CaYAlO4:Mn4+,Mg2+: An efficient far-red-emitting phosphor for indoor plant growth LEDs

Abstract

Recently, the LEDs technology has been widely used as the light source for indoor plant growth in agricultural area. Previous studies demonstrated that blue light around 450 nm (400–500 nm), red light around 660 nm (620–690 nm), and far-red light around 730 nm (700–740 nm) play important roles in reactions of photosynthesis, phototropism and photomorphogenesis. Thus, in this work, in order to find suitable far-red-emitting phosphors for plant growth LEDs, a series of CaYAlO4:Mn4+,Mg2+ (CYA:Mn4+,Mg2+) phosphors were synthesized and their crystal structure, morphology and photoluminescence properties were investigated. These CYA:Mn4+,Mg2+ phosphors had two broad excitation band in the 250–600 nm wavelength range with peaks at 348 and 469 nm. When excited by 348 nm, the CYA:Mn4+,Mg2+ phosphors emitted efficient far-red light around 710 nm, which could match well with the absorption spectrum of phytochrome PFR. The luminescence mechanism was studied in detail. The optimal doping concentrations of Mn4+ and Mg2+ ions were determined to be about 0.4 and 1 mol%, respectively. The CIE chromaticity coordinates of optimized CYA:0.4%Mn4+,1%Mg2+ sample were (0.7174, 0.2825), and its internal quantum efficiency reached as high as 48%. Thus, the CYA:Mn4+,Mg2+ phosphors would have great potential for applying in future plant growth LEDs.