Department Structure and Dynamics of Energy Materials

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 A^I₂B^IIC^IVX^VI₄ 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.