Investigation of DFT, structural and optical properties of ZnCo2O4 thin films prepared by spray pyrolysis

Spinel-type zinc cobalt oxide (ZnCo₂O₄) thin films were reported by the spray pyrolysis route. The first principle investigation was used to investigate the electronic band structure and density of states (DOS) for the ZnCo₂O₄ crystal system. Further, obtained thin films were analyzed with X-ray diffraction (XRD) and UV–visible spectroscopy. The film prepared at 400 °C substrate temperature formed highly crystalline. The thin films of ZnCo₂O₄ shown the presence of highly dense packed grains on the surface morphology to the high substrate temperature. The absorption spectra obtained from UV–VIS spectroscopy indicate that the wavelengths in the visible region are mostly absorbed by ZnCo₂O₄ thin films. The electronic bandgap values were observed to be 1.6–2.37 eV. The density functional theory (DFT) study showed the energy gap value to be 2.18 eV. The refractive index was improved from 4.8 to 1.2 with an increase in substrate temperature. The highest value of optical conductivity was around 9.5 × 10¹² (s⁻¹) at 400 °C substrate temperature. Thus, the study provides a simple, viable route to fabricate ZnCo2O4 without post-treatment to build affordable solar cells.