On the Influence of Anions in Binary Ionic Liquid Electrolytes for Monolithic Dye-Sensitized Solar Cells

Five ionic liquids (ILs) of the general formula Im + A -, where Im + = 1-methyl-3- n -butyl-imidazolium, A - = I - ( 1 ), BF 4 - ( 2 ), SCN - ( 3 ), CF 3 CO 2 - ( 4 ), and CF 3 SO 3 - ( 5 ), were used in electrolytes for dye-sensitized monolithic solar cells. The properties of the electrolytes and various characteristics of the solar cell performance, such as electron transport and electron lifetime, were studied. The composition of the binary electrolytes, i.e., the different anions, have a significant effect on the viscosity, but only a modest effect of the measured diffusion coefficient for triiodide. No significant effect of the electrolyte composition on the electron transport time in the mesoporous TiO 2 film was found, while there was a pronounced effect on the electron lifetime. Monolithic solar cells with thiocyanate, IL 3, showed overall light-to-electricity conversion efficiency up to 5.6% in 250 W m -2 simulated sunlight and have promising stability.