GAGG:Cr<sup>3+ </sup>Phosphors for Far-Infrared Light Emitting Diodes

Recently, Far-infrared Light Emitting Diodes have attracted considerable interest in the research field worldwide. Emerging light therapy requires effective red/far-infrared light resources in clinical and plant photomorphogenesis to target or promote the interaction of light with living organisms. Here, Gd3Al4GaO12:Cr3+ (hereinafter referred to as: GAGG:Cr3+) phosphor was synthesized by high-temperature solid-phase method, and the crystal structure, morphology, and luminescence properties of this series of phosphor samples were studied. Through X-ray powder diffraction to obtain pure phase GAGG:Cr3+ series phosphor. Under the excitation of 420nm blue light, a broad band emission from 640 to 850nm is obtained, which is the result of the transition of Cr3+ 4T2→4A2 level. A sharp emission peak at 693nm is the R line belonging to Cr3+ in Gd3Al4GaO12 garnet. R line is assigned to the spin-forbidden 2E→4A2 transitions of Cr3+ ions that occupy the ideal octahedral sites. As the Cr3+ doping concentration increases, the luminous intensity of the sample increases first and then decreases. When the doping concentration of Cr3+ is 0.1mol phosphor,the luminous intensity is strongest at one single broad peak at about 712nm. At 440k, the R sharp line (693nm) and broad band (712nm) emission intensity maintained 78.6% and 71.8% , compared to room temperature intensity, respectively. The change of fluorescence lifetime at different temperatures gives the mechanism of fluorescence change with temperature. The current exploration will pave a promising way to engineer GAGG:Cr3+ activated optoelectronic devices for all kinds of photobiological applications.