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

Up to now, orchestrating the coexistence of Eu2+ and Eu3+ activators in a single host lattice has been an extremely difficult task, especially for the appearance of the characteristic emission of Eu2+ and Eu3+ in order to generate white light. Nevertheless, here we demonstrate a new Eu2+/Eu3+ coactivated SrAl3BO7 nanocrystalline phosphor with abundant and excellent multichannel luminescence properties. A series of Eu2+/Eu3+ coactivated SrAl3BO7 nanocrystalline phosphors were prepared through a Pechini-type sol-gel method followed by a reduction process. With excitation of UV/NUV light, the prepared SrAl3BO7:Eu2+,Eu3+ phosphors show not only the characteristic f-f transitions of Eu3+ ion (5DJ → 7FJ,J', J, J' = 0-3), but also the 5d → 4f transitions of Eu2+ ion with comparable intensity from 400 to 700 nm in the whole visible spectral region. The luminescence color of the SrAl3BO7:Eu2+,Eu3+ 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 (Eu2+, Eu3+), and the relative ratio of Eu2+ to Eu3+ ions to some extent. A single-phase white-light emission has been realized in SrAl3BO7:Eu2+,Eu3+ phosphor. The obtained SrAl3BO7:Eu2+,Eu3+ phosphor has potential application in the area of NUV white-light-emitting diodes.