Room-Temperature Molten Salt for Facile Fabrication of Efficient and Stable Perovskite Solar Cells in Ambient Air

？ Room-temperature molten salt for facile fabrication of perovskite films in air ？ No post-deposition treatment is needed (e.g., anti-solvent) ？ The resulting perovskite solar cells are highly efficient and stable ？ A universal solvent for all common salts used in perovskite device