Perovskite promises to be less expensive and more efficient than silicon—and several companies say they’re close to producing it at scale. SAULE TECHNOLOGIES ==================================================================================== Testing perovskite solar cells in the lab used to require a decent pair of running shoes. The materials fell apart so quickly that scientists would bolt from where they made the cells to where they tested them, trying to measure their performance before the cells degraded in their hands—usually within a couple of minutes. Perovskites have long enchanted researchers with the promise of producing inexpensive, ultra-efficient solar cells. And now several companies are making major strides...