Advancing the technology of dye-sensitized solar cells (DSSCs) with liquid electrolytes from laboratory level to industrial level was impeded owing to the problems related to sealing and evaporation of liquids at high temperatures. Replacement of liquid electrolytes with ionic liquids or molten salts has been one of the strategies.
Here, we report the effects of (1) a silane substituted ruthenium complex (Fig. 1) linked with tetraethyl orthosilicate (TEOS), (2) polymers of alkyl imidazolium salts (Fig. 2), and (3) electro-spun poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) membranes on photocurrent-voltage characteristics of DSSCs. The ruthenium complex was prepared by hydrosilation between a vinyl-containing complex and trimethoxysilane, followed by linking with TEOS through formation of siloxane links. The polymeric alkyl imidazolium salts were synthesized by photo-polymerization of alkyl imidazolium salts directly in the TiO₂ film. Electrospun PVdF-HFP membrane was prepared from 16 wt% of PVdF-HFP solution in a mixture of acetone/N,N-dimethyl acetamide (7:3 wt%) at an applied voltage of 12 kV. It was then activated by immersing in 0.6 M 1-hexyl-2,3-dimethyl imidazolium iodide, 0.1 M LiI, 0.05 M I2, 0.5 M tert-butylpyridine in EC/PC(1:1 wt%) to obtain its corresponding membrane electrolyte with ionic conductivity of 10-3 S cm-1 at 25 °C.
We have found that DSSCs with polymeric additives have enhanced stabilities, compared with those obtained in the absence of the polymeric additives. The results will be discussed in terms of charge transfer resistance at the TiO₂/electrolyte interface, increased viscosity of the electrolyte solutions, and facilitated ion transfer in the electrolyte media.