Improved performance using a plasticized polymer electrolyte for quasi-solid state dye-sensitized solar cells

A PEO/P(VDF-HFP) polymer-blend electrolyte is modified by different amounts of LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfone)imide, LiTFSI). Fourier transform infrared (FT-IR) and differential scanning calorimetry (DSC) are carried out to examine the configuration changes of the polymer electrolyte. LiTFSI acts as a plasticizer influencing the ionic conductivity of the LiTFSI-modified polymer electrolyte, and improves the short-circuit photocurrent effectively. The electrochemical impedance spectroscopy (EIS) indicates that the intercalation or adsorption of overdose Li+ to the TiO2 photoanode surface positively changes the Fermi energy level and the conduction band. This improves the interface recombination in the DSSC and reduces the open-circuit voltage. With moderate LiTFSI content (0.05 g, nKI/nI2 = 7:1) modification, the DSSC exhibits a 1.6 mA cm−2 improvement of current density and an improved performance of 5.03% compared with 4.51% of the original DSSC.