Enhancement strategy of thermal stability and photoluminescent intensity of Cr3+ doped Li3+xZn2–2xGaxSbO6 phosphor in a strong crystal field

Near-infrared phosphor-converted light-emitting diodes (pc-LEDs) have shown enormous influence in various applications such as night vision, non-destructive detection，especially in the realm of plant cultivation. However, the role of phosphors presently employed in plant cultivation is typically limited, serving primarily for the purpose of illumination. In this work, a series of near-infrared phosphors Li _3+xZn _2–2xGa _xSbO ₆: 0.02Cr ³⁺(LZGS: 0.02Cr ³⁺) under 450 nm excitation was successfully synthesized by high-temperature solid-state method. Through precise modulation of Ga ³⁺ ions, a blue shift in the emission spectrum was observed, demonstrating excellent overlap with the absorption spectrum of Phytochrome. To explain two phenomena of spectral blue shift and the enhancement in luminescence intensity, density functional theory calculations have been performed. Additionally, a crystal field strength Dq/ B of 3.48 was achieved, which represents the highest value currently reported for Cr ³⁺-doped phosphors. The results offer potential applications of LZGS: 0.02Cr ³⁺ in temperature sensing, enabling precise detection of the environmental temperature for plant growth. Finally, pc-LED devices were made by combining LZGS: 0.02Cr ³⁺ with 450 nm blue light chips and applied to plant lighting, temperature measurement, and anti-counterfeiting, demonstrating the potential of LZGS: 0.02Cr ³⁺ in multifaceted applications.