Semiconductor/electrolyte interfaces for solar energy conversion: Interface studies by synchrotron induced photoelectron spectroscopy

We present three examples on the application of UHV based synchrotron induced photoelectron-spectroscopy (PES) for the characterization of semiconductor/electrolyte interfaces using surface sensitive core and valence band spectroscopy. The examples are related to semiconductor/electrolyte systems in photoelectrochemical energy conversion. Example 1 considers the interface of a dye sensitized solar cell using the triadsorption system TiO2/Ru-dye-N3/iodide-salt-PMII/acetonitrile. Example 2 considers emersion of the semiconductor electrode from electrolyte solution under potential control for the system n-GaAs/HClaq. Example 3 considers emersion experiments from alkaline and acidic electrolyte solutions of p-GaInP2 as possible water splitting system. Relevant data have been gained on the interface chemistry and electronic structure by applying in-situ (in UHV) and quasi in-situ (under inert gas) experiments, which are shown as prototype examples related to the concepts of semiconductor/electrolyte contact formation.