CuSbS₂ thin films and solar cells produced from Cu/Sb/Cu stacks via sulfurization

Phase-pure crystalline chalcostibite (CuSbS₂) thin films were prepared by depositing Cu/Sb/Cu metal stacks using a thermal evaporation method, followed by sulfurization at 400  C and 430  C for different durations. The investigation revealed the formation of a dominant orthorhombic CuSbS₂ phase accompanied by a minor Sb₂S₃ phase in the film stacks sulfurized at 400  C for 10-60 min. Extending the reaction time to 90 min triggered a decrease in the Sb₂S₃ phase and the emergence of an additional famatinite (Cu₃SbS₄) phase alongside the dominant CuSbS₂ phase. Sulfurization of the film stack at 430  C for 10 min similarly produced a Cu₃SbS₄ secondary phase. When sulfurization was maintained beyond 30 min at 430  C, it resulted in phase-pure CuSbS₂ films, characterized by a crystalline grain size of 25.9 nm, direct bandgap of 1.41 eV, and hole mobility ranging from 0.6-1.0 cm²V^-1s^-1. Thin film solar cells fabricated using the CuSbS₂ absorbers grown at 430  C for 30-90 min displayed exceptional device efficiency due to the formation of phase-pure and highly crystalline films. Specifically, solar cells fabricated using the CuSbS₂ absorber sulfurized for 60 min demonstrated a peak device efficiency of 2.2%, featuring an open-circuit voltage of 546.6 mV, short-circuit current density of 12.8 mA/cm², and a fill factor of 31.3%. This study provides a reference for preparing highly crystalline CuSbS₂ thin films for efficient solar cells.