Calculation of defect concentrations in Cu2ZnSnS4 from stoichiometry

The application of Cu₂ZnSnS₄ (CZTS) as a highly efficient solar cell absorber material is dependent on the complex behavior of the large variety of intrinsic lattice defects. In this work, a canonical approach is applied to calculate defect concentrations as a function of stoichiometry and temperature during the growth process. The corresponding chemical potentials are then obtained from the defect concentrations, relating stoichiometric conditions to the stability of CZTS compared to secondary phases. Based on this model, it is shown, that ZnS is likely to be present at Cu-poor and Zn-rich conditions, which are known to achieve the highest efficiencies.