Achieving a Balance of Good Quantum Efficiency and Thermal Stability in the Y₂CaScAl₃GeO₁₂:Cr³⁺ Broadband Phosphor for Multiple NIR Spectroscopy Applications

Near-infrared phosphor-converted light emitting diodes (NIR pc-LEDs) are considered as desirable NIR light sources to satisfy current needs owing to their numerous remarkable features. Nevertheless, as an essential component, previously reported NIR phosphors with broadband emission often suffer from inferior efficiency or thermal stability, therefore restricting their use and promotion. Herein, a novel Cr³⁺-doped garnet phosphor Y₂CaScAl₃GeO₁₂:Cr³⁺ (YCSAG:Cr³⁺) is developed via regulating the near-neighbor coordination polyhedron. Under the excitation of blue light, it exhibits a broadband NIR emission peaking near 800 nm with a full width at half-maximum (fwhm) exceeding 150 nm, owing to the increased structural distortion of the octahedron. Particularly, due to the enhanced local structural rigidity induced by lattice shrinkage, the optimal sample achieves a balance of high internal quantum efficiency (IQE) of approximately 83% and thermal stability of approximately 90% at 393 K, facilitating its practical application as an NIR light source. Eventually, using the typical YCSAG:0.04Cr³⁺ phosphor and 450 nm blue LED chip, a high-performance NIR pc-LED device has been manufactured, demonstrating potential applications in anticounterfeiting and night vision.