Structure modulation induced luminescence improvement in Gd3-Y Ga5O12:Cr3+ deep-red phosphors for dragon fruit cultivation

Deep-red phosphor-converted light-emitting diodes (pc-LEDs) have kept booming for the application in plant cultivation, but it suffers from low efficiency and low thermal quenching temperature. Here we report a series of Gd3-xYxGa5O12:Cr3+ garnet deep-red phosphors with high efficiency and excellent thermal stability. Y3+ ions with the same valence state and smaller radius were adopted to substitute Gd3+ to modulate the structure and further enhance the luminescence properties. Structure variation and microstructure of this garnet were carried out to verify the successful doping of Y3+. These phosphors show a broad excitation band from 400 nm to 650 nm and match well with blue chips. By modulating the structure, the crystal field was enhanced and the peak position shifted toward the blue direction. Representative Gd2.5Y0.5Ga5O12:Cr3+ exhibited excellent thermal stability and kept 93% emission at 423 K than that at room temperature. The internal quantum efficiency and external quantum efficiency of Gd0.5Y2.5Ga5O12:Cr3+ are 71.77% and 11.86%, respectively. As the temperature increased, the emission spectra were broadened and matched better with phytochrome PR and PFR. LED devices were fabricated by combining blue chip with this deep-red phosphor and applied to the cultivation of dragon fruit. The reducing sugar content was improved from 98.28 g/L to 111.85 g/L of the dragon fruit juice, verifying this thermally stable garnet deep-red phosphor exhibited huge potential in plant cultivation.