Low-Coordination Crystallographic Lattice Engineering to Discover Ce3+-Activated Ultra-Wide Visible-to-Near-Infrared Luminescent Materials

Development of ultra-broadband visible-to-near-infrared (VIS-NIR) luminescent materials is a challenging but rewarding endeavor, as they are highly desirable for a number of applications in photonics, optoelectronics, and biological sciences. Nevertheless, to date, rare earth-doped phosphors that can be efficiently excited by blue light and produce broadband emission in the VIS-NIR regions remain scarce. In this study, a series of Ce 3+ -doped Ba 3 M 4 O 9 (M = Sc, Lu, Y) broadband luminescent materials are designed based on low-coordination crystallographic lattice engineering. Among these materials, Ba 3 Y 4 O 9 :Ce 3+ produces a continuous ultra-wide VIS-NIR emission (λ em = 660 nm) in the range of 500–950 nm under 410 nm light excitation. This emission wavelength is the longest among those observed in Ce 3 ⁺-doped oxide materials. Structural refinement, theoretical calculation, and spectral analysis demonstrate that this VIS-NIR broadband emission is attributed to the occupying multiple distorted octahedral lattice sites by Ce 3+ in Ba 3 Y 4 O 9 . Several strategies are employed to enhance the luminescence intensity and thermal stability of this material, including the use of carbon paper coating, the incorporation of co-solvents, and the addition of GeO₂ or ZrO₂. Furthermore, the as-prepared materials demonstrate multifunctional applications in white light-emitting diodes (WLED), night vision, and fluorescent thermometers. This study offers insights into the design of Ce3+-doped ultra-wide VIS-NIR light-emitting materials.