Ultrasound-assisted wet chemical synthesis of texturized Mo/MoO3 spectrally selective solar absorber coatings

A simple, low-cost Mo/MoO3 textured spectrally selective solar absorber coating prepared using an ultrasound-assisted wet chemical technique on a Mo substrate at different chemical reaction times is presented. The X-ray diffraction structural analysis of the textured coatings revealed only peaks related to Mo from the substrate, implying that the MoO3 coatings were amorphous at ambient temperature. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy confirmed the presence of Mo+6 ions representing MoO3 in the coatings. The topologic investigations using atomic force microscopy indicated texturized growth with an average surface roughness of 53.15 nm for the sample attacked for 4 h. Absorption bands related to M=O and Mo-O stretching bonds were evident from Fourier transform infrared measurements. Scanning electron microscopy investigations confirmed the presence of surface texturing and agglomerated nanoparticles in the coatings. Optical investigations of the MoO3 coatings on the Mo substrate revealed both a high solar absorptance of 0.91 and a low thermal emittance of 0.05 at 100°C indicating very good solar selectivity. These optical properties can arise from both light trapping which favors multiple absorptions, and intrinsic effects that result from the textured and intrinsic spectrally selective solar absorber design. These results demonstrate that Mo/MoO3 textured and intrinsic coatings deposited by using ultrasound-assisted chemical bath etching and oxidation are exceptional materials for selective solar absorber applications.