Antimony Doping in Solution-processed Cu₂ZnSn(S,Se)₄ Solar Cells

Kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) is obtained using a facile precursor-solution method followed by selenization. Power-conversion efficiency of 6.0 is achieved and further improved to 8.2 after doping the absorber with 0.5 mol Sb. XRD and Raman spectroscopy show similar characteristics for the undoped and doped CZTSSe. Increasing the Sb concentration increases the grain size and lowers the series resistance. However, further Sb doping beyond 0.5 mol degrades device performance due to lower open-circuit voltage (and therefore lower fill factor). The effect of Sb doping and the doping concentration are investigated by power-dependent and temperature-dependent photoluminescence studies, revealing that trap density is significant reduced with 0.5 mol Sb doping. Additional doping beyond 0.5 mol creates more defects that quench the photoexcited carriers and decrease the open-circuit voltage.