Origin of Hysteresis in CH₃NH₃PbI₃ Perovskite Thin Films

Abstract

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.

Quantitative Electromechanical Atomic Force Microscopy

“…The initial detection of highly-ordered twin domains in MAPbI3 by PFM imaging 91 sparked a rapid rise in applications of PFM on HOIPs, as researchers attempted to unravel the hotly-debated ferroic properties of these systems. 86,[92][93][94][95][96][97][98][99][100] These efforts have led to seemingly contradictory results claiming both ferroelectric 86, 92-95, 99, 100 and non-ferroelectric 91,97 behavior.…”

On the Current–Voltage Hysteresis in Perovskite Solar Cells: Dependence on Perovskite Composition and Methods to Remove Hysteresis

“…Although experimental evidence was shown, it is still argued which ions are accumulated at electrode interface. For more information regarding theoretical and experimental studies on ion migration, please refer to the reports published elsewhere …”

“…MAPbI 3 thin films were investigated using temperature‐dependent PFM and scan rate–dependent nano/macroscopic I – V measurements to understand origin of the hysteresis, where the hysteresis could be closely related to ferroelectricity only by the observation that the PFM hysteresis loop disappeared above the Curie temperature. However, according to the nano/macroscopic I – V measurements, ion migration was proposed to be most probable factor affecting the hysteresis because ionic current was observed from macroscopic I – V curves, but nonionic current was exhibited in the nanoscopic I – V curves even under presence of ferroelectricity . This indicates that ion migration is strongly involved in the J – V hysteresis.…”

Dielectric relaxation and local domain structures of ferroelectric PIMNT and PMNT single crystals

“…In SS‐PFM measurements, a conductive scanning probe tip is fixed at the given location on the sample surface, then a triangular waveform V tip = V dc + V ac sin ωt is applied to the tip, as shown in Figure D. V dc is comprised of the “ON” state pulse ( V dc pulse is applied) and “OFF” state pulse ( V dc pulse is not applied), while the piezoresponse was measured in the “OFF” state so as to minimize the effects of electrostatic effect . V ac is the drive amplitude of standard PFM measurement.…”

“…V dc is comprised of the "ON" state pulse (V dc pulse is applied) and "OFF" state pulse (V dc pulse is not applied), while the piezoresponse was measured in the "OFF" state so as to minimize the effects of electrostatic effect. [41][42][43][44] V ac is the drive amplitude of standard PFM measurement. Figure 7E,G show Figure 8A reveals the disordered, irregular and smaller island-like 180° nanodomain structures with opposite polarization directions at V dc = 0 V. When the crystal was poled under the voltage of V dc = 0.5 V, as shown in Figure 8B, it can be found that the original dark regions of the phase image become wider, indicating that the polarization orientation of dark areas is along the direction of the applied field direction.…”