Solution Deposition of a Bournonite CuPbSbS₃ Semiconductor Thin Film from the Dissolution of Bulk Materials with a Thiol-Amine Solvent Mixture

There is considerable interest in the exploration of new solar absorbers that are environmentally stable, absorb through the visible, and possess a polar crystal structure. Bournonite CuPbSbS₃ is a naturally occurring sulfosalt mineral that crystallizes in the noncentrosymmetric Pmn2₁ space group and possesses an optimal band gap for single junction solar cells; however, the synthetic literature on this quaternary semiconductor is sparse and it has yet to be deposited and studied as a thin film. Here we describe the ability of a binary thiol-amine solvent mixture to dissolve the bulk bournonite mineral as well as inexpensive bulk CuO, PbO, and Sb₂S₃ precursors at room temperature and ambient pressure to generate an ink. The synthetic compound ink derived from the dissolution of the bulk binary precursors in the right stoichiometric ratios yields phase-pure thin films of CuPbSbS₃ upon solution deposition and annealing. The resulting semiconductor thin films possess a direct optical band gap of 1.24 eV, an absorption coefficient ∼10⁵ cm^–1 through the visible, mobilities of 0.01–2.4 cm² (V·s)⁻¹, and carrier concentrations of 10¹⁸ – 10²⁰ cm^–3. These favorable optoelectronic properties suggest CuPbSbS₃ thin films are excellent candidates for solar absorbers.