Research On High-efficient And Stable Electrolyte Additives For Mesoscopic Solar Cells

As two typical mesoscopic solar cells, Dye-sensitized solar cells (DSCs) and Perovskite solar cells (PSCs) have been extensively investigated by scientists all over the world due to their low-cost, environmental friendly and simple preparation process. Characteristics of additives play vital roles for the photovoltaic performance and long term durability of mesoscopic solar cells. Combining with the advantage of the nonvolatile ionic liquid and the special role of pyridyl in the electrolyte, this thesis focus on the investigations of two kinds of efficient and stable pyridyl functionalized ionic liquids to simplify the electrolyte system of mesoscopic solar cells and improve its stability.Firstly, we synthesized pyridyl iodides as electrolyte additive for DSCs. Compared with traditional additive4-tert/-butylpyridine (TBP), our pyridyl iodides featured dual-functional by serving as iodides and suppressing charge recombination simultaneously. For these pyridyl additives, systematical investigations were performed to characterize their thermal stability and disclose the effect of the molecular structure on the electrolyte properties and DSCs photovoltaic performances. Results indicated that, with these pyridyl iodides, the electrolyte system for DSCs can be significantly simplified, which is advantageous for cost reduction. Meanwhile, using commercial TiO2(P25) as photoanode, a high power conversion efficiencies (PCEs) of7.81%was achieved with our novel electrolyte. This result is comparable to that based on TBP-contained electrolyte. Moreover, the DSCs based on our novel electrolytes demonstrated a better long-term durability.Secondly, we introduced a stable ionic liquid N-butyl-N’-(4-pyridylheptyl)imidazolium bis(trifluoromethane) sulfonimide (BuPyIm-TFSI) as a dual-functional additive into the system of PSCs. Different from the traditional additive TBP, BuPyIm-TFSI was nontoxic, nonvolatile and more reliable. More importantly, BuPyIm-TFSI had dual functions, capable of not only improving the electrical property of hole-transporting material (HTM), but also suppressing charge combination in PSCs. It is indicated that BuPyIm-TFSI improved the conductivity of HTM (spiro-OMeTAD) and reduced the dark current of the solar cell. The PCEs greatly increased from3.83%(pristine spiro-OMeTAD) to7.91%, comparable to that based on conventional HTM containing LiTFSI and TBP. Using such dual-functional additive can effectively simplify the components of HTM and help to reduce the production cost.