Cu content dependence of Cu2Zn(SnGe)Se4 solar cells prepared by using sequential thermal evaporation technique of Cu/Sn/Cu/Zn/Ge stacked layers

Abstract

The doping of Cu2ZnSnSe4 semiconductor with Ge element has demonstrated improvements to kesterite solar cell efficiency. However, the impact of different Cu concentrations on Cu2ZnSnGeSe4/CdS solar cell performance has been poorly studied. In this work, Cu2ZnSnGeSe4 thin films with different Cu contents were synthesized by selenization of sequential thermal evaporation precursors. Solar cells based on kesterite-type Cu2ZnSnGeSe4 (CZTGSe) were fabricated and the influence of the Cu thickness on the chemical composition and morphology of the layers and electro-optical properties of solar cells was studied. The stacking process was performed at room substrate temperature. Efficiency values in the range of 2.0–6.8% are reported as a function of Cu concentration. The highest efficiency of 6.8%, was achieved for solar cell with glass/Mo/CZTGSe/CdS/i-ZnO/ITO structure using the stacking of Cu (3 nm)/Sn (248 nm)/Cu (112 nm)/Zn (174 nm)/Ge (20 nm).