A Low-Cost\nand Large-Scale Producible Polymer Multilayer\nRadiative Cooling Film for Reducing Plant Heat Stress

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