Elucidation of electrochemical properties of electrolyte-impregnated micro-porous ceramic films as framework supports in dye-sensitized solar cells

This study investigates the electrochemical properties of electrolyte-impregnated micro-porous ceramic (Al2O3) films as framework supports in dye-sensitized solar cells (DSSCs). A field-emission scanning electron microscope (FE-SEM) is used to characterize the morphology on both surfaces of the ceramic membranes, which exhibit high porosity (41-66%) and an open cylindrical pore structure. Electrochemical impedance analysis reveals that the conductivity of the electrolyte-impregnated ceramic membrane is lower (6.24-9.39 mS cm(-1)) than the conductivity of the liquid electrolyte (25 mS cm(-1)), with an Archie's relationship by a power of 1.81 to the porosity value. The diffusivity of tri-iodide ions (I-3(-)) is slowed from 1.95 x 10(-5) to 0.68 x 10(-5) cm(2) s(-1) in the ceramic-containing cells. The exchange current density at the Pt-electrolyte interface decreases slightly (less than 5%) when the Al2O3 membranes were used in the symmetric cells, implies that the contact of the denser ceramic top structure on the Pt electrode does not interfere with the I-3(-) charge transfer. The ceramic films can prevent solvent evaporation and maintain conductivity. The long-term cell efficiencies are evaluated up to 1248 h under alternating light soaking and darkness (3 days/4 days) cycles. The cells containing the ceramic films outperform the control cells. (C) 2010 Elsevier B.V. All rights reserved.