Theoretical prediction and experimental synthesis of a Ba0.5Pb0.5S alloy via the molecular precursor route†

Semiconductor materials with a wide bandgap hold significant promise in the field of tandem solar cells. Ba–Pb–S ternary alloys have received growing interest due to their robust stability, diverse physicochemical properties and broad application potential based on theoretical predictions, but the experimental synthesis of Ba–Pb–S alloys has not yet been reported. In this article, density functional theory calculations indicate that the Ba_0.5Pb_0.5S alloy possesses desirable optoelectronic properties, including a direct bandgap (1.75 eV), a high optical absorption coefficient, and high defect tolerance. Experimentally, we developed a dibutyldithiocarbamate (DBuDTC) solution process for synthesizing Ba_0.5Pb_0.5S polycrystalline powders and thin films using a discrete molecular precursor strategy. Additionally, atomic-resolution scanning transmission electron microscopy provided invaluable insights into the Ba_0.5Pb_0.5S alloy structure. Moreover, the bandgap of Ba–Pb–S ternary alloys can be adjusted, and they exhibit outstanding storage stability under high-humidity conditions. These favorable optoelectronic properties position Ba–Pb–S alloy materials as excellent candidates for both solar energy conversion and optoelectronic materials.