Transparent conductors as solar energy materials: A panoramic review

Passive daytime radiative cooling (PDRC) involves spontaneously cooling a surface by reflecting sunlight and radiating heat to the cold outer space. Current PDRC designs are promising alternatives to electrical cooling but are either inefficient or have limited applicability. We present a simple, inexpensive, and scalable phase inversion-based method for fabricating hierarchically porous poly(vinylidene fluoride-co-hexafluoropropene) [P(VdF-HFP)HP] coatings with excellent PDRC capability. High, substrate-independent hemispherical solar reflectances (0.96 ± 0.03) and long-wave infrared emittances (0.97 ± 0.02) allow for subambient temperature drops of ~6°C and cooling powers of ~96 watts per square meter (W m-2) under solar intensities of 890 and 750 W m-2, respectively. The performance equals or surpasses those of state-of-the-art PDRC designs, and the technique offers a paint-like simplicity.

https://science.sciencemag.org/content/sci/early/2018/09/26/science.aat9513.full.pdf

Hierarchically porous polymer coatings for highly efficient passive daytime radiative cooling

Radiative cooling: A review of fundamentals, materials, applications, and prospects

Radiative sky cooling cools an object on the earth by emitting thermal infrared radiation to the cold universe through the atmospheric window (8–13 μm). It consumes no electricity and has great potential to be explored for cooling of buildings, vehicles, solar cells, and even thermal power plants. Radiative sky cooling has been explored in the past few decades but limited to nighttime use only. Very recently, owing to the progress in nanophotonics and metamaterials, daytime radiative sky cooling to achieve subambient temperatures under direct sunlight has been experimentally demonstrated. More excitingly, the manufacturing of the daytime radiative sky cooling material by the roll-to-roll process makes large-scale deployment of the technology possible. This work reviews the fundamental principles of radiative sky cooling as well as the recent advances, from both materials and systems point of view. Potential applications in different scenarios are reviewed with special attention to technology viability and benefits. As the energy situation and environmental issues become more and more severe in the 21st century, radiative sky cooling can be explored for energy saving in buildings and vehicles, mitigating the urban heat island effect, resolving water and environmental issues, achieving more efficient power generation, and even fighting against the global warming problem.

Radiative sky cooling: Fundamental principles, materials, and applications

Thermochromic VO2 films for energy-efficient windows

Surface coatings for radiative cooling applications: Silicon dioxide and silicon nitride made by reactive rf-sputtering

La fonction dielectrique complexe permet de comprendre les proprietes optiques des materiaux et d'obtenir leurs performances radiatives

Dielectric function of sputter-deposited silicon dioxide and silicon nitride films in the thermal infrared.

Indium–tin–oxyfluoride (ITOF) films were prepared by dc magnetron sputtering of indium–tin in Ar + O2 + CF4. Spectrophotometric measurements in the 0.2–2.5-μm wavelength range were used to evaluate the dielectric function. Wide band gap ITOF, with a refractive index of ~1.5 in the visible and good durability, was produced at a rate of ~1.2 nms−1. ITOF is well suited for antireflecting transparent and conducting indium–tin–oxide coatings.

S. J. Jiang

Papers

Surface coatings for radiative cooling applications: Silicon dioxide and silicon nitride made by reactive rf-sputtering

Dielectric function of sputter-deposited silicon dioxide and silicon nitride films in the thermal infrared.

Low-refractive-index indium-tin-oxyfluoride thin films made by high-rate reactive dc magnetron sputtering.