Modeling of Intensity-Modulated Photocurrent/Photovoltage Spectroscopy: Effect of Mobile Ions on the Dynamic Response of Perovskite Solar Cells

Intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS) have proven to provide insights into the charge carrier dynamics of perovskite solar cells (PSCs), though the interpretation of measured spectra is not straightforward. Using a one-dimensional drift diffusion model, we investigate the effect of mobile ions on the small signal response of PSCs. The IMPS and IMVS response is derived by sinusoidal steady-state analysis and Fourier decomposition (FD) of the transient cell response to a light intensity step. The FD method links the time and frequency domain, giving an additional perspective for the interpretation of the results at the expense of numerical efficiency. The simulated spectra are characterized by two separate arcs, where the high-frequency response is attributed to the transport and recombination of electronic charges, while the low-frequency peak represents the transport of ions. We show that this model is able to reproduce qualitatively the measurements reported in the literature. The concepts presented in this paper are applicable for the analysis of the small signal response of any mixed ionic electronic conductor.