RESUMO
The well-studied star compound, CH3NH3PbI3, has attracted plenty of attention because of its remarkable optical and electrical properties. Consequently, new switching multifunctional hybrid compounds can be widely used in many fields such as solar cells, light-emitting diodes, optical data storage and so on. Therefore, switching multifunctional hybrid compounds with dielectric and semiconducting properties simultaneously will also find roles in the next generation of optoelectronic coupling materials. In fact, discovering an effective method to synthesize (multi)functional hybrid materials remains a pressing challenge. Thanks to the "quasi-spherical theory" proposed by Xiong et al., we used 7-azabicyclo[2.2.1]heptane as the quasi-spherical cation to construct molecule-based crystalline materials that exhibit responsive properties. Then, we tried to exploit the knowledge of crystal engineering and coordination chemistry to explain (multi)functional molecular materials. A layered organic-inorganic hybrid compound, (C6H12N)2Pb(NO3)4 (1), was grown and its dielectric switching property and semiconducting behaviour were investigated. Insights from differential scanning calorimetry measurements, variable-temperature X-ray structural studies, and dielectric spectroscopy revealed the origin of the phase transition, which is related to the motion of the organic ammonium and inorganic framework in solid-state crystals. Furthermore, 1 is also a wide bandgap semiconductor with an optical bandgap of 3.53 eV. The realization of switching and semiconducting properties simultaneously in layered Pb-based perovskites has a great significance toward research into hybrid compounds and the development of dielectric-optoelectronic integrated materials.
RESUMO
Substitution of A-site and/or X-site ions of ABX3 -type perovskites with organic groups can give rise to hybrid perovskites, many of which display intriguing properties beyond their parent compounds. However, this method cannot be extended effectively to hybrid antiperovskites. Now, the design of hybrid antiperovskites under the guidance of the concept of Goldschmidt's tolerance factor is presented. Spherical anions were chosen for the A and B sites and spherical organic cations for the X site, and seven hybrid antiperovskites were obtained, including (F3 (H2 O)x )(AlF6 )(H2 dabco)3 , ((Co(CN)6 )(H2 O)5 )(MF6 )(H2 dabco)3 (M=Al3+ , Cr3+ , or In3+ ), (Co(CN)6 )(MF6 )(H2 pip)3 (M=Al3+ or Cr3+ ), and (SbI6 )(AlF6 )(H2 dabco)3 . These new structures reveal that all ions at A, B, and X sites of inorganic antiperovskites can be replaced by molecular ions to form hybrid antiperovskites. This work will lead to the synthesis of a large family of hybrid antiperovskites.
RESUMO
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.
