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 degrees 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 degrees 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 degrees C revealed highly crystalline, large-grains with an average grain size of 5 mu m. Optical absorption studied suggested that the AgSbS2 film prepared at 350 degrees C exhibited a direct bandgap of 1.61 eV. Hall measurements revealed an electrical resistivity of 1.52 x 10(4) Omega cm, hole mobility of 84.5 cm(2)V(-1)s(-1), and a carrier concentration of 7.95 x 10(12) cm(-3) for the AgSbS2 film prepared at 350 degrees 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/cm(2); and fill factor, 31.0%). The device processing conditions must be optimized to further improve the efficiency.