Controlling the physicochemical and optoelectronic properties of novel quaternary chalcogenide CuSbSnS₃ using different sulphurizing agents

Copper Antimony Tin Sulphide (CATS, CuSbSnS₃) was produced through both hydrothermal and solid-state synthesis routes, employing various sulfur precursors. X-ray diffraction (XRD) analysis verified the development of a polycrystalline CuSbSnS₃ phase, with thiourea (TU) synthesis delivering the most well-defined crystal structures. Field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) analyses revealed nanocrystalline morphologies, with flake-like particles of ~ 60 nm and uniformly agglomerated nanoparticles ranging from 5 to 10 nm, indicating distinct size distributions. Optical studies showed a suitable band gap range (1.25–1.70 eV), with enhanced light absorption in the 480–1000 nm region. Post-annealing treatments improved the electrical conductivity, as a result of reduced resistivity, and inhibited grain growth. Photo-electrochemical analysis under light irradiation indicated that TU-sourced CATS exhibited superior charge transport behavior, achieving the lowest charge transfer resistance (50 Ω), highest conductivity (9.41 × 10⁶ Ω⁻¹·cm⁻¹), carrier mobility (2.50 × 10⁵ cm²·V⁻¹·s⁻¹), and bulk carrier concentration (2.35 × 10²⁰ cm⁻³). As a result, the TU-derived CATS achieved the highest power conversion efficiency of 7.77%, highlighting its strong promise for photoelectric and solar energy applications.