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.
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