A luminescent solar concentrator was prepared that was based on a bulk sheet of poly(methyl methacrylate) doped with different luminescent dyes (K1, K27, and Lpero) during the polymerization process. Photo- and thermal-stability studies revealed that the Lpero dye system is the most stable one. The electronic transition mechanism for the concentrator systems was obtained by the darktrap and phototrap spectroscopy technique. The results were correlated with the outdoor test measurements over 1 year.