Nanometric multi-scale rough, transparent and anti-reflective ZnO superhydrophobic coatings on high temperature solar absorber surfaces

We report the fabrication of a nanometric multi-scale rough, transparent and anti-reflective zinc oxide (ZnO) superhydrophobic coating on TiAlN/TiAlON/Si3N4 spectrally selective solar absorber surface, which has been developed previously for solar thermal power generation applications. The optimized ZnO superhydrophobic coating on the absorber surface demonstrates extraordinary water repellency (with contact angle >155°), improved absorptance (>0.96) and excellent broadband anti-reflection in the visible range of the solar spectrum. The multi-functional ZnO coating was stable up to 450 °C (in air and vacuum), indicating its reliability for high temperature photothermal conversion applications.