PVdF-HFP quasi-solid-state electrolyte for application in dye-sensitized solar cells

A quasi-solid-state polymer electrolyte is prepared by incorporating poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) in a propylene carbonate (PC) / 1,2-dimethoxyethane (DME) / 1-methyl-3-propylimidazolium iodide (MPII) liquid electrolyte. The amount of PVdF-HFP in the liquid electrolyte is varied from 0.1 to 0.4 g. Incorporation of 0.1 g of PVdF-HFP decreases the conductivity of the DME/PC/MPII liquid electrolyte from 1.3 × 10^-2 to 5.6 × 10^-3 S cm^-1. Conductivity decreases gradually with increasing PVdF-HFP. No-flow "jelly-like" electrolyte samples are obtained for PVdF-HFP ≥ 0.2 g. The decrease in conductivity is the result of the decrease in ion mobility. Ion mobility was calculated by impedance spectroscopy. The PVdF-HFP quasi-solid-state electrolytes were assembled into dye sensitized solar cells (DSSCs). The performance of the DSSCs was measured under illumination of a 100 mW cm^-2 Xenon light source. The DSSC without PVdF-HFP polymer shows an efficiency of 4.88% with short-circuit current density, J_sc of 11.24 mA cm^-2, fill factor, FF of 70% and open circuit voltage, V_oc of 619 mV. The presence of PVdF-HFP deteriorates the performance of DSSCs, but problems such as electrolyte leakage and volatilization are eliminated. The performance of DSSCs was found to be correlated to the conductivity behaviour of the electrolyte.