New coating synthesis comprising CuO:NiO/C to obtain highly selective surface for enhancing solar energy absorption

A novel nano coating was synthesized by spin and casting methods to obtain high-performance selective surfaces to enhance solar energy absorption. Nanomaterials (CuO:NiO) and carbon (fly ash) were used to provide a cost-efficient coating with high absorption efficiency. The materials were prepared with different carbon doping content, and the coating of the nanocomposite film was deposited by these techniques on pre-cleaned copper and glass substrates. Energy dispersive X-ray analysis was used to determine the component element for carbon (fly ash), and its diameter was measured using scanning electron microscopy. The optical properties were investigated by UV spectrometry and reflectivity tests in a range of 250–1300 nm at room temperature. The absorbance coefficient, transmittance, reflectance, skin depth, optical density, optical energy gap and Urbach’s parameters of the nanocomposite thin films were also determined. The data were analyzed and interpreted in terms of the theory of phonon-assisted direct electronic transitions. The E_g of the doped carbon was measured in different composition ratios of CuO:NiO (A = 0.5:2.5, B = 1:2, C = 1.5:1.5, D = 2:1, E = 2.5:0.5) wt.%, and fixed carbon content at 7 wt.%. The results of the doped samples revealed an energy gap value of 2.5–3.9 eV. When the ratio of the CuO content ranged from 0.5 to 2.5, composition B was found to have three regions in its figure that were dependent on the CuO content in the nanocomposite mixture. The optical band gap values were highly dependent on the CuO content in the nanocomposite films.