Bias-Dependent Normal and Inverted J–V Hysteresis in Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) typically exhibit hysteresis in current density-voltage ( J- V) measurements. The most common type of J- V hysteresis in PSCs is normal hysteresis, in which the performance in the reverse scan is better than that in the forward scan. However, inverted hysteresis also exists, in which the reverse scan performance is worse than in the forward scan; this hysteresis, however, is significantly less well studied. In this work, we show that the hysteresis decreases when the sweep rate is decreased only in cases involving a small bias range, and it does not decrease with a large bias range. Under large forward bias and slowing sweep rate, we observe enhanced normal hysteresis or inverted hysteresis in PSCs. Moreover, the degree of normal and inverted hysteresis can be adjusted by varying the bias. Here, we hypothesize that the tunable hysteresis is derived from the different distribution of ionic defects (V and V) at the electron (hole) transport layer/perovskite interface due to ionic movement in the perovskite layer under the different bias scanning conditions. This conclusion is confirmed using Kelvin probe force microscopy with different bias voltages and scanning rates, which shows surface potential hysteresis based on ionic-migration-related Fermi level shifting in perovskite films and agrees with the tunable J- V hysteresis hypothesis. Moreover, the increased time response in the milliseconds region in open-circuit voltage decay after J- V scanning further corroborates the mechanism of ionic migration under bias. Our work provides new insights into the ionic movement hypothesis for the J- V hysteresis in PSCs.

Computer Test of a New Silicene Anode for Lithium‐Ion Batteries

“…[42] A two-dimensional laminate (SiÀ C) can have a thickness of~20 nm (~20 layers of silicene), which allows you to maintain flexibility and retain the capacity of the multilayer anode design as was in the case of an amorphous silicon film of the same thickness. [43] A sandwich structure for silicene anode can be proposed: separator (polypropylene, PP)/LiPON/Silicene + graphene/Al. The thickness of the LiPON layer can be about 50 nm.…”

Self‐Aggregation‐Controlled Rapid Chemical Bath Deposition of SnO2 Layers and Stable Dark Depolarization Process for Highly Efficient Planar Perovskite Solar Cells

“…Previous studies have clearly shown that mobile ions related to ionic vacancies/interstitial defects and negatively/positively charged ions in PSCs can migrate with a small external electric field, which is more activated under illumination. [20,47,48] Figure 9 shows the schematic band diagrams with ions displaced by an electric field and diffusion in PSCs. The differences in the Fermi level between the charge-selective layers force the mobile ions to be driven by a built-in voltage to each counter electrode in the electrical contact under the dark condition until the internal electric field is screened by the ion distribution to establish an equilibrium state.…”

Detecting and identifying reversible changes in perovskite solar cells by electrochemical impedance spectroscopy

“…6a). 48 But also negatively charged ions or vacancies can act as recombination centres (right side in Fig. 6a) 37,48,49 that essentially inhibit any charge carrier to be injected into the respective transport layers and can therefore not be measured externally by an electrical measurement.…”

“…48 But also negatively charged ions or vacancies can act as recombination centres (right side in Fig. 6a) 37,48,49 that essentially inhibit any charge carrier to be injected into the respective transport layers and can therefore not be measured externally by an electrical measurement. The major part of the perovskite absorber might still be active in creating charge carriers, but this activity is screened by the recombination centres and the behaviour of the whole device mimics a smaller device.…”