Chemical effects of tin oxide nanoparticles in polymer electrolytes-based dye-sensitized solar cells

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 V_oc (oc = open circuit) and J_sc (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.