Anomalously large interface charge in polarity-switchable photovoltaic devices: an indication of mobile ions in organic-inorganic halide perovskites

It is proved that a large amount of mobile ions exist in organic-inorganic halide perovskites. The accumulated ions at the interface change the band bending of the semiconductor, leading to polarity-switchable photovoltaic devices. The interface charge significantly influences the function and performance of perovskite devices. The discovery of the interface charge has important implications for current-voltage hysteresis in perovskite solar cells.