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 Cs2MIn1–xHoxCl6-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 Cs2NaIn1–xHoxCl6, 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 Cs2NaIn1–xHoxCl6-ZBLAY sample. These findings provide a new perspective on how to achieve effective infrared emission.