Trialkylsulfonium and tetraalkylammonium cations-based ionic liquid electrolytes for quasi-solid-state dye-sensitized solar cells

Seven ionic liquids (ILs) based on asymmetric trialkyl sulfonium and tetraalkylammonium cations with bis(trifluoromethanesulfonyl)imide anion were prepared and characterized. Physico-chemical and electrochemical properties of these ionic liquids including density, decomposition temperature, viscosity and conductivity were determined. The photovoltaic parameters of dye-sensitized solar cells (DSSCs) containing these sulfonium and ammonium ion-based ILs were compared. Among these two groups of ILs, the DSSCs with sulfonium cation-based ILs show higher cell efficiencies than that of ammonium counterpart due to lower charge transfer resistance exhibited by the former when compared to the latter, as confirmed by electrochemical impedance spectroscopy (EIS). The best cell efficiency achieved in this work was 4.61%. Moreover, long-term durability of the quasi-solid-state DSSCs at 50 degrees C was investigated. (C) 2013 Elsevier Ltd. All rights reserved.