of a matrix material and acceptor molecules. The photoemission spectra clearly show that the Fermi levels shift due to the doping and that the space charge layer width changes with doping (high doping - small width). The changes in the electronic structure of the interface due to doping agree well with results of transport experiments.