A Three-Dimensional Lead Halide Perovskite-Related Ferroelectric.

Three-dimensional (3D) organic-inorganic lead halides represented by [CH3NH3]PbI3 perovskite have attracted great interest for their diverse functional properties and promising optoelectronic applications. However, 3D lead halides are still very rare and their ferroelectricity remains controversial. Here, we report an unprecedented 3D lead halide perovskite-related ferroelectric [2-trimethylammonioethylammonium]Pb2Cl6 ([TMAEA]Pb2Cl6), which contains a 3D lead chloride framework of corner- and edge-sharing PbCl6 octahedral, with the [TMAEA]+ cations occupying the voids of the framework. [TMAEA]Pb2Cl6 shows a ferroelectric-to-paraelectric phase transition with the Curie temperature as high as 412 K, a typical ferroelectric hysteresis loop at 293 K with a spontaneous polarization of 1 μC/cm2, and a clear ferroelectric domain switching. To the best of our knowledge, [TMAEA]Pb2Cl6 is the first 3D lead halide showing such an excellent ferroelectricity. Additionally, it also exhibits semiconducting property with a direct bandgap of 3.43 eV. This finding enriches the family of 3D hybrid lead halides, and inspires the exploration of 3D lead halide ferroelectrics.