Achieving High Performance Ultra-Broadband Near-infrared Emission through Multi-site Occupancy and Energy Transfer Strategy for NIR LED Applications

Abstract

Broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are considered to be at the forefront of the development of next-generation NIR light sources. However, the performance of NIR pc-LEDs is severely limited due to the narrow band emission, low quantum efficiency, and thermal quenching of NIR-emitting materials. Herein, an efficient and thermally stable broadband NIR LaMgGa11O19:Cr3+,Yb3+ (LMG:Cr3+,Yb3+) phosphor has been successfully designed by [Cr3+-Yb3+] co-doping. The broadband emission phenomenon of LaMgGa11O19:Cr3+ was confirmed to be due to selective lattice occupancy of Cr3+ ions based on the analysis of crystal structures, crystal field calculations, and fluorescence lifetimes. The NIR emission spectra in the range of 1000-1200 nm were enriched by using the highly efficient energy transfer of Cr3+→Yb3+ ions and the detailed the energy transfer mechanism is discussed in detail. The prepared LMG:Cr3+,Yb3+ phosphors exhibit highly efficient ultra-broadband NIR emission from 650 to 1200 nm under 440 nm excitation with high internal and external quantum efficiencies of 94.2%/40.5% and excellent luminescence thermal stability of 89.3%@373 K. A NIR pc-LED prototype was fabricated by combining the optimized phosphor with a commercial 440 nm blue LED chip, providing 84.5 mW NIR output power at 350 mA driven current. Finally, the potential applications of the phosphor in night vision lighting and non-destructive testing were demonstrated. The results show that this work is expected to provide a new strategy for efficient ultra-broadband NIR phosphor design.