Bismuth sulfide is a prominent non-toxic n-type semiconductor, known for its band gap energy of 1.3 eV [1]. When paired with FTO glass, it emerges as an ideal choice for optoelectronic devices, especially suited for solar cells. Its excellent light absorption properties and simple synthesis contribute to its growing significance in next-generation photovoltaic systems.
Pre-patterned FTO (fluorine-doped tin oxide) substrates were cleaned thoroughly before deposition. The first approach to bismuth sulfide thin film synthesis was a chemical bath deposition method, using \(Bi(NO_{3})_{3}\cdot5H_{2}O\), L-cysteine, and \(EDTA-Na_{2}\) as a chelating agent, whereas bismuth ions coordinate with it, forming stable \([Bi-EDTA]^{-}\) structures, which inhibits the direct bonding with \(S^{2-}\) ions. After the complete dissolution of all reagents, FTO substrates were inserted into the solution, all while keeping the bath at 90 °C for at least 8 hours to produce \(Bi_{2}S_{3}\) thin films.
The other approach to this reaction is to utilize an autoclave, which differs significantly in reaction conditions and final product characteristics. Unlike the first method, synthesis using an autoclave occurs under a high temperature and pressure. This method results in better-defined with improved purity crystals.
All samples were analyzed by X-ray diffraction analysis on the Bruker D8 Advance diffractometer. Precipitate was scanned over the range 2θ = 3-70° at a scanning speed of 1° \(min^{-1}\) using a coupled two theta/theta scan type. This test determined structural characterization of the obtained materials. In addition, crystallite size of obtained \(Bi_{2}S_{3}\) product was calculated using the Scherer equation. The acquired results were compared and discussed.