Spanning green to deep red emission: KAl₁₁O₁₇: Cr³⁺ phosphors engineer light spectra for enhanced plant growth

Plants have a limited ability to absorb green light. Additionally, the energy distribution of sunlight in the deep-red region is weak. These factors restrict the efficiency of plant growth and limit yield improvements. In this study, a novel deep-red phosphor material, KAl₁₁O₁₇: Cr³⁺, was designed and synthesized through a high-temperature solid-state method. This material exhibits deep-red light emission at a central wavelength of 697   nm under broadband excitation at 430   nm (near-ultraviolet) and 562   nm (green light). By leveraging a "light-cutting" mechanism, the phosphor converts underutilized green light into far-red light, which strongly aligns with the absorption peak of the plant photoreceptor P FR state. When applied as a thin-film coating, the material significantly enhances lettuce growth under controlled green-light irradiation. These findings demonstrate the potential of KAl₁₁O₁₇: Cr³⁺ in optimizing spectral distribution for energy-efficient agricultural lighting systems.