Highly efficient and thermostable far-red phosphor for promoting root growth in plants

Phytochrome PFR plays a key role in plant photomorphogenesis, and its perception of far-red light is essential, but how to obtain an efficient far-red phosphor to achieve accurate light filling remains a huge challenge. In this study, Gd1−y−zAl3−x(BO3)4:xCr3+,yLu3+,zSm3+ (GAB:xCr3+,yLu3+,zSm3+) series phosphors were synthesized by a high-temperature solid-state method. By doping Lu3+, the emission intensity of Cr3+ could increase as high as 20%. With the introduction of Sm3+, the emission intensity of Cr3+ was further increased by 29%. Particularly, the emission spectra can be tuned by varying the concentration ratio of Sm3+ and Cr3+, more suitable for the absorption spectrum of PFR. Moreover, the internal quantum yield and external quantum yield of GL0.1AB:0.03Cr3+ and GL0.1AB:0.03Cr3+,0.003Sm3+ were 83.1% and 24.7% and 78.1% and 26.3%, respectively. There were high anti-thermal quenching properties in the prepared phosphors at 423 K, with 107.6% (GAB:0.03Cr3+), 103.1% (GL0.1AB:0.03Cr3+), and 102.7% (GL0.1AB:0.003Sm3+,0.03Cr3+). Finally, the phosphors were made into pc-LED devices, which can realize the adjustable orange-red and far-red luminescence and meet the needs of plant lighting applications. In the light-regulated plant growth experiment, compared with the control group, far-red light promoted root growth in plants, confirming the application potential of the prepared phosphors in indoor plant cultivation.