Abstract This paper reports the chemical and optical characterization of a cost effective down-converter polymeric film based on an Eu(III) complex embedded in polymethylmethacrylate (PMMA) which placed on conventional photovoltaic (PV) glass, used for module assembly, produces an increase in the external quantum efficiency (EQE) of a reference Si-based solar cell. Our results show that the best location of the down-converter is on the front surface of the glass. The UV absorption of the down-converter protects and enhances the stability of the PMMA film. This increase in EQE is further enlarged by placing a light trap on the device, collecting most of the down-converted photons, which are isotropically emitted. Additional increases in EQE are expected after a proper encapsulation of the solar cell and the glass. Thermogravimetric measurements show that the down-converter active specie is stable up to 275 °C and the PMMA film is stable up to 225 °C, consequently, it can be applied in any step of the lamination process in the production of PV modules. Thereby, the down-converter can be profitably applied in Si-based solar cells and modules, particularly in concentrated PV systems.