PROCEEDINGS ARTICLE | February 13, 2007
Proc. SPIE. 6486, Light-Emitting Diodes: Research, Manufacturing, and Applications XI
KEYWORDS: Light emitting diodes, Scattering, Glasses, Luminescence, Crystals, Ceramics, Light scattering, YAG lasers, Cerium, Absorption
Fluorescence techniques are known for their high sensitivity and are widely used as analytical tools and detection
methods for product and process control, material sciences, environmental and bio-technical analysis, molecular
genetics, cell biology, medical diagnostics and drug screening. According to DIN/ISO 17025 certified standards are
used for fluorescence diagnostics having the drawback of giving relative values for fluorescence intensities only.
Therefore reference materials for a quantitative characterization have to be related directly to the materials under
investigation. In order to evaluate these figures it is necessary to calculate absolute numbers like absorption/excitation
cross section and quantum yield. This can be done for different types of dopants in different materials like glass, glass
ceramics, crystals or nano crystalline material embedded in polymer matrices. Here we consider a special type of glass
ceramic with Ce doped YAG as the main crystalline phase. This material has been developed for the generation of white
light realized by a blue 460 nm semiconductor transition using a yellow phosphor or converter material respectively.
Our glass ceramic is a pure solid state solution for a yellow phosphor. For the production of such a kind of material a
well controlled thermal treatment is employed to transfer the original glass into a glass ceramic with a specific
crystalline phase. In our material Ce doped YAG crystallites of a size of several µm are embedded in a matrix of a
residual glass. We present chemical, structural and spectroscopic properties of our material. Based on this we will
discuss design options for white LED's with respect to heat management, scattering regime, reflection losses, chemical
durability and stability against blue and UV radiation, which evolve from our recently developed material. In this paper
we present first results on our approaches to evaluate quantum yield and light output. Used diagnostics are fluorescence
(steady state, decay time) and absorption (remission, absorption) spectroscopy working in different temperature regimes
(10 - 350 K) of the measured samples in order to get a microscopic view of the relevant physical processes and to prove
the correctness of the obtained data.
