Strongly enhanced luminescence of Sr4Al14O25:Mn4+ phosphor by co-doping B3+ and Na+ ions with red emission for plant growth LEDs

Development of a more cost-effective radiation source for use in plant-growing facilities would be of significant benefit for commercial crop production applications. A series of co-doped B 3+ and Na + ions Sr 4 Al 14 O 25 :Mn 4+ inorganic luminescence materials which can be used for plant growth were successfully synthesized through a conventional high-temperature solid-state reaction. Powder X-ray diffraction was used to confirm the crystal structure and phase purity of the obtained samples. Then scanning electron microscopy elemental mapping was undertaken to characterize the distribution of the doped ions. Detail investigations on the photoluminescence emission and excitation spectra revealed that emission intensity of tetravalent manganese ions can be well enhanced by monovalent sodium ions and trivalent boron ions under near-ultraviolet and blue excitation. Additionally, crystal field parameters and energies of states are calculated and discussed in detail. Particularly we achieve a photoluminescence internal quantum yield as high as 60.8% under 450 nm blue light excitation for Sr 4 Al 14 O 25 :Mn 4+ , Na + , B 3+ . Therefore, satisfactory luminescence properties make these phosphors available to LEDs for plant growth. (a) Emission spectrum of LEDs fabricated with 445 nm blue chip and Sr 2 Si 5 N 8 :Eu 2+ red phosphor. (b) Emission spectrum of LEDs fabricated with 445 nm blue chip and Sr 4 Al 14 O 25 :Mn 4+ phosphor. (c and d) Absorption spectrum of chlorophyll-b and chlorophyll-a.