A terbium-sensitized Eu3+-activated deep-red-emitting phosphor for plant growth LED application

• A novel terbium-sensitized Eu 3+ -activated phosphor, Ca 2 TbSn 2 Al 3 O 12 :Eu 3+ , has been designed and synthesized. • The solid-state MAS NMR spectra have been used to confirm the reasonability of the XRD structural refinements. • The far red emission of Eu 3+ is extremely dominant, which can well match the absorption spectra of P fr in plants. • Terbium is one of the host composition elements, and thus, highly efficient Tb 3+ -Eu 3+ energy transfer can be realized. • An experimental evidence that proves the existence of terbium bridge energy transfer has been discussed in detail. Traditional Eu 3+ -activated inorganic phosphors are habitually used for general lighting and display because they generally emit either intense orange ( 5 D 0 - 7 F 1 ) or red ( 5 D 0 - 7 F 2 ) light whose wavelength is shorter than 630 nm. However, less known nor focused is that Eu 3+ at sites with specific symmetry can intensify its 5 D 0 - 7 F 4 transition, enabling Eu 3+ itself to emit deep red light (>700 nm) even stronger than the above orange and red ones. Herein, a novel Eu 3+ -activated phosphor, Ca 2 TbSn 2 Al 3 O 12 :Eu 3+ , is developed from the garnet structure. Differing from other Eu 3+ -activated phosphors, the 5 D 0 - 7 F 4 transition of Eu 3+ in the host is dominant and the orange, red and deep red emissions are balanced. Such special features of Eu 3+ luminescence mainly meet the need of phytochromes (P FR and P R ) in plants. Additionally, bridge style energy transfer from the host composition element Tb 3+ to the activator Eu 3+ can be observed. It is found the Tb 3+ -Eu 3+ energy transfer here takes through the mechanism of dipole-dipole interaction and the simulation on decay curve of Eu 3+ upon Tb 3+ excitation, for the first time, confirms the existence of terbium bridge energy transfer. For the Ca 2 Tb 0.60 Sn 2 Al 3 O 12 :0.40Eu 3+ , the energy transfer efficiency is as high as 94.4% and the emission color is totally red. Thermal quenching studies reveal that the emission intensity of the phosphor at 425 K sustains 80% of its initial intensity at room temperature. By fabricating the phosphor with a 380 nm LED chip, a plant-growth LED device can be obtained.