Grain boundaries in Cu(In, Ga)(Se, S)2 thin-film solar cells

The paper reviews the current status of the research on grain boundaries in polycrystalline Cu(In, Ga)(S, Se)2 alloys used as absorber materials for thin-film solar cells. We discuss the different concepts that are available to explain the relatively low electronic activity of grain boundaries in these materials. Numerical simulations that have been undergone so far to model the polycrystalline solar cells are briefly summarized. In addition, we give an overview on the experiments that have been conducted so far to elucidate the structural, defect-chemical, and electronic properties of grain boundaries in Cu(In, Ga)(S, Se)2 thin-films.