On a hot summer day, accidents may occur when leaving children alone in a car because solar heat coming through the window increases the indoor temperature. If solar heat is blocked while maintaining the function of the window, such accidents can be prevented.

The electrical conversion performance of "solar cells" that absorb the sunlight to generate electricity can significantly be increased using the same principle. The sunlight that is not converted into electricity becomes heat, increasing solar cells' temperature, and decreasing performance.

To solve this problem, Professor Kim Dong-rip of Hanyang University School of Mechanical Engineering and his team developed a visibly clear radiative cooling metamaterial. The newly developed metamaterial, which overcomes the limits of opaque radiative cooling materials, is considered easy to commercialize as it is convenient to apply like paint and has excellent cooling performance.

Professor Kim's team confirmed that the temperature drops by up to 9 degrees Celsius when using transparent, radiative cooling metamaterials. In particular, they found that significantly lowering the temperature increase of solar cells can improve the electrical conversion performance of solar cells by more than 1.5 times. In addition, they experimentally verified that the production of glass using metamaterials can greatly lower the increase in indoor temperature due to solar heat.

The research team's results are significant in that they have developed a new visibly clear material that can paint while having excellent radiative cooling performance using nanotechnology. Based on this, Professor Kim's team is currently developing a glass that can be cooler in summer and warmer in winter.

Professor Kim Dong-rip said, "Right now, we are striving to realize global carbon neutrality. If this new technology can be applied to our daily lives, it will considerably contribute to energy-saving and renewable energy production."

This research result (title: Visibly Clear Radiative Cooling Metamaterials for Enhanced Thermal Management in Solar Cells and Windows) was supported by the Ministry of Science and ICT's Basic Research Project (Intermediate Research) and was published in the international academic journal Advanced Functional Materials.