Influence of the solvents of electrolyte on the performance of quantum-dot-sensitized solar sells studied by impedance

In this paper, two electrolytes with water and dimethylformamide as solvents are prepared for the quantum-dot-sensitized solar cells. The impedance spectroscopy method is used to study the influence of the solvents of electrolyte on the performance of quantum-dot-sensitized solar cells. The results show that the cell with dimethylformamide as the solvent exhibits higher charge-transfer resistance between the electrons in TiO2 film and the polysulfide in the electrolyte, leading to longer life time and diffusion length of the electrons. Meanwhile, the dimethylformamide can negatively shift the conduction band edge of TiO2. However, the solubility of the polysulfide in dimethylformamide is too low to meet the requirements of quantum-dot-sensitized solar cells, which results in the lower efficiency of the solar cells based on dimethylformamide compared with that of water.