Solar windows turn some of the light shining through into electricity. They've been on the market for years. But many of these windows absorb some visible light, leaving them with a reddish or brownish hue, a trait frowned on by architects. Now, new versions are on the way that absorb invisible ultraviolet (UV) and infrared light, allowing visible light to pass through. One class uses upstart solar materials called perovskites that are strong UV absorbers. Another uses organic molecules to capture UV and infrared. And a third class uses tiny semiconductor particles called quantum dots to redirect light energy to the window frames where embedded conventional solar cells turn that energy into electricity. Whichever technology wins out, soon glass covered skyscrapers could generate much of the energy they need.