Promising deep-red emitting Cr³⁺-doped SrAl₁₂O₁₉ phosphors for plant growth LEDs

Recently, deep-red-emitting phosphors that can be excited by ultraviolet (UV) and near-ultraviolet (NUV) light have been extensively investigated for plant growth LED applications. However, due to the harmful effects of these high-energy rays on plants, violet- or blue-excited deep-red-emitting phosphors are considered a more appropriate solution. In this work, SrAl₁₂O₁₉:Cr³⁺ phosphors were synthesized using a simple solid-state reaction, revealing a strikingly sharp deep-red emission band centered at 694 nm and effective excitation by violet light. The optimal SrAl₁₂O₁₉:1.0%Cr³⁺ phosphor, annealed at 1500°C, exhibits an extended lifetime of 0.549 ms, an energy activation level of 0.239 eV, a good quantum efficiency (QE) of 36.2%, and superior color purity at 100%. Further, an LED prototype with a precise absorption spectrum for far-red phytochrome (P_fr) has been demonstrated. These results indicate that the synthesized SrAl₁₂O₁₉:1.0%Cr³⁺ phosphors could be used as a promising deep-red-emitting phosphor for plant growth LED.