Radiative sky cooling cools an object on the Earth’s surface by emitting thermal radiation through the atmospheric window to the cold universe. As a passive technique to reduce cooling energy requirements without power input

radiative cooling provides a new avenue to address the challenges of the energy crisis and global warming. Over the past few decades

radiative cooling has been limited to nighttime applications. With recent technological advancements in nanophotonics and metamaterials

daytime radiative cooling has been demonstrated. In this review

the current research status of radiative sky cooling is discussed

including its fundamental principles

advanced materials

and structures. Furthermore

applications and prospects in radiative sky cooling are summarized and the challenges are analyzed to promote the development of radiative sky cooling. As the energy security and environmental issues escalate

exploring the application of radiative sky cooling in different scenarios

such as energy saving in buildings

mitigation of the heat island effect

and improving the efficiency of solar cell generation

will considerably contribute to energy saving and emission reduction.