CZTSe thin film growth via a co-evaporation process using a ZnSe effusion source

Abstract

The compositional distribution of elements is known to be significant for the high conversion efficiency of CZTSe solar cells. As detailed understanding of the Cu/(Zn+Sn) ratio in the light absorption layer is important, Cu2ZnSnSe4 (CZTSe) films grown via the co-evaporation process under different copper fluxes were characterized. It is difficult to evaluate the Cu content effect on the properties of CZTSe films grown using a co-evaporation process with Cu, Zn, Sn, and Se elemental effusion sources because the Cu flux variation during the process also induces other element ratio changes. Furthermore, the Zn/Sn ratio shows significant correlation to the Cu/(Zn+Sn) ratio variation in CZTSe thin films. Replacing the zinc metal effusion source with the ZnSe compound source resulted in less fluctuation in the Zn/Sn variation according to Cu flux change during the CZTSe co-evaporation. This can be useful in evaluating the effect of the different Cu ratios on the CZTSe solar cell characteristics.