Spectroscopic ellipsometry study of Cu2ZnSn(SxSe1-x)4 bulk polycrystals

Abstract

The pseudo dielectric function of Cu2ZnSn(SxSe1-x)4 [x = 0.35, 0.62, 0.81] bulk polycrystals is determined over the range 1.1–4.6 eV at room temperature from the analysis of spectroscopic ellipsometry data using the Adachi model. From the analysis, the lowest E0 transition and high energy E1A and E1B transitions are clearly identified, and used to follow the evolution of the pseudo dielectric function as a function of the composition. It is shown that the fundamental E0 and high energy E1A transitions can be tuned by increasing the sulfur content over a range of 0.3 eV. These results show the potential of the kesterite compounds for the design of efficient tailored photovoltaic solar cells.