Structural, wettability, optical, and electrical modifications by varying precursor solutions of sprayed Co3O4 thin films for solar cell applications

Abstract

Co₃O₄ thin films were successfully deposited by spray pyrolysis with different precursor solutions, including cobalt nitrate, cobalt acetate, and cobalt chloride. The effect of these precursor solutions on the properties of the obtained Co₃O₄ thin films was extensively studied. XRD analysis revealed that all three films exhibited polycrystalline nature with a preferred crystal orientation along the (311) plane. The crystallite size was observed to decrease for the films prepared using three different precursors: cobalt nitrate, cobalt chloride, and cobalt acetate, respectively. Raman spectroscopy provided further confirmation of the successful formation of the Co₃O₄ spinel structure. AFM analysis demonstrated the significant impact of the cobalt source on surface morphology. The cobalt nitrate-based film exhibited a significantly lower surface roughness value of 15.29 nm, in contrast to the films prepared from cobalt chloride and cobalt acetate, which exhibited higher roughness values of 60.30 nm and 65 nm, respectively. Contact angle analysis revealed that all the samples exhibited a hydrophobic nature. UV–visible transmission spectra revealed that the film produced using cobalt nitrate has high light absorption and a smaller optical band gap. Electrical characterization further demonstrated that the Co₃O₄ film prepared with cobalt nitrate had the lowest electrical resistivity (ρ = 2.905 × 10^–1 Ω.cm) among the films.