Tuning Far-Red Luminescence Properties of KAlSi ₂ O ₆ :Cr ³⁺ Phosphors via Partial Cation Substitution

Far-red phosphors are critically important for advancing plant growth lighting. In this work, a novel far-red phosphor, KAlSi2O6:Cr3+, was synthesized and optimized. The material crystallizes in a tetragonal structure with space group I41/a. It exhibits two excitation bands at 428 nm (4A2 → 4T1) and 571 nm (4A2 → 4T2) and emits a dominant peak at 710 nm (R-line) with a weak shoulder at 730 nm (N2-line). XRD Rietveld refinement results reveal that the doped Cr3+ and Rb+ preferentially occupy K+ sites, while Ga3+ substitutes for Al3+ sites. Raman and XPS analyses show that these dopants induce lattice distortion, suppress high-frequency phonons, and slightly alter the electron cloud distribution of Cr3+ ions. Notably, Ga3+-Rb+ codoping shifts the main emission to 695 nm and markedly improves thermal stability (I423 K/I303 K increases from 46.01% to 66.52%). By leveraging the spectral overlap with phytochrome PFR absorption, pc-LED devices were fabricated. Pc-LEDs based on the Ga3+-doped or Ga3+–Rb+ codoped phosphors not only promote mint growth but also enable clear imaging in night-vision scenarios, demonstrating strong potential for dual-functional lighting.