Quasi-solid-state dye-sensitized solar cells based on gel electrolytes containing different alkali metal iodide salts

Gel electrolytes were prepared by adding different alkali metal iodide salts RI (R+ = Li+, Na+, K+, Rb+ or Cs+) and I2 into acetonitrile gelated with poly(ethylene-oxide) (PEO). KI, RbI and CsI, poorly soluble in liquid electrolyte, can dissolve completely in PEO gel electrolyte due to a strong interaction of cation and PEO chains. All gel electrolytes exhibit high conductivity in the range of 10− 3 S/cm and contain I− with concentration of 0.3 M. The effect of R+ in PEO gel electrolyte on the performance of quasi-solid-state dye-sensitized solar cells (DSCs) was investigated. The results showed that the open circuit voltage (Voc) increases with the increased radius of alkali metal cation. It is explained by the rise of electron Fermi level (EF) of TiO2 caused by a decrease in I3− diffusion with the increase of radius of R+.