Selective Emitter Based on MgF₂ Photonic Structure for Subambient Radiative Cooling

Area of Science:

• Materials Science
• Nanotechnology
• Thermodynamics

Background:

• Passive radiative cooling is a key technology for energy-efficient refrigeration and carbon neutrality.
• Optimizing radiative cooling requires minimizing solar absorption while maximizing infrared emission.
• Existing solutions often face limitations in performance and applicability.

Purpose of the Study:

• To develop advanced photonic radiative coolers for effective subambient cooling.
• To investigate the performance of a fluoride-metal multilayer stack structure.
• To demonstrate the practical application and efficiency of the developed cooling technology.

Main Methods:

• Fabrication of photonic radiative coolers using a fluoride-metal multilayer stack.
• Characterization of spectral properties, including reflectance and emissivity, of the MgF2 emitter.
• Field testing and real-world application tests to evaluate cooling performance under various conditions.

Main Results:

• The selective MgF2 emitter demonstrated high reflectance (97.2%) and atmospheric window emissivity (0.80).
• All-day subambient cooling exceeding 19 °C was achieved, irrespective of the season.
• Real-world tests showed a maximum cooling effect of 14 °C under sunlight and 2 °C at night.

Conclusions:

• The developed photonic radiative cooler based on MgF2 offers a promising strategy for deep radiative cooling.
• The technology demonstrates significant potential for broad energy-saving applications.
• This innovation contributes to sustainable refrigeration and global carbon neutrality goals.