Recent advances and progresses in photonic devices for passive radiative cooling application: a review

Cooling represents a significant sector of energy consumption.¹ It is the most significant driver of peak electricity demand as well as considerable end use of energy globally.² The global energy consumption can be reduced by adopting a cooling strategy that can cool without any electrical input, which is also known as passive cooling technique. The cooling can be achieved if one is able to reach and maintain a temperature below ambient temperature. Radiative cooling, as a passive radiative cooling scheme, does not require any external active devices, such as fans, air conditioners, or thermoelectric.^{3 – 5} It works on the principle that the atmosphere is almost transparent between 8 and $13\mu \mathrm{m}$ (also known as ‘‘sky window”). Thus, utilizing outer space as a heat sink by allowing the emission of thermal radiation from surface to the universe.^6,7