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A collaborative research effort between POSTECH and Korea University has led to the development of a groundbreaking transparent film designed to provide solar heat regulation and lower interior temperatures. Published in Advanced Functional Materials, this innovative film, resembling an insect screen, offers both sun protection and cool comfort, paving the way for energy-efficient solutions in architecture and beyond.
The research team, led by Professors Junsuk Rho and Heon Lee, along with PhD candidates Byoungsu Ko, Jaebum Noh, and Dongwoo Chae, has engineered a film that utilizes radiative cooling—a process that enables surfaces to naturally release absorbed heat without external power. This cooling effect, if harnessed effectively, could revolutionize how buildings and other structures manage temperature, reducing the reliance on air conditioning and cutting energy consumption.
Typically, objects exposed to sunlight absorb solar heat, but they also have the ability to cool down by emitting radiation in the form of infrared light. However, conventional transparent films often struggle with this because they allow too much solar heat to pass through, limiting their cooling potential.
To overcome this, the team developed a novel solution using a combination of materials: a perforated silver (Ag) substrate, a Bragg mirror, and a polydimethylsiloxane (PDMS) coating. The Bragg mirror, a multi-layer thin-film structure, serves to reflect near-infrared light, which is largely responsible for the sun’s heat. This helps keep the interior space cooler by preventing excessive heat absorption.
The perforated design—akin to an insect screen—features micrometer-scale holes in the silver substrate, allowing visible light to pass through while still reflecting heat. This design not only ensures that the film remains transparent but also significantly enhances its cooling performance by allowing far-infrared radiation to be emitted efficiently through the atmospheric window.
In experimental tests, glass coated with this novel film remained 22.1°C cooler than glass treated with only the PDMS coating, demonstrating its effectiveness in both transparency and heat regulation.
“This technology is ready for mass production and has significant potential in architecture and environmental applications,” said Professor Junsuk Rho of POSTECH. “Most importantly, it efficiently dissipates heat and reduces energy consumption, positioning it as a key technology for a sustainable future.”
The project was supported by the POSCO Holdings N.EX.T IMPACT Metasurface-based Planar Optics Technology Lab, the Leading Research Lab of the Ministry of Science and ICT, and the National Research Foundation of Korea.
With this breakthrough, the future of sustainable, energy-efficient buildings could be closer than ever, as the new film offers a promising solution to combating rising temperatures and energy demands.
