Cold white light generation through the simultaneous emission from Ce3+ and Tb3+ in sodium germanate glass

• Published in: Optical materials 2014-11, Vol.37, p.451-456
• Main Authors: Álvarez, E., Zayas, Ma.E., Rodríguez-Carvajal, D., Félix-Domínguez, F., Duarte-Zamorano, R.P., Falcony, C., Caldiño, U.
• Format: Article
• Language: English
• Subjects: Ce3; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Germanate glass; Glasses, quartz; Non-radiative energy transfer; Optical materials; Optics; Photoluminescence; Physics; Tb3; White light
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2014.06.038

•Sodium germanate glass is optically activated with Ce3+/Tb3+ (GNCT).•Non-radiative energy transfer Ce3+→Tb3+ takes place in GNCT.•Cold white light (0.30, 0.32) is generated by GNCT pumped with 310nm-UV light. A spectroscopic investigation of sodium germanate glasses activated with Ce3+, Tb3+ and Ce3+/Tb3+ is carried out by analyzing their photoluminescence spectra and decay times. Non-radiative energy transfer from Ce3+ to Tb3+ is observed upon near-UV excitation at 310nm (peak emission wavelength of AlGaN-based LEDs). The non-radiative nature of this energy transfer is inferred from the increase in the decay rate of the Ce3+ emission when the glass is co-doped with Tb3+. From an analysis of the Ce3+ emission decay time curve it is inferred that an electric dipole–quadrupole interaction might to be the dominant mechanism for the Tb3+ emission sensitized by Ce3+. Energy transfer from Ce3+ to Tb3+ leads to a simultaneous emission of these ions in the blue, green, yellow and red, resulting in white light with CIE1931 chromaticity coordinates, x=0.30 and y=0.32, which correspond to cold white light with a colour temperature of 7320K and very small deviation from the Planckian black-body radiator locus (0.005).