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.