The preparation of carbon dots/ionic liquids-based electrolytes and their applications in quasi-solid-state dye-sensitized solar cells

A facile means to generate carbon dots/ionic liquids (ILs) blend using ionic liquid-assisted electrochemical exfoliation was demonstrated. Two kinds of ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), were used in this work. Transmission electron microscopy and UV-vis spectrum were employed to characterize the formed carbon dots/lLs. The carbon dots/lLs were used for fabricating quasi-solid-state dye-sensitized solar cells (DSSCs), where 1-butyl-3-methylimidazolium iodide and LiI/I-2 were added to enhance the performance of DSSCs. Effects of the varied contents of components in the complex on the performance of DCCSs have been studied in detail at ambient temperature. The electrochemical impedance spectroscopy showed that the introduction of carbon dots into ionic liquids can enhance the electrical properties by facilitating charge transfer processes of the electrolytes. The overall energy-conversion efficiency (eta) was 2.71% and 2.41% for carbon dots/[bmim][PF6] and carbon dots/[bmim][BF4] based blend electrolytes, respectively. A 82% enhancement in eta was obtained by introduction of carbon dots into [bmim][PF6] comparing with pure [bmim][PF6] (eta = 1.49%). In addition, the cells exhibited good stability under continuous illumination in room temperature without any further sealing. (C) 2012 Elsevier Ltd. All rights reserved.