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

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 E-0 transition and high energy E-1A and E-1B 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 E-0 and high energy E-1A 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. (C) 2020 Elsevier B.V. All rights reserved.