In Situ Polymerization Polyurethane Gel Electrolytes For DSSCs

Dye-sensitized solar cells (DSSCs) have attracted significant attention due to their easy-fabrication, low-cost and relatively high energy conversion efficiency. Among these, the electrolyte plays an important role because it can transport holes and make dye regeneration in the cell. In-situ polymerization gel electrolyte has become one of research focus because of its characteristics. Before gelation it has the advantages of liquid electrolyte, which can easily infiltrate into the porous TiO2film. After curing it can overcome the shortcomings such as volatility and unstability of liquid electrolyte. In this paper, a novel in-situ polymerization polyurethane (PU) gel electrolyte system was studied. Polyether and polyester polyurethane gel electrolyte were prepared respectively. The DSSCs based on these PU gel electrolyte were assembled by in-situ and non-situ modes, and their photovoltaic properties were characterized.(1) The preparation conditions of the polyether type polyurethane gel electrolyte were studied. It was found that polyether polyurethane gel electrolyte with a highest conductivity of6.72mS/cm was obtained by PEG10000and TDI to synthesize poly ether polyurethane, and then absorb the liquid electrolyte mixed with organic solvent GBL and Nal/I2The electrolyte was characterized by FTIR and DMTA. The results showed that the polyether polyurethane electrolyte prepared was in a gel state. In addition, the structure of polyether polyurethane gel electrolyte was characterized by SEMn DSC and XRD. The test results indicated that the polyurethane gel electrolyte has a micro three-dimensional network structure, good thermalstability and amorphous phase structure.(2) A series of polyester polyurethane gel electrolyte were prepared by optimizing the conditions such as PEG molecular weight, isocyanate monomers, the kinds of alkali metal salts and organic solvents. The highest conductivity of the optimized polyester polyurethane gel electrolyte was5.61mS/cm. The structure of the polyester polyurethane gel electrolyte was characterized by FTIR, DMTA, SEM, DSC and XRD. It was found that the structure and properties of polyester polyurethane gel electrolyte were similar to those of polyether polyurethane gel electrolyte.(3) The DSSCs based on optimized polyeter PU gel electrolyte were assembled by in-situ and non-situ modes, and their power conversion efficiency were5.15%,4.80%under100mW/cm2irradiation, respectively. And the photoelectric conversion efficiency of the cells based on polyester PU gel electrolyte fabricated in situ and non-situ were4.06%and3.78%, respectively. It can be seen that the photoelectric conversion efficiency of the cell in-situ assembled is higher than that of the cell non-situ assembled. From the results of SEM and EIS, it was found that DSSC in situ assembled was more advantageous to improve the electrolyte impregnated into porous TiO2film, to reduce the internal impedance of the cell, and then improve the optical performance of the cell.