Research On High Efficiency And Low Cost Dye-Sensitized Solar Cell Based On Ionic Liquid Electrolytes

As one of the best solvent in the 21 century, ionic liquid has been applied to the organic chemical reaction, the separation and purification of the substance, electrochemistry and so on. The ionic liquids (ILs) show unique properties such as negligible vapor pressure, high thermal and chemical stability, wide electrochemical window and so on. These properties indicate that ILs could be good electrolytes used for DSCs. Based on this issue, we chose a series of binary ionic liquids and subsequently prepared a series of the electrolytes with them in order to investigate the effects of the electrolytes on the performance of DSCs. The main content is outlined as follows:1. We chose six kinds of binary ionic liquid electrolytes for dye-sensitized solar cells (DSCs). Amongst them, the electrolyte based on 1-butyl-3-methylimidazolium iodide (BMII) and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) reached the highest photoelectric conversion efficiency (PCE) of 4.98%. Measurements of Electrochemical impendence spectroscopy (EIS), UV-Vis spectroscopy, and photovoltaic performance of DSCs using the binary ionic liquid electrolyte based on BMII and EMIMBF4 were performed at varying concentration of iodine. The results showed that the charge-transfer resistance (Rct) and Warburg impedance (Zw) decreased as the iodine concentration increased. In contrast, the absorption intensity of the electrolytes increased. When the concentration of iodine was 0.25 M, the highest PCE of 5.20% was obtained for the DSC based on the binary BMII/EMIMBF4 ionic liquid electrolyte under light intensity of 100 mW cm-22. We synthesized a new redox couple in the form of ionic liquids named 1-ethyl-3-methylimidazolium thiolate (EMIT) and prepared a new binary ionic liquid electrolyte with 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4). Using different counter electrode, we found that the carbon electrode had a better catalytic activity for the redox couple than the Platinum electrode, although it was unfavorable for the diffusion of ionic liquid electrolytes. Finally, with the Platinum electrode, the highest PCE of 2.16% was obtained for the DSC based on the binary EMIT/EMIMBF4 ionic liquid electrolyte under light intensity of 100 m W cm-2.