The measurements of maximal power increase of silicon photovoltaic cells coated with polymethyl methacrylate foil containing Rhodamine-6G were carried out. The photoelements were irradiated from the solar radiation simulator. Two different amplification values were obtained: ~ 20% and 50%. An equation that describes the change of photoluminescence intensity as a function of fluorescent molecules and that takes into account the reabsorption and secondary fluorescence is derived. The expression obtained is compared with the results of photoluminescence measurements for Rhodamine-6G and 2,5-bis[5'-tert-butylbenzoxazol-(2')]-thiopen; good agreement is evident.