Mixing Halogens To Assemble an All‐Inorganic Layered Perovskite with Warm White‐Light Emission

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, Rb 2 CdCl 2 I 2 , which emits “warm” white light with a high color rendering index of 88. To date, Rb 2 CdCl 2 I 2 is the first single‐component white‐light‐emitting material with an all‐inorganic layered perovskite structure. Furthermore, Rb 2 CdCl 2 I 2 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 [CdCl 4 I 2 ] 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 Rb 2 CdCl 2 I 2 . These findings indicate that mixing halogens is an effective route to design and synthesize new single‐component white‐light‐emitting materials.