Polychromatic long persistent luminescence of CaAlSiN3:Ln (Ln=Eu, Ce, Dy, Pr, Tb, Gd, Sm, Tm, Nd) phosphors prepared by combustion synthesis

Although the phosphors based on CaAlSiN3 (e.g. CaAlSiN3:Eu2+, CaAlSiN3:Ce3+) have been extensively studied in phosphor-converted white light emitting diodes (w-LEDs) due to its outstanding luminescent properties, there have been rare literatures on the persistent luminescence of CaAlSiN3 except for the red afterglow emission of CaAlSiN3:Eu2+. In our work, a series of CaAlSiN3:Ln (Ln=Eu, Ce, Dy, Pr, Tb, Gd, Sm, Tm, Nd) phosphors have been successfully prepared by combustion synthesis and their polychromatic visible afterglow emissions were observed. The long persistent luminescent properties of the phosphors were studied systematically, among which, CaAlSiN3:Eu2+ and CaAlSiN3:Ce3+ show the best red and yellow long persistent luminescence with persistent time of 4980 s and 4860 s at the 0.32 mcd/m2 threshold value, respectively, and other phosphors show relatively weak persistent luminescence performance with other afterglow emission colors. Moreover, Eu2+, Ce3+ co-doped CaAlSiN3 were synthesized to enhance the red long persistent luminescence performance, whose persistent time has reached 6300 s due to a more appropriate trap depth distribution of 0.83–0.9 eV compared with Eu2+ and Ce3+ singly doped CaAlSiN3. We believe that this work is of significance for extending the studies of CaAlSiN3 system to a host material for polychromatic long persistent luminescence.