We here report on our investigation of the properties of polysiloxane rubber waveguides doped with Lumogen Red 305 for the production of luminescent solar concentrator (LSC) devices. Samples with different dye concentrations were produced and their optical properties were characterized by absorption and fluorescence spectroscopy measurements. Moreover, different concentrations of Au nanoparticles were dispersed in the matrix in order to study the possibility of enhancing the fluorophore fluorescence yield. The light output from the edges of the samples, irradiated with a solar simulator was measured with an integrating sphere and the light yield was compared to that obtained with polycarbonate waveguides containing the same amount of the fluorescent dye BASF Lumogen Red305. Preliminary results from measurements with a GaAs photovoltaic cell and a silicon photodiode coupled to the polysiloxane waveguides are also presented.