Molecular Precursor Route to Bournonite (CuPbSbS₃) Thin Films and Powders

Quaternary metal chalcogenides have attracted attention as candidates for absorber materials for inexpensive and sustainable solar energy generation. One of these materials, bournonite (orthorhombic CuPbSbS₃), has attracted much interest of late for its properties commensurate with photovoltaic energy conversion. This paper outlines the synthesis of bournonite for the first time by a discrete molecular precursor strategy. The metal dithiocarbamate complexes bis(diethyldithiocarbamato)copper (II) (Cu(S₂CNEt₂)₂, (1)), bis(diethyldithiocarbamato)lead (II) (Pb(S₂CNEt₂)₂, (2)), and bis(diethyldithiocarbamato)antimony (III) (Sb(S₂CNEt₂)₃, (3)) were prepared, characterized, and employed as molecular precursors for the synthesis of bournonite powders and the thin film by solvent-less pyrolysis and spray-coat-pyrolysis techniques, respectively. The polycrystalline powders and thin films were characterized by powder X-ray diffraction (p-XRD), which could be indexed to orthorhombic CuPbSbS₃. The morphology of the powder at the microscale was studied using scanning electron microscopy (SEM). Energy-dispersive X-ray spectroscopy (EDX) was used to elucidate an approximately 1:1:1:3 Cu/Pb/Sb/S elemental ratio. An optical band gap energy of 1.55 eV was estimated from a Tauc plot, which is close to the theoretical value of 1.41 eV.