Assessment of TiO₂ Blocking Layers for Cu^II/I-Electrolyte Dye-Sensitized Solar Cells by Electrochemical Impedance Spectroscopy

The TiO₂ blocking layer in dye-sensitized solar cells is the most difficult component to evaluate at thicknesses below 50 nm, but it is crucial for the power conversion efficiency. Here, the electrode capacitance of TiO₂ blocking layers is tested in aqueous [Fe(CN)₆]^3-/4- and correlated to the performance of photoanodes in devices based on a [Cu(tmby)₂]^2+/+ electrolyte. The effects of the blocking layer on electronic recombination in the devices are illustrated with transient photovoltage methods and electrochemical impedance analysis. We have thus demonstrated a feasible and facile method to assess TiO₂ blocking layers for the fabrication of dye-sensitized solar cells.