Emission of Rhodamine B in PMMA opals for luminescent solar concentrators

In conventional luminescent solar concentrators (LSC) incident light is absorbed by luminophores and emitted isotropically. Most of the emitted light is trapped inside the LSC by total internal reflection and guided to solar cells at the edges. Light emitted towards the surfaces, however, is lost in the escape cone. Furthermore, when the luminophore emits light in its absorption range, light is lost due to reabsorption. To overcome these losses, we embed the luminescent material in photonic structures to influence the emission characteristics. Directional and spectral redistribution of emission is supposed to enhance the light guiding in LSCs and reduce reabsorption losses. For this purpose, we prepared opal films from PMMA colloids, in which Rhodamine B was embedded during the polymerization process. In direction-resolved luminescence measurements a strong dependence of the emitted spectrum on the detection direction was observed. Further, the light collection efficiency of the samples was determined with optical measurements and light guiding due to the intended absorption and emission process was observed. The overall performance, however, suffers from cracks and defects in the photonic crystal.