To overcome the long-term stability problems of dye-sensitized solar cells (DSSC) due to solvent evaporation and leakage, gelling the electrolyte with polymers is an appropriate option. Especially for future applications of textile-based DSSCs, which require cost-effective and environmentally friendly materials, such an improvement of the electrolyte is necessary. Therefore, the temporal progressions of efficiencies and fill factors of non-toxic glass-based DSSCs resulting from different gel electrolytes with poly(ethylene oxide) (PEO) are investigated over 52 days comparatively. Dimethyl sulfoxide (DMSO) proved to be a suitable non-toxic solvent for the proposed gel electrolyte without ionic liquids. A PEO concentration of 17.4 wt% resulted in an optimal compromise with a relatively high efficiency over the entire period. Lower concentrations resulted in higher efficiencies during the first days but in a poorer long-term stability, whereas a higher PEO concentration resulted in an overall lower efficiency. Solvent remaining in the gel electrolyte during application was found advantageous compared to previous solvent evaporation. In contrast to a commercial liquid electrolyte, the long-term stability regarding the efficiency was improved successfully with a similar fill factor and thus equal quality.
Keywords: dimethyl sulfoxide (DMSO); dye-sensitized solar cells (DSSC); efficiency; gel electrolyte; long-term stability; natural dyes; non-toxic; poly(ethylene oxide) (PEO).