Structural Insights and Multi-center Luminescence in Cr³⁺-Doped Gallogermanate for High-Efficiency Near-Infrared...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are crucial for spectroscopy and bioimaging.
• Conventional NIR phosphors typically use isolated Cr³⁺ ions in octahedral sites, limiting broadband emission.
• Designing NIR phosphors with tetrahedral sites or Cr³⁺ ion pairs presents significant challenges.

Purpose of the Study:

• To explore ultrabroadband NIR emission in Cr³⁺-doped gallogermanate (Ga₆Ge₂O₁₃, GGO) phosphors.
• To investigate the role of multisite occupancy of Cr³⁺ ions in achieving broad emission spectra.
• To provide a new design strategy for advanced broadband NIR phosphors.

Main Methods:

• Low-temperature spectroscopy
• X-ray absorption near-edge structure (XANES) analysis
• Electron paramagnetic resonance (EPR) spectroscopy
• Cr³⁺ concentration engineering

Main Results:

• Identified three distinct luminescent centers for Cr³⁺ in GGO: octahedral sites (650-850 nm), Cr³⁺ ion pairs (750-950 nm), and tetrahedral sites (850-1400 nm).
• Achieved tunable ultrabroadband NIR emission spanning 650-1400 nm.
• Optimized GGO:6% Cr³⁺ showed good thermal stability (60% at 423 K), high absorption efficiency (69%), and external quantum efficiency (36%).
• Fabricated NIR-LED achieved 55.59 mW output power at 180 mA.

Conclusions:

• Multisite occupancy of Cr³⁺ ions in GGO enables ultrabroadband NIR emission.
• This provides fundamental insights into Cr³⁺ luminescence mechanisms.
• Offers a promising new avenue for designing advanced NIR phosphors for applications in nondestructive testing and bioimaging.