The required features of all dye molecules used for fluorescent solar concentrators are a high extinction coefficient, strong fluorescent properties, a high quantum yield, and, last but not least, a long photostability. Absorption and emission spectroscopic techniques are applied to study some dye molecules: fluorescein, eosine, erythrosine, rhodamine B, rhodamine 6G, acridine orange, alone and in solution (polyethylene glycol 400, 600, 700), in order to establish the changes in photochemical properties (photostability) of these dyes, which could be used for fluorescent solar concentrators.