Novel cryogenic dual-emission mechanism of lead-free double perovskite Cs₂AgInCl₆ and using SiO₂ to enhance their photoluminescence and photostability

Lead halide perovskite have attracted world-wide attention regarding their serious hazards on ecological environment and human health. To improve both the emission intensity and stability of Cs₂AgInCl₆, this study explores using SiO₂ to structurally adjust Cs₂AgInCl₆. Note that including SiO₂ changed the growth style and crystal morphology of Cs₂AgInCl₆ from an octahedron to a truncated octahedron. After structural adjustment, the unit cells scattered, and the absorption limit broke. Moreover, SiO₂ was demonstrated to passivate the material's surface to form an anti-oxidation protective layer. Consequently, the photoluminescence emission intensity increased by 181.5% and the stability of Cs₂AgInCl₆ improved by 83.11%. This work provides a methodology and reference for future improvements to the luminescence of Cs₂AgInCl₆. Furthermore, a novel double-emission phenomenon (λ_ex = 365 nm: λ_em ≈ 580 nm; λ_ex = 325 nm: λ_em ≈ 505 nm) of Cs₂AgInCl₆ at cryogenic temperatures (20 K) was discovered; this phenomenon explains the shoulder emission problem of 400-450 nm at room temperature and clarifies the luminescence mechanism of Cs₂AgInCl₆.