Cooperative kinetics of depolarization in CH3NH3PbI3 perovskite solar cells

Abstract

Power law voltage decay in perovskite solar cells shows cooperative relaxation phenomena.

Despite the large photovoltaic performance recently achieved, many aspects of the working principles of hybrid organic–inorganic perovskite solar cells remain to be unveiled. We analyze the experimental features observed in the decay of photovoltage and provide an interpretation of the different depolarization regimes at distinct time scales. We introduce an instantaneous relaxation time that shows the type of relaxation for each separate mechanism. The decay of photovoltage is characterized by electronic events at the ms time scale followed by a power law relaxation in the 10–100 s time window. The latter process is associated with the slow dielectric relaxation of CH ₃NH ₃PbI ₃ perovskite and it points to cooperative kinetics of polarization and depolarization of ferroelectric domains. These findings provide an important tool for interpretation of kinetic features in the perovskite ferroic solar cells.