A new efficient deep-red-emission phosphor Al₂O₃:Cr³⁺/Y₃Al₅O₁₂:Ce³⁺ for plant growth

Two new types of inexpensive mixed phosphors, Al2O3:Cr3+/YAG:Ce3+ and Al2O3:Cr3+/(Ba,Sr)2SiO4:Eu2+, were designed and synthesized using a high-temperature solid-state method. The emission intensity under blue excitation was reported to be of the order of Al2O3:Cr3+/YAG:Ce3+ > Al2O3:Cr3+/(Ba,Sr)2SiO4:Eu2+ > Al2O3:Cr3+. By adding YAG:Ce3+ to Al2O3:Cr3+, the excitation spectrum of the new phosphor was changed; blue excitation corresponding to 4f → 5d transition appeared because of the good overlap between the yellow emission of YAG:Ce3+ and the yellow excitation of Al2O3:Cr3+. The emission intensity of deep red (696 nm) under excitation at 460 nm demonstrates a significant enhancement and the quantum yield increases to 1.45 times that of Al2O3:Cr3+. Moreover, the new phosphor can be excited by light in a range between 325 and 650 nm, which could be considered as the widest excitation in the visible light region of the known deep red oxide phosphors. The temperature dependency of the emission under blue excitation is unique (I150 °C/I25 °C = 84%), which is much better than that of yellow excitation and that at 400 nm. The reflection-emission spectrum recorded under white light from a Xe lamp resembling sunlight demonstrated that the new phosphor has provided a strong deep-red light. The above results indicated that the new phosphor provides a comprehensive assistance in promoting plant growth both under a combination with a blue LED chip and under the Sun.