Green synthesis of single layered SS/CuO nanocoatings as solar selective absorber: Morphological, Structural and optical properties

Abstract

Herein, spectrally selective single-layered CuO nanocoatings were successfully demonstrated via green synthesis, and deposited on stainless steel (SS) substrates using spin-coater at 700, 800, 900 and 1000 rpm. The morphological surface, structural, and compositional analysis of the obtained nanocoatings were studied using SEM, XRD, EDX, and Raman spectroscopy. The SEM images shows a nanorod-like structure surfaces with a dense surface morphology. The XRD patterns confirm the presence of peaks indexed to a monoclinic structural phase of CuO. The EDX spectra clearly reveals the presence of Cu, and O elements and XPS spectra reveals peaks of Cu2p and O1s core levels which are typical characteristics of Cu (II) and O(II), respectively in CuO. Raman spectra shows peaks at 305, 344, and 642 cm− 1 attributed to Raman active (Ag+2Bg) modes for Cu-O stretching. Rutherford backscattering spectrometry (RBS) determines content of the elements, and changes in thicknesses of the coatings with rotational speed (RS) of the spin coater. The elemental content of Cu, and O atoms are respectively 54, and 46 at %, and the thicknesses are calculated to be 1.406×1018 atoms/cm2 (296.3 nm), 1.286×1018 atoms/cm2 (271.0 nm), 1.138×1018 atoms/cm2 (239.8 nm), and 0.985×1015 atoms/cm2 (207.5 nm) at 700, 800, 900 and 1000 rpm, respectively. The optical properties of CuO nanocoatings was characterized using UV-Vis-NIR, and FTIR spectrometers, and its vital solar selectivity parameters of solar absorptance (α), and emissivity(ε) were evaluated in the range of 0.3–2.5, and 2.5–20µm wavelengths, respectively, and exhibits the solar parameters (α = 0.91, and ε = 0.31) associated to 700 rpm due to an intrinsic and interference-induced absorption as well as higher attenuation of light.