A Self-Adaptive Integration of Photothermal and Radiative Sky Cooling for Continuously Efficient Harvesting of Energy From the Sun and Outer Space

The sun (~6000 K) and outer space (~3 K) are two significant renewable thermodynamic resources for human beings on Earth. The solar thermal conversion by photothermal (PT) and harvesting the coldness of outer space by radiative sky cooling (RSC) have already attracted tremendous interest. However, most of the approaches for PT and RSC are static and mono-functional, which can only provide heating or cooling under sunlight or darkness. Here, we develop a spectrally self-adaptive absorber/emitter (SSA/E) with strong solar absorption and switchable emissivity within the atmospheric window (i.e., 8-13μm) for the dynamic combination of PT and RSC, corresponding to continuously efficient energy harvesting from the sun and universe. The as-fabricated SSA/E not only can be heated to ~170°C above ambient temperature under sunshine and but also be cooled to 20°C below ambient temperature, and thermal modeling captures the high energy harvesting efficiency of the SSA/E, enabling new technological capabilities.