Radiative-Cooling Composites with Enhanced Infrared Emissivity by Structural Infrared Scattering through Indium Tin Oxide Nanoparticles in a Polymer Matrix

Radiative cooling has attracted tremendous interest as it can tackle global warming by saving energy consumption in heating, ventilation, and air conditioning (HVAC) in buildings. Polymer materials play an important role in radiative cooling owing to their high infrared emissivity. Along this line, numerous studies on optically optimized geometries were carried out to enhance the selective wavelength absorption for high infrared emissivity; however, the polymer material itself relatively was not investigated and optimized enough. Herein, we investigate the infrared radiation (IR) absorption coefficient of various polymer types, and introduce a new concept of radiative-cooling composites. By dispersing the IR scattering medium in a polymer matrix, IR can be effectively scattered and attenuated by the polymer matrix. Indium tin oxide was utilized as the IR scattering medium in a cellulose acetate polymer matrix in this report. The window film was made with this composite and showed an effective cooling performance by outdoor thermal evaluation. This composite opens a new venue to endow materials with enhanced radiative-cooling property regardless of the polymer types.