Highly Efficient Broadband NIR Phosphor Ca3ZrNbGa3O12: Cr3+, Yb3+ in pc-LED Applications

Abstract

The development of biomedicine, military and other fields has led to an increasing demand for near-infrared light sources, and near-infrared phosphorescent conversion light-emitting diodes (NIR pc-LED) occupy a critical position in these fields. However, the problems of weak luminescence intensity and poor thermal stability have generally been exhibited by the near-infrared fluorescent materials reported to date. This article synthesized a series of Ca₃ZrNbGa₃O₁₂: Cr³⁺ phosphors by the high-temperature solid-phase method. Under 342 nm excitation, the phosphors produced emission light covering the wavelength range of 650–1150 nm. The luminescence center was 783 nm, corresponding to the ⁴T₂ → ⁴A₂ transition of Cr³⁺, and the full width at half maximum (FWHM) was 129 nm. Subsequently, with the continuous introduction of Yb³⁺ into the system, the ²F_5/2 → ²F_7/2 transition of Yb³⁺ generates multiple luminescent centers in the near-infrared region, thereby broadening the spectral coverage range. The incorporation of Yb³⁺ ions enables efficient energy transfer from Cr³⁺ to Yb³⁺ in the system. When the concentration of Yb³⁺ is 8%, the energy transfer efficiency reaches 64.1%. The Photoluminescence quantum yield (PLQY) was also improved from 41.4% of Ca₃ZrNbGa₃O₁₂: 0.7% Cr³⁺ to 69.3% of Ca₃ZrNbGa₃O₁₂: 0.7% Cr³⁺, 0.6% Yb³⁺. The thermal stability at 150°C was also improved from 36.06% to 43.06%. A near-infrared pc-LED device was fabricated through the integration of Ca₃ZrNbGa₃O₁₂: 0.7% Cr³⁺, 0.6% Yb³⁺ phosphor with a 365 nm LED chip, thereby validating the material's potential for application as a novel near-infrared illumination source.