A photosynthetically active radiative cooling film

The sequestration of atmospheric CO2 through plant photosynthesis helps to mitigate climate change while providing other ecological benefits. However, heat and drought stress can limit plant growth and thus the mitigation potential of vegetation, particularly in drylands. Here we present a photosynthetically active radiative cooling film that decreases the ambient air temperature, minimizes the level of water evaporation and increases photosynthesis in dryland plants. This film comprises a photonic crystal layer sandwiched between polydimethylsiloxane and antifogging polyacrylamide hydrogel layers. The polydimethylsiloxane layer, featuring high mid-infrared emissivity (92% for wavelengths of 2.5-20 mu m), enables maximal radiative cooling, the photonic crystal permits the selective transmission of photosynthetically active sunlight (71% for wavelengths of 0.4-0.5 mu m and 77% for wavelengths of 0.6-0.7 mu m) to boost photosynthesis and the polyacrylamide layer prevents the shading effect, thereby supporting plant growth. Field experiments indicated that our film decreases the air temperature by 1.9-4.6 degrees C and the level of water evaporation by 2.1-31.9%, consequently increasing the biomass yield of plants by 20-370%. According to our assessment, global application of the film on dryland plants could result in an approximately 40% increase in carbon sink compared with the case without the film (2.26 +/- 1.43 PgC yr-1). This work highlights the development of next-generation technologies that can address the water-food-energy nexus of climate change. This study presents a film design that can maximize radiative cooling, transmit photosynthetically efficient light and reflect remaining sunlight in favour of photosynthsis and plant growth.