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, KAlSi 2 O 6:Cr 3+, was synthesized and optimized. The material crystallizes in a tetragonal structure with space group I 41/ a . It exhibits two excitation bands at 428 nm ( 4 A 2 → 4 T 1 ) and 571 nm ( 4 A 2 → 4 T 2 ) and emits a dominant peak at 710 nm (R-line) with a weak shoulder at 730 nm (N 2 -line). XRD Rietveld refinement results reveal that the doped Cr 3+ and Rb + preferentially occupy K + sites, while Ga 3+ substitutes for Al 3+ sites. Raman and XPS analyses show that these dopants induce lattice distortion, suppress high-frequency phonons, and slightly alter the electron cloud distribution of Cr 3+ ions. Notably, Ga 3+ -Rb + codoping shifts the main emission to 695 nm and markedly improves thermal stability ( I 423 K / I 303 K increases from 46.01% to 66.52%). By leveraging the spectral overlap with phytochrome P FR absorption, pc-LED devices were fabricated. Pc-LEDs based on the Ga 3+ -doped or Ga 3+ –Rb + codoped phosphors not only promote mint growth but also enable clear imaging in night-vision scenarios, demonstrating strong potential for dual-functional lighting.