Impedance Spectroscopy of Perovskite Solar Cells: Studying the Dynamics of Charge Carriers Before and After Continuous Operation

Abstract

The issue of long-term stability is one of the main obstacles challenging the progress of perovskite solar cells (PSCs). To alleviate this issue, a thorough understanding of the degradation mechanisms of the device is required. Herein, electrochemical impedance measurements in combination with maximum power point (MPP) tracking are applied to characterize PSCs, aiming to gain an understanding of the charge carrier dynamics in the photoactive bulk and at the contact-absorber-interfaces under operation. Electrochemical impedance spectroscopy (EIS) results show that the device charge transport resistance and interface capacitance associated with charge accumulation at the interfaces are both increasing upon continuous operation. This suggests ion migration from the photoactive perovskite layer to the charge transport layer interfaces leaving defects in the bulk. This suggests that reduction of the device performance upon continuous operation is mainly related to the changes in the bulk of the photoactive perovskite film and ions migration.