(Digital Presentation) Cr-Doped High-Efficiency Broadband Near-Infrared Luminescent Materials

Cr-doped high efficiency broadband near-infrared (NIR) luminescent materials have attracted huge research interests in food analysis, plant growth, night vision and biomedical imaging owing to their invisibility and characteristic absorptions by certain molecules. Transition metal element Cr 3+ with [Ar]3d 3 configuration serves as an ideal activator for broadband NIR emission due to the broad absorption bands in the blue and orange-red spectral regions, among which the blue band matches well with the commercial blue LED chips. Besides, the NIR emissions of Cr 3+ -doped phosphors are greatly affected by the crystal field strength of the matrix lattice. In the weak crystal field, the spin-allowed 4 T 2 → 4 A 2 transitions give out the preferable wide-band emissions. However, the NIR luminescence of Cr 3+ encounters several problems aiming at further developments. The materials with main emission peak beyond 800 nm are lacking. Meanwhile, the quantum efficiency and thermal luminescence stability need improvement to fulfil the application requirements. Also, it remains a challenge to predict the Cr 3+ luminescence by crystal-field theory theoretically. To address those problems, we introduce several high-efficiency Cr 3+ doped materials with distinct crystal structures, such as SrGa 12 O 19 :Cr 3+ , LaMgGa 11 O 19 :Cr 3+ , LiInGe 2 O 6 :Cr 3+ , and Sr 2 ScSbO 6 :Cr 3+ , together with the structural confinement strategy to improve the NIR performance. The further research topic including the local structure is also discussed.