Absence of ferroelectricity in methylammonium lead iodide perovskite

Ferroelectricity has been proposed as one of the potential origins of the observed hysteresis in photocurrent-voltage characteristics of perovskite based solar cells. Measurement of ferroelectric properties on perovskite solar cells is hindered by the presence of (in)organic charge transport layers. Here we fabricate metal-perovskite-metal capacitors and unambiguously show that methylammonium lead iodide is not ferroelectric at room temperature. We propose that the hysteresis originates from the movement of positive ions rather than ferroelectric switching.