Discovery of an Antiperovskite Ferroelectric in [(CH)NH](MnBr)(MnBr).

It is known that perovskites with the general chemical formula of ABX (A, B = cations, X = anion) have been intensively studied over the last half century because of their diverse functional properties, such as ferroelectricity in BaTiO, piezoelectricity in PZT (lead zirconate titanate), and recently developed photovoltaic properties in CHNHPbI. However, rather less attention has been paid to their "inverse" analogs, antiperovskites, which have a chemical formula XBA, where A and B are anions and X is a cation. Although most of important ferroelectrics are perovskites, no antiperovskite ferroelectrics have been found since the discovery of antiperovskites in 1930. Here, for the first time, we report a XBA antiperovskite ferroelectric (CH)NH(MnBr) (where (CH)NH is X, MnBr is B, and MnBr is A), which shows outstanding ferroelectricity with a significantly high phase transition temperature of 458 K as well as fascinating photoluminescence properties with two intense emissions. This finding opens a new avenue to explore the golden area of antiperovskites for high-performance functional materials.