Engineers have shone new light on an emerging family of solar-absorbing materials that could clear the way for cheaper and more efficient solar panels and LEDs. The materials, called perovskites, are particularly good at absorbing visible light, but had never been thoroughly studied in their purest form: as perfect single crystals. Using a new technique, researchers grew large, pure perovskite crystals and studied how electrons move through the material as light is converted to electricity.