The effects on the photovoltaic performance of the incorporation of SnO2 nanoparticles into the polymer of a solid-state dye-sensitized solar cell (DSC) based on the poly(ethylene oxide)/poly(ethylene glycol) dimethyl ether solid electrolyte are studied in this paper. It has been found that the addition of SnO2 nanoparticles to the solid electrolyte produces several key changes in the properties of the solid-state DSC that produced a better performance of the device. Therefore, we have measured an improvement in electrolyte conductivity by a factor of 2, a linear rise in the TiO2 conduction band position, a reduction in the electron recombination rate, and a decrease in charge-transfer resistance at the counterlectrode/electrolyte interface. All these improvements produced an increase in the power conversion efficiency from 4.5 to 5.3% at 1 sun condition, a consequence of the increase of both Voc (oc = open circuit) and Jsc (sc = short circuit) without any sacrifice in FF (fill factor). The origin of these changes has been associated to the strong Lewis acidic character of SnO2 nanoparticles yielding to the formation of a I 3- percolation layer for holes at the surface of SnO 2 and the reduction of the concentration of free I3 - and K+ ions inside the pores of TiO2. From these results, it is concluded that the physicochemical effects of inorganic nanofiller in the polymer electrolyte may also be considered a good route in designing the high efficiency solid-state DSCs employing the polymer electrolyte.