Alkali-induced surface defects and interface passivation in chalcogenide solar cells

The project addresses the ambivalent physical effects of alkali atoms acting on surfaces and interfaces of chalcogenide semiconductors Cu(In,Ga)(Se,S)2 and Cu2ZnSnSe4 and their solar cell devices. Starting point is the preliminary work of the applicants which shows that the alkali element Sodium can contribute to formation and passivation of surface and interface defects. These unexpected results are not yet understood although alkali doping of chalcogenide semiconductors is standard and many of its facets are well known. In the project, tailored sample preparation, surface spectroscopy, electronic defect spectroscopy, and computer simulation shall be combined.