Development of pyrargyrite Ag3SbS3 absorber films through sulfurization of Ag-Sb stacks for thin-film photovoltaics

Pyrargyrite Ag3SbS3, which consists of naturally abundant and non-toxic elements, has attracted attention as a promising solar cell material. A two-stage fabrication method was been developed to synthesize Ag3SbS3 thin films through a solid-state reaction between Sb and Ag metallic layers by sulfurizing at 250–350 oC. The Ag3SbS3 film prepared at a sulfurization temperature of 250 oC contained Ag2S and Sb2S3 secondary phases with non-stoichiometric composition, distinct grain growth, a bandgap energy of 1.4 eV, and an electrical resistivity of 5.74x10−4 Ωcm. Through sulfurization of the stacks at 300 oC, the Ag2S and Sb2S3 secondary phases disappeared, and dominant Ag3SbS3 films were obtained with a minor AgSbS2 secondary phase. A compact and uniform near-stoichiometric Ag3SbS3 composition with large grains was obtained with an increased bandgap energy of 1.64 eV and electrical resistivity of 6.19x104 Ωcm. A further increase in the sulfurization temperature to 350 oC resulted in an increase in the crystallite and grain sizes of Ag3SbS3 with a decreased bandgap energy of 1.62 eV and electrical resistivity of 2.90x104 Ωcm. AgSbS2 remained as a minor secondary phase in this film. Thin-film solar cells prepared with the Ag3SbS3 absorber synthesized at a sulfurization temperature of 300 oC exhibited an open-circuit voltage of 473.85 mV, short-circuit current density of 1.47 mA/cm2, fill factor of 41.6%, and an efficiency of 0.3%. These results demonstrate that Ag3SbS3 is a potential candidate for thin-film solar cells.