SILICON OXYNITRIDE MULTILAYERS AS SPECTRALLY SELECTIVE MATERIAL FOR PASSIVE RADIATIVE COOLING APPLICATIONS

Silicon oxynitride has optical properties that makes it attractive as radiative cooling material. Because of the interface contributions, mu ltilayered configurations provide a very promising way to enhance the device performances. Three silicon oxynitride multilayers deposited on to aluminum-coated glass substrate were prepared and tested. A broaden ing of the absorption peak within the atmospheric window was observed. Radiative cooling parameters e(S2)(-H) and eta(H) were deduced from i nfrared reflection measurements. They correspond to temperature drops of 52, 48 and 56 degrees C (from ambient temperature of 27 degrees C), and cooling powers of 125, 118 and 119 Wm(-2). Temperature drops and cooling power remain competitive for practical uses, even after non ra diative exchange processes are taken into account.