Multichannel Luminescence Properties of Mixed-Valent Eu²⁺/Eu³⁺ Coactivated SrAl₃BO₇ Nanocrystalline Phosphors for Near-UV LEDs

Abstract

Up to now, orchestrating the coexistence of Eu 2+ and Eu 3+ activators in a single host lattice has been an extremely difficult task, especially for the appearance of the characteristic emission of Eu 2+ and Eu 3+ in order to generate white light. Nevertheless, here we demonstrate a new Eu 2+ /Eu 3+ coactivated SrAl 3 BO 7 nanocrystalline phosphor with abundant and excellent multichannel luminescence properties. A series of Eu 2+ /Eu 3+ coactivated SrAl 3 BO 7 nanocrystalline phosphors were prepared through a Pechini-type sol–gel method followed by a reduction process. With excitation of UV/NUV light, the prepared SrAl 3 BO 7:Eu 2+,Eu 3+ phosphors show not only the characteristic f–f transitions of Eu 3+ ion ( 5 D J → 7 F J, J ′, J, J ′ = 0–3), but also the 5d → 4f transitions of Eu 2+ ion with comparable intensity from 400 to 700 nm in the whole visible spectral region. The luminescence color of the SrAl 3 BO 7:Eu 2+,Eu 3+ phosphor can be tuned from blue, blue-green, white, and orange to orange-red by changing the excitation wavelength, the overall doping concentration of europium ions (Eu 2+, Eu 3+ ), and the relative ratio of Eu 2+ to Eu 3+ ions to some extent. A single-phase white-light emission has been realized in SrAl 3 BO 7:Eu 2+,Eu 3+ phosphor. The obtained SrAl 3 BO 7:Eu 2+,Eu 3+ phosphor has potential application in the area of NUV white-light-emitting diodes.