High reflective polyethylene glycol terephthalate package layer for passive daytime radiative cooling in photovoltaic cells

Passive daytime radiative cooling is a promising new field for solving the energy shortage all over the world. Especially for passive radiant cooling technology on photovoltaic field, the radiant cooling film must also have high transmittance, which undoubtedly puts forward higher requirements. At present, monocrystalline silicon photovoltaic cell are the dominant products in the photovoltaic market. Many passive cooling equipment such as temperature plates, fins, and phase change blocks will increase the weight and the complexity of photovoltaic cell, so radiative cooling thin films are attracting more and more attention due to lightweight and easy replacement. In this paper, it is proposed a composite structure of polyethylene glycol terephthalate (PET) film combined with a high-reflective layer in part of the wave band, which has a maximum transmittance of 0.97 in 0.3–1.1 μm and a maximum reflectance of 0.91 in 1.1–4.0 μm. In addition to the transmittance and reflectivity of the corresponding wavelength, the effects of electrical efficiency and cooling power are also studied. It was found that the photoelectric conversion efficiency increased, meanwhile the cooling power 211.34 W·m−2 can be reached, and the working temperature of the photovoltaic cell can be reduced by 11.65℃ under the maximum temperature 75.80℃ in normal operating conditions. Due to its excellent performance, this proposed structure may have potential practical applications in daytime radiation cooling of photovoltaic cells on sale.