Optical properties of Cu2ZnSn(SxSe1-x)4 by first-principles calculations

TL;DR

This study uses first-principles calculations to analyze the structural, electronic, and optical properties of Cu2ZnSn(SxSe1-x)4 semiconductors, highlighting the importance of Brillouin zone sampling and the effectiveness of hybrid functionals.

Contribution

It introduces a k·p based interpolation scheme to compare hybrid functional results with GGA and meta-GGA calculations for optical properties.

Findings

Dielectric constants and band-gaps vary linearly with S concentration.

Hybrid functionals best match experimental dielectric functions.

Dense Brillouin zone sampling is crucial for accurate optical property calculations.

Abstract

Structural, electronic and optical properties of Cu2ZnSn(SxSe1-x)4 semiconductors are studied theoretically for different concentration of S and Se anions. The optical properties are calculated at three levels of theory, in the generalized gradient approximation (GGA), meta-GGA, and with a hybrid functional. The GGA and meta-GGA calculations are corrected with an on-site Coulomb Ud term. Lattice constants, dielectric constants, and band-gaps are found to vary almost linearly with the concentration of S. We also show that a dense sampling of the Brillouin zone is required to accurately account for the shape of the dielectric function, which is hard to attain with hybrid functionals. This issue is resolved with a recently developed k dot p based interpolation scheme, which allows us to compare results of the hybrid functional calculations on an equal footing with the GGA and meta-GGA results. We find that the hybrid functionals provide the overall best agreement with the experimental dielectric function.