Near-Infrared Phosphors with Significantly Improved Luminescence Intensity and Zero-Thermal-Quenching for...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• High-performance near-infrared (NIR) lighting requires phosphors with excellent luminous efficiency and thermal stability.
• Existing NIR phosphors often face challenges balancing emission intensity with thermal robustness.

Purpose of the Study:

• To synthesize and characterize novel NIR phosphors based on Ln₂CaGa₄GeO₁₂:Cr³⁺ (Ln = Lu, Y, Gd).
• To enhance the emission intensity and thermal stability of these phosphors for improved NIR lighting applications.
• To investigate the potential of these optimized phosphors in NIR Light Emitting Diodes (LEDs).

Main Methods:

• Synthesis of Ln₂CaGa₄GeO₁₂:Cr³⁺ compounds via solid-state reactions.
• Luminescence property analysis, including concentration-dependent studies and thermal quenching evaluation.
• Material optimization through Al³⁺ substitution and Lu³⁺-Al³⁺ cosubstitution to form solid solutions (Lu_2+zCa_1-zAl_4+zGe_1-zO₁₂:Cr³⁺).
• Fabrication and testing of NIR LEDs using the optimized phosphors.

Main Results:

• Lu₂CaGa₄GeO₁₂:Cr³⁺ exhibited the most intense emission among the synthesized Ln compounds.
• Replacing Ga³⁺ with Al³⁺ significantly boosted emission intensity (3.69-fold) but reduced thermal stability.
• A novel solid solution design (Lu_2+zCa_1-zAl_4+zGe_1-zO₁₂:Cr³⁺) achieved near-zero thermal quenching, maintaining ~100% emission intensity at 423 K for z=0.3.
• NIR LEDs fabricated with these phosphors demonstrated promising performance.

Conclusions:

• The cosubstitution strategy effectively addresses the trade-off between emission intensity and thermal stability in NIR phosphors.
• The developed Lu_2+zCa_1-zAl_4+zGe_1-zO₁₂:Cr³⁺ phosphors exhibit exceptional thermal stability and high luminous efficiency.
• These phosphors hold significant potential for applications in nondestructive detection and night vision technologies.