Band-Gap Engineering in Cu2ZnSn(S,Se)4 Solar Cells by Post-Sulphurization of Selenized Absorber Layers

A post-sulphurization process for kesterite Cu
₂
ZnSn(S,Se)
₄
solar cell absorber layers is developed in order to control the sulphur concentration and thus the band gap of the resulting solar cell absorber layers. It is shown that at sulphurization temperatures above 450°C an efficient incorporation of S takes place. Varying temperature between 450°C and 600°C and hold time between 5 min and 1 hour the sulphur content can accurately be controlled, thus allowing bandgap tuning in the complete range between about 1 eV and 1.5 eV.