Coloured Solar-thermal Absorbers – A Comparative Analysis of Cermet Structures

Novel coloured solar-thermal absorber coatings are obtained as thin films of alumina infiltrated with pigment oxides (Fe2O3 and V2O5) and sulfides (CuS). The coatings are stepwise obtained in successive spray pyrolysis depositions, using inorganic precursors. The composite layers have good crystallinity degree and develop various morphologies, with very different matrix- pigment infiltration; the addition of gold nanoparticles differently influences the properties, depending on the interactions with the precursor species: it can strongly decrease the thermal emittance, when embedded in the layers structure (Fe2O3) or it can form large aggregates on the matrix (V2O5) without significant effect on the optical properties. Bright red spectral selective coatings, with spectral selectivity of 12 were obtained using Fe2O3 hematite pigments.