Luminescent Solar Concentrators

Luminescent materials are able to spectrally concentrate a wide range of the solar spectrum to a single wavelength. At the same time they are able to spatially concentrate this light, without the use of lenses or mirrors, to a narrow surface area. These two unique properties are combined in a so-called Luminescent Solar Concentrator (LSC). When a luminescent coating is applied on a window it can absorb part of the solar spectrum and re-emit this energy as luminescence. This emitted light is trapped, just like in a fibre optical cable and can only escape from the edges of the window where strip shaped solar cells convert light into electricity.

 

SiAlON window coatings

 

Thin films coatings based on the elements Al, Si, O and N (SiAlON) are applied routinely by the glass industry on a large scale, e.g. for scratch-protection and anti-reflection purposes, because of their  strength,  inertness and thermal resistance. We have expanded the application range of SiAlON coatings by functionalizing them with luminescence centers like Ce, Sm, Eu, Tm and Yb that can absorb and convert parts of the solar spectrum for electricity generation, utilizing the principle of a luminescent solar concentrator (LSC).

Photon fate

To understand why the efficiency of a luminescence solar concentrator (LSC) is high or low, it it crucial to know the fate of each photon that impinges on the LSC. By combining experimental optical data from various measurements with our LSC-models, we can calculate the fractions of reflected, absorbed, transmitted, emitted, trapped, escaped, wave-guided and concentrated sunlight. From such a clear understanding LSC efficiency improvement strategies can be implemented for example by changing the composition of the luminescent material or the quality of the wave-guide.