A dual-emission Ca9MgLi(PO4)7: Ce3+, Mn2+ phosphor with energy transfer for plant-lighting

Abstract A series of multicolor-tunable Ca9MgLi(PO4)7 (CMLPO):Ce3+, Mn2+ phosphors have been prepared by high-temperature solid-state reaction process under the reductive atmosphere and the luminescence properties have been explored. The photoluminescence excitation (PLE) spectra and emission (PL) spectra reveal that the bands are centered at 345 and 365 nm occupying the Ca3 site with respect to the CMLPO:Ce3+ phosphors, while the bands located at 386 and 411 nm are ascribed to the emission of Ce3+ ions occupying the eight-coordinated center (Ca1 and Ca2), according to the Van Uitert formula. In addition, an asymmetric broad band with the maximum at ~361 nm stemmed from the 5d → 4f transition can be observed, under 291 nm excitation. Also, the PL spectra display a broad band at ~650 nm, which is assigned to the 4T1(4G) → 6A1(6S) spin-forbidden transition of Mn2+ for the CMLPO:Mn2+ samples. Furthermore, the Ce3+ can transfer a part of its energy to Mn2+ and the energy transfer (ET) efficiency reaches as high as ~94.02%. Subsequently, the CMLPO:Ce3+, Mn2+ phosphors present a series of colors by modulating the contents of Mn2+ through an effective resonance-type ET and the dipole-quadrupole (d-q) interaction governs the ET process. Importantly, the emission band of Mn2+ distributed exactly in red and far-red regions, which can match well with the red light wavelength required for plant photosensitive pigments (PR, PFR). In view of the aforementioned results, the as-prepared phosphors could open ideas for designing the plant growth LEDs.