Bias-Induced Modulation of Charge Transport and Relaxation Dynamics in Perovskite Solar Cells: An Impedance Spectroscopy Approach

In this study, we employ impedance spectroscopy to investigate the internal mechanisms influencing the efficiency and performance of perovskite solar cells (PSCs). Using SCAPS-1D software (version 3.3.10), we simulate the FTO/ZnO/MASnI3/NiOx/Au heterostructure to analyze the complex impedance (Z*) and electric modulus (M*). This approach allows us to differentiate between bulk material properties and interface phenomena, such as ion migration, charge transport, and recombination dynamics. Through Nyquist and Bode plots, we identify three distinct relaxation processes associated with charge migration, interface polarization, and charge injection/extraction at the electrodes. To achieve a more comprehensive understanding, we model the impedance and modulus spectra using an equivalent electrical circuit, which accurately reproduces the experimental data. Our analysis reveals that increasing the bias voltage extends the relaxation times for charge transport and interface polarization, highlighting a decline in performance under higher operational voltages. This performance drop is attributed to elevated resistive losses and enhanced recombination processes, which become more pronounced at higher fields. These findings emphasize the importance of optimizing both bulk material properties and interface engineering to mitigate losses and improve the overall performance and stability of PSCs.