Kesterites are semiconductors of the composition Cu2ZnSn(S/Se)4. They are made of only abundant and cheap materials. They show p-type behaviour without external doping, a high absorption coefficient and band gaps between 1.0 and 1.5 eV. Therefore they are considered a promising material for absorbers in thin film solar cells. Solar cells based on these materials have reached efficiencies above 10%.
Although the crystal structure of kesterites is derived from chalcopyrites, which are very successfully used as absorbers in thin film solar cells, kesterites appear more challenging in many ways: their phase diagram, their crystal modifications, their electronic band structure are challenging. Solar cells made from these films are thought to suffer from interface recombination and high series resistance.
The presentation will discuss the main challenges and present recent progress made in the understanding of the material and the efficiency of solar cells.