A Novel Multifunctional and Broadband Near-Infrared Phosphor, Lu3MgGa3GeO12:Cr3+, Yb3+, Nd3+ Achieved through a Chemical Unit Substitution and Energy Transfer Strategy

Cr³⁺-doped near-infrared (NIR) phosphors have attracted significant attention in recent years. Despite this, achieving high-performance NIR phosphors with broadband emission and excellent thermal stability remains a considerable challenge. This study presents Lu₃Ga₅O₁₂:Cr³⁺, which demonstrates a tunable emission peak ranging from 705 to 759 nm and an increased full-width at half-peak maximum (FWHM) from 46 to 139 nm by substituting the [Mg²⁺-Ge⁴⁺] chemical unit for the [Ga³⁺-Ga³⁺] unit. Additionally, in Lu₃MgGa₃GeO₁₂:Cr³⁺, Yb³⁺, an energy transfer channel (Cr³⁺-Yb³⁺) is constructed. Under blue light excitation, the characteristic emission peaks of Cr³⁺ (600–900 nm) and Yb³⁺ (900–1100 nm) are observed simultaneously. However, the emission band between 850 and 900 nm is relatively weak, resulting in a discontinuous emission spectrum. To address this, Lu₃MgGa₃GeO₁₂:Cr³⁺, Yb³⁺, Nd³⁺ phosphors are proposed, which exhibit a continuous broadband NIR emission with a FWHM of 253 nm and internal quantum efficiency of 47.3%. The luminescence intensity retains 81% of its room temperature value even at 423 K. Combining this new phosphor with a blue LED chip results in a portable NIR light source with potential applications in non-destructive detection, information encryption, bio-imaging, and NIR remote control. This work offers a novel perspective for developing high-performance NIR phosphors.