Thermodynamics of the S-Sn system: Implication for synthesis of earth abundant photovoltaic absorber materials

Development of earth-abundant, non-toxic, and environmentally friendly thin-film photovoltaic (PV) absorber materials motivates the present thermodynamic study of the S-Sn system, which is modeled using the CALPHAD (CALculation of PHase Diagram) technique aided by first-principles calculations. The temperature-composition (T-x), pressure-composition (P-x) and pressure-temperature (P-T) phase diagrams obtained from the modeling identify stability regions for different tin sulfides. This provides quantitative information regarding growth windows and annealing conditions for intelligent discovery and design of synthesis routes to produce low-cost, high-efficiency thin film PV absorber materials such as SnS, SnS2, Sn2S3, and Cu2ZnSn(S,Se)4.