Design of Metal-Halide Inverse-Hybrid Perovskites

We recently introduced a new class of perovskites, with inorganic anions on the A- and B-sites and an organic cation on the X-site, the so-called inverse-hybrid perovskites (IHPs). We found compounds that are predicted to be stable, possess large polarization, and span a wide range of electronic properties. Here, we present the materials search strategy that enabled these results. We demonstrate the design principles in terms of ion and site composition. Overall, we consider elements from most main groups of the periodic table, investigating their ability to form mono- or divalent anions in the framework of IHPs. We observe structural changes based on tolerance factor. Compounds are found in the perovskite or the related CaIrO3 structure, and different orientations of the employed organic cation (methylammonium) lead to different B···X···B bridging motifs. Furthermore, we demonstrate how the perovskite structure can be favored by interchanging B- and A-site anions and adjusting the ions within groups of the periodic table accordingly. Besides chalcogenide halides, we find that elements of groups XIII to XV can successfully form mono- or divalent anions by partly filling their valence p shell. Spin–orbit coupling in the heavier elements leads to interesting electronic motifs. Furthermore, while light divalent elements show a tendency toward protonation, this is suppressed by employing heavier elements of the same group. Evaluating the stability of these novel compounds also requires us to investigate largely unknown methylammonium compounds with mono- and divalent anions.我们近期报道了一类新型钙钛矿（perovskites），其A位与B位为无机阴离子、X位为有机阳离子，即所谓的反杂化钙钛矿（inverse-hybrid perovskites，IHPs）。我们筛选得到了一批预测稳定、具有强极化特性且电子性质覆盖范围广泛的化合物。本文详述了支撑上述研究成果的材料筛选策略，并从离子与位点组成维度阐释了其设计原则。整体而言，我们选取了元素周期表多数主族的元素，探究它们在反杂化钙钛矿框架内形成一价或二价阴离子的能力。我们观测到基于容忍因子（tolerance factor）的结构变化。所获化合物可归为钙钛矿结构或类CaIrO3结构，所用有机阳离子为甲胺阳离子（methylammonium），其不同取向会导致各异的B···X···B桥联基元。此外，我们阐明了通过交换A、B位阴离子，并相应调整元素周期表各族内的离子种类，以稳定钙钛矿结构的可行路径。除硫族卤化物外，我们还发现第13至15族元素可通过部分填充其价层p轨道，成功形成一价或二价阴离子。重元素中的自旋轨道耦合（spin–orbit coupling）会催生极具研究价值的电子基元。此外，轻量二价元素易发生质子化，但通过选用同族的重元素可抑制该现象。为评估这类新型化合物的稳定性，我们还需探究此前鲜有报道的、结合一价与二价阴离子的甲胺阳离子化合物。