China develops transparent coating to turn windows into solar panels

Researchers at Nanjing University in China have developed a transparent, colorless solar concentrator coating that can be applied directly to standard window glass, enabling windows to generate solar power without altering their appearance. This innovation uses multilayer cholesteric liquid crystal (CLC) films to selectively diffract circularly polarized sunlight, guiding it toward photovoltaic (PV) cells installed at the window edges. Unlike conventional solar concentrators, this system maintains high visual clarity with an average visible transmittance of 64.2% and a color rendering index of 91.3%, allowing up to 38.1% of incident sunlight to be harvested while keeping the glass visually indistinguishable from ordinary windows. The technology offers significant scalability and efficiency advantages. Simulations indicate that a two-meter-wide coated window can concentrate sunlight up to 50 times its normal intensity, potentially reducing the required PV cell area by 75%, lowering material costs, and enabling new energy-efficient building designs. A prototype demonstrated the ability to power