Europium‐doped NaBaB₉O₁₅ phosphors with controllable blue/red dual-band emissions through self-reduction for plant growth LEDs

Novel Eu-doped NaBaB₉O₁₅ phosphors were successfully prepared by a traditional solid-phase method in air. It is found that Eu³⁺ ions can be reduced to Eu²⁺ spontaneously even in a non-reducing atmosphere due to the charge compensation and the rigid three-dimensional structure of the NaBaB₉O₁₅ matrix. Eu²⁺/Eu³⁺ co-doped NaBaB₉O₁₅ phosphors exhibit blue/red dual-band emission in the 370–450 nm and 580–750 nm wavelength regions, attributed to the 5d-4f transition of Eu²⁺ and the 4f-4f transition of Eu³⁺, respectively. The ratio of red/blue emission intensities can be easily tuned by changing the synthesis conditions, ranging from 0.07 to 2.67. Importantly, the emission bands of NaBaB₉O₁₅:Eu phosphors match well with the absorption peaks of chlorophyll. This study suggests that this dual-band emitting phosphors might be a potential candidate for indoor plant growth LEDs.