WO2021133085A2 - Preparation method for organic halide for preparation of perovskite, perovskite prepared thereby, and solar cell - Google Patents

Abstract

The present invention relates to a preparation method for an organic halide for preparation of perovskite, perovskite prepared thereby, and a solar cell. According to the present invention, an organic halide for perovskite can be prepared by an ion-exchange method using alkali metal iodide or alkali metal bromide.

Description

Method for producing organic halide for production of perovskite, perovskite produced thereby, and solar cell

The present invention relates to a method for preparing an organic halide for preparing perovskite, the perovskite produced thereby, and a solar cell. Specifically, the present invention relates to the above production method, characterized in that an alkali metal iodide or bromide is used, a perovskite produced thereby, and a solar cell.

Perovskite solar cells have developed very rapidly over the past few years as a potential alternative to crystalline silicon solar cells, which currently account for 93% of the global solar cell market. Organic halides such as methylammonium halide (MAX, X=I or Br) and formamidinium halide (FAX) are important materials used for the photoactive layer of organometallic trihalides in perovskite solar cells. Perovskite solar cells have excellent photo-electric properties in terms of high light absorption efficiency, long charge carrier lifetime, and long diffusion distance of charge carriers. % to 25.2%, a dazzling improvement. Whereas conventional thin-film solar cells (e.g., those based on Cu(In,Ga)(S,Se) and CdTe) are fabricated by sputtering or deposition under vacuum, the perovskite photoactive layer is in solution. It is prepared by a simple spin coating method using an organic halide and a PbX _{2 precursor.} Due to the characteristics of the solution process, organometallic trihalide-based perovskite solar cells have higher economic efficiency and competitiveness than thin film solar cells that rely on vacuum technology.

Among organic halides, methylammonium iodide (MAX, X=I) not only has high reproducibility, but the MAPbI _3- based perovskite solar cell manufactured using it has excellent photo-electrical properties and an electric power of ~21.2%. Because of its conversion efficiency, methylammonium iodide is an important precursor. In addition, when the MA portion is replaced with FA, the light absorption wavelength is extended to a longer wavelength region, so that the absorption range of the solar spectrum is wider, so that the power production of the solar cell is improved. However, the synthetic procedures for MAX and FAX are mostly related to the use of toxic and expensive hydrogen halide precursors. For example, MAI is synthesized by an acid-base reaction between aqueous methylamine and HI, and FAI is likewise prepared by the reaction between formamidinium acetate (FAAc) and HI. Although the method for preparing organic iodide has relatively high yield and reproducibility, since HI is used in the synthesis, great care must be taken in the treatment of the reaction mixture during synthesis. HI is the strongest acid among hydrogen halides (pKa of HI = -9.3) and is easily oxidized to I ₂ by oxygen when exposed to air, so according to the 2006 air pollution standards set by UK experts, HI and HBr Concentrations of 0.1 ppm and 0.2 ppm or less are recommended. In addition, the perovskite solar cell has the advantage of low production cost, but excessive use of HI to increase the reaction yield in the reaction of MA or FA with HI increases the manufacturing cost, so the perovskite solar cell economic efficiency will be lowered.

From the point of view of the manufacturing process, special care is required in the process of depressurizing water and unreacted HI or HBr to separate the product from the toxic aqueous mixture. In conclusion, developing an economical and environmentally friendly method for synthesizing organic halides is important for the industrial production of perovskite solar cells. Methods for improving the stability and power conversion efficiency of perovskite solar cells have been extensively studied in recent years, but few studies and patents addressing the issues of organic halide precursor preparation have been reported.

One object of the present invention is to provide a method for preparing an organic halide for preparing perovskite, which does not use toxic conventional HI or HBr.

Another object of the present invention is to provide a perovskite prepared by using an organic halide that can be prepared by the above production method as a precursor.

Another object of the present invention is to provide a solar cell including the perovskite.

According to a first aspect of the present invention, there is provided a method for preparing an organic halide for preparing perovskite, comprising the step (a) of reacting methylammonium chloride or formamidinium chloride with an alkali metal iodide or alkali metal bromide is provided

According to a second aspect of the present invention, there is provided a perovskite prepared by using the organic halide prepared by the above production method as a precursor.

According to a third aspect of the invention, there is provided a first electrode, a second electrode opposite the first electrode, and a photoactive layer disposed at least partially between the first electrode and the second electrode, comprising: There is provided a solar cell comprising a photoactive layer comprising a perovskite obtained by including and using an organic halide prepared by the present invention as a precursor.

In the present invention, by using alkali metal iodide or alkali metal bromide instead of using conventional toxic HI or HBr as a halide source, a perovskite precursor can be prepared in an easy and environmentally friendly way. According to the prior art, when strong acids such as HI or HBr are used, they are oxidized by reacting with oxygen when stored for a long time in air, so special storage conditions are required, so they are not suitable for mass production and can be used in drug manufacture. It is a List I compound from the Administration (DEA) and subject to monitoring. In addition, an additional cooling system is required due to the strong exothermic nature of the acid-base reaction. On the other hand, according to the present invention, since such a strong acid is not used, manufacturing equipment can be simplified, raw material cost is low, and waste disposal can be easily carried out, thereby enabling a safer and simpler mass production design. In addition, the manufacturing method according to the present invention has a high production yield. Therefore, the manufacturing method of the present invention has significantly higher economic efficiency than the prior art method.

Figure 1a is a schematic diagram of a method for producing an organic halide for perovskite according to the prior art, Figure 1b is a schematic diagram of a production method according to an embodiment of the present invention.

2 shows the yields of four organic halides prepared under reflux conditions using ethanol (EtOH) or water as a solvent according to an experimental example of the present invention.

3 shows the yields of four organic halides prepared at room temperature using ethanol (EtOH) or water as a solvent according to an experimental example of the present invention.

^{4 shows hydrogen nuclear magnetic resonance (1} H NMR) spectra of samples prepared according to an experimental example of the present invention.

5 shows X-ray diffraction patterns of samples prepared according to an experimental example of the present invention.

6 is a table showing X-ray fluorescence analysis (XRF) elemental analysis results of samples prepared according to an experimental example of the present invention, and a number in parentheses is an analysis result after recrystallization of the prepared samples.

7a shows the UV-Vis absorption spectrum of a perovskite film prepared using an organic halide prepared according to an experimental example of the present invention or a commercially available organic halide, and FIG. 7b is prepared according to an experimental example of the present invention. The XRD pattern of the perovskite film prepared using the organic halide or commercially available organic halide is shown. 7c and 7d are top views of SEM images of perovskite films prepared using organic halides prepared according to an experimental example of the present invention or commercially available organic halides, respectively.

8A to 8C are enlarged views of the XRD pattern of FIG. 7B of an organic halide prepared according to an experimental example of the present invention or a perovskite film prepared using a commercially available organic halide.

9A shows the structure of a mesoporous perovskite solar cell (PSC) prepared in an experimental example of the present invention, and FIG. 9B shows a cross-sectional SEM image of the solar cell. 9c to 9g are current density-voltage curves (JV curves) of PSCs prepared using organic halides prepared according to an experimental example of the present invention and PSCs prepared using commercially available organic halides (Fig. 9c) ), short circuit current density (Jsc) (FIG. 9D), open circuit voltage (Voc) (FIG. 9E), charge factor (FF) (FIG. 9F), and power conversion efficiency (PCE) (FIG. 9G).

Hereinafter, the terms used in the present application are used only to describe specific embodiments and are not intended to limit the present invention. Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Throughout this specification, when a part "includes" a component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

Throughout this specification, "perovskite" refers to an organic-inorganic halide in which cations (R and M) and anions (X) are _{composed of the chemical formula of RMX 3 , and have the same crystal structure as CaTiO 3} , the first perovskite-type material. means material.

Throughout this specification, "perovskite solar cell" refers to a solar cell comprising an organic-inorganic halide material having a perovskite crystal structure.

Method for the preparation of organic halides for the production of perovskite

According to a first aspect of the present invention, in the method for preparing an organic halide for preparing perovskite of the present invention, methylammonium chloride or formamidinium chloride is used as an alkali metal iodide or alkali metal bromide. and reacting with (a).

In the alkali metal iodide or alkali metal bromide of the present invention, the alkali metal is not particularly limited as long as it reacts with the methylammonium chloride or formamidinium chloride, and specifically lithium, sodium, potassium, and the like. According to one embodiment of the present invention, the alkali metal iodide or alkali metal bromide may be sodium iodide (NaI) or sodium bromide (NaBr). The NaI and NaBr may be useful in that they have high solubility in solvents such as water and alcohol.

The organic halide in the preparation method of the present invention may be methylammonium iodide (MAI), methylammonium bromide (MABr), formamidinium iodide (FAI), or formamidinium bromide (FABr).

According to one embodiment of the present invention, the reaction step (a) may be performed by an ion exchange reaction in a solvent. The solvent may be water or an alcohol, wherein the alcohol may be a monohydric or dihydric alcohol having 1 to 5 carbon atoms, specifically, a monohydric alcohol having 1 to 5 carbon atoms, more specifically ethanolyl can

In addition, according to one embodiment of the present invention, the reaction step (a) may be carried out in a solvent at room temperature or under reflux. A suitable temperature for the reflux may be appropriately determined depending on the solvent used, for example, 100° C. when water is used as a solvent, and 78° C. when ethanol is used as a solvent. The reaction time may be determined according to the reaction rate and desired yield, and for example, may be carried out from 1 minute to 24 hours under stirring. However, the present invention is not limited thereto and may be performed for 24 hours or more.

In addition, according to another embodiment of the present invention, after the reaction step (a), the step (b) of filtering the product of the reaction step (a), and the step (c) of removing the solvent further comprising can do. NaCl, a reaction by-product, may be removed by the filtration step (b). In addition, in the solvent removal step (c), when the solvent is water, the water is first removed in step (c), then the product may be dissolved in alcohol and the filtration step (b) may be performed. On the other hand, when the solvent is an alcohol, the filtration step (b) may be performed first, and then the step (c) may be performed, and wherein the step (c) may be performed by evaporating the alcohol.

According to another embodiment of the present invention, the step (d) of removing the alkali metal chloride by recrystallization from the organic halide produced in the reaction step (a) may be further included. The organic halide produced in step (a) inevitably contains ionic salt impurities (eg, alkali metal chloride, alkali metal iodide, methylammonium chloride, or formamidinium chloride) according to the ion exchange method. there may be Therefore, after performing step (a), if necessary, further performing steps (b) and/or (c), and then recrystallizing to further remove ionic salt impurities, specifically alkali metal chloride, etc. can

Perovskite prepared from organic halide of the present invention

According to a second aspect of the present invention, there is provided a perovskite prepared by using the organic halide prepared by the method for producing an organic halide as described above as a precursor.

The perovskite has a RMX ₃ structure, and according to the present invention, R may be a methylammonium cation or a formamidinium cation, X may be an iodide anion or a bromide anion, M is Pb ^{2 It} may be a divalent metal cation selected from the group consisting of + , Sn ²⁺ , Ge ^{2+ , and combinations thereof.}

solar cell

According to a third aspect of the present invention, there is provided a photoactive layer disposed at least partially between a first electrode, a second electrode opposite the first electrode, and between the first electrode and the second electrode, comprising an organic as described above. A solar cell comprising a photoactive layer comprising a perovskite obtained by including and using an organic halide prepared by the method of halide as a precursor is provided.

According to one embodiment of the present invention, the perovskite may be obtained by reacting an _{organic halide as described above with a compound of Formula MX 2 .} Here, X may be an iodide anion or a bromide anion, and M may be a divalent metal cation selected from the group consisting ^{of Pb 2+} , Sn ²⁺ , Ge ^{2+ and combinations thereof.} The photoactive layer comprising the perovskite can be prepared simply by, for example, spin coating using _{the organic halide in solution and the compound of Formula MX 2 .}

According to one embodiment of the present invention, the first electrode may be one of an anode and a cathode, and the second electrode may be the other one of an anode and a cathode. According to another embodiment of the present invention, any one or both of the first electrode and the second electrode may be coated on the substrate. According to another embodiment of the present invention, the solar cell may further include an electron transport layer and a hole transport layer between the first electrode and the second electrode. In addition, in the solar cell, the photoactive layer may further include a photoactive material other than the perovskite material, for example, a semiconductor material. In addition, the photoactive layer may further include, in addition to the perovskite layer, a layer comprising another photoactive material, for example, a semiconductor layer.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[Example]

material used

The following materials were used as received without further purification: NaI (99.5%, from Wako), NaBr (99.5%, from Junsei), methylammonium chloride (MACl, 98.0%, from Junsei), FAAc (98%, TCI) product), ethanol (EtOH, 99.5%, manufactured by _{Samchun Chemical), diethyl ether (Et 2} O, ≥99.7%, manufactured by Sigma-Aldrich), methylamine solution (40 wt% in water, manufactured by TCI), hydroiodic acid ( HI, 57 wt% in water, from Sigma-Aldrich), hydrobromic acid (HBr, 48 wt% in water, from Sigma-Aldrich), titanium diisopropoxide bis(acetylacetonate) (75 wt% in isopropanol, Sigma-Aldrich), 1-butanol (99%, from Sigma-Aldrich), terpineol (anhydrous, from Sigma-Aldrich), PbI ₂ (99.9%, from TCI), N,N-dimethylformamide (DMF) , 99.8%, from Sigma-Aldrich), dimethyl sulfoxide (DMSO, ≥99.9%, from Sigma-Aldrich), acetonitrile (anhydrous, 99.8%, from Sigma-Aldrich), 2,2',7,7'- Tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-MeOTAD, >99.5%, from Luminescence Technology Corp.), bis(trifluoromethane)sulfone Amide lithium salt (Li-TFSI, 99%, from Alfa Aesar), tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine) cobalt(III) tri[bis(trifluoromethane) )sulfonamide] (Co-TFSI, FK209, from Greatcell Solar), and 4-tert-butylpyridine (96%, from Sigma-Aldrich). Formamidinium chloride (FACl) was prepared in a conventional manner, namely by reaction of FAAc and HCl solution (see I. Levchuk, A. Osvet, X. Tang, M. Brandl, JD Perea, F. Hoegl, GJ Matt, R. Hock, M. Batentschuk and CJ Brabec, Nano Lett. 2017, 17 , 2765-2770])

1. Experimental example

1-(1). Synthesis of MAX and FAX (X = Br and I) organic halides

1-(1)-①. Synthesis of MAI

Organic halides of MAX and FAX were synthesized by reacting NaX (X = Br or I) with MACl or FACl in water (or EtOH) at a suitable temperature. For the synthesis of MAI via ion exchange reaction, 20 mmol (3.0 g) of NaI and 20 mmol (1.35 g) of MACl were each separately dissolved in 100 mL of deionized water and then together in a 500 mL round bottom flask at room temperature. put The reaction was carried out for 3 hours under reflux (or at room temperature) while vigorously stirring the mixed aqueous solution under reflux conditions of 100° C. or higher (about 78° C. for EtOH). After completion of the reaction, water was removed from the reaction mixture under vacuum. A yellowish white powder was produced, which was dispersed in EtOH (or isopropanol) and filtered to remove NaCl (when isopropanol is used, more than EtOH is required, but the amount of NaCl as an impurity is greatly reduced). EtOH (or isopropanol) was evaporated under vacuum. The obtained product was _{washed several times with Et 2} O, and the residual solvent was evaporated to obtain MAI of high purity. When EtOH was used instead of water as solvent, MAI was obtained immediately after _{MAI filtration and subsequent EtOH evaporation and washing with Et 2 O.} When the reaction was carried out using EtOH as a solvent, after cooling to room temperature under reflux conditions, NaCl was filtered and the solvent was removed to obtain MAI.

1-(1)-②. Synthesis of MABr, FABr, and FAI

Other organic halides were prepared using different precursors, maintaining the same synthetic conditions used for MAI above: MACl and NaBr were used to prepare MABr; FACl and NaBr were used to prepare FABr; FAI was prepared using FACl and NaI.

1-(1)-③. Synthesis of MAI

Except that 7.36 g of MACl and 16.34 g of NaI were dissolved in 100 mL of EtOH, MAI was synthesized under the same conditions as those used for the MAI of 1-(1)-①.

1-(1)-④. Synthesis of FAI

Except that 14.92 g of FACl and 27.79 g of NaI were dissolved in 100 mL of EtOH, FAI was synthesized by maintaining the same conditions as those used for MAI in 1-(1)-①.

1-(2). Fabrication of perovskite solar cells (PSCs)

For comparison of device performance, MAI (abbreviated as IE-MAI in the device characterization part) and commercially available MAI (≥99.5%) prepared by the ion exchange method according to the above-mentioned 1-(1)-① of the present invention , a product of Xi'an Polymer Light Technology Corp.) (abbreviated as CO-MAI in the device characterization part) was used to manufacture solar cells. Both IE-MAI and CO-MAI used for solar cell production were obtained by recrystallization from a mixed solvent of _{Et 2 O and EtOH.}

All devices were prepared according to conventional methods. Fluorine-doped tin oxide (FTO) substrates of 2 X 2 cm ² (Pilkington TEC8) were cleaned in an ultrasonic bath for 15 minutes using sequentially acetone, deionized water and isopropyl alcohol. The cleaned substrate was dried under a _{N 2 gas stream.} First, a 1-butanol solution in which 0.15 M titanium diisopropoxide bis(acetylacetonate) was dissolved was spin-coated at 3000 rpm for 20 seconds to prepare _{a TiO 2} dense layer (c-TiO _{2 ).} The c-TiO ₂ /FTO was baked at 125° C. for 5 minutes, then _{immersed in a 0.05 M TiCl 4} solution at 70° C. for 30 minutes, and rinsed with deionized water and isopropyl alcohol. Thereafter, _{a diluted TiO 2} paste (SC-HT040, manufactured by SCHARECHEM Co.) _{composed of TiO 2} nanoparticles (~50 nm average diameter) was _{spin-coated to form a mesoporous TiO 2} (mp-TiO ₂ ) layer. was formed. The TiO ₂ paste was diluted in a mixed solvent (1-propanol to terpineol in a 3.5:1 ratio) to a paste to solvent ratio of 1:3.5 ratio. The mp-TiO ₂ layer was then baked at 125° C. for 5 minutes and annealed at 500° C. for 30 minutes.

The MAPbI ₃ membrane was prepared through a conventional solvent engineering method. _{A MAPbI 3} film was coated _{on the prepared mp-TiO 2} /c-TiO ₂ /FTO/glass substrate by spin coating the precursor solution at 4000 rpm for 20 seconds. The precursor solution was prepared by dissolving 52 wt% of the precursor, ie, PbI ₂ and the desired MAI (IE-MAI or CO-MAI), in a mixed solvent of anhydrous DMF and DMSO at a volume ratio of 7.33:1. Then, 0.5 mL of Et ₂ O was injected into the substrate during spin coating. Next, the substrates were sequentially annealed at 65° C. (1 min) and 130° C. (10 min). A hole transport layer was spin coated on the perovskite layer at 3000 rpm for 30 seconds. The hole transport material precursor solution was prepared by sequentially adding 18 μL of Li-TFSI solution and 14.7 mg of Co-TFSI to 1 mL of spiro-MeOTAD solution. The Li-TFSI solution was prepared by dissolving 566 mg of Li-TSFI in 1 mL of acetonitrile. The spiro-MeOTAD solution was prepared by sequentially dissolving 80 mg of spiro-MeOTAD and 32 μL of 4-tert-butylpyridine in 1 mL of chlorobenzene. Finally, an Au electrode was deposited on the hole transport layer at ^{a deposition rate of 1 Ås −1 according to a thermal evaporation method.}

2. Characterization

¹ H nuclear magnetic resonance (NMR) spectra were obtained using a Bruker AVANCE III 500 spectrometer. X-ray diffraction (XRD) patterns were recorded on a PANalytical X'Pert PRO MPD equipped with a Cu Kα radiation source (λ=1.5405 Å), with a step size of 0.016 ^o . Elemental analysis was performed using a wavelength dispersive X-ray fluorescence (WD-XRF) spectrometer (Bruker S8 Tiger). To investigate the performance of the perovskite solar cell, a solar simulator (Newport Oriel Solar 3A Class, 94023A) with a source meter (Keithley 2450) was used. The solar simulator was calibrated to irradiate ^{AM 1.5G (100 mAcm -2} ) using a standard Si reference cell (Newport, 91150V). Current density-voltage (JV) curves were recorded from forward bias (0V to 1.2V) to reverse bias (1.2V to 0V) at scan rates of 30 mVs-1 or 100 mVs-1. The active area of each device was 0.107 cm ² .

Experiment result

2-(1). Synthesis of organic halides by ion exchange method

Among the various alkali metal halides, NaI and NaBr, because of their high solubility in both water and EtOH used as solvents in this experiment (~46 g NaI and 2.32 g NaBr per 100 g EtOH), ions using MACl or FACl It was most suitable as an exchange reactant. On the other hand, the low solubility properties of the reaction by-product NaCl (~0.065 g/100 g EtOH) allow MAI to be separated from the reaction mixture by simple filtration. 2 shows the yields of four organic halides (MAI, MABr, FAI, and FABr) prepared under reflux conditions according to 1-(1)-① and 1-(1)-② described above. In addition, although not shown in FIG. 2, in the case of MAI prepared according to 1-(1)-③ and FAI prepared according to 1-(1)-④, the yields were 98% and 94.2%, respectively. It can be seen that, in all cases of this experiment, excellent yields were achieved even by a simple ion exchange reaction (a yield similar to that achieved through a conventional procedure using hydrogen halide).

With respect to the heat of reaction, the ion exchange method allows the design of safer and simpler mass production. In the case of the HX route of organic halide synthesis according to the prior art, an additional cooling system is required due to the strong exothermic nature of the acid-base reaction. In contrast, only a very slight increase in temperature is observed in the ion exchange reaction. These results reflect that the ion exchange method is highly applicable to the mass production of organic halide precursors. In addition, according to the present invention, the negligible level of corrosiveness of solid state MACl and NaX and the absence of special storage conditions for these reactants, a distinct advantage in mass production compared to the HI route of the prior art do.

Replacing water with EtOH as solvent has the advantage that the water removal step can be omitted, which simplifies the synthesis method, and the final organic halide product can be isolated directly from the reaction mixture by filtration, thereby reducing energy consumption in mass production. . However, when the ion exchange was performed in an EtOH solvent at room temperature, the reaction yield was substantially reduced compared to when water was used as the solvent (see FIG. 3 ). On the other hand, referring to FIG. 3 , the reaction yield clearly depended on the characteristics of the anion rather than the cation of the product. That is, MAI and FAI had much higher reaction rates compared to MABr and FABr, and the final yield of MAI and FAI at room temperature was ~70%, whereas the final yield of MABr and FABr was ~50%. On the other hand, the synthesis temperature strongly affects the reaction kinetics when EtOH is used as a solvent. When EtOH as a solvent is replaced with water, almost 100% reaction yield was achieved at room temperature regardless of the characteristics of the halide anion (see Fig. 3). .

2-(2). Characterization of organic halide synthesized by ion exchange method

The purity of the organic halide samples synthesized by ion exchange according to 1-(1)-① and 1-(1)-② described above ^{was confirmed with 1} H NMR spectrometer (FIG. 4). All spectra showed pure MAX and FAX without organic contaminants (eg -NH _{2 of methylamine at 2.0 ppm).}

In order to further confirm the product purity, X-ray diffraction patterns of MAI, MABr, FAI, and FABr synthesized according to 1-(1)-① and 1-(1)-② described above were obtained (FIG. 5). As can be seen from FIG. 5 , all of the diffraction peaks of the sample prepared according to the present invention were in good agreement with the diffraction peaks of MAX and FAX for reference. However, ionic salt impurities such as NaCl and NaI cannot be avoided in the ion exchange method. Therefore, elemental analysis of the sample prepared by the ion exchange reaction ^{was performed by XRF on impurity ions not detected in 1} H NMR analysis, and the results are shown in FIG. 6 . For example, a small amount of Na and Cl were detected in the as-prepared samples, and Na and Cl were not detected in all of MAI, MABr, FAI, and FABr after recrystallization using methanol.

2-(3). Characterization of Perovskite Membrane

Methylammonium lead triiodide _{(CH 3} NH _{3 PbI 3} , MAPbI ₃ ) perovskite thin film was prepared using IE-MAI synthesized according to 1-(1)-① of the present invention, and its The optical, structural, and morphological properties were investigated. _{For comparison, a MAPbI 3} membrane using commercial MAI instead of IE-MAI of the present invention was also prepared using the same manufacturing method.

Figure 7a shows the UV-Vis absorption spectrum of the perovskite film. There was no difference in optical absorption properties according to the type of MAI. Both films had exactly the same absorbance and absorption edge over the entire wavelength range. Since the two MaPbI _{3 films have the same thickness, the extinction coefficient α value of the MaPbI 3} material (α = 2.303 A/t, where A is the absorbance and t is the thickness) is the same even if the MAI source is different.

Figure 7b shows the XRD pattern of the MAPbI _{3 film.} The diffraction pattern of tetragonal perovskite ( I4/mcm ) is clearly observed for both films, indicating that the matrix of both films is MAPbI ₃ . The small peak at 12.7 ^{o is} from a small amount of PbI ₂ , which is a common residue in solvent engineering methods. It is noteworthy that the peak intensities of PbI ₂ for IE-MAPbI ₃ and CO-MAPbI ₃ are different (see Fig. 8a).

MAPbI ₃ (110) peak and 12.7 ^o PbI compared based on the intensity ratio between the _two peaks, the relative amounts of PbI ₂ in _{IE-MAPbI 3 (IE-MAPbI} 3 and CO-MAPbI ₃ 0.04 and 0.13 for a) from It is smaller than 1/3 of the amount of PbI ₂ in this CO-MAPbI _{3 .} This _{difference in the amount of PbI 2} appears to be due to the difference in the amount of chlorine in the MAI precursor. According to XRF analysis, 0.12% chlorine was detected in IE-MAI, whereas no chlorine was detected in CO-MAI. It is reported that chlorine _{promotes the formation of MAPbI 3} resulting in less _{PbI 2} extraction from the perovskite layer. When PbI ₂ is present, the efficiency of the solar cell is adversely affected, so that _{the amount of PbI 2} is small is preferable for the state of the solar cell device. Therefore, since in the XRD peak intensity data as described above, the strength of PbI ₂ of the IE-MAPbI ₃ relatively weak seems small, the amount of PbI ₂ present in the perovskite layer, whereby, page with IE-MAPbI ₃ It can be seen that the rovskite layer will provide relatively better performance than the perovskite layer using CO-MAPbI _{3 .}

Another major difference between the XRD patterns of IE-MAPbI ₃ and CO-MAPbI ₃ is the peak area and full width at half maximum (FWHM) of the _{MAPbI 3 (110) peak.} Gaussian fitting results measured from the XRD peaks are summarized in Table 1 below. The (110) peak areas obtained by Gaussian fitting _{are 0.67 and 0.45 for IE-MAPbI 3} and CO-MAPbI ₃ , respectively (see FIG. 8 and Table 1), indicating higher crystallinity of _{IE-MAPbI 3 .} In addition, the FWHM of the _{MAPbI 3 (110) peak was found to be 13.33 and 12.14 in the patterns of IE-MAPbI 3} and CO-MAPbI ₃ , respectively, according to the Scherrer equation [B = Kλ/Lcosθ, where B is the FWHM. , where K is the shape factor (close to 1 here), λ is the X-ray wavelength, θ is the Brack angle, and L is the average grain size], IE-MAPbI ₃ is more determinant than CO-MAPbI _{3 .} It indicates that the size is 10% larger.

[Table 1]

In addition, it was confirmed in the SEM image that the particle size of the _{IE-MAPbI 3 film was slightly larger.} 7c and 7d show top views of SEM images of _{IE-MAPbI 3} membrane and CO-MAPbI _{3 , respectively.} The particle sizes of IE-MAPbI ₃ and CO-MAPbI ₃ were 343 nm and 304 nm, respectively, as measured by the average particle intercept method, which was consistent with the results of XRD analysis. The high crystallinity and large particle size may be due to the presence of chlorine in the IE-MAI precursor. It is reported that incorporation of chlorine ions promotes crystallization of perovskite and accelerates grain growth.

2-(4). Characterization of Perovskite Solar Cells (PCS)

_{In order to evaluate the MAPbI 3} film based on IE-MAI, a perovskite solar cell (PCS) was prepared (IE-MAI synthesized according to 1-(1)-① described above was used). For comparison, PSCs based on CO-MAI were prepared in the same manner. Figure 9a shows the structure of the prepared mesoporous PSC (FTO substrate as a conductive transparent electrode, dense TiO ₂ (c-TiO ₂ ) and mesoporous TiO ₂ (mp-TiO ₂ ) film as an electron transport layer, photoactive It consisted of a MAPbI ₃ perovskite film as a layer, a spiro-MeOTAD film as a hole transport layer, and an Au electrode as a counter electrode). The thicknesses of the FTO, TiO ₂ , MAPbI ₃ , spiro-MeOTAD and Au films are as shown in Fig. 9b showing cross-sectional SEM images of PSCs, 600 nm, 220 nm, 430 nm, 200 nm, and 100 nm, respectively. it was

Twelve of each type of PSC (i.e., IE-PSC vs CO-PSC) were fabricated and their power conversion efficiency was measured by plotting current density-voltage (JV) curves under ^{simulated sunlight (AM 1.5G, 100 mWcm −2 ).} Recorded and inspected. 9C compares the JV curves of IE-PSC and CO-PSC. The statistical analysis results for parameters such as short circuit current density (Jsc), open circuit voltage (Voc), charge factor (FF), and power conversion efficiency (PCE) are shown in FIGS. 9D to 9G , respectively, and the results are shown in FIGS. are summarized in [Table 2] below.

[Table 2]

Both IE-PSCs exhibited excellent diode-type JV curves with relatively small hysteresis. Jsc of IE-PSC was slightly higher than that of CO-PSC. It is known that the photocurrent of PSC is mainly affected by the light absorption capacity and charge transportability of the perovskite layer. As described above, the _{absorbance of the IE-MAPbI 3} film and the CO-MAPbI ₃ film is the same. Therefore, the higher Jsc of the IE-PSC film may be due to the improvement of the charge transportability of the _{IE-MAPbI 3 film.} The IE-MAPbI ₃ film has a higher crystallinity and a larger particle size than the CO-MAPbI _{3 film.} High crystallinity and large particles will result in a larger charge conversion factor. Also, the larger the crystal size, the lower the density of grain boundaries will result in less charge trapping. Higher diffusion coefficient and longer lifetime increase diffusion length (L =

, where L is the diffusion length, D is the diffusion coefficient, and τ is the lifetime). The best devices show a fairly high PCE of >18%. The mean PCE (17.5%) of IE-PSC was the same as that of CO-PSC in the reverse scan (17.5%), and was similar with only a 0.3% difference in the forward scan. Therefore, it can be concluded that the power conversion efficiency of IE-PSC is similar to that of CO-PSC, so when the production scale of the ion exchange method for the preparation of the organic halide precursor is expanded, the perovskite solar It proves applicability to the battery industry.

conclusion

In the present invention, as an alternative to the conventional method using HI and HBr for mass production of MAI, MABr, FAI, and FABr, a simple and environmentally friendly ion exchange method was used. The process proceeded with ion exchange between NaI (or NaBr) and MACl (or FACl), and NaCl was produced as a by-product. The yield after separation for the four organic halides was 96-100%. Considering the production yield from a thermodynamic point of view, in the case of MAI, almost 100% of the reactants are converted in the ion exchange method. By recrystallizing the prepared MAI, the highest purity was possible, which was similar to that of a commercially available material.

PSCs were prepared using MAI prepared by the ion exchange method of the present invention in order to examine industrial applicability (IE-PSC). The IE-PSC exhibited similar or slightly higher PCE compared to commercial MAI-based solar cells (CO-PSC). Traces of Cl ⁻ ions were incorporated into the MAI after recrystallization, which promoted the formation of larger crystals during the coating of the perovskite layer, thereby improving the PCE.

The ion exchange method of the present invention for PSC precursor is expected to contribute substantially to the field of PSC as an industrial-scale technology.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the following claims. You will understand that you can.

Claims (10)

1. A method for preparing an organic halide for preparing perovskite, comprising the step (a) of reacting methylammonium chloride or formamidinium chloride with an alkali metal iodide or alkali metal bromide.
2. The method according to claim 1, wherein the alkali metal iodide or alkali metal bromide is sodium iodide or sodium bromide.
3. The method according to claim 1, wherein the reaction step (a) is carried out by an ion exchange reaction in a solvent.
4. The process according to claim 1, characterized in that the reaction step (a) is carried out at room temperature or under reflux in water or alcohol as a solvent.
5. The method of claim 1, further comprising the steps of (b) filtering the product of reaction step (a), and (c) removing the solvent.
6. The method according to claim 1, further comprising the step (d) of recrystallizing and removing alkali metal chloride from the resulting organic halide.
7. A perovskite prepared by using the organic halide prepared by the method of claim 1 as a precursor.
8. a first electrode;

   a second electrode opposite the first electrode; and

   A photoactive layer disposed at least partially between the first electrode and the second electrode, comprising a photoactive layer comprising a perovskite obtained by using as a precursor the organic halide prepared by the method of claim 1 . solar cells.
9. The method according to claim 8, wherein the perovskite is an organic halide prepared by the method of claim 1 and a compound of formula MX2 (X may be an iodide anion or a bromide anion, M is Pb ²⁺ , Sn ²⁺ , A solar cell obtained by reacting Ge ²⁺ and a divalent metal cation selected from the group consisting of combinations thereof.
10. The solar cell of claim 8 , further comprising an electron transport layer and a hole transport layer between the first electrode and the second electrode.

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