Bismuth oxide is a compound of bismuth, with the chemical formula Bi2O3. It has seen extensive study for its ionic conductivity, but its most mature use is as a colorant in pyrotechnics.
Passive daytime radiative cooling —also called passive radiative cooling, daytime passive radiative cooling, radiative sky cooling, photonic radiative cooling, and terrestrial radiative cooling—is the
Bismuth(III) oxide
…similar to those produced by toothpaste. Bismuth oxide was used to develop a scalable colored surface high in solar reflectance and heat emissivity for passive radiative cooling. The paint was non-toxic and demonstrated a reflectance of 99% and emittance of 97%. In field tests the coating exhibited significant cooling power and…
PDRC can lower temperatures with zero energy consumption or pollution by radiating heat into outer space. Widespread application has been proposed as a solution to global warming.
PDRC maximizes outgoing infrared radiation (shown in orange) and minimizes the absorption of solar radiation (shown in yellow).
A photonic radiator film based on the longicorn beetle Neocerambyx gigas exhibited 95% solar irradiance and 96% emissivity.