Tunable blue-green color emission and energy transfer of Sr3NaSc(PO4)3F:Eu2+,Tb3+ phosphors with near-UV broad band excited for white LEDs

Abstract

A series of Eu2+ and/or Tb3+ doped Sr3NaSc(PO4)3F phosphors were prepared under a high temperature solid-state reaction. The crystal structure and morphology of the phosphors were characterized by the X-ray diffraction and field emission scanning electron microscopy. Blue phosphor Sr3NaSc(PO4)3F:Eu2+ has the high quantum efficiency and can be excited by the intense broad excitation from 220 to 420 nm, matching well with the commercial near-UV chips. The photoluminescence properties and quantum efficiency are substantially improved by the doping of Eu2+ ions into the Sr3NaSc(PO4)3F:Tb3+ phosphors, which is attributed to the efficient energy transfer from Eu2+ to Tb3+. Furthermore, the energy transfer process from Eu2+ to Tb3+ in Sr3NaSc(PO4)3F is demonstrated by fluorescence spectra and decay time, where a resonant type via a dipole-dipole mechanism was demonstrated. In addition, the color tunable emission from blue to green can be realized by adjusting the Eu2+/Tb3+ ratio. The temperature-dependent photoluminescence results of as-prepared samples revealed that the Sr3NaSc(PO4)3F:Eu2+ and Sr3NaSc(PO4)3F:Eu2+,Tb3+ phosphors have excellent thermal stability, being available to near-UV LEDs.