Diffusion impedance and space charge capacitance in the nanoporous dye-sensitized electrochemical solar cell

A measurement of the true space charge capacitance of the dye-sensitized solar cell (DSC) is presented here that shows good qualitative agreement with our simple physical model presented earlier [J. Phys. Chem. B 1999, 103, 5743]. This space charge capacitance does not show any significant increase with rising applied forward bias. In contrast, recently published impedance data show an exponential increase of the apparent capacitance [J. Phys. Chem B 2000, 104, 2044]. A simple analytical model is presented here for the impedance behavior of the DSC under forward bias revealing its nature as diffusion effect. The prediction of this model shows good qualitative agreement with the experimental results.