Improved stability of quasi-solid-state dye-sensitized solar cell based on poly (ethylene oxide)-poly (vinylidene fluoride) polymer-blend electrolytes

We report two improved stability dye-sensitized TiO2 solar cells using poly (ethylene oxide)-poly (vinylidene fluoride) (PEO-PVDF) polymer-blend electrolytes modified with water and ethanol as hydroxyl-rich small-molecule additives. The effect of additive on the thermal property, viscosity, conductivity and the corresponding performance of the dye-sensitized solar cell (DSSC) were studied. After introducing the water and ethanol into the PEO-PVDF polymer-blend electrolytes, the conductivity is improved compared to that of the un-added electrolyte. This is due to the enhanced free ion concentration and ion transport channels in the electrolyte because of the cross-linking ability of these hydroxyl-rich additives. The increased ion concentration can be proved by the enhanced concentration of I- and I-3(-) in the additive-modified electrolytes from UV-vis studies. The increased cross-linking network can be explained by the increased glass transition temperature (T,) and viscosity of these additive-modified electrolytes from DSC and theology studies. A more hornogeneous morphology of ethanol-modified electrolyte from SEM study is used to further explain the better conductivity and stability of the cells based on these additive-modified electrolytes. From the evaluation of additive effect on the performance of the corresponding DSSC, we find that introducing water and ethanol leads to an increase in short-circuit photocurrent density (J(sc)). This is due to the efficient transport of 1(-)/1(3-) caused by enhanced 1(-)/1(3-) concentration and increased ion transport channels in the electrolyte by adding additives. The best efficiency of 3.9% is achieved in the cell with ethanol-modified electrolyte. (C) 2008 Elsevier B.V. All rights reserved.