Influence of Cadmium Salt Anion on Crystal Structure and Optical Properties of Supersaturated Solid Solution CdxPb1-xS Films

Solid solution CdxPb1-xS films were synthesized by chemical bath deposition method from aqueous solutions of lead acetate and cadmium salts with different anionic component concentrations up to C-[CdAn]=0.06 mol/L in the presence of thiourea and complexing agents. According to X-ray structural analysis, introducing cadmium salts resulted in a decrease in the lattice parameter. The lowest value of the lattice parameter is observed for salts containing oxygen in the anionic component. The cadmium content of these films is estimated to be x = 0.24. Analysis of the absorption spectra of CdxPb1-xS films in the near IR range indicates the increase in the bandgap width of lead sulfide when cadmium is added. When the anion of the cadmium salt changes from iodide-ion to acetate-ion, the bandgap increases from 0.62 to 0.77 eV. The larger bandgap is consistent with the greater cadmium concentration in the films determined from the X-ray structural analysis and indicates the beneficial effect of oxygen on the introduction of cadmium into the lead sulfide lattice.