Characterization of Organic and Perovskite Solar Cells by ImpedanceSpectroscopy

摘要

Impedance Spectroscopy (IS) is a non-destructive characterization technique that has been extensively applied to differentelectronic devices, such as LEDs1, photodiodes and solar cells2. This technique provides access to valuable informationabout dynamical mechanisms (minority carrier recombination, diffusion, etc.) taking place in the different layers of thedevice. Besides, material and device parameters, such as dielectric constant, built-in potential, and carrier mobilities canbe extracted3.Impedance spectra results from applying a small AC signal over a steady DC bias and measuring the resulting small ACcurrent over a frequency range, typically from 1 Hz to 1 MHz, ( ) = (V_(AC)/I_(AC)). The Nyquist plot of the complex impedance(imaginary part vs real part) generally presents one or more features (mainly semicircles), depending on the number ofmechanisms governing the device. Fitting an electrical equivalent circuit to the complete impedance spectra providesparameters 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 simplecircuital model containing two resistances and two capacitances has been used to fit the measured IS spectra. Theinterpretation of extracted circuital parameters and its relationship with the physical model of the device will be discussed.