The Study Of The Quasi-solid Polymer Electrolyte For Dye-sensitized Solar Cells

Due to the fexibility on the structure design, non-volatility, chemical and electrochemicalstabilities, the quasi-solid electrolyte based on polymer has attracted more and more attentionduring the strudies of the quasi-solid electrolytes. PEO is the best choise to replace the liquidelectrolyte during so many polymers to form polymer electroyte not only due to its ability ofresolving the alkali metal salts, but also because of the high ionic conductivity.PEO/P（VDF-HFP）/SiO₂composite polymer electrolytes （CPE） were introduced in this thesisto replace the liquide electrolyte. In order to resolve the problems of CPE, the low ionicconductivity, the recombination and the low diffusion coefficient, furthermore to improve thephotoelectric performance of DSSC, the CPE are modified by different methods to discuss theconductivity in polymer electrolyte, check how the additive affected the ionic conductivity and theDSSC’s performance. In this paper, the specific research contents and main conclusions are asfollows:1. The ionic conductivity of polymer electrolyte is lower then that of liquid electrolyte, whichaffects the current density and the performance of cell. In this paper, CPE is modifed by differentamounts of LiN（SO₂CF3）2（lithiumbis（trifuoromethanesulfone）imide, LiTFSI）. Fourier transforminfrared （FT-IR） and differential scanning calorimetry （DSC） are carried out to examine theconfguration changes of the polymer electrolyte. The experiment shows that the glass-transitiontemperature decreases while the ionic conductivity increases after the LiTFSI-modification.2. The interfacial electron recombination is another key factor influencing the performance ofDSSC. To overcome this problem, quasi-solid-state dye-sensitized solar cells （DSSCs） arefabricated using acetamide-modifed PEO/P（VDF-HFP） composite polymer electrolytes （CPEs）along with KI and I2. The EIS experiment shows that the acetamide-modifcation prolongs theelectron lifetime, furthermore decreases the recombination process; at the same time, the ionicconductivity increases due to the coordination between the NH2group, the C=O group inacetamide and K⁺, I₃^-.3. The ionic conductivity of polymer electrolyte is lower then that of liquid electrolyte, whichdues to the lower ionic diffusion coefficient. In this paper, Et₄NBF₄was incorporated into PEO/P（VDF-HFP） composite polymer electrolytes （CPEs） to increase the ionic conductivity ofpolymer electrolyte by one order of magnitude, and further increases the current density.