Assessment of TiO2 Blocking Layers for CuII/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.