Perovskite Solar Cells (PSC) have attracted great attention due to the high efficiencies achieved in the past few years (up to 24.2 %). Perovskite semiconductors show excellent light absorption and large charge-carrier mobilities. In addition, device fabrication is low cost and easily up-scalable. However, the current density-voltage curve (J-V) shows hysteresis and devices suffer from stability issues which are still poorly understood. Among all perovskite materials, mixed-cation lead mixed-halide PSC have become very popular due to their high efficiencies and reasonably good stabilities1,2. On the other hand, Impedance Spectroscopy (IS) is a very valuable non-destructive technique to obtain information about dynamical mechanisms occurring both in the bulk and at the interfaces3 . In this work, J-V curves and the impedance response have been measured for CsFAPbIBr-based PSC from 1 Hz up to 1 MHz, under different illumination levels (from 0.06 mW/cm2 to 100 mW/cm2 ) both at 0 V (short circuit) and at Voc (open circuit). Impedance spectra show two significant arcs, associated to different recombination and charge accumulation mechanisms. IS data have been fitted to a circuital model that consists of a low-frequency RCPE subcircuit in series with a high frequency resistance, all shunted with a high-frequency capacitance. Dependence of the circuital parameters with Voc and Isc will be discussed.
Impedance Spectroscopy (IS) is a non-destructive characterization technique that has been extensively applied to different electronic devices, such as LEDs, photodiodes and solar cells. This technique provides access to valuable information about dynamical mechanisms (minority carrier recombination, diffusion, etc.) taking place in the different layers of the device. Besides, material and device parameters, such as dielectric constant, built-in potential, and carrier mobilities can be extracted. Impedance spectra results from applying a small AC signal over a steady DC bias and measuring the resulting small AC current over a frequency range, typically from 1 Hz to 1 MHz, 𝑍(jω) = VAC/1AC. The Nyquist plot of the complex impedance (imaginary part vs real part) generally presents one or more features (mainly semicircles), depending on the number of mechanisms governing the device. Fitting an electrical equivalent circuit to the complete impedance spectra provides parameters related to each feature (resistance and capacitance). In this work, IS has been used to characterize organic and perovskite solar cells (OSCs and PSCs, respectively). Measurements have been performed in dark and under illumination conditions at different bias (from 0 V to VOC). A simple circuital model containing two resistances and two capacitances has been used to fit the measured IS spectra. The interpretation of extracted circuital parameters and its relationship with the physical model of the device will be discussed.