Eu-, Tb-, and Dy- Doped Oxyfluoride Silicate Glasses for LED Applications

Luminescence glass is a potential candidate for the light-emitting diodes (LEDs) applications. Here, we study the structural and optical properties of the Eu-, Tb-, and Dy-doped oxyfluoride silicate glasses for LEDs by means of X-ray diffraction, photoluminescence spectra, Commission Internationale de L'Eclairage (CIE) chromaticity coordinates, and correlated color temperatures (CCTs). The results show that the white light emission can be achieved in Eu/Tb/Dy codoped oxyfluoride silicate glasses under excitation by near-ultraviolet light due to the simultaneous generation of blue, green, yellow, and red-light wavelengths from Tb, Dy, and Eu ions. The optical performances can be tuned by varying the glass composition and excitation wavelength. Furthermore, we observed a remarkable emission spectral change for the Tb3+ single-doped oxyfluoride silicate glasses. The D-5(3) emission of Tb3+ can be suppressed by introducing B2O3 into the glass. The conversion of Eu3+ to Eu2+ takes place in Eu single-doped oxyfluoride aluminosilicate glasses. The creation of CaF2 crystals enhances the conversion efficiency. In addition, energy transfers from Dy3+ to Tb3+ and Tb3+ to Eu3+ ions occurred in Eu/Tb/Dy codoped glasses, which can be confirmed by analyzing fluorescence spectra and energy level diagrams.