Identifying ion and carrier behavior in perovskite solar cells through impedance spectra
Abstract Due to the interference of ion dynamics in perovskite materials, specifically the mixed ionic-electronic conduction property, the impedance response of perovskite solar cells exhibits numerous anomalous features. Herein, we conduct numerical simulations using the drift-diffusion model coupled with ion migration to elucidate how ionic and carrier behavior govern the impedance response. Here we show that, in the Nyquist plot, the low frequency and high frequency semicircular features of direct current voltage-dependent impedance spectroscopy are determined by ion migration and carrier transport, respectively. The low-frequency semicircular feature disappears when ion migration is fully suppressed. As ion mobility or mobile ion concentration increases, both the low-frequency decay region of the real component and low-frequency peak of the imaginary component in frequency-domain impedance plot shift toward higher frequencies. As the bulk or interface carrier recombination rate increases, both the high frequency decay region of the real component and the high frequency peak of the imaginary component shift toward higher frequencies.