Distinction between capacitive and noncapacitive hysteretic currents in operation and degradation of perovskite solar cells

Abstract

Perovskite solar cells suffer from significant performance distortions under working conditions, usually known by the generic label of hysteretic effects. A classification of the fluctuations associated with current–voltage curves, centered on capacitance analysis, including measurements in voltage sweep, is provided here. Scan rate constitutes an easy-to-implement probing technique able to differentiate between capacitive and noncapacitive contributions to the overall hysteretic response. Capacitive hysteresis shows a distinctive response with scan rate and mainly originates at TiO2 interfaces contacting perovskite materials. It relies on the interfacial ability to accommodate both ionic and electronic charges in a highly reversible way. Noncapacitive hysteresis points to the occurrence of interfacial energetics modification or contact reactivity caused by perovskite ionic motion. It exhibits positive values for reverse scans, in opposition to what is observed for capacitive currents. Connections between irreversible noncapacitve currents and device degradation are highlighted. The interfaces between the perovskite absorber and extracting layers play a determining role in the overall mechanisms of operation of this type of solar cell.