Highly efficient Cr3+-doped K3Ga2(PO4)3 NIR-I phosphors with exceptional thermal quenching resistance for night vision monitoring and biomedical imaging applications

Abstract

Near-infrared (NIR) spectroscopic technology has shown extensive application prospects. However, developing NIR phosphors with tunability and high thermal stability is a huge challenge. In this work, a highly promising phosphate compound, K₃Ga₂(PO₄)₃, has been successfully synthesized. When doped with Cr³⁺ ions, it is particularly noteworthy that Cr³⁺ exhibits highly efficient and thermally stable broadband NIR luminescence in the tetrahedral coordination environment. This unique property makes K₃Ga₂(PO₄)₃:Cr³⁺ a compelling candidate for advanced photonic applications. Therefore, studying the luminescent properties of Cr³⁺ rare earth ions doped into tetrahedral sites is of great significance. In the tetrahedral coordination environment of K₃Ga₂(PO₄)₃:Cr³⁺ ions exhibit broadband near-infrared emission spanning from 700 to 1100 nm (λ_em = 822 nm, FWHM = 124 nm) under 452 nm blue light excitation. Remarkably, the quantum efficiency reaches as high as 70.9%, demonstrating its exceptional potential for advanced photonic applications. In addition, the phosphors demonstrated exceptional thermal stability with near-zero thermal quenching. The NIR luminescence intensity at 373 K and 423 K retained 109.0% and 90.4% of its initial room-temperature value, respectively. This remarkable performance can be attributed to the material's ultra-wide band gap, and minimal electron–phonon coupling. The NIR pc-LED devices, fabricated by integrating the optimized K₃Ga_1.93(PO₄)₃:0.07Cr³⁺ phosphors with a blue LED chip (λ_ex = 455 nm), achieved a near-infrared output power of 274 mW with a conversion efficiency of 5.42% under a driving current of 100 mA. Experimental results demonstrate that the fabricated NIR pc-LED exhibits significant potential for applications in night vision and vein imaging technologies. This study provides a strategic framework for designing high-performance NIR pc-LED devices, utilizing K₃Ga₂(PO₄)₃:Cr³⁺ as an efficient phosphor-converted light source, and offers valuable insights for practical implementation in advanced optical systems.