Abstract
Dye-sensitized Solar Cells (DSCs) based on ruthenium complex N719 as sensitizer have received much attention due to their affordability and high efficiency. However, their best performance is only achieved when using volatile organic solvents as electrolyte solutions, which are unstable under prolonged thermal stress. Thus, we developed a new series of 1-alkenyl-3-methylimidazolium trifluoromethanesulfonate ionic liquids used as robust DSC electrolytes. These ionic liquids exhibit low viscosity, high conductivity, and thermal stability. The implementation of 1-but-3-enyl-3-methyl-imidazolium trifluoromethanesulfonate, [ButMIm]OTf, into DSCs gave the best photovoltaic performance. The results are fairly comparable to those reports for other popular ionic liquid electrolytes currently used in DSC field. An insightful discussion on the relationship between the structure of these new ionic liquids and the J–V characterization as well as electrochemical impedance measurement of DSCs will give more interesting information. The results are useful for large-scale outdoor application of DSCs.
Highlights
Dye-sensitized solar cells (DSCs) have been developed as promising photovoltaic devices since their rst invention by Gratzel and O'Regan.[1,2,3] The three basic components constructing a simple DSC are mesoporous metal oxide semiconductor layers deposited on one out of two conductive transparent electrodes, a photosensitizer thoroughly loaded onto the mesoporous lm, and an electrolyte solution lled up the space between the as-prepared electrode and the other one to assemble a functional DSC
An efficiency of 12% has been so far reported as the highest power conversion using this kind of liquid electrolytes in DSC devices applied Ruthenium dyes.[4]
The alkylation of imidazole by alkyl bromides followed by anion metathesis with lithium tri ate resulted in the formation of three new ionic liquids, 1-allyl-3methylimidazolium tri uoromethanesulfonate [AMIm]OTf, 1but-3-enyl-3-methyl-imidazolium tri uoromethanesulfonate [ButMIm]OTf, and 1-pent-4-enyl-3-methylimidazolium tri uoromethanesulfonate [PentMIm]OTf (Scheme 1)
Summary
The ionic liquids are entirely composed of cations (ammonium, phosphonium, guanidinium, pyridinium, and sulfonium) and anions (halides and complex anions such as BF4, PF6, OTf, NTf2, etc.) with low melting point below 100 C.18–21 By virtue of this property, ionic liquids have gained widespread applications in DSCs led as solvents in liquid electrolytes and organic salts in quasi-solid-state electrolytes.22–27 1-Hexyl-3methylimidazolium iodide was rstly used in DSCs by Papageorgiou's group with the aim of reducing the volatility of electrolyte.[28]. The ionic liquids are entirely composed of cations (ammonium, phosphonium, guanidinium, pyridinium, and sulfonium) and anions (halides and complex anions such as BF4, PF6, OTf, NTf2, etc.) with low melting point below 100 C.18–21. Bidikoudi reported the use of the electrolytes prepared by blending a low viscosity ionic liquid 1-ethyl-3-methylimidazolium dicyanamide with methylimidazolium iodide to enable the devices to attain the efficiencies of 4.4 to 6.5%.34. These DSCs devices showed the high conversions, the long-term stability was not good. The cells were nally characterized by J–V curve and electrochemical impedance measurement
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