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.
Uniform perovskite films are achieved by HCl-assisted one-step spin-coating at room temperature. By this method, a highest power conversion efficiency of 17.9% is obtained for perovskite solar cells (PSCs). The devices retain ≈95% of their original efficiency after storage in air for two months. The highest efficiency obtained for large-area PSCs (0.86 cm ) is 15.7%.
has certain superiority in the improvement of its charge carrier mobilities and exciton diffusion lengths, besides the stability of the black phase. [32] Meanwhile, the slightly doped chlorine could increase the open circuit voltage (V oc ), attributed to the increase of the bandgap of FA perovskite. It is unfavorable that the over doping of chlorine would shorten the photoabsorption region of the perovskite compounds. Hence, the controllable chlorine doping in the perovskite films is significantly important to optimize solar cell performance. In the literatures, FAPbI 3−x Cl x perovskites were prepared by means of the remaining FACl in the annealed film through either the reaction of FAI with PbCl 2 or adding FACl into the PbI 2 and FAI solution. [33][34][35] However, in the above processes, it is difficult to control the chlorine content in perovskite films and meanwhile, thermal annealing at relatively high temperature (≥140 °C) to remove the additives would result in undesirable pinholes or cracks. The reported highest PCE of FAPbI 3−x Cl x is about 14%.Here, we have developed a one-step solution method for the preparation of FAPbI 3−x Cl x perovskite active layer with quantitatively doping of chlorine by the reaction of PbI 2 , FAI, FACl, and MACl with ratios of 1:(1 − x):x:1 at mild-temperature (100 °C). The chlorine doped fraction of FA perovskites can be continually varied with the amount of FACl in precursor solution. The average PCE of FA perovskite planar heterojunction photovoltaic cells increased from 15.2% to 17.0% when 20% FAI was replaced by FACl in the precursor solution. Figure 1 presents a schematic diagram of the formation of FA perovskite films with the MACl as additive by means of spin-coating. First, the precursor solutions containing PbI 2 , FAI, FACl, and MACl with a ratio of 1:(1 − x):x:1 in anhydrous dimethyl formamide (DMF) were spun onto the fluorine-doped tin oxide (FTO) glasses covered by compact TiO 2 layers. Then, the as-prepared films were annealed at 100 °C on a hot plate. In this process, MACl was used to adjust the crystallization process of FA perovskite and the use of equal-molar MACl:PbI 2 resulted in forming black FA perovskite layer with the nearly complete coverage ( Figure S1, Supporting Information). In addition, the chlorine amount doped in the perovskite was controlled by means of partly substitution of FACl for FAI in the precursor solution.To investigate the effect of chlorine doping amount on their optical and electronic properties, a series of FA perovskites were synthesized with the doped fractions x (FACl/(FAI+FACl)) in the precursor solution from 0 to 0.40. The X-ray diffraction (XRD) peaks of FAPbI 3 perovskites at 14.2°, 28.5°, and 43.2° were ascribed to the (110), (220), and (330) lattice planes, respectively (Figure 2a), exhibiting a preferential orientation along the [110] crystallographic direction, which were Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted tremendous attention owing to the outstanding optical and electronic propert...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.