Cu(Mn_0.748Ni_0.252)₂O₄/SiO₂ Nanoparticle Layers for Wide-Angle Spectral Selectivity and High Thermal Stability

Spectrally selective absorber coatings (SSACs) have attracted tremendous research attention owing to their high efficiency of conversion of solar energy into heat with minimal emittance. In this regard, we have developed a new spinel material (Cu(Mn0.748Ni0.252)2O4) as SSAC by the dip-coating technique. The dual-functional layer (SiO2) is deposited on a spinel absorber to serve as an antireflective and thermal barrier layer for the improvement of solar absorptance and thermal stability. The developed tandem absorber exhibits an excellent solar absorptance (α) of 0.95, low spectral emittance (ε) of 0.14, and good thermal stability up to 500 °C for 250 h. Additionally, the tandem absorber has exhibited outstanding wide-angle solar absorptance with a net enhancement of 5–74% over an angle of incidence ranging from 10 to 80°. The developed coatings were widely characterized by grazing incidence X-ray diffraction, thermogravimetric techniques, high-resolution transmission electron microscopy, and Universal Measurement Accessory to determine the properties. Our findings indicate that the development of spinel-based tandem SSAC by the wet chemical method may reduce the cost of solar thermal systems, and the wide-angle absorption with high thermal stability may open the possibilities of high photothermal conversion efficiencies.