Enhanced Infrared Emission from Rare-Earth Double Perovskite Embedded in Fluoride Glass with Different B-Site Cation Structures for N₂O Sensing in a Hydrogen Stream

Rare-earth halide perovskites can lead to a distinctive infrared luminescence. However, achieving tunable infrared luminescence presents significant challenges. The leptons of their f-f ubiquitous forbidden ring influence the energy level splitting, and the substitution of atoms in perovskite by rare-earth ions also distorts the crystal structure. The research on achieving tunable mid-infrared emission by altering the crystal structure of rare-earth perovskites is limited. The crystal structure can be modified by changing the matrix B-site cation for a series of Cs₂MIn_1-<i>x</i>Ho_<i>x</i>Cl₆-ZBLAY (M = Na and Ag) rare-earth perovskites coated with a glass matrix that have been prepared. On this basis, we revealed the local electronic structure of Cs₂MInCl₆ (M = Na and Ag) perovskites and proposed an effective charge transfer strategy to achieve an efficient infrared emission of Ho³⁺ ions at 1.2 and 2.87 μm. The contribution of Na s and Na p is minor in Cs₂NaIn_1-<i>x</i>Ho_<i>x</i>Cl₆, which leads to poor interactions between Na⁺ and Cl^- and promotes charge transfer of Ho³⁺-Cl^- in the [HoCl₆]^3- octahedron. The charge transfer mechanism of Cs₂NaInCl₆:Ho³⁺-Cl^- is validated by executing density functional theory calculations. Furthermore, a device that identifies N₂O gas levels in hydrogen energy was built using the Cs₂NaIn_1-<i>x</i>Ho_<i>x</i>Cl₆-ZBLAY sample. These findings provide a new perspective on how to achieve effective infrared emission.