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

Abstract

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:0.01Eu²⁺,0.12Mn²⁺. The above results indicate that NLSO:Eu²⁺,Mn²⁺ could be a candidate as a green to yellowish-orange component for UV-excited w-LEDs.