Kesterites – complex quaternary compound semiconductors
As some of the chalcopyrite type absorber materials are well known minerals(Roquesite—CuInS2, Gallite—CuGaS2), there is a variety of stand-by chalcogenide minerals that can be used as reservoirs for the search of new, In-free materials suitable for solar cell absorbers. Recently it has come to light that the mineral kesterite (Cu2ZnSnS4) and also the selenium counterpart Cu2ZnSnSe4 might be suitable to replace the indium-containing absorber layer in thin film solar cells.
Quaternary AI2BIICIVXVI4 chalcogenides with A-Cu; B-Zn; C-Si, Ge, Sn and X-S, Se are compound semiconductors with a direct optical gap in a range suitable for photovoltaic applications. These materials belong to the Adamantine compound family, which are featured by a tetrahedral coordination, i. e. each atom has four nearest neighbours. The well-defined tetrahedral bonding structure is advantageous in controlling the semiconducting properties of the material.
We study the crystal structure of quaternary chalcogenides like Cu2ZnSn(S,Se)4, Cu2FeSn(S,Se)4, Cu2ZnGe(S,Se)4 and Cu2ZnSi(S,Se)4 as well as their solid solutions.