Tunable green to yellowish-orange phosphor Na3LuSi2O7:Eu2+, Mn2+ via energy transfer for UV-LEDs

A series of Eu2+, Mn2+-doped Na3LuSi2O7 (NLSO) phosphors have been prepared via the high-temperature solid-state reaction route. X-ray diffraction (XRD), Raman and Fourier transform infrared (FT-IR) spectra, fluorescent decay times, photoluminescence (PL) including temperature-dependent PL properties and scanning electron microscopy (SEM) were used to characterize the as-prepared samples. In Eu2+ singly-doped NLSO samples, an intense green emission is presented under UV excitation. A tunable color from green to yellowish-orange was generated when Mn2+ ions were co-doped into the NLSO: Eu2+, which is based on the energy transfer from Eu2+ to Mn2+ ions. The energy transfer from Eu2+ to Mn2+ ions can be speculated to be due to the wide spectral overlap between the Eu2+ emission and Mn2+ excitation spectra in Eu2+ or Mn2+ singly-doped NLSO samples. This is demonstrated by the similar excitation spectra of the Eu2+ and Mn2+ emission bands and the decreases in Eu2+ emission intensity and decay lifetime with the increase of Mn2+ concentration in the NLSO: Eu2+, Mn2+ samples. The energy transfer mechanism from Eu2+ to Mn2+ ions was determined to be a dipole-quadrupole interaction by the concentration quenching and spectral overlap methods. The maximum quantum yield can reach 51.5% for NLSO: 0.01Eu(2+), 0.12Mn(2+). The above results indicate that NLSO: Eu2+, Mn2+ could be a candidate as a green to yellowish-orange component for UV-excited w-LEDs.