Physical properties of photoconductive Ag-Sb-S thin films prepared by thermal evaporation

We used thermal evaporation and post-deposition thermal treatment to prepare photoconductive Ag-Sb-S thin films. Firstly, to obtain the Ag ₂S/Sb ₂S ₃/substrate samples, we sequentially evaporated both Sb ₂S ₃ and Ag ₂S precursors. Secondly, we converted the double-layered structure in Ag-Sb-S thin films through a post-annealing treatment. Finally, considering the variation in both temperature of this treatment and amount of evaporated Ag ₂S, we evaluated the formation of AgSbS ₂ and Ag ₃SbS ₃ ternary phases in the films. As a result, we identified the coexistence of cubic and monoclinic AgSbS ₂ and monoclinic and hexagonal Ag ₃SbS ₃ phases. In addition, the evolution from metastable to stable phases of AgSbS ₂ and Ag ₃SbS ₃ is presented. Using Raman vibrational modes at 267 cm ^-1 for the monoclinic and 323 cm ^-1 for the hexagonal phases and X-ray diffraction results, we identified the dominant Ag ₃SbS ₃ crystalline structure. Furthermore, we found that, respectively, the optical band gap, electrical conductivity and photosensitivity are in the range of 1.7–1.85 eV, 1.3 × 10 ^-7 to 7.4 × 10 ^-5 (Ω-cm) ^-1 and 29 to 0.5. Consequently, the Ag-Sb-S thin films are suitable as the absorber layer in photovoltaic solar cells.