A simple numerical model for the charge transport and recombination properties of dye-sensitized solar cells: A comparison of transport-limited and transfer-limited recombination

A simple model is presented for the charge transport and recombination characteristics of dye-sensitized solar cells (DSCs), based on solving the continuity equation for electrons using numerical methods. We analyze two models, in which the recombination kinetics are determined by either the electron transport kinetics in the nanostructured metal oxide film or the electron transfer rate across the metal oxide–electrolyte solution interface. It is found that transport-limited recombination results in ideal diode behaviour, in which case the open-circuit voltage is proportional to the logarithm of the light intensity with a slope of 26 mV, while the transfer-limited model allows for a different slope that depends on the trap distribution parameter, α, and the electron transfer coefficient, b.