Green synthesis method of perovskite crystal powder

Abstract

The invention discloses a green synthesis method of perovskite crystal powder. The preparation method comprises the following specific steps: mixing methylamine, formamidine acetate or cesium acetate as a raw material with HX according to a molar ratio of 1: (1-1.8), and reacting for 2-8 hours to generate AX molecules, X being selected from Cl <->, Br <-> or I <->; purifying the AX molecules by recrystallization; in cyclopentyl methyl ether, AX molecules and BX2 molecules are mixed to react, B is selected from Pb < 2 + > or Sn < 2 + >, and the molar ratio of the AX molecules to the BX2 molecules is (1-1.8): 1; and precipitating an ABX3 product by using ethyl acetate as an anti-solvent, and drying at 70-95 DEG C for 18-24 hours. According to the synthesis method, the pollution risk of a toxic solvent to air, soil and water resources is remarkably reduced, the high environment-friendly characteristic is reflected, and meanwhile sustainable utilization of resources is promoted.

Description

Technical Field

[0001] This invention belongs to the field of crystal chemical synthesis technology, specifically relating to a green synthesis method for perovskite crystal powder. Background Technology

[0002] Perovskite material (ABX3, where A stands for MA) + FA + or Cs + Equal monovalent cations, B is Pb 2+ or Sn 2+ Equal divalent metal cations, X is Cl - ,Br - Or I - Perovskite anions (PAOs) have attracted significant attention in materials science due to their unique photoelectric properties. These materials possess advantages such as high light absorption coefficients, tunable band gaps, long carrier diffusion lengths, and high charge mobility, making them highly promising for applications such as high-efficiency solar cells, light-emitting diodes (LEDs), photodetectors, and lasers. In recent years, the power conversion efficiency of perovskite solar cells has increased from 3.8% in 2009 to over 25%, approaching the performance of traditional silicon-based solar cells, demonstrating their commercial potential in the renewable energy sector.

[0003] However, traditional methods for preparing perovskite crystals present significant technical and environmental challenges. First, conventional synthesis processes typically rely on highly toxic organic solvents such as dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or chlorobenzene. These solvents pose serious threats to the environment and human health during production, storage, and wastewater treatment. For example, DMF is classified as a potential carcinogen, its high volatility can lead to air pollution, and its water solubility increases the risk of water pollution. DMSO's high boiling point (approximately 189°C) makes solvent removal energy-intensive and can potentially trigger thermal decomposition of the crystal structure. Furthermore, these solvents have poor biodegradability, and wastewater treatment requires complex processes and costly facilities, limiting the sustainability of the process.

[0004] Secondly, traditional methods have shortcomings in stoichiometric control. The photoelectric properties of perovskite crystals are highly dependent on the integrity of their chemical composition and crystal structure. However, traditional direct mixing or solution methods often lead to the formation of non-stoichiometric phases or impurities due to fluctuations in raw material purity, reaction conditions, or inhomogeneities in solvent-precursor interactions. For example, excessive halides or metal oxides may be doped into the crystal, reducing photoelectric efficiency and affecting device stability. Furthermore, traditional processes require precise control of reaction conditions, such as temperature, humidity, and solvent evaporation rate, increasing production complexity and cost.

[0005] Furthermore, while the high polarity of traditional solvents (such as DMF and DMSO) is beneficial for precursor dissolution, their high boiling points and strong coordination abilities can trigger side reactions during crystal nucleation and growth, leading to crystal defects or the formation of non-perovskite phases. Some improved methods attempt to optimize crystal quality through co-solvents, additives, or complex post-treatments (such as annealing), but these measures often sacrifice process simplicity and economy. In addition, large-scale production using traditional methods faces strict environmental regulations; solvent toxicity and wastewater treatment issues make industrial applications costly.

[0006] In recent years, the concept of green chemistry has driven the development of low-toxicity, sustainable solvents. Cyclopentyl methyl ether (CPME), as a novel green solvent, possesses advantages such as low toxicity (non-carcinogenic), a moderate boiling point (approximately 106 °C), high chemical stability, and good biodegradability. CPME has shown potential to replace traditional highly toxic solvents in organic synthesis, pharmaceutical preparation, and materials science. Its hydrophobicity helps reduce moisture interference in the reaction system, thereby improving the stability and quality of perovskite crystals. Furthermore, CPME exhibits excellent solubility for a variety of chemical precursors, and its moderate volatility facilitates removal during the drying process after crystal preparation, reducing energy consumption. However, systematic research on the application of CPME in perovskite crystal powder preparation is still limited, especially in achieving high stoichiometric accuracy and industrial scalability, which requires further exploration.

[0007] This invention addresses the shortcomings of traditional methods by proposing a method for synthesizing perovskite crystal powder using CPME as a green solvent. The aim is to achieve efficient, environmentally friendly, and low-cost production while ensuring high purity and excellent photoelectric properties of the crystals, thus providing technical support for the widespread application of perovskite materials in the global energy transition. Summary of the Invention

[0008] To address the limitations of current technologies, this invention proposes a green synthesis method for perovskite crystal powder, solving one or more technical problems existing in the prior art and providing at least one beneficial alternative or creating favorable conditions. The method provided by this invention is cost-effective, environmentally friendly, and effectively avoids potential non-stoichiometric ratios and the appearance of non-perovskite phase substances during the preparation process. Therefore, this invention provides a practical and feasible means for the efficient and high-quality preparation of perovskite crystal powder, possessing significant practical application value.

[0009] The green synthesis method provided by the first aspect of this invention includes the following steps: (1) In cyclopentylmethyl ether, methylamine (MA, CAS: 74-89-5), formamidine acetate (FAI, CAS: 3473-63-0), or cesium acetate (CsI, CAS: 3396-11-0) are mixed with HX in a molar ratio of 1:1 to 1.8 and reacted for 2 to 8 hours to generate AX molecules, wherein X is selected from Cl - ,Br - Or I - ; (2) Purification of AX molecules by recrystallization; (3) In cyclopentylmethyl ether (CPME), AX molecules and BX2 molecules are mixed and reacted, where B is selected from Pb. 2+ or Sn 2+ The molar ratio of the AX molecule to the BX2 molecule is 1~1.8:1; (4) Use ethyl acetate (EA) as an antisolvent to precipitate the ABX3 product and dry it at 70~95°C for 18~24 hours.

[0010] The present invention has the following beneficial effects: I. The green synthesis method described uses low-toxicity, biodegradable CPME as a solvent to replace traditional highly toxic solvents (such as DMF and DMSO), significantly reducing the risk of pollution to air, soil, and water resources during the production process. Waste liquid is recovered through distillation, with a solvent recovery rate of over 90%, which is in line with the concept of green chemistry.

[0011] II. By precisely controlling the precursor ratio (molar ratio of AX to BX2 is 1~1.8:1) and reaction conditions (temperature 70~95℃, inert gas protection), the generation of non-stoichiometric phases and impurities is effectively avoided, resulting in crystal purity of over 99%, uniform crystal structure, and regular morphology.

[0012] III. The synthesized perovskite crystals have high crystallinity and low defect density, significantly improving the light absorption coefficient and charge mobility. They can be used in high-efficiency solar cells (power conversion efficiency can reach over 20%), light-emitting diodes (external quantum efficiency improved by 10%), photodetectors and lasers, etc., with an expected extension of device lifespan of 20-30%, providing high-performance materials for the renewable energy and optoelectronic industries.

[0013] IV. CPME is reasonably priced, has a moderate boiling point (approximately 106°C), low drying energy consumption, a simple process that requires no complex post-processing, and is suitable for laboratory and industrial production. Its production cost is 15-20% lower than that of traditional methods.

[0014] V. By optimizing parameters such as reaction temperature, stirring rate, and antisolvent addition rate, controllability of crystal particle size (100nm to 10μm) and morphology was achieved, the process has high repeatability, and it is suitable for large-scale production.

[0015] According to some embodiments of the present invention, the AX molecule includes at least one selected from methylamine iodide (MAI, CAS: 14965-49-2), formamidine iodide (FAI, CAS: 879643-71-7), cesium iodide (CsI, CAS: 7789-17-5), methylamine bromide (MABr, CAS: 6876-37-5), formamidine bromide (FABr, CAS: 146958-06-7), cesium bromide (CsBr, CAS: 7787-69-1), methylamine chloride (MACl, CAS: 593-51-1), formamidine chloride (FACl, CAS: 6313-33-3), and cesium chloride (CsCl, CAS: 7647-17-8).

[0016] According to some embodiments of the present invention, the BX2 molecule is selected from at least one of lead iodide (PbI2, CAS: 10101-63-0), lead bromide (PbBr2, CAS: 10031-22-8), lead chloride (PbCl2, CAS: 7758-95-4), tin iodide (SnI2, CAS: 10294-70-9), tin bromide (SnBr2, CAS: 10031-24-0), and tin chloride (SnCl2, CAS: 7772-99-8).

[0017] According to some embodiments of the present invention, the reaction in step (1) is carried out under ice bath conditions.

[0018] According to some embodiments of the present invention, the reaction in step (1) uses ethanol as a stabilizer.

[0019] According to some embodiments of the present invention, the mixing reaction conditions in step (3) are room temperature or 70°C oil bath.

[0020] According to some embodiments of the present invention, the molar ratio of the CPME to the BX2 molecules is ≥4:1.

[0021] According to some embodiments of the present invention, the mixing reaction time is 16 to 26 hours.

[0022] According to some embodiments of the present invention, step (4) further includes solid-liquid separation and purification of the product in sequence before drying.

[0023] According to some embodiments of the present invention, the solid-liquid separation includes at least one of conventional filtration, pressure filtration, and vacuum filtration.

[0024] The synthesized perovskite crystal powder can be used in solar cells, light-emitting diodes, or photodetectors. Attached Figure Description

[0025] Figure 1 This is the XRD pattern of the perovskite crystal powder obtained in Example 1 of this invention; Figure 2 This is a SEM image of the perovskite crystal powder obtained in Example 1 of this invention; Figure 3 This is the XRD pattern of the perovskite crystal powder obtained in Example 2 of the present invention; Figure 4 This is a SEM image of the perovskite crystal powder obtained in Example 2 of the present invention; Figure 5 This is the XRD pattern of the perovskite crystal powder obtained in Example 3 of the present invention; Figure 6 This is a SEM image of the perovskite crystal powder obtained in Example 3 of the present invention; Figure 7 This is the XRD pattern of the perovskite crystal powder obtained in Comparative Example 1 of this invention; Figure 8 This is a SEM image of the perovskite crystal powder obtained in Comparative Example 1 of this invention. Figure 9 This is a JV curve diagram of the perovskite solar cells prepared from the perovskite crystal powder obtained in Examples 1-3 of this invention. Detailed Implementation

[0026] In the description of this invention, the use of terms such as "first," "second," etc., is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated.

[0027] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0028] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present invention.

[0030] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0031] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0032] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0033] It should be noted that the ice bath in the synthesis method of this invention refers to an ice-water mixture, i.e., ≤0℃.

[0034] Unless otherwise specified, the specific implementation method is as follows: Methylamine (MA) was purchased from Aladdin as a 30-33 wt% ethanol solution with a concentration of ρ = 0.785 g / mL. Formamidin acetate (FAAc) was purchased from Maclean's Reagent Network with a purity of 99 wt%. Cesium acetate (CsAc) was purchased from Maclean's Reagents website with a purity of 99 wt%. Hydroiodic acid (HI) was purchased from Merrill as an aqueous solution with a purity of 55-58 wt% and a density of ρ = 1.74 g / mL. Anhydrous diethyl ether (Et2O) was purchased from Shanghai Lingfeng, with a purity of ≥99.7 wt%. Lead iodide (PbI2) is available in low-purity and high-purity versions. The low-purity version was purchased from Aladdin with a purity of 98 wt%, while the high-purity version was purchased from THIAI with a purity of 99.99 wt%. Cyclopentyl methyl ether (CPME) was purchased from Bid Pharmaceuticals and had a purity of 99.95 wt%. Ethyl acetate (EA) was purchased from Anengji and had a purity of 99.5 wt%. Formamidinium iodide (FAI) was purchased from Greatcell Solar with a purity of 99.999 wt%.

[0035] Example 1 This embodiment synthesizes a perovskite crystal powder. The specific synthesis method includes the following steps: S1. Add 0.38 mol HI to a 100 mL round-bottom flask, add 16 mL of anhydrous ethanol dropwise to the round-bottom flask, then slowly add 0.25 mol MA, and react in an ice bath for 2 hours. S2. After rotary evaporation of the above product, recrystallize it after cooling in an oil bath, and then purify it with anhydrous diethyl ether 15 times; repeat the recrystallization and purification process 3 times. S3. Use a dropper to transfer the sample from the round-bottom flask to a sample vial, place it in a vacuum oven to dry at room temperature, and obtain MAI after 24 hours. Then transfer the sample to a vacuum glove box for storage. S4. Place a 250 mL round-bottom flask in an oil bath at 70°C, add 0.18 mol of PbI2 to the round-bottom flask, then add 1.358 mol of CPME dropwise, and then slowly add 0.21 mol of MAI prepared in step S3. Continue the reaction for 24 hours. S5. Use a dropper to transfer the sample from the round-bottom flask to the filter cup of the assembled vacuum filtration apparatus. A PTFE filtration membrane with a pore size of 0.22 μm is used for vacuum filtration at room temperature. Use a dropper to take 30 mL of ethyl acetate and quickly drip it around the wall of the filter cup. Continue vacuum filtration and repeat this operation 6 times until the clear liquid is clear. S6. Collect the powder sample into a 100 mL sample bottle, dry it in a vacuum oven at 40 °C, and transfer the sample to a vacuum glove box for storage after 24 h.

[0036] Example 2, Example 3 Examples 2 and 3 respectively synthesized a perovskite crystal powder. The specific synthesis methods differed from those in Example 1 as follows: In Examples 2 and 3, step S4 reaction conditions were at room temperature; and the types of raw materials and products were different, with specific compositions shown in Tables 1 and 2.

[0037] Table 1. Raw materials and [A] site molecular products used in Examples 1-3

[0038] Table 2. Raw materials and perovskite crystal powder products in Examples 1-3

[0039] Comparative Example 1 This comparative example prepared a perovskite crystal powder by a mixing reaction in an acetonitrile system. The specific steps were the same as in Example 2, except that the reaction system was replaced with acetonitrile. The perovskite crystal powder was prepared in this way. δ -FAPbI3.

[0040] Comparative Example 2 This comparative example prepared a perovskite crystal powder. High-purity PbI2 and FAI raw materials were mixed and reacted in a PC system to obtain the perovskite crystal powder. The specific steps were the same as S4-S6 in Example 2. The powder was prepared in this way. δ -FAPbI3.

[0041] Comparative Example 3 A perovskite single crystal was prepared in this comparative example. The preparation process is as follows: (1) Weigh 0.12 g FAI and 0.32 g PbI2, dissolve them in 2 mL CPME, and sonicate for 10 minutes and stir for 30 minutes to obtain a clear solution of 0.9 mol / L FAPbI3 perovskite precursor.

[0042] (2) The precursor solution was placed in a microwave reactor and heated in a gradient at 250 W: 70℃, 80℃, and 90℃ for 5 minutes each, 100℃ for 10 minutes, and finally 110℃ for 5 minutes. After the reaction was completed, yellow microcrystals precipitated in the solution, and after filtration and washing, α-FAPbI3 perovskite single crystals were obtained.

[0043] Comparative Example 4 This comparative example prepared a perovskite crystal powder by mixing and reacting it in a toxic solvent acetonitrile system. The specific steps were the same as in Example 1, except that the reaction system was replaced with acetonitrile. MAPbI3 was thus prepared.

[0044] Comparative Example 5: This comparative example prepared a perovskite crystal powder by mixing and reacting it in a green solvent dimethyl carbonate system. The specific steps were the same as in Example 1, except that the reaction system was replaced with dimethyl carbonate. MAPbI3 was thus prepared.

[0045] Table 3. Partial synthesis process parameters and product properties of Examples 1-3 and Comparative Examples 1-5

[0046] Analysis of the data in Table 3 shows that this invention significantly improves the yield of perovskite by optimizing the synthesis method of perovskite crystal powder. Comparison of the products from Example 2 with those from Comparative Examples 1-3 reveals that the perovskite crystals prepared using the green solvent exhibit a bright yellow color and extremely high powder purity, with no PbI2 residue.

[0047] The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses together indicated the specific type of perovskite, particularly identifying it through XRD patterns. Specifically: The XRD pattern of the product obtained in Example 1 is highly consistent with the standard pattern of MAPbI3, exhibiting tetragonal crystal characteristics, and no obvious impurity peaks are observed in the pattern, indicating that the product of Example 1 is high-purity MAPbI3. Furthermore, the SEM image of the perovskite from Example 1 further verifies its high crystallinity, clear preferred orientation, accurate stoichiometry, and good phase distribution and structural arrangement. The XRD pattern and SEM image of Example 1 are shown below. Figures 1 to 2 As shown.

[0048] like Figures 3 to 4 As shown, the XRD and SEM images of the perovskite obtained in Example 2 are similar to those in Example 1, proving that the product is high-purity δ-FAPbI3 and exhibits hexagonal crystal characteristics; while the XRD and SEM images of the product obtained in Example 3 (as shown) Figures 5 to 6 As shown in the figure, it is high-purity γ-CsPbI3 with orthorhombic crystal system characteristics.

[0049] In contrast, the XRD and SEM images of the perovskite obtained in Comparative Example 1 (such as...) Figures 7 to 8 The XRD pattern (shown) reveals that the purity of δ-FAPbI3 is low, and a small amount of PbI2 residue can be seen in the XRD pattern. The main product has a hexagonal crystal structure.

[0050] Example 4 Inverted (pin) perovskite solar cells were prepared using the perovskite crystal powders obtained in Example 1 and Comparative Example 5 as control experiments.

[0051] Device configuration: ITO / 4-PACz / perovskite / C 60 / BCP / Cu (1) The product synthesized in Example 2 δ FA was prepared by mixing -FAPbI3, MAPbI3 synthesized in Example 1, and γ-CsPbI3 synthesized in Example 3 in a ratio of 0.85:0.1:0.05. 0.85 MA 0.1 Cs 0.05 PbI3 crystal powder was mixed with 10% MACl as an additive to prepare a perovskite precursor solution. The sample was ultrasonically cleaned with deionized water and isopropanol (IPA) respectively. The resistance was 10 Ω / sq. The dimensions were 1.5 × 1.5 cm. 2 Dry the indium tin oxide (ITO) glass for 20 minutes. Then clean the glass substrate with UV-ozone for 20 minutes. 4-PACz was dissolved in IPA solvent to prepare a hole transport layer solution of 0.3 mg / mL. 40 μL of this solution was used to spin-deposit the film at 5000 rpm for 60 seconds, followed by annealing at 100 °C to obtain the hole transport layer. The perovskite solution was spin-coated onto the substrate at 5000 rpm for 60 seconds. At the 12th second of the spin-coating process, 150 μL of the anti-solvent chlorobenzene (CB) was added dropwise, followed by annealing at 100°C for 30 minutes. Surface passivation was performed using a choline chloride (CC) solution (CC dissolved in IPA to prepare a passivating agent with a concentration of 1 mg / mL), followed by annealing at 100°C for 5 minutes. At a vacuum pressure of 4×10 −5 Under torr conditions, C is subjected to a rate of 0.3 Å / s. 60 Electron transport layer was obtained by thermal evaporation deposition of 30 nm ethylene and pentadiene (8 nm) onto a substrate; A metal cathode was prepared by thermally evaporating copper (100 nm) onto a substrate at a rate of 0.5 Å / s.

[0052] The JV curve of the fabricated inverse perovskite solar cell is as follows: Figure 9 As shown, FA 0.85 MA 0.1 Cs 0.05 The PbI3 perovskite device has an open-circuit voltage of 1.189 V and a short-circuit current density of 25.82 mA / cm². 2 The fill factor is 84.94%, and the photoelectric energy conversion efficiency is 25.82%.

[0053] (2) The product synthesized in Example 2 δ FA was prepared by mixing -FAPbI3, MAPbI3 synthesized in Comparative Example 5, and γ-CsPbI3 synthesized in Example 3 in a ratio of 0.85:0.1:0.05. 0.85 MA 0.1 Cs 0.05 A perovskite precursor solution was prepared by adding 10% MACl as an additive to PbI3 crystal powder. The device fabricated using this method exhibited an open-circuit voltage of 1.182 V and a short-circuit current density of 24.86 mA / cm². 2 The fill factor is 84.64%, and the photoelectric energy conversion efficiency is 23.66%.

[0054] The performance comparison of the two groups of perovskite solar cells shows that the performance of perovskite crystal devices prepared with green solvent DMC is significantly lower than that of perovskite crystal devices prepared with green solvent CPME.

[0055] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A green synthesis method for perovskite crystal powder, characterized in that, Including the following steps: (1) Using methylamine, formamidine acetate, or cesium acetate as raw materials, mix with HX at a molar ratio of 1:1 to 1.8 and react for 2 to 8 hours to generate AX molecules, wherein X is selected from Cl - ,Br - Or I - ; (2) Purification of AX molecules by recrystallization; (3) In cyclopentylmethyl ether, AX molecules and BX2 molecules are mixed and reacted, where B is selected from Pb. 2+ or Sn 2+ The molar ratio of the AX molecule to the BX2 molecule is 1~1.8:1; (4) Use ethyl acetate as an antisolvent to precipitate the ABX3 product and dry it at 70~95°C for 18~24 hours.

2. The green synthesis method according to claim 1, characterized in that, The AX molecule is methylamine iodide, formamidine iodide, cesium iodide, methylamine bromide, formamidine bromide, cesium bromide, methylamine chloride, formamidine chloride, or cesium chloride.

3. The synthesis method according to claim 1, characterized in that, The BX2 molecule is selected from at least one of lead iodide, lead bromide, lead chloride, tin iodide, tin bromide, and tin chloride.

4. The green synthesis method according to claim 1, characterized in that, The reaction in step (1) was carried out under ice bath conditions.

5. The green synthesis method according to claim 1, characterized in that, The reaction in step (1) uses ethanol as a stabilizer.

6. The green synthesis method according to claim 1, characterized in that, The mixing reaction conditions in step (3) are room temperature or 70°C oil bath.

7. The green synthesis method according to claim 1, characterized in that, The molar ratio of the cyclopentylmethyl ether to the BX2 molecule is ≥4:

1.

8. The green synthesis method according to claim 1, characterized in that, The mixing reaction time is 16-26 hours.

9. The green synthesis method according to claim 1, characterized in that, Step (4) before drying also includes solid-liquid separation and purification of the product in sequence.

10. The green synthesis method according to claim 9, characterized in that, The solid-liquid separation includes at least one of conventional filtration, pressure filtration, and vacuum filtration.

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