Cr3+ activated Na3RESi3O9 (RE = Y, Lu, Sc) silicate broadband near-infrared phosphors for luminescence towards NIR-II region via a multi-site occupancy strategy

Phosphor-converted near-infrared light-emitting diodes (NIR pc-LEDs) are finding applications in various fields including food quality analysis, biomedical imaging, night vision, and biomedicine. The crucial factor in the development of NIR pc-LEDs devices lies in the advancement of high-performance broadband NIR phosphors. In this work, novel Cr³⁺-activated silicate phosphors NaRESi₃O₉ (RE = Y, Lu, Sc) are reported. This silicate has a special 3D network structure in which RE has four different sites, forming four octahedrons and providing suitable occupation sites for Cr³⁺. The phosphors demonstrate a wide emission spectrum ranging from 750 to 1450 nm when excited by light at 468 nm. The full width at half maximum (FWHM), which benefits from the presence of Cr³⁺ ions occupying multiple sites, is measured to be 203 nm. Notably, the strongest emission peak is observed at a longer wavelength of 984 nm compared to most other systems activated by Cr³⁺. The Na₃ScSi₃O₉ lattice provides a weak crystal field (Dq/B = 1.97) and weak phonon-photon coupling for Cr³⁺, and the integrated emission intensity of Na₃ScSi₃O₉:0.03Cr³⁺ is 4.66 times stronger than that of Na₃YSi₃O₉:0.03Cr³⁺.