Red-emission improvement of Eu2+-Mn2+ co-doped Sr2Si5N8 phosphors for white light-emitting diodes

Eu2+ and Mn2+ ions co-doped Sr2Si5N8 phosphors with enhanced luminescence properties were successfully prepared in this study. Under blue excitation at 420 nm, Sr2Si5N8: Eu2+ displayed a broad emission band peaking at about 615 nm, which originated from the 4f65d1→4f7 transitions of Eu2+ ions. Sr2Si5N8: Mn2+ exhibited a broad band at around 608 nm owing to the 4T1(4G)→6A1(6S) transitions of Mn2+ ions. As Mn2+ ions were incorporated into Sr2Si5N8: Eu2+, an increase in the emission intensity in the red region was observed. The improvement in the emission intensity was attributed to the energy transfer from Mn2+ to Eu2+ ions. The mechanism of the energy transfer was confirmed to be a dipole-dipole interaction and the critical distance between Eu2+ and Mn2+ ions was evaluated. Sr2Si5N8: Mn2+, Eu2+ with enhanced luminescence properties and improved thermal stability is demonstrated to be a promising red-emitting phosphor for applications in white LEDs.