Is one obliged to justify the mimesis of these pages? If it were a case (as far as the object is concerned) of “literature” or “philosophy,” of a “discourse,” then indeed yes, one would be so obliged. But since in this case the text (the object) offers nothing outside itself, then the answer is no.
—  Jacques Derrida, Spurs: Nietzsche’s Styles/Eperons: Les Styles de Nietzsche

[ Authors ]
J. Beilsten-Edmands, G. E. Eperon, R. D. Johnson, H. J. Snaith, P. G. Radaelli
[ Abstract ]
We present measurements of conductance hysteresis on CH3NH3PbI3 perovskite thin films, performed using the double-wave method, in order to investigate the possibility of a ferroelectric response. A strong frequency dependence of the hysteresis is observed in the range of 0.1 Hz to 150 Hz, with a hysteretic charge density in excess of 1000 {\mu}C/cm2 at frequencies below 0.4 Hz - a behaviour uncharacteristic of a ferroelectric response. We show that the observed hysteretic conductance, as well as the presence of a double arc in the impedance spectroscopy, can be fully explained by the migration of mobile ions under bias on a timescale of seconds. Our measurements place an upper limit of approximately 1 {\mu}C/cm2 on any intrinsic frequency-independent polarisation, ruling out ferroelectricity as the main cause of current-voltage hysteresis and providing further evidence of the importance of ionic migration in modifying the efficiency of CH3NH3PbI3 devices.