Enhanced Infrared\nEmission from Rare-Earth Double\nPerovskite Embedded in Fluoride Glass with Different B‑Site\nCation Structures for N<sub>2</sub>O Sensing in a Hydrogen Stream

Rare-earth halide perovskites can lead to a distinctive\ninfrared\nluminescence. However, achieving tunable infrared luminescence presents\nsignificant challenges. The leptons of their f–f ubiquitous\nforbidden ring influence the energy level splitting, and the substitution\nof atoms in perovskite by rare-earth ions also distorts the crystal\nstructure. The research on achieving tunable mid-infrared emission\nby altering the crystal structure of rare-earth perovskites is limited.\nThe crystal structure can be modified by changing the matrix B-site\ncation for a series of Cs<sub>2</sub>MIn<sub>1–<i>x</i></sub>Ho<sub><i>x</i></sub>Cl<sub>6</sub>-ZBLAY (M = Na\nand Ag) rare-earth perovskites coated with a glass matrix that have\nbeen prepared. On this basis, we revealed the local electronic structure\nof Cs<sub>2</sub>MInCl<sub>6</sub> (M = Na and Ag) perovskites and\nproposed an effective charge transfer strategy to achieve an efficient\ninfrared emission of Ho<sup>3+</sup> ions at 1.2 and 2.87 μm.\nThe contribution of Na s and Na p is minor in Cs<sub>2</sub>NaIn<sub>1–<i>x</i></sub>Ho<sub><i>x</i></sub>Cl<sub>6</sub>, which leads to poor interactions between Na<sup>+</sup> and\nCl<sup>–</sup> and promotes charge transfer of Ho<sup>3+</sup>-Cl<sup>–</sup> in the [HoCl<sub>6</sub>]<sup>3–</sup> octahedron. The charge transfer mechanism of Cs<sub>2</sub>NaInCl<sub>6</sub>:Ho<sup>3+</sup>-Cl<sup>–</sup> is validated by executing\ndensity functional theory calculations. Furthermore, a device that\nidentifies N<sub>2</sub>O gas levels in hydrogen energy was built\nusing the Cs<sub>2</sub>NaIn<sub>1–<i>x</i></sub>Ho<sub><i>x</i></sub>Cl<sub>6</sub>-ZBLAY sample. These\nfindings provide a new perspective on how to achieve effective infrared\nemission.