Aluminium Nitride Doping for Solar Mirrors Self-Cleaning Coatings

Abstract

Soiling severely reduces solar mirror performance, requiring dispendious water consumption for cleaning operations and causing an increase in the levelized cost of energy (LCOE). An emerging technology for facing this problem consists of developing transparent self-cleaning coatings, able to be washed with a small amount of water by virtue of the modulation of surficial wetting properties. Nevertheless, the beneficial effects of coatings decrease in the first year, and coated mirrors show even higher soiling than non-coated ones. Moreover, it is important that coating production processes are economically convenient, consistent with the intended reduction of overall costs. The aim of this work is the research and development of a cheap and scalable solution, compatible with mirror fabrication steps and, in such a sense, economically advantageous. It involves the substitution of the alumina last layer of solar mirrors with more hydrophobic, potentially auxetic aluminum compounds, such as nitrides. In particular, 2D inorganic aluminum nitride thin films doped with metals (such as aluminum and silver) and non-metals have been fabricated by means of reactive sputtering deposition and characterized for the purpose of studying their self-cleaning behavior, finding a trade-off between wetting properties, optical clarity, and stability.