Achieving Nearly Quantitative (≈100%) Iqe and 42.3% EQE Across Nir‐I And Nir‐II Regions with Cr³⁺‐doped Cs₂NaScCl₆ Under 300 nm Excitation

Abstract

Lead‐free rare‐earth‐based perovskites have received widespread attention for their unique optical properties, although achieving efficient broadband near‐infrared (NIR) emission with these materials remains a challenge. Here the synthesis of a rare earth‐based double perovskite (Cs₂NaScCl₆) by an improved solid phase method is reported. The doping of Cr³⁺ led to the formation of [CrCl₆]³⁻ octahedron, which exhibited a broadband NIR emission peaked at 950 nm and a half‐peak width of 162 nm. It is worth noting that with the same actual Cr³⁺ content, the luminous intensity of Cs₂NaScCl₆ synthesized by the improved solid‐phase synthesis is four times higher than the product synthesized by the hydrothermal method. an efficient Cl⁻‐Cr³⁺ charge transfer sensitization facilitated by localized electrons in [CrCl₆]³⁻ octahedron is the mechanism for the strong NIR emission of Cr³⁺ is proposed. Calculations based on density functional theory and Bader charge analysis support the notion that electrons in [CrCl₆]³⁻ octahedrons are strongly localized in Cs₂NaScCl₆:Cr³⁺, which is conducive to the Cl⁻–Cr³⁺ charge transfer process, resulting the internal quantum efficiency of 100% and external quantum yield as 42.3%. The highly efficient ultra‐broadband NIR emission with excellent stability offers many opportunities for applications in the field of NIR night vision and bio‐imaging.