[Zn2+–Ge4+] co-substitutes [Ga3+–Ga3+] to coordinately broaden the near-infrared emission of Cr3+ in Ga2O3 phosphors

Abstract

Here, a “chemical unit co-substitution” method is used to improve the near-infrared (NIR) emission of phosphors, using [Zn²⁺–Ge⁴⁺] to co-substitute [Ga³⁺–Ga³⁺] sites to reduce crystal field splitting to affect the structure of gallium oxide. A series of broadband NIR phosphors are synthesized by a high-temperature solid-phase method, and their phase structures, crystal structures, morphologies, diffuse reflectance spectra, and luminescence lifetimes are investigated. The Ga_1.68(Zn–Ge)_0.3O₃:0.02Cr³⁺ (GZGOC) phosphor exhibits NIR wide-band emission, with a peak wavelength of 766 nm and a half-width of 138 nm. Meanwhile, the quantum yield of photoluminescence can reach 81.2%. The phosphor has good thermal stability. When the temperature reaches 373 K, its emission intensity still remains at 73.4% of that at room temperature. A 460 nm LED chip and this phosphor are used to fabricate a phosphor-converted light emitting diode (pc-LED) device which can be used as a NIR light source. All these results show the application potential of the as-prepared phosphor in NIR imaging.