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The aim was to design a multi-chromatic phosphor based on the colour mixing principle, whereby white light can be produced from an appropriate mixture of blue, green, and red emissions by a single phosphor. In this perspective, Tm 2 O 3 , Tb 4 O 7 , and Eu 2 O 3 were simultaneously doped in single host glass matrix. A series of Tm 2 O 3 single- as well as Tm/Tb/Eu triple-doped glasses were synthesised. The photoluminescence behaviour and luminescence quenching were investigated for Tm 2 O 3 single-doped glasses. Keeping Tm 2 O 3 constant at the saturation concentration in the Tm/Tb/Eu triple-doped glasses and varying the doping ratio of the two other lanthanides (Tb 4 O 7 and Eu 2 O 3 ) in the host glass allow to some extent the control of the spectral composition and consequently the generation of tunable colour impressions. The latter can also be adjusted by keeping the concentration ratio of the three lanthanides constant and varying the excitation wavelength. Upon 358-nm excitation of the Tm/Tb/Eu triple-doped glasses, white light emission is achieved and the corresponding correlated colour temperatures are also determined. The different energy transfers occurring in between the three lanthanides are investigated and possible energy transfer routes are proposed. [ABSTRACT FROM AUTHOR]

Rare-earth (RE) doped borate glasses are investigated for their potential as photon down-shifting cover glass for CdTe solar cells. The barium borate base glass is doped with trivalent rare-earth ions such as Sm 3+ , Eu 3+ , and Tb 3+ showing an intense luminescence in the red (Sm 3+ , Eu 3+ ) and green (Tb 3+ ) spectral range upon excitation in the ultraviolet and blue. Additionally, the glasses are double-doped with two RE ions for a broad-band absorption. The gain in short-circuit current density of CdTe solar cells with different thicknesses of the CdS buffer layer is calculated. Though the single-doped glasses already reveal a slight increase in short-circuit current density, the double-doped glasses allow for higher efficiency gains since a significant broader spectral range is covered for absorption. For a Tb 3+ /Eu 3+ double-doped glass with a RE doping level of 1 at% each, an efficiency increase of 1.32% can be achieved. [ABSTRACT FROM AUTHOR]

Abstract Lanthanide-doped borate glasses represent an attractive alternative as frequency-converter for white-light generation. The CIE colour coordinates of Tm 3 + , Tb 3 + , and Eu 3 + double- and triple-doped glasses can be tuned over a broad spectral range by varying the lanthanide doping concentrations and ratios accordingly. In addition, double- and triple-doping allow for a change in colour coordinates by using different excitation wavelengths. To overcome the problem of poor optical absorption of the doped lanthanide ions and to increase the optical path length for the excitation light, the as-made glass is successfully processed to a glass ceramic. The amount of crystallites grown in the glass is controlled by appropriate choice of annealing time and temperature. The glass ceramics do not only offer enhanced optical properties, but also improved thermal properties. The thermal diffusivity of the glass ceramic is one order of magnitude higher than that of the glass. Highlights • Lanthanide-doped borate glasses as frequency-converter for white light generation. • Enhanced optical properties through thermal processing from glass to glass ceramic. • Controlled crystallization by appropriate choice of annealing time and temperature. • Thermal diffusivity of glass ceramic one order of magnitude higher than that of glass. [ABSTRACT FROM AUTHOR]