Vacuum-free preparation of 7.5% efficient Cu2ZnSn(S,Se)4 solar cells based on metal salt precursors

A solution-based preparation route for 7.5% efficient thin-film solar cells with a kesterite-type Cu2ZnSn(S,Se)4 absorber is reported that allows low carbon residues after a rapid selenization step. Metal salts are dissolved in dimethyl sulfoxide and subsequently coated and selenized in a simple process that uses only earth abundant elements. Despite the observation of a layered structure, no clear differences are distinguishable in the chemical composition or phase formation within the absorber layer. However, there is evidence of a ZnSe-rich layer at the molybdenum back contact.