Strain tuning of native defect populations: The case of Cu2ZnSn(S,Se)4

Native defects are ubiquitous especially in compound semiconductors and dominate the properties of many materials. Applying first principles calculations, we propose a novel strategy to tune native defect populations in Cu2ZnSn(S,Se)4 which is an emerging photovoltaic absorber material. The formation of Cu vacancies (VCu), which are predicted to be shallower acceptors than Cu on Zn antisites (CuZn), can be greatly promoted by compressive strain. Additionally, nonlinearities are found in the strain dependence of the VCu formation energy. Both uniform and non-uniform strains may be present in physical samples implying probable variations in native defect concentrations.