The Intrinsic Relation between the Dynamic Response and Surface Passivation in Dye-Sensitized Solar Cells Based on Different Electrolytes

In the electrolyte containing Li+ and TBA(+) (tert-n-butylammonium), the band edge movement, trap state distribution, electron recombination and electron transport in dye-sensitized solar cells (DSSCs) before and after TiO2 film surface coating with Yb2O3 is studied in this paper. It is found that whether surface coating could improve the performance of DSSCs depends on the compositions of the electrolytes. After surface coating, the band edge shifts negatively in the Li+ electrolyte, but no significant negative shift was observed in the TBA(+) electrolyte. The changes of the trap state distribution also depend on the combined effects of the electrolytes and surface coating. In both types of electrolytes, the Yb2O3-coated TiO2 film suppresses the recombination and slows down the electron transport. These findings are important for improving the performance of the DSSC using the surface coating, which could explain the reasons why the photoelectric efficiency could not improve by coating, doping, and core-shell TiO2 in DSSCs.