Near-Infrared Luminescence in Mo⁴⁺-Activated Metal Halide for Advanced Optoelectronics

Area of Science:

• Materials Science
• Solid-State Chemistry
• Optoelectronics

Background:

• Efficient, stable, broadband near-infrared (NIR) phosphors are crucial for smart devices.
• Existing NIR phosphors face challenges with quantum efficiency and spectral range.

Purpose of the Study:

• To engineer a novel Mo⁴⁺-activated NIR phosphor with enhanced properties.
• To explore crystal field distortion engineering in Cs₂ZnCl₄ for NIR luminescence.

Main Methods:

• Crystal field distortion engineering in zero-dimensional Cs₂ZnCl₄ host.
• Investigating Mo⁴⁺ doping and its coordination environment.
• Fabrication and testing of NIR phosphor-converted LEDs (pc-LEDs).

Main Results:

• Achieved unprecedented broadband NIR emission (960 nm, fwhm ∼ 206 nm) from Mo⁴⁺ in Cs₂ZnCl₄.
• Observed a distortion-driven transformation to octahedral Mo⁴⁺ coordination, yielding 78.7% internal quantum efficiency.
• Demonstrated thermal stability, environmental robustness, and successful application in NIR pc-LEDs for imaging.

Conclusions:

• Crystal field distortion engineering is a viable strategy for developing efficient NIR phosphors.
• Mo⁴⁺-activated Cs₂ZnCl₄ offers a promising material for advanced optoelectronic devices.
• The study expands applications of 4d transition-metal ions in optoelectronics.