Simulation and electrochemical impedance spectroscopy of dye-sensitized solar cells

Here, we report on simulating the steady-state j-V characteristics of dye-sensitized solar cells (DSSCs). First, a set of differential equations describing the kinetic processes involving the charge carriers electron, iodide, triiodide, and dye cation - are derived. We consider non-linearity both in transport and in the recombination of electrons. Also, we consider that the charge transport occurs only by diffusion. Moreover, Boltzmann statistics relate electron density and Fermi level in TiO2, a quasi-static equilibrium holds between free and total electrons, and traps in the semiconductor fit to an exponential distribution of energies. Most importantly, we assume that electron transport occurs according to the multipletrapping model. The numerical solution provides j-V characteristics of the photoelectrode. To establish a relationship between the photovoltaic performance of the photoelectrode and that of the overall DSSCs, we consider the potential drops due to series-resistive elements according to the device physics of DSSCs. Finally, the model is applied to simulate the photovoltaic performance of real DSSCs with varying TiO2 film thickness and electrolyte composition. The critical parameters of the model were extracted from electrochemical impedance spectroscopy (EIS) data of the DSSCs. The model successfully reproduced the j-V curves of the DSSCs. (c) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.