New smart windows darken in the sun—and generate electricity at the same time

Solar power has undergone a revolution in recent years, thanks to an upstart family of crystalline materials called perovskites. Now, perovskites are transforming windows, keeping them clear on cold days, but turning them dark in the hot summer sun. Two research groups report that they’ve created perovskite-tinted windows that not only transition based on the temperature, but also harvest power like solar cells. The new technology could one day help cool buildings by shading out sunlight and generating power to boot