This presentation will discuss the chemical and electronic surface properties of Cu(In,Ga)(S,Se)₂- and GaInP₂-based materials in view of their use in solar water-splitting devices. Many of the primary requirements for photoelectrochemistry (such as efficiency and stability) are directly related to such properties, but it is generally quite difficult to paint a comprehensive surface picture, in particular in operando environments.

The talk will focus on results obtained with a tool chest of soft x-ray and electron spectroscopies, with primary emphasis on high-brilliance synchrotron radiation experiments. It will be shown how photoelectron spectroscopy (PES), also under “ambient pressure” conditions, inverse photoemission (IPES), x-ray emission spectroscopy (XES), and x-ray absorption spectroscopy (XAS) can be suitably combined to derive surface electronic band gaps, study local chemical bonding and electronic level alignment, and gain insights into chemical stability.