Fabrication of solar cells based on Cu 2 ZnSnS 4 films grown with optimized chemical composition homogeneity

Abstract

Solar cells with Mo/CZTS/ZnS/ZnO structure were fabricated using Cu 2 ZnSnS 4 (CZTS) films as the absorber layer. These films were grown by simultaneous evaporation of its precursors with a coaxial evaporation source whose advanced design allowed to improve significantly the homogeneity of the chemical composition in the entire volume. Through X-ray diffraction (XRD) measurements we were able to verify that under optimized growing conditions, it is possible to get single phase Cu 2 ZnSnS 4 films; through X-ray photoelectron spectroscopy (XPS) depth profile analysis we confirmed that the chemical composition of the samples prepared from a coaxial source had a better homogeneity throughout the volume than the samples deposited from three separated evaporation sources. We also found that the conversion efficiencies of solar cells fabricated using a CZTS absorber layer grown from a coaxial evaporation source was significantly greater than that of cells fabricated using CZTS layers prepared from separate evaporation sources. We obtained conversion efficiencies of 5.6%, short circuit current of 18.3 mA/ cm 2 and open-circuit voltage of 0.52 V.