Highly Reflective Polymeric Coating for Passive Radiative Cooling Under Tropical Climate

Radiative cooling is a passive technology that lowers surface temperatures, which has shown great potential in temperate regions. However, cooling performance characterised by high solar irradiance and humidity under tropical climate still lacks exploration. Herein, we propose a highly reflective polymeric coating with BaSO4 particles dispersed in P(VdF-HFP) matrix for radiative cooling. Through the strong Mie scattering of sunlight and intrinsic bond vibration, the average substrate-independent solar reflectance and infrared emittance within the 8 to 13 μm atmospheric window could reach 97% and 94.2%, respectively. Under direct exposure to the sky, surfaces could maintain close to ambient temperatures even when the solar intensity was as high as 1000 W/m 2 , while separately achieving 5.7 °C below ambient during night-time with an effective cooling power of 54.4 W/m2. With a scalable fabrication-process, our cost-effective single-layer coating can be easily applied to diverse substrates, which is suitable for real-world applications in the tropics.