Luminescent down-shifting for CdTe solar cells: A review of dyes and simulation of performance

The luminescent materials that have been used for luminescent down-shifting (LDS) range from organic molecules and organometallic complexes to quantum dots (QDs), each of them with certain strengths and weaknesses. In this work, we introduce five figures of merit to quantitatively evaluate how the properties of these materials compare with the desirable properties of an optimum LDS layer, focusing our attention in the cadmium sulfide/cadmium telluride (CdS/CdTe) PV technology. In order to elaborate a quantitative ranking with the candidate materials, we have used a ray-tracing simulation software to calculate the expected enhancement in a CdTe module conversion efficiency. Finally, we briefly discuss the issues that directly affect the industrial application of these dyes for LDS, such as the amount of material required, its cost and its stability under the sunlight.