Novel cryogenic dual-emission mechanism of lead-free double perovskite Cs2AgInC16 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 (lambda(ex) = 365 nm: lambda(em) approximate to 580 nm; lambda(ex) = 325 nm: lambda(em) approximate to 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.