In this work, the effects of silver doping with different Ag/(Ag + Cu) ratios (i.e., 2%, 5% and 10% at.% in the spray solution) on the structural, morphological, optical, electrical and antibacterial properties of Cu₂MgSnS₄ (CMTS) thin film grown by spray pyrolysis have been studied. The X-ray diffraction (XRD) and selected area electron diffraction (SAED) results have shown that the kesterite phase of CMTS thin films has a maximum crystallite size of about 19.60 nm for 5% Ag/(Ag + Cu). Scanning electron microscopy (SEM) images have shown spherical grain shapes. The transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) microscopy observations confirmed the intrinsic reticular planes of CMTS thin film with (112) as a preferred orientation and interplanar spacing value of 3.1 Å. The optical properties showed high absorbance and an absorption coefficient of about 10⁴ cm⁻¹ in the visible region with an optical band gap energy of 1.51 eV. Impedance analysis spectroscopy demonstrated good electrical properties of the CMTS film obtained using 5% Ag/(Ag + Cu). The antibacterial activity of the undoped and Ag-doped particles of CMTS obtained using 5% Ag/(Ag + Cu) against different strains of pathogenic bacteria was tested using the agar well diffusion method. These results showed a significant antibacterial activity of the Ag-doped CMTS particle, which was much higher than the undoped CMTS particles. These experimental findings may open new practices for the Ag-doped CMTS compound, especially the one obtained using 5% Ag/(Ag + Cu), in antibacterial application.

This chapter deals with the synthesis of quaternary Cu₂MgSnS₄ (CMTS) thin films, through the Spray Pyrolysis technique (SP). SP is a simple, cost-effective deposition technique that depends upon various factors. Furthermore, the advantages and disadvantages of the SP method have been explored. Moreover, the discussion has been made through the case study of the influence of deposition parameters, particularly substrate temperature, on the structural, morphological, optical, and electrical properties of CMTS thin films. The crystallization of CMTS in the kesterite phase at 300°C leads to the improvement in crystallinity and grain morphology, and favorable optical properties such as a high absorption coefficient and a suitable band gap energy of 1.47 eV. Lastly, the application of doping by Ag using Spary Pyrolysis on the physical properties of Cu₂MgSnS₄ thin films is briefly discussed, highlighting their potential for antibacterial activity. This chapter can open a new avenue for researchers working in the field by combining a general understanding of CMTS thin films with particular experimental insights.