Bromine-Substitution-Induced High- Two-Dimensional Bilayered Perovskite Photoferroelectric.

High-Curie-temperature () ferroelectrics have exhibited broad applications in optoelectronic devices. Recently, two-dimensional multilayered perovskite ferroelectrics with excellent photoelectric attributes are attracting increasing interest as new systems of photoferroelectrics. However, the effective tuning of the value of a multilayered perovskite photoferroelectric system still remains a huge challenge. Here, by a halogen substitution strategy to introduce bromine atoms on -propylamine cations, the hybrid perovskite photoferroelectric (3-bromopropylaminium)(formamidinium)PbBr () with a high value (348.5 K) was obtained. It is notable that adopts a two-dimensional bilayered inorganic framework, with tight linking to the organic cation by C-Br···Br-Pb halogen···halogen interactions and N-H···Br hydrogen bonds. Intriguingly, in comparison with the prototypical compound (-propylaminium)(formamidinium)PbBr, a remarkable augmentation of 85.2 K in the resulting value of is clearly observed, which further broadens the temperature range of its application. In combination with the remarkable ferroelectric and semiconducting attributes, the reversible bulk photovoltaic effect was realized in single crystals of . This finding can not only enhance the hybrid perovskite ferroelectric family but also further promote the photoelectric application of ferroelectrics.