Although in the perovskite case the binding energy shifts towards the interfaces could successfully be interpreted as the formation of space charge regions, we doubt that this is the case on the III-V samples measured here. On a p-Gep-GaInP junction, no band bending is expected, and the III-V materials have a strong tendency to form gap states at the surface and at the interface with their oxides to which the TCS surfaces will be pinned. Therefore, we suppose, that the concentration of these gap states gradually varies along the TCS towards the interface, which leads to gradually varying pinning positions. The gradual increase of the oxidation of GaInP towards the TCS interface was indicated in the O2p intensity increase depicted in Figures , and S5.