A comprehensive study on Cu₂SnS₃ prepared by sulfurization of Cu–Sn sputtered precursor for thin-film solar cell applications

In this work, a comprehensive study on the influences of the various synthesizing parameters of monoclinic Cu₂SnS₃ using the RF sputtering method, followed by the sulfurization process, is investigated. In particular, the impact of sputtering power and pressure on multi-material target Cu–Sn (compositional ratio Cu:Sn of 52:48%) was examined. All samples exhibited a monoclinic structure with similar split bandgaps around 0.9 eV. Increasing sputtering power showed direct effects on the sputtered Cu/Sn atoms ratio and the secondary phases obtained. The increase of sputtering pressure causes gas droplets and blistering on the film surfaces. The effects of changing the sulfurization temperature and the sulfur powder amount were also studied. The increase in the sulfurization temperature reduces the surface roughness, increases film crystallinity, and minimizes Cu-based secondary phases. The sulfur amount used during the sulfurization process showed a vital impact on film formation. Using a small amount of sulfur produced a partially sulfurized film that exhibited a poor performance solar cell. A power conversion efficiency of 1.94% is achieved with the optimized condition for the bare Cu₂SnS₃ without doping or heat treatment for the fabricated cell.