Dual deep red and far red emitting Cr-doped garnet-perovskite based phosphors with excellent responsiveness to P _fr for plant growth LED lighting

Cr³⁺-activated phosphors, with their 3d³ electronic configuration, efficiently absorb blue/violet light and emit deep to far-red wavelengths, perfectly matching the optimal absorption bands for plant growth. In this work, we report the synthesis of Y₃Al₅O₁₂-YAlO₃:1.3%Cr³⁺ (YAG-YAP:Cr³⁺) phosphors exhibiting a broad emission spanning deep to far-red light, closely aligned with the far-red phytochrome (P_fr) absorption spectrum in plants. The optimized sample, sintered at 1600 °C for 5 hours, demonstrates outstanding photoluminescence performance, including an exceptional activation energy of 0.34 eV, a long luminescence lifetime of 1.86 ms, perfect color purity (100%), and a high internal quantum efficiency of 74.9%. A prototype plant-growth LED was fabricated by coating this phosphor onto a 415 nm violet LED chip, achieving a strong spectral overlap (65% SR index) with the P_fr absorption band. These results demonstrate that YAG-YAP:Cr³⁺ phosphors are highly promising candidates for efficient, targeted far-red LEDs tailored for enhanced plant cultivation.