High performance {Nb₅TaX₁₂}@PVP (X = Cl, Br) cluster-based nanocomposites coatings for solar glazing applications

The development of highly ultraviolet (UV) and near-infrared (NIR) absorbent transparent coatings is an important enabling technology and area of research for environmental sustainability and energy conservation. Different amounts of K₄[{Nb₅TaXⁱ ₁₂}X^a ₆] cluster compounds (X = Cl, Br) dispersed into polyvinylpyrrolidone matrices were prepared by a simple, nontoxic and low-cost wet chemical method. The resulting solutions were used to fabricate visibly transparent, highly UV and NIR absorbent coatings by drop casting. The properties of the solution and films were investigated by complementary techniques (optical absorption, electrospray ionization mass spectrometry and Raman spectroscopy). The UV and NIR absorption of such samples strongly depended on the concentration, dispersion and oxidation state of the [{Nb₅TaXⁱ ₁₂}X^a ₆] nanocluster-based units. By varying and controlling these parameters, a remarkable improvement of the figures of merit T_L/T_E and S_NIR for solar-glazing applications was achieved compared to the previous results on nanocomposite coatings based on metal atom clusters.