  Cu2ZnSnS4 (CZTS) is a promising material as an absorber in photovoltaic
applications. The measured efficiency, however, is far from the theoretically
predicted value for the known CZTS phases. To improve the understanding of this
discrepancy we investigate the structural, dynamical, and dielectric of the
three main phases of CZTS (kesterite, stannite, and PMCA) using density
functional perturbation theory (DFPT). The effect of the exchange-correlation
functional on the computed properties is analyzed. A qualitative agreement of
the theoretical Raman spectrum with measurements is observed. However, none of
the phases correspond to the experimental spectrum within the error bar that is
usually to be expected for DFPT. This corroborates the need to consider cation
disorder and other lattice defects extensively in this material.
