Berlin 2018 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 68: Poster: Complex Fluids, Glasses, Granular
DY 68.20: Poster
Thursday, March 15, 2018, 15:30–18:00, Poster A
Photometric far-field studies on luminescent borate glass ceramics for LED applications — •Juliane Schuppich1, A. Charlotte Rimbach1, Peter W. Nolte2, Franziska Steudel2, and Stefan Schweizer1,2 — 1South Westphalia University of Applied Sciences, Lübecker Ring 2, 59494 Soest — 2Fraunhofer Application Center for Inorganic Phosphors, Branch Lab of Fraunhofer Institute for Microstructure of Materials and Systems IMWS, Lübecker Ring 2, 59494 Soest
The most common white light emitting diodes (LEDs) are based on a blue-emitting LED chip coated with a yellow-emitting phosphor; the phosphor acts as a frequency-downshifter for a significant part of the blue light to generate white light. Luminescent glasses represent an interesting alternative to the commonly used phosphor/polymer composite due to their higher thermal and chemical stability. The glasses are optically activated by additional lanthanide ion doping. However, since the optical absorption coefficient of the lanthanide ions is low, the as-made glasses are processed to glass ceramics in a subsequent annealing step. The glass ceramics provide a longer optical path length for the incident blue light due to scattering at the grown crystallites in the glass. In this work, photometric far-field studies on europium-doped lithium borate glass ceramics are presented to show the potential of these systems as frequency-downshifter for LED applications. The experimental results are compared with optical simulations to optimize the glass ceramics with respect to lanthanide ion concentration, crystallite size distribution as well as degree of crystallization.