A simple and versatile nanoparticle ink could help next-generation perovskite solar cells to be printed at scale and become the dominant force in commercial photovoltaics. Made from tin oxide, the ink is created with just one key step at relatively low temperature using microwave technology, and without any need for further purification. It’s then used in solar cells to help selectively transport electrons, a crucial step in generating electricity. Prototype devices built with this method ...