Structural, Morphological and Optical Comparison of In-S Films Deposited by CBD and Ultrasonic Pyrolytic Spraying, as a Buffer Layer in CIGS So-lar Cells

Indium sulphide (In2S3) has positioned itself as an environmentally friendly and efficient option compared to traditional CdS, used as a buffer layer in thin-film solar cells that use Cu(In,Ga)Se2 (CIGS) as an absorbent material. This study provides a comparative analysis of two techniques for depositing thin films of In2S3: chemical bath deposition (CBD) and ultrasonic pyrolytic spraying. Their structural, morphological, compositional, and optical properties were evaluated. The films obtained by pyrolytic spraying, showed adequate crystallinity and uniformity. On the other hand, the films deposited by CBD had better stoichiometry (In2:S3 ≈ 40:60% at.) and higher bandgap values (up to 4.5 eV), which favors optical transmission in the blue region of the solar spectrum. All films produced by both techniques remained within the optimal thickness range (50–100 nm) to function as a buffer layer. In summary, both methods proved to be viable for the fabrication of In2S3 layers, with CBD excelling in optical and compositional characteristics, while pyrolytic spraying excels in structural quality and morphology. These findings consolidate In2S3 as a promising and sustainable candidate to CdS in the manufacture of thin-film solar cells.