Sasa Wang

Most of single‐component white‐light‐emitting materials focus on organic–inorganic hybrid perovskites, metal–organic frameworks, as well as all‐inorganic semiconductors. In this work, we successfully assembled an all‐inorganic layered perovskite by mixing two halogens of distinct ionic radii, namely, Rb₂CdCl₂I₂, which emits “warm” white light with a high color rendering index of 88. To date, Rb₂CdCl₂I₂ is the first single‐component white‐light‐emitting material with an all‐inorganic layered perovskite structure. Furthermore, Rb₂CdCl₂I₂ is thermally highly stable up to 575 K. A series of luminescence measurements show that the white‐light emission arises from the lattice deformation, which are closely related to the [CdCl₄I₂]²⁻ octahedra with high distortion from the distinct ionic radii of Cl and I. The first‐principles calculations reveal that both the Cl and I components make significant contributions to the electronic band structures of Rb₂CdCl₂I₂. These findings indicate that mixing halogens is an effective route to design and synthesize new single‐component white‐light‐emitting materials.

Cesium‐lead halide perovskites (e.g. CsPbBr₃) have gained attention because of their rich physical properties, but their bulk ferroelectricity remains unexplored. Herein, by alloying flexible organic cations into the cubic CsPbBr₃, we design the first cesium‐based two‐dimensional (2D) perovskite ferroelectric material with both inorganic alkali metal and organic cations, (C₄H₉NH₃)₂CsPb₂Br₇ (1). Strikingly, 1 shows a high Curie temperature (T_c=412 K) above that of BaTiO₃ (ca. 393 K) and notable spontaneous polarization (ca. 4.2 μC cm⁻²), triggered by not only the ordering of organic cations but also atomic displacement of inorganic Cs⁺ ions. To our knowledge, such a 2D bilayered Cs⁺‐based metal–halide perovskite ferroelectric material with inorganic and organic cations is unprecedented. 1 also shows photoelectric semiconducting behavior with large “on/off” ratios of photoconductivity (>10³).

Cesium‐lead halide perovskites (e.g. CsPbBr₃) have gained attention because of their rich physical properties, but their bulk ferroelectricity remains unexplored. Herein, by alloying flexible organic cations into the cubic CsPbBr₃, we design the first cesium‐based two‐dimensional (2D) perovskite ferroelectric material with both inorganic alkali metal and organic cations, (C₄H₉NH₃)₂CsPb₂Br₇ (1). Strikingly, 1 shows a high Curie temperature (T_c=412 K) above that of BaTiO₃ (ca. 393 K) and notable spontaneous polarization (ca. 4.2 μC cm⁻²), triggered by not only the ordering of organic cations but also atomic displacement of inorganic Cs⁺ ions. To our knowledge, such a 2D bilayered Cs⁺‐based metal–halide perovskite ferroelectric material with inorganic and organic cations is unprecedented. 1 also shows photoelectric semiconducting behavior with large “on/off” ratios of photoconductivity (>10³).