Crystal-Field-Weakening Engineering Unlocks Ultra-Efficient Eu²⁺ Near-Infrared Emission for Emerging Spectroscopic...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Europium (Eu²⁺) ions are promising blue-light-excitable near-infrared (NIR) emitters due to their parity-allowed 5d → 4f transition.
• Achieving efficient Eu²⁺ NIR luminescence is challenging due to large Stokes shifts and the trade-off between emission wavelength and efficiency.

Purpose of the Study:

• To overcome the intrinsic trade-off between emission wavelength and luminescence efficiency in Eu²⁺-based NIR phosphors.
• To enhance NIR emission efficiency by proposing a crystal-field-weakening engineering strategy.

Main Methods:

• Developed a crystal-field-weakening strategy in Ca₃ScHfAlSi₂O₁₂: Eu²⁺ phosphor.
• Investigated mechanisms including intracenter relaxation and energy migration.
• Fabricated a blue-light-pumped pc-NIR-LED device.

Main Results:

• Achieved a record internal quantum efficiency of 69.7% at 780 nm with high thermal stability.
• Suppressed non-radiative relaxation, intracenter relaxation, and energy migration.
• Demonstrated a pc-NIR-LED with high NIR output power (101.52 mW at 350 mA).

Conclusions:

• Crystal-field weakening effectively reduces Stokes shift and suppresses non-radiative relaxation, enhancing NIR emission efficiency.
• This strategy breaks the conventional trade-off, paving the way for high-performance Eu²⁺-based NIR phosphors.
• The developed phosphor shows potential for applications in plant lighting, night vision, and non-destructive testing.