Cooperative kinetics of depolarization in CH3NH3PbI3 perovskite solar cells
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 CH3NH3PbI3 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. ; The research leading to these results has received funding from the European Union Seventh Framework Program [FP7/2007 – 2013] under grant agreement 316494, MINECO of Spain under project MAT2013-47192-C3-1-R, Generalitat Valenciana (project ISIC/2012/008) and the National Research Foundation of Korea (NRF) grants funded by the Ministry of Science, ICT & Future Planning (MSIP) of Korea under contract no. NRF- 2012M3A6A7054861 (Global Frontier R&D Program on Center for Multiscale Energy System). HW Han and LF Liu acknowl- edge nancial support from the National Natural Science Foundation of China (91433203, 61474049) and the Ministry of Science and Technology of China (863, SS2013AA50303).