Electrical response of optimized DSSC’s by different dye-mordant-assistant combinations: A multi-time-hierarchical theoretical approach

The electrical response of dye-based photovoltaic cells upon a sudden illumination is explained in terms of a theoretical approach based on a time-hierarchical emergence of several physical processes. Our approach ensures the coupling the four main processes that take place, namely, the photochemical activation of the cell, the electrical current associated with electron transport, the relaxation of the polarization due to the motion of ions and, finally, the elastic–osmotic effect that produces rapid oscillations in the output photocurrent of the cell when is suddenly illuminated. The model shows that mordants control/modify three relaxation times: the characteristic time of the photochemical activation due to a partial light-blocking, the characteristic time for the electrical current associated with the electron transport due to mordant adsorption into the mesoporous surface, and the polarization relaxation due to a change in the ions transported to the electrodes. The model fits with high-precision the experimental data of the photo-induced current showing highly non-linear time-dependent oscillations.