Synthesis and luminescent properties of highly thermally stable GdGa3(BO3)4:Cr3+ broadband near-infrared phosphors for near-infrared LED applications

Developing near-infrared (NIR) phosphors with high thermal stability and broadband emission is pivotal for advancing NIR light sources. In this study, we synthesized a novel borate phosphor, GdGa3(BO3)4:Cr3+, via a high-temperature solid-state reaction. This phosphor demonstrates exceptional thermal stability, maintaining 94% of its initial intensity even at 150°C. Upon blue light excitation, it emits a broad spectrum from 650 to 1100 nm, peaking at 770 nm with a full width at half maximum (FWHM) of ∼130 nm. We conducted a comprehensive investigation to understand the mechanisms underlying its thermal stability. Additionally, by combining the GdGa3(BO3)4:15%Cr3+ phosphor with a commercial blue light chip, we fabricated an NIR LED device achieving a NIR output power of 6.45 mW and a photoelectric conversion efficiency of 1.57% at 120 mA. This study offers valuable insights into the design of advanced NIR phosphors with superior thermal stability for NIR light source applications.