Cooling colors below the ambient temperature

The colors of objects are generally originated from reflecting desired light in the desired direction and absorbing the undesired light, which will substantially produce heating. Many efforts have been made to focus on cooling the colorful objects. However, a cooling strategy to cool colorful objects beyond a limit of temperature below the ambient temperature while fully preserving the excellent color properties of high saturation and large viewing field is still a great challenge, as it is rather difficult to independently control the four light bands simultaneously: high diffusion of desired light, low absorption of undesired complementary visible light, low absorption of near-IR light, and high emission of mid-IR light. Inspired by Morpho butterflies, we reported here a robust configure consisting of a multilayer, a disorder structure, and a total reflection layer to cool colorful objects to overcome the challenge. Numerical simulations and experimental measurements demonstrated that our configure can cool a class of colorful objects to not only a temperature of around 2 °C below the ambient temperature, but also with ultra-high saturations (100%) and a wide range of viewing angles (±60°), indicating a great potential for energy sustainability of colorful objects such as buildings, vehicles, facilities, and equipment.