Two-Dimensional Organic–Inorganic Hybrid Rare-Earth Double Perovskite Ferroelectrics

As a major branch of hybrid perovskites, two-dimensional
(2D) hybrid
double perovskites are expected to be ideal systems for exploring
novel ferroelectric properties, because they can accommodate a variety
of organic cations and allow diverse combinations of different metal
elements. However, no 2D hybrid double perovskite ferroelectric has
been reported since the discovery of halide double perovskites in
the 1930s. Based on trivalent rare-earth ions and chiral organic cations,
we have designed a new family of 2D rare-earth double perovskite ferroelectrics,
A4MIMIII(NO3)8, where A is the organic cation, MI is the alkaline metal
or ammonium ion, and MIII is the rare-earth ion. This is
the first time that ferroelectricity is realized in 2D hybrid double
perovskite systems. These ferroelectrics have achieved high-temperature
ferroelectricity and photoluminescent properties. By varying the rare-earth
ion, variable photoluminescent properties can be achieved. The results
reveal that the 2D rare-earth double perovskite systems provide a
promising platform for achieving multifunctional ferroelectricity.