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.作为杂化钙钛矿的重要分支，二维（2D）杂化双钙钛矿有望成为探索新型铁电特性的理想体系，因其可容纳多种有机阳离子，并允许不同金属元素的多样组合。然而，自20世纪30年代卤化物双钙钛矿被发现以来，尚未有二维杂化双钙钛矿铁电体的相关报道。基于三价稀土离子与手性有机阳离子，我们设计了一类新型二维稀土双钙钛矿铁电体A₄MIMIII(NO₃)₈，其中A为有机阳离子，MI为碱金属离子或铵离子，MIII为稀土离子。这是首次在二维杂化双钙钛矿体系中实现铁电性。这类铁电体兼具高温铁电性与光致发光特性。通过调控稀土离子种类，可获得可变的光致发光性能。研究结果表明，二维稀土双钙钛矿体系为实现多功能铁电性提供了极具潜力的平台。