Two-stage-processed AgSbS₂ films for thin-film solar cells

AgSbS₂ has shown promise as an earth-abundant, sustainable light-harvesting material for thin-film solar cells owing to its suitable optoelectronic properties and high stability. Here, we report the fabrication of AgSbS₂ thin films using a two-stage process (sequential evaporation of Sb/Ag layers and sulfurization at 300–400 °C for 30 min) and their characterization. X-ray diffractometry revealed the formation of Ag₃SbS₃ and Sb₂S₃ phases, single-phase AgSbS₂, and slight decomposition of AgSbS₂ and the emergence of monoclinic AgSbS₂ at sulfurization temperatures of 300, 350, and 400 °C, respectively. The AgSbS₂ films have a cubic crystal structure with a lattice parameter (a) of 0.565 nm. X-ray photoelectron spectroscopy confirmed that the valence states of Ag, Sb, and S were +1, +3, and -2, respectively. Microstructural analysis of the film prepared at 350 °C revealed highly crystalline, large-grains with an average grain size of 5μm. Optical absorption studied suggested that the AgSbS₂ film prepared at 350 °C exhibited a direct bandgap of 1.61 eV. Hall measurements revealed an electrical resistivity of 1.52 × 10⁴ Ωcm, hole mobility of 84.5 cm²V⁻¹s⁻¹, and a carrier concentration of 7.95 × 10¹² cm⁻³ for the AgSbS₂ film prepared at 350 °C. Finally, AgSbS₂ solar cells with glass/Mo/AgSbS₂/CdS/indium-tin-oxide/Ag configuration were fabricated (optimal device parameters: efficiency, 1.1%; open-circuit voltage, 519.6 mV; short-circuit current density, 6.63 mA/cm²; and fill factor, 31.0%). The device processing conditions must be optimized to further improve the efficiency.