A New Perspective and Design Principle for Halide Perovskites: Ionic Octahedron Network (ION)

The metal halide ionic octahedron, [MX6] (M = metal cation, X = halide anion), is considered to be the fundamental building block and functional unit of metal halide perovskites. By representing the metal halide ionic octahedron in halide perovskites as a super ion/atom, the halide perovskite can be described as an extended ionic octahedron network (ION) charge balanced by selected cations. This new perspective of halide perovskites based on ION enables the prediction of different packing and connectivity of the metal halide octahedra based on different solid-state lattices. In this work, a new halide perovskite Cs8Au3.5In1.5Cl23 was discovered on the basis of a BaTiO3-lattice ION {[InCl6]­[AuCl5]­[Au/InCl4]3}8–, which is assembled from three different ionic octahedra [InCl6], [AuCl6], and [Au/InCl6] and balanced by positively charged Cs cations. The success of this ION design concept in the discovery of Cs8Au3.5In1.5Cl23 opens up a new venue for the rational design of new halide perovskite materials.

金属卤化物离子八面体[MX₆]（M为金属阳离子，X为卤族阴离子）被认为是金属卤化物钙钛矿（metal halide perovskites）的基本构筑基元与功能单元。将卤化物钙钛矿中的金属卤化物离子八面体抽象为超离子/超原子，则可将该类钙钛矿描述为一种由选定阳离子实现电荷平衡的扩展型离子八面体网络（ionic octahedron network，缩写为ION）。这种基于扩展离子八面体网络的卤化物钙钛矿研究新视角，可实现基于不同固态晶格的金属卤化物八面体堆积方式与连接模式的预测。本研究依托钛酸钡（BaTiO₃）晶格的扩展离子八面体网络{[InCl₆]‑[AuCl₅]‑[Au/InCl₄]₃}⁸⁻，成功发现了新型卤化物钙钛矿Cs₈Au₃.₅In₁.₅Cl₂₃；该网络由[InCl₆]、[AuCl₆]与[Au/InCl₆]三种不同的离子八面体组装而成，并由带正电的铯阳离子实现电荷平衡。该扩展离子八面体网络设计理念在Cs₈Au₃.₅In₁.₅Cl₂₃发现中的成功应用，为新型卤化物钙钛矿材料的理性设计开辟了全新的研究路径。