Phosphor research is not only triggered by new application areas, the reverse situation can also occur. Quantum dots are a very good example of this [5.233-5.235]. Due to size quantization effects, which occur in semi-conductors with radii typically less than 10 nm, the spectral position of the emission can be shifted over a large spectral range (e. g. over the complete visible spectral range), just by varying the particle size. This enables tunable narrow band emission. Furthermore with diameters of 2 to 10 nm, quantum dots are small enough to realize transparent non-scattering luminescent layers. This latter property is extremely interesting for applications such as electroluminescent displays and flexible light sources. Moreover, quantum dots are promising luminescent markers for optical imaging in medicine [5.234, 5.236, 5.237].
Taking these few examples from amongst many others, it can be seen that research on luminescent materials is still extremely challenging. Driven by both new materials and new application areas, the search for new and improved luminescent materials is an important research topic both in industry and academia.
[1] With increasing absorption index к, the absorption of very small particles increases.
[2] Hydrothermal crystallization for the production of a-Fe2O3 in platelet form [3.45].
[3] the active pigment surface in the coating (particle shape and size, particle size distribution, dispersibility).