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 metallic stacks using a thermal evaporation method, followed by sulfurization at 400 oC and 430 oC 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 oC 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 oC for 10 min similarly produced a Cu3SbS4 secondary phase. When sulfurization was maintained beyond 30 min at 430 oC, it resulted in phase-pure CuSbS2 films, characterized by a crystalline grain size of 105 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 oC 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.