<p>In this study, we have successfully synthesized the stannite phase of Cu₂FeSnS₄ (CFTS) by a single-step electrodeposition method, followed by sulfurization-free annealing at temperatures between 400 and 500 °C. This innovative method eliminates the often-costly sulfurization step. Before electrodeposition, electrochemical investigations were carried out, including cyclic voltammetry to analyze the electrochemical behaviors of the elements Cu, Fe, Sn, and S, and in situ electrochemical impedance spectroscopy to study the electrical properties of the system during electrodeposition at a potential of − 1.05 V. CFTS thin films were then characterized to determine their physical, morphological, compositional, and optical properties. X-ray diffraction (XRD) and Raman spectroscopy confirmed the formation of the CFTS stannite phase. In particular, the film annealed at 450 °C, without a sulfurization step, revealed a well-crystallized stannite phase with a crystallite size of 21.075 nm. This size, considered relatively large, is advantageous for photovoltaic applications. Energy dispersive spectroscopy (EDS) analysis validated the presence of Cu, Fe, Sn, and S in the film. The resulting surface is characterized by its homogeneity and compactness, with well-defined grains. Moreover, the optical bandgap energy, measured at 1.35 eV, is within the optimum range of 1.2 to 1.5 eV for CFTS materials, reinforcing their potential for high-performance photovoltaic applications.</p>