Polymer electrolyte photoelectrochemical cells with involatile plasticizers: I. The n-Si/I^-/I₂ cell

We report results for a photoelectrochemical (PEC) cell based on n-Si-Pt/plasticized polymer electrolyte (with dissolved iodine/ iodide redox couple). All elements except the electrolyte are kept the same as in earlier cells with bare (and platinized) silicon but "dry" polymer electrolyte, in order to separate out the electrolyte plasticization effect. The study is a precursor to a detailed study of novel electrolyte-containing PECs to be reported in a separate article. In the present study, the plasticizer is tetramethylene sulfone, and its incorporation is shown to increase the short circuit current by a factor of 44. Changes in iodide concentration produce an additional improvement. Effects of light intensity on photovoltage and photocurrent are reported. Short circuit photocurrents as high as 7 mA/cm² (vs. 17 mA/cm² with more appropriate redox couples) can be reached at 1 sun incident light intensity, without recourse to special coatings on the silicon photoanode. Factors affecting the efficiency of energy conversion are discussed.