Chemical unit co-substitution enabling broadband and tunable near-infrared emission in garnet-type Lu3Sc2Ga3O12:Cr3+ phosphors

Although near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are desired for non-visible light source applications, the design of broadband NIR phosphors remains a challenge. Inspired by the chemical unit co-substitution strategy for the modification of composition and local structure, we realize a tunable redshift emission from 706 to 765 nm in garnet-type Lu3Sc2Ga3O12:Cr3+ with a broadened full width at half maximum and enhanced photoluminescence intensity by introducing a [Mg2+-Si4+] unit into the [Sc3+-Ga3+] couple. Structural and spectral analyzes demonstrate that the co-substitution reduces the local symmetry and crystal field strength of the [CrO6] octahedra, thus leading to inhomogeneous widening of the 4T2→4A2 emission and enhanced blue absorption. Furthermore, the 4T2→4A2 emission exhibits a phonon-assisted character at low temperatures due to the thermal coupling effect with the 2E level. The fabricated NIR pc-LED based on the optimized NIR phosphor exhibits excellent potential in night vision and imaging applications.