Researchers achieve near‑perfect symmetry in 2D perovskites, enabling micrometer‑scale exciton diffusion
Researchers from Rice University, Northwestern University, City University of New York, University of Rennes (CNRS), University of Lille (CNRS) and University of Nebraska-Lincoln have developed a new family of FA-based two-dimensional metal halide perovskites that come very close to a “perfect” crystal at room temperature.

These hybrid (organic–inorganic) semiconductors are engineered to achieve near-maximal crystallographic symmetry, adopting a tetragonal P4/mmm space group without in-plane or out-of-plane octahedral distortions. In contrast to most 2D perovskites, whose softer lattices tend to distort and lower symmetry, the new materials maintain a highly ordered framework inspired by three-dimensional cubic (α-phase) FAPbI₃ (FA = formamidinium).