Tunable full-color emitting Na2Ba6(Si2O7)(SiO4)2:Ce3+,Eu2+,Tb3+,Mn2+ phosphor for UV white LEDs: Photoluminescence and energy transfer

Highlights: • The Na₂Ba₆(Si₂O₇) (SiO₄)₂:Ce³⁺,Eu²⁺,Tb³⁺,Mn²⁺ phosphors have been synthesized. • Energy transfer in this host is systematically investigated and their origins are to be revealed. • Commission on illumination value of color tumble emission as well as luminescence quantum yield can be tuned. • All these results indicate that the phosphor is a promising full-color emitting phosphor for white LED. Tunable full-color emitting Na₂Ba₆(Si₂O₇) (SiO₄)₂:Ce³⁺,Eu²⁺,Tb³⁺,Mn²⁺ phosphors have been prepared and investigated. X-ray diffraction (XRD), photoluminescence (PL) spectra, absolute quantum yield and lifetimes were used to characterize the samples. When doped with Ce³⁺ or Eu²⁺ they present blue luminescence under UV excitation. Results of luminescence spectra and decay time measurements reveals that an energy transfer (ET) from Ce³⁺ to Tb³⁺ occurred mainly via a dipole–quadrupole mechanism, and the critical distances of the ion pairs (R_C) were calculated by the spectral overlap method. The energy-transfer efficiencies of Ce³⁺ to Eu²⁺ are discussed in detail. Commission on illumination value of color tumble emission as well as luminescence quantum yield (9.8–42.1%) can be tuned by controlling the content of Ce³⁺, Tb³⁺ and Eu²⁺. A white LED with CIE chromaticity coordinates of (0.30, 0.41), superior color-rendering index (R_a) of 87.5 and correlated color temperature (CCT) of 6518 K was fabricated by combining a 365 nm UV-InGaN chip and a phosphor blend of white-emitting Na₂Ba₆(Si₂O₇) (SiO₄)₂:Ce³⁺,Eu²⁺,Tb³⁺,Mn²⁺ phosphor. All results suggest that it is suitable for UV white LEDs.