Composition dependence of luminescence of Eu and Eu/Tb doped silicate glasses for LED applications

The Eu and Eu/Tb doped silicate glasses are good candidates for light emitting diode (LED) applications. But the optical performance of these glasses is sensitive to variations in chemical composition. In this paper we report our recent findings about the effect of addition of minor components such as B₂O₃, Al₂O₃ and CaF₂ on the luminescent properties of the above-mentioned glasses. We explore the role of Eu³⁺ ions as a structural probe of the glasses by determining the asymmetry factor, i.e., the ratio of the emission intensity of the ⁵D₀→⁷F₂ transition to that of the ⁵D₀ →⁷F₁ transition. The results show that the asymmetry factor and luminescence lifetimes of as-prepared materials are dependent on composition. White fluorescence is achieved in Eu/Tb co-doped glasses, which can be attributed to the simultaneous generation of red, green and blue wavelengths from Eu3+ and Tb3+ ions. The variation of the excitation wavelength can tune the emission spectra as well as Commission Internationale de L’Eclairage (CIE) chromaticity coordinates of Eu/Tb co-doped glasses for specific applications. The energy transfer from Tb³⁺ to Eu³⁺ ions is investigated by analyzing fluorescence spectra and decay curves.