The Origin of Photoinduced Capacitance in Perovskite Solar Cells: Beyond Ionic-to-Electronic Current Amplification

Photoinduced capacitances of perovskite solar cells exhibit peculiarities such as an apparently high capacitance and an inductive feature, so-called negative capacitance, which are not easily explained with typical carrier dynamics. Consequently, the origins of the photoinduced capacitances in perovskite solar cells have been intensively debated over the past several years. Here, the photoinduced capacitances of perovskite solar cells are analyzed by impedance spectroscopy. The analysis clarifies that the photoinduced capacitances of perovskite solar cells comprise several Debye relaxation-type capacitance components. Among these components, the photoinduced capacitance in the low-frequency range is attributed to ionic-to-electronic current amplification. However, the photoinduced capacitances in the middle- and high-frequency ranges originate from bipolar injection. The clear elucidation of the origins of the photoinduced capacitances in perovskite solar cells provides comprehensive insights for analyzing properties of perovskites in either the time or frequency domain.