Impact of I2 Additions on Iodide Transport in Polymer Electrolytes for Dye-Sensitized Solar Cells: Reduced Pair Formation versus a Grotthuss-Like Mechanism

We find evidence that the enhancement of charge transfer with increasing additions of I-2 to poly(ethylene oxide) with dissolved NaI may be due to reduced cation-anion pair formation rather than the operation of a Grotthuss-like transport mechanism. This conclusion can be drawn from a combination of conductivity measurements with I-125 and Na-22 radiotracer diffusion experiments over a wide temperature range and their simultaneous evaluation within a comprehensive ion-transport model. The results are relevant to the understanding and optimization of charge transport in dye-sensitized solar cells based on the I-/I-3(-) redox couple.