Effect of lead and zinc composition on the optical and structural characteristics of PbZnS thin films fabricated by spray pyrolysis

In this study, PbZnS thin films with varying concentrations of lead (Pb) and zinc (Zn) were successfully produced using the spray pyrolysis method. The structural, optical and surface properties of the films were systematically investigated as a function of the Pb/Zn ratio. Xray diffraction (XRD) analysis confirmed the polycrystalline nature of the films, showing a cubic zinc blende structure with improved crystallinity as Pb content increased. Initially, with the increase in Pb concentration, larger crystallite sizes and decreased microstress were observed, but with the increase of Pb addition, the formation of secondary phases and the emergence of lattice distortions caused a decrease in grain size and an increase in microstress. Optical measurements showed a tunable bandgap in the range of 3.25 eV to 1.30 eV as Pb content increased. The narrowing of the bandgap is attributed to the lower energy gap of PbS compared to ZnS, which allows for enhanced absorption of longerwavelength light, especially in the visible and near-infrared regions. These findings highlight the potential of PbZnS thin films for optoelectronic applications, where the ability to tune the bandgap and enhance absorption through compositional adjustments is crucial for optimizing device performance. The surface morphology of the PbZnS thin films was analyzed using scanning electron microscopy (SEM). The SEM images showed notable changes in grain size and surface roughness as Pb content increased, with larger grains and a more distinct surface structure observed in films with higher Pb concentrations. This work demonstrates the versatility of spray pyrolysis in fabricating thin films with controllable properties, offering valuable insights for future applications in energy conversion technologies, including solar cells and photodetectors.