“To the growing list of two-dimensional semiconductors, such as graphene, boron nitride, and molybdenum disulfide, whose unique electronic properties make them potential successors to silicon in future devices, you can now add hybrid organic-inorganic perovskites. However, unlike the other contenders, which are covalent semiconductors, these 2D hybrid perovskites are ionic materials, which gives them special properties of their own. Researchers at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have successfully grown atomically thin 2D sheets of organic-inorganic hybrid perovskites from solution. The ultrathin sheets are of high quality, large in area, and square-shaped. They also exhibited efficient photoluminescence, color-tunability, and a unique structural relaxation not found in covalent semiconductor sheets.”