Process Optimization of Copper Antimony Sulfide Thin Films via Chemical Bath Deposition for High-Performance Photovoltaic Applications.

Copper antimony sulfide (CuSbS₂) has the potential to be an excellent absorber material for thin-film solar cells. It has an optimal direct band gap of 1.5 eV, strong absorption coefficients >10⁴ cm⁻¹, and is composed of non-toxic and earth-abundant elements. However, the difficulty in growing properly stoichiometric and well-crystallized CuSbS₂ thin films by chemical bath deposition remains. This work aims to optimize the CBD conditions for the deposition of CuSbS₂ thin films by enhancing the uniformity, crystallinity, and optical quality of the material, which are critical for its application in solar cells. TiO_₂ electron transport layers on FTO glass substrates were prepared by the doctor blade technique. This technique provided a smooth surface for the CuSbS₂ thin film, which adhered properly. The CuSbS₂ thin film was prepared by dissolving SbCl₃ in acetone, Na₂S₂O₃, and CuCl₂ in a precursor solution. The thin film was then deposited at room temperature for 3 hours in a 50 ml bath. Solar cell architecture is described as follows: FTO/TiO₂/CuSbS₂/CuI/Pt-glass. The XRD patterns show the proper formation of the orthorhombic chalcocite CuSbS₂ phase. The strong (111) peak indicates the high crystallinity of the CuSbS₂ thin film. The scanning electron microscope (SEM) showed densely packed grains with minimal void spaces, indicating good surface coverage. The optical measurements, which included UV-Vis spectroscopy and Tauc plots, showed a direct band gap of 1.6 eV, which is optimal for solar energy absorption. The current research has shown that with optimized CBD conditions, good-quality CuSbS₂ films can be deposited, which is useful for efficient and sustainable solar energy conversion.