Thermal photonics advances enable efficient subambient daytime radiative cooling for vertical surfaces

Radiative heat transfer is one of the most critical energy transfer mechanisms in nature. However, traditional blackbody radiation, due to its inherent characteristics, such as its non-directional, incoherent, broad-spectrum, and unpolarized nature, results in energy exchange between the radiating body and all surrounding objects, significantly limiting heat transfer efficiency and thermal flow control. These limitations hinder its practical application.