Hysteresis Analysis Based on the Ferroelectric Effect in Hybrid Perovskite Solar Cells

Abstract

The power conversion efficiency (PCE) of CH3NH3PbX3 (X = I, Br, Cl) perovskite solar cells has been developed rapidly from 6.5 to 18% within 3 years. However, the anomalous hysteresis found in I-V measurements can cause an inaccurate estimation of the efficiency. We attribute the phenomena to the ferroelectric effect and build a model based on the ferroelectric diode to explain it. The ferroelectric effect of CH3NH3PbI3-xClx is strongly suggested by characterization methods and the E-P (electrical field-polarization) loop. The hysteresis in I-V curves is found to greatly depend on the scan range as well as the velocity, which is well explained by the ferroelectric diode model. We also find that the current signals show exponential decay in ∼10 s under prolonged stepwise measurements, and the anomalous hysteresis disappears using these stabilized current values. The experimental results accord well with the model based on ferroelectric properties and prove that prolonged stepwise measurement is an effective way to evaluate the real efficiency of perovskite solar cells. Most importantly, this work provides a meaningful perspective that the ferroelectric effect (if it really exists) should be paid special attention in the optimization of perovskite solar cells.

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

“…[189] Li et al [115] also mentioned the often-observed kinks illustrated in Figure 6 in the J-V curve measurement. Several groups have observed a similar behavior, [15,117,128,190,191] and this phenomenon especially prevails when using fast scan rates. In the context of the ion-migration model, the authors found an explanation for this kink in the J-V curve.…”

Ionic Reactivity at Contacts and Aging of Methylammonium Lead Triiodide Perovskite Solar Cells

“…In spite of the spectacular advances in cell efficiency many important aspects of the experimental observations on this system are not understood. Particularly intriguing is the hysteresis features in the response of the current density-voltage ( V J − ) curves [10][11][12][13] that have been related to a number of different explanations, as ferroelectric properties of the perovskite materials, [14][15][16] delayed electronic trapping processes, [17] or slow ion migration. [11,18,19] The recognition that the solar cell performance is heavily affected by time scale of the measurement and preconditioning procedures [9,17,20,21] has raised many concerns about the stability of the device and reliability for long time operation.…”

Ionic charging by local imbalance at interfaces in hybrid lead halide perovskites

“…2 Also, in photovoltaics, perovskitebased solar cells constitute a special type of light-harvesting devices because, in addition to electronic mechanisms, the presence of moving ionic species is believed to modify current-voltage curves. 3,4 Among other explanations related to either ferroelectricity [5][6][7] or electronic trapping properties of perovskites, 8 there is growing consensus that the ionic kinetics lies behind the commonly observed current-voltage hysteretic response, [9][10][11] and switchable photovoltaic characteristics. 12 Several studies have analyzed the defect chemistry of hybrid perovskite materials, and the inherent dependence of their doping character on the processing route.…”