Organic-inorganic hybrid perovskite solar cells are attracting the attention of researchers owing to the high level of performance they exhibit in photo voltaic device applications. However, the attainment of an even higher level of performance is hindered by their anomalous current-voltage (I-V) hysteresis behavior. Even though experimental and theoretical studies have suggested that the perovskite materials may have a ferroelectric nature, it is still far from being fully understood. In this study, the origin of the hysteresis behavior in CH 3 NH 3 PbI 3 perovskite thin films is investigated. The behavior of ferro electricity using piezoresponse force microscopy is first examined. Then, by comparing the scanratedependent nano/macroscopic I-V curves, it is found that ion migration assisted by the grain boundaries is a dominant origin of I-V hysteresis from a macroscopic viewpoint. Consequently, the observa tions suggest that, even though ferroelectricity exists in the CH 3 NH 3 PbI 3 perovskite materials, ion migration primarily contributes to the macroscopic I-V hysteresis. The presented results can provide fundamental guidelines to the resolution of hysteresis issues in organic-inorganic hybrid perovskite materials.

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