Tin-based perovskite microcrystal synthesis method based on NH4X regulation and control

Abstract

The invention discloses a tin-based perovskite microcrystal synthesis method based on NH4X regulation and control, and belongs to the technical field of tin-based perovskite material synthesis. According to the method disclosed by the invention, NH4X is introduced into the precursor solution for coordination regulation, so that a stable two-dimensional NH4SnX3 intermediate phase at a high temperature is formed, Sn < 2 + > oxidation is effectively inhibited, meanwhile, the problem of relatively poor solubility of SnX2 in green solvents such as alcohols and the like is solved, and the crystallization quality is improved. In the cooling process, A-site cations can replace NH4 < + >, a two-dimensional intermediate phase NH4SnX3 is converted into stable three-dimensional tin-based perovskite ASNX3 microcrystal precipitates, and NH4X can be removed through vacuum heating in the process to avoid introduction of impurities. When the method disclosed by the invention is applied to the preparation of the perovskite solar cell, the efficiency of the device is 7.55% and is obviously improved, while the efficiency of the device prepared by a traditional method without NH4X is only 1.05% and is obviously lower, which proves that the method disclosed by the invention has obvious advantages in the aspects of material quality and device performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of synthesis of tin-based perovskite materials. BACKGROUND

[0002] The basic structural formula of tin-based perovskite material is ASnX3, A is a monovalent cation, and X is a halogen or halogen-like ion. It has great application potential in the field of photovoltaics due to its narrow band gap and high carrier mobility. However, there is currently a lack of a green, efficient and simple method for synthesizing tin-based perovskite microcrystals. Specifically, 1) SnX2 has poor solubility in green solvents such as alcohols, making it difficult to fully react with organic salts, resulting in low crystallinity and many defects in the product; 2) SnX2 is easily oxidized to SnX4, further reducing the purity and performance of the product. Therefore, it is urgent to develop a new synthesis method to solve the above problems. 2+ 4+

[0003] Literature research shows that NH4 + ion, due to its strong Lewis basicity, is more easily combined with Sn 2+ than formamidinium ion (FA + ) ("Intermediate phase engineering of halide perovskites for photovoltaics." Joule 6.2 (2022): 315-339.), forming a two-dimensional (2D) intermediate phase NH4SnX3. However, this 2D structure NH4SnX3 cannot exist in a stable form at room temperature. In contrast, FASnI3 exists in a stable 3D structure at room temperature and at higher temperatures (Layered structures of organic / inorganic hybrid halide perovskites." Physical Review B 93.9 (2016): 094105). Therefore, by introducing NH4X coordination regulation, it is expected to break through the limitations of existing technology and obtain a new method for synthesizing tin-based perovskite microcrystals, improving the crystalline quality of tin-based perovskite microcrystals and the performance of devices. SUMMARY

[0004] To solve the above problems, the present application proposes a method for synthesizing tin-based perovskite microcrystals based on NH4X regulation, the specific steps of which are as follows: 1) Add raw materials NH4X, AX, and SnX2 to an organic solvent, heat and stir to dissolve to obtain a clear solution; wherein X represents one or a combination of I, Br, Cl, and SCN, and A represents formamidinium ion (FA + ), methylamine ion (MA + ​​one or more of the following: dimethylamine ion (DMA + ) and / or a combination thereof; The strong Lewis basicity of NH4X during the process of heating and stirring dissolution, preferentially forms stable and soluble two-dimensional NH4SnX3 intermediate phase with SnX2, inhibits Sn 2+ oxidation.

[0005] The reaction equation in the process is: NH4X + SnX2 = NH4SnX3 2) precipitate black precipitate by cooling the solution, remove the supernatant in an inert environment, and then remove NH4X by vacuum heating to obtain tin-based perovskite ASnX3 microcrystals.

[0006] During cooling, the A-site cation will replace NH4 + , and the two-dimensional intermediate phase NH4SnX3 is converted into stable three-dimensional tin-based perovskite ASnX3 microcrystalline precipitate.

[0007] The reaction equation in the process is: NH4SnX3 + AX = ASnX3 + NH4X Preferably, the raw materials NH4X, AX and SnX2 are weighed according to a molar ratio of 1:1:1. Further preferably, the concentration of NH4X, AX and SnX2 is 0.5 mol / L.

[0008] Preferably, the temperature of heating and stirring in step 1) is 85℃, and the time is 20 min.

[0009] Preferably, the temperature is cooled to 25℃ in step 2).

[0010] Preferably, the temperature of vacuum heating in step 2) is 80℃, and the heating time is 2 hours.

[0011] Preferably, the organic solvent is ethanol or isopropanol.

[0012] The beneficial effects of the present application are: The method of the present application introduces NH4X coordination regulation in the precursor solution, forms a stable two-dimensional NH4SnX3 intermediate phase at high temperature, effectively inhibits Sn 2+ oxidation, and at the same time solves the problem of poor solubility of SnX2 in green solvents such as alcohols, and improves the crystallization quality. During cooling, the A-site cation will replace NH4 + , and the two-dimensional intermediate phase NH4SnX3 is converted into stable three-dimensional tin-based perovskite ASnX3 microcrystalline precipitate, and this process can remove NH4X by vacuum heating to avoid introducing impurities.

[0013] When the method is applied to the preparation of perovskite solar cells, the device efficiency is 7.55%, which is significantly improved, while the device efficiency prepared by the traditional method without NH4X is only 1.05%, which is obviously lower, proving that the method has obvious advantages in material quality and device performance. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 NMR spectra of NH4I and NH4I+SnI2.

[0015] Figure 2 XRD patterns of thin films prepared from microcrystals of Comparative Example 1 and Example 1.

[0016] Figure 3 XPS patterns of thin films prepared from microcrystals of Comparative Example 1 and Example 1.

[0017] Figure 4 J-V diagrams of tin perovskite solar cells prepared from microcrystals of Comparative Example 1 and Example 1. DETAILED DESCRIPTION

[0018] The technical solutions of the present application will be further explained and described in the form of specific examples below.

[0019] Example 1: SnI2, NH4I and FAI were added to 10 mL of ethanol at a molar ratio of 1:1:1, and the concentrations of SnI2, NH4I and FAI were all 0.5 mol / L. The solution was stirred at 85°C for 20 minutes, then cooled to 25°C, and black precipitates were precipitated. In an inert environment, the supernatant was removed, and FASnI3 microcrystals were obtained after vacuum heating at 80°C for 2 hours.

[0020] Example 2: SnI2, NH4I and MAI were added to 10 mL of ethanol at a molar ratio of 1:1:1, and the concentrations of SnI2, NH4I and MAI were all 0.5 mol / L. The solution was stirred at 85°C for 20 minutes, then cooled to 25°C, and black precipitates were precipitated. In an inert environment, the supernatant was removed, and MASnI3 microcrystals were obtained after vacuum heating at 80°C for 2 hours.

[0021] Example 3: SnI2, NH4Cl and FAI were added to 10 mL of ethanol at a molar ratio of 1:1:1, and the concentrations of SnI2, NH4Cl and FAI were all 0.5 mol / L. The solution was stirred at 85°C for 20 minutes, then cooled to 25°C, and black precipitates were precipitated. In an inert environment, the supernatant was removed, and FASnI3 microcrystals were obtained after vacuum heating at 80°C for 2 hours.

[0022] Example 4: SnI2, NH4I, MAI, and FAI were added to 10 mL of ethanol at a molar ratio of 1:1:0.5:0.5. The concentrations of SnI2, NH4I, MAI, and FAI were 0.5 mol / L, 0.5 mol / L, 0.25 mol / L, and 0.25 mol / L, respectively. The mixture was stirred at 85°C for 20 minutes. After the solution was clarified, it was cooled to 25°C to precipitate a black precipitate. The supernatant was removed in an inert environment and heated at 80°C in vacuum for 2 hours to obtain MA 0.5 FA 0.5 SnI3 microcrystals.

[0023] Comparative Example 1: SnI2 and FAI were added to 10 mL of ethanol at a molar ratio of 1:1. The concentrations of SnI2 and FAI were both 0.5 mol / L. The mixture was stirred at 85°C for 20 minutes. The solution became a black suspension. The mixture was cooled to room temperature, the supernatant was removed, and FASnI3 microcrystals were obtained after vacuum heating at 80°C for 2 hours.

[0024] Characterization analysis: like Figure 1 As shown, the nuclear magnetic resonance (NMR) test results show that pure NH4 + The hydrogen spectrum in the solution is a single peak, but after adding SnI2, the hydrogen spectrum at 7.1 ppm is split into three peaks, indicating that NH4 + Coordinated with SnI2 to form NH4SnI3 intermediate phase, changing NH4 + chemical environment.

[0025] The microcrystals prepared in Example 1 and Comparative Example 1 were further subjected to X-ray diffraction (XRD) analysis (see Figure 2 ), the results show that the diffraction peak intensity of Example 1 is significantly higher than that of the control group. The peak intensity of Control Example 1 at the 14° position is only half that of Example 1, indicating that the crystallites of Example 1 have higher crystallinity. In Control Example 1, due to the direct reaction of SnI2 with FAI, the FASnI3 precipitate easily aggregates on the SnI2 surface, hindering the full reaction of SnI2. This results in poor quality of the resulting crystallites, and thus significantly weakens its XRD diffraction peak.

[0026] like Figure 3 As shown, X-ray photoelectron spectroscopy (XPS) further verified the results. The oxygen peak intensity of the sample prepared in Control Example 1 was significantly higher than that of the other examples, and Sn 4+ The shoulder peak indicates that Sn 2+ More easily oxidized. In Example 1, due to NH4 + With Sn 2+ Forming a stable coordination structure, effectively inhibiting Sn 2+The oxidation of the microcrystalline improves the purity and stability of the microcrystalline.

[0027] On this basis, two kinds of microcrystalline were used to construct ITO / PEDOT:PSS / FASnI3 / Indene-C 60 The current density-voltage (J-V) curves of the perovskite solar cells with bis-adduct (ICBA) / bathocuproine (BCP) / Ag structure were tested Figure 4 The results show that the device prepared in Example 1 has an efficiency as high as 7.55%, while the control Example 1 is only 1.05%. The above characterization results fully demonstrate that the coordination regulation strategy of NH4X has a significant advantage in improving the quality of tin-based perovskite microcrystalline and the performance of the device.

Claims

1. A method for synthesizing tin-based perovskite microcrystals based on NH4X regulation, characterized in that: The specific steps of this method are: 1) adding raw materials NH4X, AX, and SnX2 to an organic solvent, heating and stirring to dissolve to obtain a clear solution; wherein X represents a combination of one or more of I, Br, Cl, and SCN, and A represents a combination of one or more of formamidinium ion, methylamine ion, and dimethylamine ion; 2) The solution was cooled to precipitate a black precipitate, the supernatant was removed in an inert environment, and then vacuum heated to remove NH4X to obtain tin-based perovskite ASnX3 microcrystals.

2. The method for synthesizing tin-based perovskite microcrystals based on NH4X regulation according to claim 1, characterized in that: The raw materials NH4X, AX, and SnX2 were weighed in a molar ratio of 1:1:

1.

3. The method for synthesizing tin-based perovskite microcrystals based on NH4X regulation according to claim 2, characterized in that: The concentrations of NH4X, AX, and SnX2 are all 0.5 mol / L.

4. The method for synthesizing tin-based perovskite microcrystals based on NH4X regulation according to claim 1, characterized in that: The heating and stirring temperature in step 1) is 85° C. and the time is 20 min.

5. The method for synthesizing tin-based perovskite microcrystals based on NH4X regulation according to claim 1, characterized in that: In step 2), cool to 25°C.

6. The method for synthesizing tin-based perovskite microcrystals based on NH4X regulation according to claim 1, characterized in that: In step 2), the vacuum heating temperature is 80° C. and the heating time is 2 hours.

7. The method for synthesizing tin-based perovskite microcrystals based on NH4X regulation according to claim 1, characterized in that: The organic solvent is ethanol or isopropanol.

Images