High-Output-Power Broadband Near-Infrared Phosphor Suitable for Various LED Applications.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Broadband near-infrared (NIR) phosphors are crucial for advanced optical applications.
• Chromium-doped (Cr³⁺) garnet phosphors offer potential for NIR emission when excited by blue light.
• Existing phosphors have limitations in emission bandwidth and wavelength.

Purpose of the Study:

• To synthesize and characterize a novel garnet-type phosphor, La₃In₂Ga₃O₁₂:Cr³⁺, for broadband NIR emission.
• To optimize the phosphor's luminescence properties using a fluxing agent strategy.
• To evaluate the performance of the developed phosphor in a near-infrared LED device.

Main Methods:

• High-temperature solid-state synthesis method.
• X-ray diffraction (XRD) for structural analysis.
• Optical spectroscopy for luminescence characterization (excitation/emission spectra, full width at half-maximum).
• Thermal quenching studies to determine activation energy.
• Fabrication of a near-infrared LED device.

Main Results:

• Successfully synthesized La₃In₂Ga₃O₁₂:Cr³⁺ with a garnet structure (space group Ia$\overline{3}$d).
• Achieved broadband NIR emission (700-1000 nm) with a peak at 826 nm and a full width at half-maximum of 149 nm when excited at 490 nm.
• Identified boric acid (H₃BO₃) as the optimal fluxing agent, enhancing luminescence.
• Demonstrated good thermal stability with 50% intensity remaining at 423 K (activation energy of 0.340 eV).
• Fabricated NIR LED achieved 9.72% luminous efficiency and 978 mW output power.

Conclusions:

• The novel La₃In₂Ga₃O₁₂:Cr³⁺ phosphor exhibits excellent broadband NIR emission characteristics.
• The fluxing agent strategy effectively improved phosphor crystallinity and luminescence.
• The developed NIR LED device shows significant promise for applications in night vision, security screening, and biological imaging.