Universal Color Retrofit to Polymer-Based Radiative Cooling Materials.

Polymers with broad infrared emission and negligible solar absorption have been identified as promising radiative cooling materials to offer a sustainable and energy-saving venue. Although practical applications desire color for visual appearance, the current coloration strategies of polymer-based radiative cooling materials are constrained by material, cost, and scalability. Here, we demonstrate a universally applicable coloration strategy for polymer-based radiative cooling materials by nanoimprinting. By modulating light interference with periodic structures on polymer surfaces, specular colors can be induced while maintaining the hemispheric optical responses of radiative cooling polymers. The retrofit strategy is exemplified by four different polymer films with a minimum impact on optical responses compared to the pristine films. Polymer films feature low solar absorption of 1.7-3.7%, and daytime sub-ambient cooling is exemplified in the field test. The durability of radiative cooling and color are further validated by dynamic spectral analysis. Finally, the potential roll-to-roll manufacturing empowers a scalable, low-cost, and easy-retrofitting solution for colored radiative cooling films.