A Low-Cost and Large-Scale Producible Polymer Multilayer Radiative Cooling Film for Reducing Plant Heat Stress

The greenhouse effect exacerbates plant heat stress, which poses a serious threat to global food production and atmospheric cycling. Spectrally selective radiative cooling films have been proven to have great potential in alleviating plant heat stress. However, their high cost and slow production speeds due to vacuum-based fabrication techniques have hindered widespread application. Here, we propose a strategy to reduce plant heat stress by using a polymer multilayer radiative cooling film. This film consists of two spectrally selective polymer multilayer film stacks and a polymer emitter. The polymer multilayer film stacks selectively transmit photosynthetically active radiation (52% for wavelengths of 0.4–0.48 μm and 85% for wavelengths of 0.6–0.7 μm) to boost photosynthesis, and the polymer emitter has high infrared emissivity to achieve excellent cooling performance. Field experiments indicated that this film reduces air temperature by 2.3–5.0 °C and the temperature at 3 cm below the soil surface by 2.1–4.1 °C, decreasing soil water evaporation by 11.2–32.4%. Consequently, plant biomass yield increases by 21.1–195.9%. Furthermore, the polymer multilayer radiative cooling film prepared by multilayer coextrusion has the advantages of low cost, fast processing speed, rich variety of candidate materials, and a simple structure. This work accelerates the process of large-scale practical application of passive radiative cooling technology in alleviating plant heat stress and promoting plant growth.