Super-wide-range tunable emission across NIR-II and NIR-III achieved by B-site cation co-substitution in Ni2+-doped double perovskites for NIR light sources

Abstract

Long-wavelength (1000–2500 nm) near-infrared (LWNIR) phosphors present important application prospects in biomedical and nondestructive testing. A major challenge for current researchers is obtaining phosphors with super-wide-range emission across the NIR-II and NIR-III spectral regions, which is highly advantageous for the development of NIR light sources. Ni²⁺ is a prominent activator for LWNIR emission and is sensitive to the octahedral crystal field environment. Herein, a series of Ni²⁺-doped Sr₂B′B′′O₆ (B′³⁺ = Ga, Sc; B′′⁵⁺ = Ta, Sb) phosphors with double perovskite structures was investigated. Through crystal field engineering of B-site cations, specifically Sc³⁺–Sb⁵⁺ co-substitution for Ga³⁺–Ta⁵⁺, the emission peak of Ni²⁺ was tuned from 1295 to 1665 nm. Such a super-wide-range tunable emission of up to 370 nm was unprecedented. The emission spectra of Sr₂Ga_1−xSc_xTa_1−ySb_yO₆:0.01Ni²⁺ solid solution phosphors ranged from 1000 to 2100 nm (across NIR-II and NIR-III). The excitation peak was correspondingly shifted from 398 to 454 nm, which was suitable for commercial near-ultraviolet and blue LEDs. The potential applications of our phosphors in biomedical imaging and nondestructive testing were demonstrated. This work not only developed an efficient super-wide-range tunable emission phosphor suitable for LWNIR light sources but also revealed the emission characteristics of Ni²⁺-doped double perovskites, providing important technical guidance for achieving LWNIR emission and developing large-range tunable phosphors.