Direct Observation of the Tunneling Phenomenon in Organometal Halide Perovskite Solar Cells and Its Influence on Hysteresis

Recently, organometal halide perovskites have shown the unprecedented success in solar cell application and attracted widespread attention as next-generation photovoltaic materials. Regardless of the remarkable achievements, the hysteretic behavior of the organometal halide perovskite solar cells is not fully understood yet, and its origins suggested are still in dispute, even though the hysteresis deteriorates the stability of the perovskite solar cells and, thus, prevents their commercialization. Here we report direct observation of the tunneling phenomenon by using nm-scale in situ current density–voltage characterization and suggest that the tunneling phenomenon can induce hysteresis in the perovskite solar cells. We identified that the tunneling phenomenon originated from the local-heavy doping caused by the electrostatic dipole at a rough interface and that the hysteresis of the perovskite solar cells possibly originated by piling the tunneling currents. This Letter shows a new possible origin of the hysteresis and the importance of the interface condition in perovskite solar cells.