Flexible structural polyethylene films for dynamically tunable energy harvesting from the sun and outer space

Passive daytime radiative cooling (PDRC) achieves a sub-ambient temperature without any electricity input, which is of great significance for global energy savings and minimum carbon footprint, especially, in hot seasons. However, due to the static performance of most PDRC materials, it may cause overcooling and high heating energy consumption in cold seasons. Here we establish a structural surface on ubiquitous polyethylene (PE) films and demonstrate an asymmetric electromagnetic transmission with forward/backward transmittance ratios of 2.61 and 1.67 in both solar irradiance and long-wave infrared (LWIR) spectral ranges, enabling it to work as a multispectral self-adaptive window (MSW). By integrating the MSW with the PDRC material, the originally static PDRC can be transformed into a dynamic one that allows the switching between temperatures 4.3 degrees C lower and 3.4 degrees C higher than the ambient temperature of the chamber interior. The cooling and heating modes are achieved through electrically actuating the MSW, which originates from the dynamically tunable energy harvesting from the sun and outer space. The MSW features transition-temperature-independent switching, broad spectral tunability, lightweight, robust mechanical strength, low cost, and scalable manufacturability, benefiting both an in-depth insight into the dynamical interaction of terrestrial objects with nature thermodynamics resources and broad applications.