A strategy for producing stable and commercially available perovskite solar cells (PSCs) has been proposed by Kai Zhu and Keith Emery at the Energy Department’s National Renewable Energy Laboratory (NREL), in collaboration with Nam-Gyu Park (Korea), Michael Grätzel (Switzerland), and Tsutomu Miyasaka (Japan).   Solar cells using a halide perovskite with an organic cation such as methylammonium and/or formamidinium have attracted considerable attention because of their excellent photovoltaic pe...