A group of researchers in China has developed a nearly invisible coating for standard windows that redirects sunlight toward the glass’s edge, where it can be harvested by solar cells, tells Live Science. The coating uses cholesteric liquid crystals (CLC), a colorless, helical-structured film, which, when layered, form a colorless unidirectional solar concentrator (CUSC). This design guides incident light along the glass plane without disrupting clarity or visibility.
Conventional solar windows today use photovoltaic cells or tinted glass, often limiting light transmission and adding cost. Those approaches tend to reduce transparency and efficiency, capping energy capture at about 20%. The CUSC, in contrast, maintains a high visible transmittance (~64.2 %) and strong color rendering (~91.3), avoiding the visual distortions typical in other transparent solar tech.
In lab tests, the coating was able to channel up to 38.1% of incoming green light toward the edges of the window, where integrated silicon cells converted it into usable electricity. Even small prototypes have been capable of powering a fan, demonstrating proof of concept in real conditions.
This innovation could be especially relevant in dense urban settings and high-rise buildings, where roof area is limited and window surface dominates facades. By turning windows themselves into power generators, architects and builders might integrate energy harvesting into the design, rather than treating it as an add-on.
Challenges remain around scaling up, durability, and cost, but the approach points to a future where glass facades play both a structural and an energetic role. As cities look to reduce carbon footprints, technologies like this might help buildings generate power without sacrificing design or daylight.