The effect of Cu/In molar ratio on the analysis and characterization of CuInS2 nanostructures

Copper indium sulfide (CuInS 2 ) nanostructures have been successfully deposited on silicon substrates using the electrospinning method. As a result, different copper to indium (Cu/In) molar ratios have been used: 0.1, 0.5, 0.8, 1.2, and 1.4 at annealing temperature 300 °C. The optical properties have been measured using photoluminescence spectroscopy (PL), which indicated a decrease in the optical band gap from 1.6 to 1.53 eV with increasing Cu/In molar ratio. The structural properties have been deduced using X-ray diffraction (XRD), which improved the crystallinity size and quality by increasing the Cu/In molar ratio. The c/a ratio at different Cu/In molar ratios ranges from 2.004 to 2.037 due to the zinc blende structure, and the crystallite size was varied from 22.53 to 56.33 nm. The average grain size was approximately 39 nm, and the lattice parameters vary from 5.53 to 5.5 Å and from 11.09 to 11.2 Å for a and c, respectively. The compositional properties are studied using energy-dispersive X-ray spectroscopy (EDX), which showed that the samples are almost stoichiometric with S-deficient and Cu-rich composition. The best-formed structure’s value was at molar ratio 1.4, where the real phase is 60.5%, and the secondary phase is 39.5% due to the increase in grain size, and that in turn occurred due to the decrease in the energy band gap. The morphological properties have been depicted using field emission scanning electron microscopy (FESEM). FESEM images indicated a change in the grain particles’ homogeneity and agglomeration due to changing the Cu/In molar ratio. According to the available literature, the obtained results promise to use CuInS 2 as absorber material in photovoltaic devices’ nanostructure.