Impact of Capacitive Effect and Ion Migration on the Hysteretic Behavior of Perovskite Solar Cells

In the past five years, perovskite solar cells (PSCs) based on organometal halide perovskite have exhibited extraordinary photovoltaic (PV) performance. However, the PV measurements of PSCs have been widely recognized to depend on voltage scanning condition (hysteretic current density–voltage [J–V] behavior), as well as on voltage treatment history. In this study, we find that varied PSC responses are attributable to two causes. First, capacitive effect associated with electrode polarization provides a slow transient non-steady-state photocurrent that modifies the J–V response. Second, modification of interfacial barriers induced by ion migration can modulate charge-collection efficiency so that it causes a pseudo-steady-state photocurrent, which changes according to previous voltage conditioning. Both phenomena are strongly influenced by ions accumulating at outer interfaces, but their electrical and PV effects are different. The time scale for decay of capacitive current is on the order of seconds, whereas the slow redistribution of mobile ions requires several minutes.The authors gratefully acknowledge the financial support through the U.S. Army under Contract No. W15P7T-13-C-A910. The work at the National Renewable Energy Laboratory was supported by the U.S. Department of Energy SunShot Initiative under the Next Generation Photovoltaics 3 program (DE-FOA-0000990) under Contract No. DE-AC36-08-GO28308. S.P. and C.W. also appreciate support from the NSF I/UCRC: Center for Energy Harvesting Materials and Systems through Fundamental Research Program. The work at INAM-UJI was supported by Generalitat Valenciana project PROMETEO/2014/020