Dye-sensitized nanostructured solar cells (DSC) is a promising new class of photovoltaic devices for the harvesting of solar energy. Besides improving cell efficiencies there is interest towards roll-to-roll production of DSCs on flexible plastic substrates. In this case, the cell preparation is restricted to relatively low temperatures, which usually leads to reduced photocurrent output. We have studied the photocurrent limiting factors of DSCs with nanostructured TiO₂ photoelectrodes prepared by compression technique on glass using both steady state and dynamic techniques.

A new methodology for quantitative spectral decoupling of the IPCE into the partial quantum efficiencies of light harvesting, electron injection, and electron collection is presented and demonstrated with experimental results, analyzing the data as a function of photoelectrode film thickness (d). The injection efficiency was relatively low and strongly wavelength dependent (Figure a), attributed to a poor energetic matching between the dye excited states and the TiO₂ acceptor states. Self-consistent estimation of the effective electron diffusion length (L) at the short circuit condition was achieved in the spectral region of constant electron generation rate. Strikingly, L was an increasing function of d (Figure b), attributed tentatively to the electron concentration dependence of L, resulting in increase of the electron collection efficiency with d.

The steady state analysis will be complemented and contrasted with results from dynamic characterization of these cells with frequency domain (EIS, IMPS, IMVS), time domain and charge extraction techniques, making remarks on the interpretation, relevance and usability of the steady state vs. transient methods.