A High-efficient Daytime Radiative Cooling Film

The increase in cooling demand of diurnal human activities using mechanical systems to dissipate heat to the surroundings consumes large amounts of energy with excess heat production and CO2 emissions. The passive cooling process of the earth by infrared thermal radiation through the atmospheric transparency window (8~13 μm) inspires people to use the outer space as a heat sink where the waste heat can be dumped without energy consumption. However, there are strict material restrictions for daytime radiative cooling to realize high cooling power and large-scale applications simultaneously. Herein, based on the classical Drude-Lorentz oscillator model, we design the molecular chains to manipulate the absorption spectrum from ultraviolet-visible-infrared and propose a high-performance see-through polymer film. The film with averaged sunlight absorption of ~0.004 (0.3~2.5 µm) and thermal emittance of ~0.93 (8~13 μm) ensures an excellent daytime cooling power, which is far more efficient than currently published results. Furthermore, it can be fabricated by the roll-to-roll process and covered on silicon solar cells and window glasses without sacrificing their aesthetics or functionality. We model the potential impact of this transparent film when used on roofs, walls, and glasses of a midrise apartment, indicating energy savings about 6 MW·h every year in warm and humid climates c…