White light emission through energy transfer processes in barium gallogermanate glasses co-doped with Dy3+-Ln3+ (Ln =Ce, Tm)

Fully amorphous rare earth co-doped barium gallo-germanate glasses were synthesized using the traditional melt quenching-technique. The glass systems were doped with selected pairs of rare earths Dy3+/Ce3+ and Dy3+/Tm3+ ions. To study the spectroscopic properties of gallo-germanate glasses co-doped with Dy3+ and Ln3+ (Ln=Ce, Tm) ions, the luminescence spectra and luminescence decay curves were recorded. It was observed that luminescence bands corresponding to characteristic transitions of Ln3+ (Ln=Ce, Tm) and dysprosium ions are present in the emission spectra measured under direct excitation of Ln3+. The experimental results indicate that energy transfer between dysprosium and cerium/thulium ions is effective. From the emission spectra, the Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (x, y) were calculated in relation to the potential application of gallo-germanate glasses for white LEDs. It has been proved that our glass systems exhibit white emission originating from the simultaneous generation of several bands of Dy3+, Ce3+/Tm3+ under the UV-visible light excitation.