Effect of cation size on solid polymer electrolyte based dye-sensitized solar cells.

We report the preparation of a series of solid polymer electrolytes with different cations but with the same anion. We have chosen a PEO:PEG blend (at 40:60 by w/w) and complexed it with LiI, NaI, KI, NH4I, 1-ethyl-3-methylimidazolium iodide (EMII), and 1-hexyl-3-methylimidazolium iodide (HMII) with the same ion to monomer ratio. The role of different cations in terms of their size has been investigated on the conductivity of the polymer electrolyte films. The electrolyte properties have been explained in terms of the changes in the number of free charge carriers and the variation in crystallinity of the matrix. The cell performance of the dye-sensitized solar cells (DSSC) fabricated with these systems also showed strong dependence on the cation radii. The concept of ion intercalation and surface adsorption used for the liquid electrolyte systems has been extended to the polymer electrolytes and discussed in this paper.