Enhanced Luminescence in Mn⁴⁺, Bi³⁺ Co‐Doped Deep‐Red SrMgGaAl₉O₁₇ Phosphors for Plant‐Cultivation Light‐Emitting Diodes

In modern agricultural lighting, Mn 4+ ‐doped red phosphors synthesized via high‐temperature solid‐state method play a critical role in enhancing plant photosynthesis and photomorphogenesis, addressing the growing demand for efficient and sustainable plant cultivation technologies. Herein, a novel red phosphor, SrMgGaAl 9 O 17 :Mn 4+ , Bi 3+ (SMGA:Mn 4+ , Bi 3+ ), designed for plant‐growth light‐emitting diodes (LEDs), has been reported. Under excitation at the optimal wavelength of 335 nm, the Mn 4+ ions exhibit a broad red emission band (600–700 nm). Through Bi 3+ co‐doping, the emission intensity of SMGA:Mn 4+ is significantly enhanced without additional luminescence from Bi 3+ itself, as confirmed by absorption, excitation, and emission spectral analyses. When the prepared material is encapsulated with an LED chip, its broad red emission band exhibits excellent spectral overlap with the absorption curve of plant pigments, demonstrating great potential as a red‐emitting component in LED systems. Thus, Bi 3+ as a non‐luminescent sensitizer playing a key role in enhancing Mn 4+ luminescence, providing a simple and efficient strategy for developing high‐performance red phosphors for agricultural lighting applications.