Ultrathin Solar Absorber Layers of Silver Bismuth Sulfide from Molecular Precursors

Here we present a robust molecular precursor-based approach to synthesize high-quality thin films of silver bismuth sulfide (AgBiS₂). Pure-phase cubic AgBiS₂ thin films are prepared, which are smooth and dense down to thicknesses less than 40 nm. Comprehensive structural and morphological analysis of the as-prepared films as a function of processing temperature and composition is presented, including X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The optical properties of the films and their electronic band structure are also presented. The as-prepared films show impressive light absorption properties with absorption coefficients reaching 10⁵ cm^-1 for energies above ca. 950 nm. Finally, their photoactivity is demonstrated through photoconductivity measurements on lateral electrodes. The methods outlined herein enable the fabrication of AgBiS₂ semiconductor thin films at low processing temperatures (150 °C) with a dense morphology and tunable Ag/Bi composition. Such films provide an excellent platform for the fabrication of AgBiS₂-based optoelectronic devices, specifically solar cells.