The Synthesize And Study Of The Guanidinium Ionic Liquids(GILs) As Electrolyte In Dye-sensitized Solar Cells

The shortage of energy sources and the environmental pollution will be restricting the future society's sustainable development more and more, renewable energy sources such as solar energy and so on represent the development direction of clean energy. The photovoltaic industry of solar energy as one of sustainable social development is gradually enter into people's daily life, and will become the important component of renewable energy in the future. The dye-sensitized solar cells (DSSCs), one kind of new solar energy cells were developed by simulating photosynthesis principle. The studies of DSSCs have already confirmed that the electrolytes used in DSSCs have important effect on the conversion efficiencies and long-term stability of DSSCs The ionic liquids (ILs) show useful properties such as negligible vapor pressure, hig thermal and chemical stability, wide electrochemical window, and the adjustable solubility for inorganic or organic compounds through design of the anions and the cations of ILs. ILs were classified according to different cations, the common types of the cations include alkyl ammonium cations, N-alkylpyridine cations, N, N'-dialkylimidazolium cations and N-alkyl guanidinium cations, etc.. In present, the corresponding studies of ILs mostly focus on the synthese and applications of imidazolium ILs. The ILs used in DSSCs include those ILs which can provide the I- of the oxidation-reduction pairs I-/I3 and can be used as solvents. At present, the applications of ILs used as the electrolytesof the DSSCs mostly focus on imidazolium ILs.In recent years, our group has beeen engaged in the studies of the syntheses and applications of guanidinium ionic liquids (GILs), and we have obtained some preferable results. We have studied the related physical and chemical properties of GILs systematically, and successfully applied them in organic reactions such as Heck reaction, Knoevenagel reaction, Michael addition reaction and esterification reaction. Because of special properties of GILs such as high dispersive degree of positive charge, good chemical and thermal stability and designability of the substituents on N atoms, we have designed and synthesized a series of hexalkyl guanidinium iodides and prepared a series of the electrolytes with them in order to investigate the effect of the electrolytes containg aforementioned GILs on the performance of DSSCs. The main content is outlined as follows:(i) Using 1,3-dimethylimidazolone and oxalyl chloride as starting materials, six guanidinium iodide salts with linear alkyl chains or ring-closure alkyl chains were synthesized by appropriate design. The thermal stability and the electrochemical properties of the guanidinium iodide salts were studied.(ii) A series of the electrolytes containing different guanidinium iodide salts were prepared and the prototype devices of the DSSCs with aforementioned electrolytes were prepared. Subsequently, the performance of the corresponding DSSCs were investigated. The results showed that the open-circuit voltage (Voc), the short-circuit photocurrent density (Jsc) , the fill factor (FF) and the conversion efficiency of the DSSCs with the electrolytes containing n-butyl guanidinium iodide salts enhanced significantly, compared with the performances of the DSSCs with the electrolytes containing n-dodecyl guanidinium iodide salts. when the substituent groups of three N(2) atoms are consistent in the cations of guanidinium iodide salts, with the volume of guanidium cations increased, the static interaction between the cations of GILs and the counter iodine anion is weakened so that the Voc and the Jsc increase, however, the FF decrease.(iii) We have prepared a series of the electrolytes based on GILs and studied the performances of the DSSCs with the electrolytes based on GILs. The results showed that (a) with the volume of guanidium cations increased, the recombination of the I3- in the nanoporous TiO2 film can be suppress effectively and the Voc can be enhanced effectively. (b) with the volume of guanidium cations increased, the viscosity of the electrolytes based on GILs increased and that make the transport of the charge carriers become slower. These factors are useful for the recombination of I3- in solution so that the FF decrease.In this thesis, we have investigated the effect of the electrolytes containing GILs on the photovoltaic performance of DSSCs, and made the foundation for the further application of GILs.