Transient photocurrents in dye-sensitized nanocrystalline solar cells

The time varying photocurrent response of dye-sensitized solar cells to switching on illumination and then switching the illumination off after steady state has been reached has been measured and modeled with a multiscale Monte Carlo and continuum approaches within the multiple trapping picture, where electrons in the porous TiO2 electrodes undergo successive trapping and detrapping events. These models are more detailed than the more common formalism employing an effective diffusion coefficient as they take into account the large variation in conduction electron density with distance and time near the extracting electrodes. Agreement between the three sets of results using a trap concentration and trap energy distribution width from a separate set of measurements using charge extraction shows that the multiple trapping formalism holds.