Effect of molarity on the optical and structural properties of CdS thin films deposited by spray pyrolysis on flexible plastic substrates

Solar cell substrates made from high-temperature polymer bases can be applied to various types of thin-film devices. Studying how different substrates impact the properties of semiconductor films is crucial. In this research, chemical spray pyrolysis (CSP) was utilized to coat thin layers of cadmium sulfide (CdS) on polyimide (PI) plastic bases. The coating process involved using distinct precursor solutions with molar concentrations of 0.1, 0.2, 0.3, and 0.4 M. X-ray diffraction (XRD) analysis was applied to assess the crystal structural characteristics. The XRD findings demonstrated the correct phase development in the CdS structure. The outcomes revealed that the crystallite size was directly related to the molarity concentration, with larger crystals forming at higher concentrations. Larger crystallites can lower grain boundary density, which can affect the film's electrical and mechanical properties. Furthermore, a hexagonal structure was observed in the CdS layers. The optical band gap values of the CdS thin films increased from 2.16 to 2.21 eV as the molarity concentrations were elevated.