Enhancing the Transparency–Temperature Trade-Off Through Spectral Engineering and Radiative Cooling

Abstract

Excess solar heat gain limits greenhouse productivity in tropical climates, where conventional polymer covers accumulate thermal energy and allow near-infrared (NIR) transmission. Here, we demonstrate a scalable multilayer greenhouse film that mitigates daytime heat stress through spectral management of solar radiation combined with radiative cooling. A TiO<inf>2</inf>-embedded polyethylene terephthalate (PET) scattering layer is laminated with ultraviolet (UV)–IR selective films to prevent excess heat while allowing appropriate photosynthetically active radiation (PAR) transmission. Two configurations are designed to address crop-dependent light requirements: a higher-transmittance film (∼57% PAR) and a stronger heat-rejection film (∼37% PAR). The multilayer structures suppress NIR transmission (up to 80–92% rejection), reduce UV exposure, and exhibit near-unity emissivity within the 8–13 µm atmospheric window (ε¯ ≈ 0.99), enabling efficient radiative heat dissipation. Outdoor rooftop measurements under tropical sunlight demonstrate consistent daytime temperature reductions of 3–5°C compared with those of commercial greenhouse films; the PET-based laminate also provides high mechanical robustness (69–92 MPa tensile strength). These results establish spectral engineering as a practical strategy to manage the transparency–cooling trade-off for passive greenhouse cooling in hot climates.