OICC Press Journal of Theoretical and Applied Physics 2251-7235 20 2 2026 04 30 Optimization of ‎Copper Ion ‎Concentration into ‎the Lattice of ‎Barium Sulphide ‎Nanoparticles ‎Synthesized via a ‎Chemical ‎Approach 10.57647/jtap.2026.2002.12 EN McDonald Chukwudi OKAFOR Department of Physics Education, Federal College of Education (Technical) Asaba, Delta State, ‎Nigeria Lawrence Ese ESIEKPE Department of Physics Education, Federal College of Education (Technical) Asaba, Delta State, ‎Nigeria Vivian Anulichukwu ATTOH Department of Physics Education, Federal College of Education (Technical) Asaba, Delta State, ‎Nigeria Nwando Blessing OKEKE Department of Physics Education, Federal College of Education (Technical) Asaba, Delta State, ‎Nigeria Azuka Bright OKWUELUM Department of Physics Education, Federal College of Education (Technical) Asaba, Delta State, ‎Nigeria Joseph Onyeka EMEGHA‎ Department of Physics, Hensard University, P.O.Box 1036, Yenagoa, Bayelsa State, Nigeria‎ https://orcid.org/0000-0001-6392-8867 Journal Article 2026 04 30 Copper barium sulphide ( ) thin films (TFs) were fabricated via the chemical bath deposition (CBD) approach on glass substrates. The study used solutions of copper (II) sulphate, barium chloride dihydrate, and thiourea as the sources of the elements (copper, barium, and Sulphur). The thin films were characterized using the x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and ultraviolet-visible spectroscopy. XRD examination of the films revealed that they were polycrystalline and increased with doping concentrations.  However, increasing copper incorporation led to an increase in the average crystallite sizes from 18.80 to 21.96 nm, accompanied by a decrease in dislocation density (δ) ( , and strain (ε) (  respectively. Energy-dispersive X-ray analysis reveals good agreement between detected and selected element ratios with different stoichiometry. Optical examination indicated that  TFs have a transmittance that increased from 20% to 50% with an increase in copper concentrations, while the optical band gap varied from 1.65 to 3.12 eV. These results indicate that the synthesized  TFs hold significant potential for applications in solar energy and optoelectronics.