Antireflection and radiative cooling difunctional coating design for silicon solar cells.

Passive daytime radiative cooling (PDRC) as a zero-energy consumption cooling method has broad application potential. Common commercial crystalline silicon (c-Si) solar cell arrays suffer working efficiency loss due to the incident light loss and overheating. In this work, a radiative cooler with PDMS (polydimethylsiloxane) film and embedded SiO2 microparticles was proposed to use in silicon solar cells. Both anti-reflection and radiative cooling performance can be improved through numerical parametric study. For the best performing of PDMS/SiO2 radiative cooler, the thickness of PDMS layer, volume fraction and radius of the embedded SiO2 particles have been determined as 55 µm, 8% and 500 nm, respectively. 94% of emissivity in first atmospheric window band (8-13 µm) for radiative cooling and 93.4% of solar transmittance at the crystalline silicon absorption band (0.3-1.1 µm) were achieved. We estimated that the PDMS/SiO2 radiative cooler can lower the temperature of a bare c-Si solar cell by 9.5°C, which can avoid 4.28% of efficiency loss. More incident light can enter and be utilized by silicon layer to enhance the efficiency of the solar cells. The proposed difunctional radiative cooling coating may become guidance for next generation encapsulation of crystalline silicon solar cells.

Ordered-Porous-Array Polymethyl Methacrylate Films for Radiative Cooling.

Passive radiative cooling is a spontaneous pattern of reflecting sunlight and radiating heat into the cold outer space through transparent atmosphere windows. In this work, an ordered-porous-array polymethyl methacrylate (OPA-PMMA) film with the properties of excellent radiative cooling is designed and studied. An ultra-high emissivity of 98.4% in the mid-infrared region (3-25 µm) and a good solar reflectance of 85% in the ultraviolet and near-infrared solar spectra (0.2-2.5 µm) were achieved. The surface temperature of the OPA-PMMA film is 16 °C lower than that of the smooth-surface PMMA films and is 8.6 °C lower than that of the commercial white paint in the outdoor test. The structure of the OPA plays an important role in improving solar reflectivity and emissivity. The films are fabricated using a one-step low-cost process that can be applied for large-scale production. It is vital for promoting radiative cooling as a viable energy technology for buildings, fabric, or equipment that need a cooling environment.