Copper-antimony-sulfide (CuSbS2) is a promising absorber for use in thin-film solar cells. In this study, we report the fabrication of CuSbS2 films by sulfurizing sequentially evaporated Cu/Sb/Cu stacks at 450 °C for 5 min and investigate the influence of Cu thickness (Cu-poor, Cu-correct, and Cu-rich) on the phase evolution. The film prepared with a Cu-poor composition exhibited the formation of phase-pure CuSbS2 with several micron-sized grains uniformly grown on the surface, a bandgap energy of 1.55 eV, an electrical resistivity of 16.8 Ωcm, and a carrier concentration of 7.27 × 1017 cm−3. The CuSbS2 film fabricated with the stoichiometric and Cu-rich composition contained a minor Cu12Sb4S13 and Cu3SbS4 secondary phases with increased grain size, decreased bandgap (1.55–1.51 eV), electrical resistivity (8.63–5.59 Ωcm), and increased carrier concentration (1.63–2.28 × 1018 cm−3 cm−3). This investigation reveals that a slightly Cu-poor composition is required for the growth of phase-pure CuSbS2 films suitable for thin-film solar cells.

Understanding phase evolution in CuSbS2 absorbers via rapid sulfurization of Cu/Sb/Cu stacks