New clear coating can turn any window Into a solar panel

Imagine every office tower or apartment block quietly generating its own power through the windows. A team from Nanjing University in China has taken a step toward that vision, developing a transparent coating that transforms standard glass into a solar panel without blocking the view.

The material, called a colorless and unidirectional diffractive-type solar concentrator (CUSC), works by steering some of the sun's rays to the edges of the glass, where photovoltaic strips convert them into electricity. The rest of the light passes through normally, keeping the window bright and clear, reports Science Alert.

"The CUSC design is a step forward in integrating solar technology into the built environment without sacrificing aesthetics," said optical engineer Wei Hu. "It represents a practical and scalable strategy for carbon reduction and energy self-sufficiency."

Made from stacked layers of cholesteric liquid crystals, the coating only diverts one type of polarized light, which allows it to remain largely transparent. In lab tests, a prototype managed 18.1% efficiency under natural light while still letting more than 64% of visible light through and preserving color accuracy.

"By engineering the structure of cholesteric liquid crystal films, we create a system that selectively diffracts circularly polarized light, guiding it into the glass waveguide at steep angles," explained team member Dewei Zhang.

The researchers have already built a one-inch prototype powerful enough to run a small fan. Scaled up, they believe the coating could help buildings generate a meaningful share of their own electricity. For now, efficiency remains relatively low at 3.7% overall, and the team says manufacturing methods need to improve before the material is ready for commercial use.

Still, the idea of turning windows into silent, invisible solar generators offers a glimpse of what future cities might look like.