阅读说明：本技术 一种微波法高效制备钙钛矿微晶的方法 (Method for efficiently preparing perovskite microcrystal by microwave method ) 是由 匡代彬 钟均星 吴武强 于 2021-07-07 设计创作，主要内容包括：本发明涉及钙钛矿材料领域,公开了一种微波法高效制备钙钛矿微晶的方法,所述钙钛矿微晶的化学通式为MA-(X)FA-(1－X)PbI-(3),其制备方法包括：(1)按照目标产物各元素之间的摩尔质量比称取有机组分和无机组分,并将有机组分和无机组分溶解于碳酸丙烯酯中,即得钙钛矿前驱体溶液；(2)采用微波法加热钙钛矿前驱体溶液,控制加热温度为70～130℃,加热时长为10～30min；(3)反应完全后析出黑色微晶,经过滤洗涤之后得到钙钛矿微晶。本发明采用微波法和合适的钙钛矿前驱体溶剂,可快速、均匀、低能耗地使钙钛矿前驱体溶液内外部同时加热、同时升温,均匀析晶,保证晶体的质量,提高产率。(The invention relates to the field of perovskite materials, and discloses a method for efficiently preparing perovskite microcrystal by a microwave method, wherein the chemical general formula of the perovskite microcrystal is MA X FA 1－X PbI 3 The preparation method comprises the following steps: (1) weighing an organic component and an inorganic component according to the molar mass ratio of elements of a target product, and dissolving the organic component and the inorganic component in propylene carbonate to obtain a perovskite precursor solution; (2) heating the perovskite precursor solution by a microwave method, controlling the heating temperature to be 70-130 ℃, and heating for 10-30 min; (3) and precipitating black microcrystals after the reaction is completed, and filtering and washing to obtain the perovskite microcrystals. The invention adopts a microwave method and a proper perovskite precursor solvent, can quickly, uniformly and simultaneously heat the inside and the outside of the perovskite precursor solution with low energy consumption and simultaneously raise the temperatureUniform crystallization, ensured crystal quality and improved yield.)

1. The method for efficiently preparing the perovskite microcrystal by the microwave method is characterized by comprising the following steps:

(1) weighing an organic component and an inorganic component according to the molar mass ratio of elements of a target product, and dissolving the organic component and the inorganic component in propylene carbonate to obtain a perovskite precursor solution;

(2) heating the perovskite precursor solution by a microwave method, controlling the microwave heating temperature to be 70-130 ℃, and controlling the microwave heating time to be 10-30 min;

(3) and after the reaction is completed, separating out black microcrystals from the perovskite precursor solution, and filtering and washing the black microcrystals to obtain crystals with metallic luster, wherein the crystals are the perovskite microcrystals.

2. The microwave method for efficiently preparing perovskite microcrystals according to claim 1, wherein in the step (2), when the perovskite precursor solution is heated by the microwave method, the heating temperature is controlled by gradient heating.

3. The method for efficiently preparing perovskite microcrystals by using the microwave method according to claim 2, wherein the gradient heating manner comprises heating at 70 ℃ for 5min, heating at 80 ℃ for 5min, heating to 90 ℃ for 5min, heating to 100 ℃ for 10min, and heating to 110 ℃ for 5 min.

4. The microwave process for efficiently preparing perovskite microcrystals according to claim 1, wherein in the step (1), the organic component is MAI and/or FAI, wherein MA represents CH₃NH₃ ⁺FA represents HC (NH)₂)₂ ⁺The inorganic component is PbI₂；

In the step (3), the chemical general formula of the perovskite microcrystal is MA_XFA_1－XPbI₃。

5. The method for microwave-efficient preparation of perovskite microcrystals as claimed in claim 4, wherein in step (1), the organic component and the inorganic component are weighed according to the molar mass ratio between the elements of the target product, wherein the sum of the molar masses of MAI and/or FAI and PbI₂The molar mass ratio of (1): 1.

6. the microwave process for efficiently preparing perovskite microcrystals according to claim 4, wherein in the step (1), MAI and/or FAI and PbI are added₂Dissolving in propylene carbonate, performing ultrasonic treatment for 10-20 min, and continuously stirring for 30-40 min to obtain a clear solution, wherein the clear solution is a perovskite precursor solution.

7. The method for efficiently preparing perovskite microcrystals by using the microwave method according to claim 1, wherein in the step (2), the microwave heating temperature is 100-110 ℃, and the microwave heating time is 10-15 min.

8. The microwave method for efficiently preparing perovskite microcrystals according to claim 1, wherein in the step (1), the concentration of the perovskite precursor solution is 0.4 mol/L-0.5 mol/L.

9. A perovskite microcrystal is characterized in that the general formula of the perovskite microcrystal is MA_XFA_1－XPbI₃Wherein MA represents CH₃NH₃ ⁺FA represents HC (NH)₂)₂ ⁺The perovskite microcrystal is prepared by the method for efficiently preparing the perovskite microcrystal by the microwave method according to any one of claims 1 to 8.

10. Optoelectronic use of a perovskite crystallite of claim 9 for the production of a perovskite solar cell.

Technical Field

The invention relates to the field of perovskite materials, in particular to a method for efficiently preparing perovskite microcrystal by a microwave method and photoelectric application of the perovskite microcrystal.

Background

In recent years, organic-inorganic metal halide perovskite materials have been widely used in various photovoltaic fields, especially in the field of perovskite solar cells, due to excellent semiconductor properties such as strong light absorption capability, adjustable band gap, high carrier mobility, and long carrier diffusion distance. At present, the record of the highest authentication efficiency of the perovskite solar cell is up to 25.5%, and the perovskite solar cell can be comparable to the traditional crystalline silicon cell. Therefore, perovskite solar cells are considered as one of the most promising new photovoltaic power generation products.

With the rapid development of perovskite solar cells, the biggest challenge facing the realization of commercialization process in the future is how to realize the transformation from small-area devices on a laboratory scale to large-area devices that can meet market demands. Large scale production of perovskite solar cells requires a high purity, stable supply of perovskite raw materials as a basis. At present, high-efficiency perovskite solar cells basically depend on high-purity raw materials, such as lead iodide, lead bromide, methylamine iodide, formamidine iodide and the like, and are very sensitive to material production brands, batches and solubility. Secondly, perovskite thin films prepared from the raw materials are generally inaccurate in stoichiometric ratio and poor in uniformity, and the thin films are high in impurity and lattice defects, so that the performance of devices is poor. More importantly, the high purity perovskite raw material has high cost, which can increase the device preparation cost. In addition, the material has poor stability, is sensitive to humidity, is easy to absorb moisture, also seriously shortens the quality guarantee period of the material, and has more rigorous storage or preparation conditions. Therefore, how to break through the limitation of the traditional process and realize the high-quality perovskite raw material which has low cost and high quality and can be stably prepared in batches is the key for promoting the commercialization of the perovskite solar cell.

Compared with perovskite polycrystalline materials, the perovskite single crystal has the advantages of high purity, lower defect density, long carrier diffusion distance, high mobility, long carrier service life and stable chemical properties. Various perovskite-based photoelectric devices can be prepared by directly utilizing perovskite single crystals, and better photoelectric properties can be obtained. Particularly, the perovskite crystal is re-dissolved, a precursor solution with more stable chemical property can be obtained, and the prepared perovskite film has accurate stoichiometric ratio, good uniformity and low defect density. More importantly, the process for obtaining the high-purity perovskite microcrystal by primarily purifying and crystallizing the raw materials with low price and low purity can reduce the manufacturing cost of the perovskite solar cell. Therefore, realization of a crystal material having high crystallinity, high purity, and being capable of stably mass-producing various perovskite components is equivalent to one of core technologies grasping development in this field.

Currently, there are three main methods for preparing perovskite crystals: cooling crystallization of water solution, solvent vapor resistant auxiliary crystallization and temperature raising crystallization. The water solution cooling crystallization method has certain universality, and mainly utilizes the characteristic that the solubility of a perovskite material in a hydrogen halide water solution is reduced along with the reduction of temperature, and the crystal growth is regulated and controlled by controlling the cooling speed. However, the perovskite crystal obtained by cooling crystallization is generally small in size and has high requirement on temperature control. Due to long-time heating and temperature control, the ordered growth of crystals can be influenced by solution convection, and more impurities can be on the surface. The anti-solvent steam auxiliary crystallization method is characterized in that an anti-solvent is slowly volatilized into a perovskite precursor solution in a closed environment, so that the solubility of the anti-solvent is gradually reduced, and then crystals are slowly separated out. The method usually needs a long time to volatilize and permeate the solvent, and the selected anti-solvent is dichloromethane, chlorobenzene, toluene, dichlorobenzene and the like, and has high toxicity. Neither of the above two methods is an ideal perovskite crystal synthesis method. The temperature-rising crystallization method utilizes the fact that the solubility of perovskite in a specific solvent decreases with the increase in temperature, thereby precipitating crystals. Usually, only 50-100 ℃ is needed to heat to precipitate crystals. The crystallization method has the advantages of short time consumption, simple process and larger size of the obtained crystal. However, since the heating method of the temperature-increasing crystal is heat conduction, heat is transferred from the outside to the inside of the object, and the object is heated from the front to the back with a gradient, it is inevitable that the inside of the object is heated unevenly, the temperature gradient is poor, and local overheating may occur. The crystals thus precipitated are not uniform, resulting in large differences in the quality of the crystals.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for efficiently preparing perovskite microcrystals by a microwave method and photoelectric application of the perovskite microcrystals.

In order to achieve the above object, a first aspect of the present invention provides a method for efficiently preparing perovskite crystallites by a microwave method, the method comprising the steps of:

(1) weighing an organic component and an inorganic component according to the molar mass ratio of elements of a target product, and dissolving the organic component and the inorganic component in propylene carbonate to obtain a perovskite precursor solution;

(2) heating the perovskite precursor solution by a microwave method, controlling the microwave heating temperature to be 70-130 ℃, and controlling the microwave heating time to be 10-30 min;

(3) and after the reaction is completed, separating out black microcrystals from the perovskite precursor solution, and filtering and washing the black microcrystals to obtain crystals with metallic luster, wherein the crystals are the perovskite microcrystals.

By adopting the scheme, the Propylene Carbonate (PC) solution with weaker coordination capacity is used as the solvent, and the propylene carbonate solvent has less donor number, is difficult to coordinate with metal ions in the perovskite precursor solution, has low crystallization temperature, is easy to crystallize and precipitate, better protects the crystal surface from being etched by mother liquor, keeps the crystal to have better metal luster, and is vital to the quality and quality of the perovskite microcrystal. In addition, the perovskite precursor solution is heated by a microwave method, dipole molecules in a heating body reciprocate in a high frequency mode under the microwave irradiation to generate 'internal friction heat', so that the temperature of the heated material is increased, and the heating mode can heat and raise the temperature of the interior and the exterior of the perovskite precursor solution simultaneously quickly, uniformly and with low energy consumption, so that crystals are uniformly precipitated; meanwhile, the microwave heating temperature is controlled to be 70-130 ℃, the heating time is 10-30 min, the crystallization degree of the precipitated black microcrystal is high, and the yield is high.

As a further improvement of the above scheme, in the step (2), when the perovskite precursor solution is heated by the microwave method, the heating temperature is controlled by gradient heating.

As a further improvement of the scheme, the gradient temperature rise heating mode is that the temperature is firstly heated at 70 ℃ for 5min, then heated at 80 ℃ for 5min, then heated to 90 ℃ for 5min, then heated to 100 ℃ for 10min, and finally heated to 110 ℃ for 5 min.

By adopting the scheme, in order to further improve the quality of the prepared perovskite microcrystal, the nucleation number is reduced by gradient temperature control, so that the size of the crystal is larger, and the perovskite microcrystal with higher crystallinity is obtained.

As a further improvement of the above scheme, in the step (1), the organic component is MAI and/or FAI, wherein MA represents CH₃NH₃ ⁺FA represents HC (NH)₂)₂ ⁺The inorganic component is PbI₂；

In the step (3), the chemical general formula of the perovskite microcrystal is MA_XFA_1－XPbI₃。

As a further improvement of the above scheme, in the step (1), the organic component and the inorganic component are weighed according to the molar mass ratio among the elements of the target product, wherein the sum of the molar masses of MAI and/or FAI and PbI₂The molar mass ratio of (1): 1.

by adopting the scheme, the method for heating the perovskite precursor solution by the microwave method has universality, and high-quality perovskite microcrystals with different components can be efficiently prepared by adjusting the molar mass of each component in the perovskite precursor solution.

As a further improvement of the above scheme, in the step (1), MAI and/or FAI and PbI are/is added₂Dissolving in propylene carbonate, performing ultrasonic treatment for 10-20 min, and continuously stirring for 30-40 min to obtain a clear solution, wherein the clear solution is a perovskite precursor solution.

As a further improvement of the scheme, in the step (2), the heating temperature is 100-110 ℃, and the heating time is 10-15 min.

As a further improvement of the scheme, in the step (1), the concentration of the perovskite precursor solution is 0.4 mol/L-0.5 mol/L.

By adopting the above-described scheme, the inventors found that another factor determining the yield, in addition to the microwave temperature, is the concentration of the perovskite precursor solution. If the concentration of the perovskite precursor solution is too low to reach a saturated state, no product is precipitated, so that the concentration of the perovskite precursor solution is selected to be 0.4-0.5 mol/L, preferably 0.45mol/L, the perovskite precursor solution can be ensured to reach a supersaturated state, and a high yield is ensured.

In a second aspect, the present invention provides a perovskite crystallite of the general formula MA_XFA_1－XPbI₃Wherein MA represents CH₃NH₃ ⁺FA represents HC (NH)₂)₂ ⁺The perovskite microcrystal is prepared by the method for efficiently preparing the perovskite microcrystal by using the microwave method.

A third aspect of the invention is to provide a photovoltaic application of perovskite crystallites for the preparation of perovskite solar cells.

Compared with the prior art, the invention has the beneficial effects that:

1. the perovskite microcrystal is prepared by combining the propylene carbonate solvent with the microwave heating method for the first time, the synthesis method is simple, the preparation cost is low, the large-scale stable synthesis can be realized, the preparation speed is high, and the yield is high;

2. the preparation method disclosed by the invention is short in time consumption, the yield can be remarkably improved by combining the propylene carbonate solvent, the mother solution can be prevented from corroding the surface of the crystal to the greatest extent, and the metallic luster of the surface of the crystal is maintained;

3. compared with the traditional grinding method and stirring method, the method adopts a microwave heating mode, so that the degree of crystallinity of the synthesized perovskite microcrystal is better, and the phase purity is higher;

4. the preparation method has certain universality and is suitable for preparing microcrystals with various components.

Drawings

FIG. 1 is a schematic diagram of preparation of perovskite crystallites according to examples 1 to 6 of the present invention;

FIG. 2 is a graph showing the results of X-ray diffraction of the perovskite microcrystalline powder product obtained in examples 1-2 of the present invention (example 1-FA)_0.75MA_0.25PbI₃(ii) a Example 2 FA_0.25MA_0.75PbI₃)；

FIG. 3 shows the number of donor atoms in a common solvent and their relationship to Pb²⁺A schematic diagram of ion coordination capacity;

FIG. 4(a) is an optical image of the product obtained in comparative example 1 of the present invention using butyrolactone as a solvent;

FIG. 4(b) is an optical image of a product obtained in example 4 of the present invention using propylene carbonate as a solvent;

FIG. 5 is a graph showing the results of X-ray diffraction of perovskite microcrystal products obtained in example 4 of the present invention and comparative example 1 (example 4-PC; comparative example 1-GBL);

FIG. 6(a) is a MAPbI obtained by conventional milling method in comparative example 2 of the present invention₃A schematic of the powder;

FIG. 6(b) is a MAPbI obtained by a conventional stirring method in comparative example 3 of the present invention₃A schematic of the powder;

FIG. 7 is a graph showing the X-ray diffraction results of perovskite microcrystal products obtained by three different preparation methods in example 4 of the present invention and comparative examples 2 to 3 (example 4-microwave method; comparative example 2-grinding method; comparative example 3-stirring method);

FIG. 8 is a graph showing the results of X-ray diffraction of the perovskite microcrystal products obtained in example 4 and example 6 of the present invention (example 4-direct heating; example 6-gradient heating).

Detailed Description

To better illustrate the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to the following embodiments and accompanying drawings.

The experimental procedures, which are not specified in the following examples, are generally carried out under conventional conditions, and various common chemical reagents or samples used in the examples, unless otherwise specified, are commercially available products.

In order to achieve rapid production of perovskite microcrystalline powders in large quantities, the inventors originally conceived of conventional milling processes and solution reaction processes. The grinding method is to weigh MAI (methylamine iodide, CH) with equal molar ratio₃NH₃I) And PbI₂(lead iodide) was ground in a mortar in a glove box for 30min to obtain a black powder. The stirring method is to weigh MAI and dissolve the MAI in a proper amount of acetonitrile, and then add PbI with equal molar ratio₂And stirring for 1.5h to obtain black powder. However, both processes give a matte, low crystallinity and impure powder, mixed with different amounts of impurities.

In exploring microwave conditions, MAPbI was initially introduced₃Selecting conventional butyrolactone (GBL) as solvent, microwave parameters of 120 deg.C (heating temperature), 10min (heating time length) and 250W (microwave reactor power), and obtaining black granular MAPbI₃. When the particles are observed under an optical microscope, the surface etching of the particles is found to be serious, which proves that regular crystals are difficult to obtain by using GBL as a solvent.

Analysis has found that, probably due to the high solubility of butyrolactone (GBL) for perovskites, the mother liquor etches the crystal surface after the temperature is reduced.

Therefore, according to the solvent and the coordination capacity, Propylene Carbonate (PC) with weaker coordination capacity is selected as the solvent. Subsequently, the inventors found that the choice of microwave temperature affects the purity of the product. Selecting MAI and PbI₂Dissolving in Propylene Carbonate (PC) to obtain 0.5M solution, adjusting microwave temperature to 150 deg.C, and standing for 10min to obtain yellow-black mixture. After several attempts at the same microwave parameters, a yellow-black mixture was still obtained. The reason for the analysis may be that the PC solvent is volatilized due to too high temperature, PbI₂Precipitation resulted in the precipitation of a yellow material. Then the microwave temperature is adjusted to 70-130 ℃, and the mixture is heated for 10-30 min under the same other conditions, so that black microcrystals are separated out and the crystallinity is higher. In addition to microwave temperature, the inventors have found that another factor determining the yield is the concentration of the perovskite precursor solution. When the concentration of the perovskite precursor solution is too low, no supersaturation state is achieved, and no product is precipitated, so that it is necessary toEnsuring that the perovskite precursor solution reaches a supersaturated state so as to ensure higher yield.

Examples

Examples 1 to 3:

efficient preparation of perovskite Microcrystal (MA) by microwave method_XFA_1－XPbI₃) As shown in fig. 1, comprising the steps of:

(1) weighing MAI (methylamine iodide, CH) according to the molar mass ratio among elements of a target product₃NH₃I) FAI (formamidine iodide, HC (NH)₂)₂I) And PbI₂(FAI + MAI and PbI)₂In a molar ratio of 1: 1) wherein the molar ratio between MAI and FAI is shown in Table 1, adding MAI, FAI and PbI₂Dissolving in propylene carbonate, performing ultrasonic treatment for the time shown in Table 1, and continuously stirring for the time shown in Table 1 to obtain a clear solution, wherein the clear solution is MA_XFA_1－XPbI₃Perovskite precursor solution, MA_XFA_{1－ X}PbI₃The concentration of the perovskite precursor solution is shown in table 1;

(2) mixing MA_XFA_1－XPbI₃Putting the perovskite precursor solution into a small beaker, transferring the small beaker into a microwave reactor for heating, setting the power of the microwave reactor to be 250W, controlling the heating temperature as shown in table 2, and controlling the heating time as shown in table 2;

(3) after the reaction is complete, from MA_XFA_1－XPbI₃Separating out black microcrystals from the perovskite precursor solution, filtering and washing the black microcrystals to obtain crystals with metallic luster, wherein the crystals are MA_XFA_1－XPbI₃The perovskite microcrystal and the specific chemical formula of the perovskite microcrystal product are shown in the table 1.

By the preparation method of the embodiment, the molar ratio of MAI to FAI can be adjusted to obtain perovskite Microcrystals (MA) with different component ratios_XFA_1－XPbI₃)。

TABLE 1 Components and Process parameters of examples 1-3

Example 4

Efficient preparation of perovskite microcrystal (MAPbI) by microwave method₃) As shown in fig. 1, comprising the steps of:

(1) weighing MAI (methylamine iodide, CH) according to the molar mass ratio among elements of a target product₃NH₃I) And PbI₂(FAI + MAI and PbI)₂In a molar ratio of 1: 1) mixing MAI and PbI₂Dissolving in propylene carbonate, performing ultrasonic treatment for 10min, and stirring for 30min to obtain clarified solution, which is MAPbI₃Perovskite precursor solution, MAPbI₃The concentration of the perovskite precursor solution is 0.45 mol/L;

(2) MAPbI is added₃Putting the perovskite precursor solution into a small beaker, transferring the small beaker into a microwave reactor for heating, setting the power of the microwave reactor to be 250W, controlling the heating temperature to be 100 ℃, and heating for 10 min;

(3) after completion of the reaction, from MAPbI₃Precipitating black microcrystals in the perovskite precursor solution, filtering and washing the black microcrystals to obtain crystals with metallic luster, wherein the crystals are MAPbI₃Perovskite crystallites.

Example 5:

efficient preparation of perovskite microcrystal (MAPbI) by microwave method₃) The method (3) is the same as in example 4 except that: the temperature of the microwave heating in the step (2) is changed to 100 ℃, and the time of the microwave heating is changed to 20 min.

Example 6:

efficient preparation of perovskite microcrystal (MAPbI) by microwave method₃) The method (3) is the same as in example 4 except that: in step (2), MAPbI is added₃The perovskite precursor solution is contained in a small beaker and transferred to a microwave reactor for heating, the power of the microwave reactor is set to be 250W, the heating temperature is controlled by a gradient heating mode, and the perovskite precursor solution is heatedThe heating time is as follows: 70-5 min, 80-5 min, 90-5 min, 100-10 min and 110-5 min.

Application example

Application examples 1 to 6

Perovskite Microcrystal (MA)_XFA_1－XPbI₃) The perovskite crystallites are prepared by the methods of examples 1-6 above, respectively, and the perovskite crystallites are used for preparing perovskite solar cells.

Comparative example

Comparative example 1:

efficient preparation of perovskite microcrystal (MAPbI) by microwave method₃) The method (3) is the same as in example 4 except that: replacing Propylene Carbonate (PC) in the step (1) with butyrolactone (GBL) as a solvent.

Comparative example 2:

preparation of perovskite microcrystal (MAPbI)₃) As shown in fig. 6, the following preparation method is adopted: weighing a mixture with a molar ratio of 1: 1 MAI and PbI₂After 30min of grinding in a mortar and glove box, black powder, which is MAPbI, can be obtained₃Perovskite crystallites.

Comparative example 3:

preparation of perovskite microcrystal (MAPbI)₃) As shown in fig. 6, the following preparation method is adopted: weighing MAI, dissolving in proper amount of acetonitrile, and adding PbI₂MAI and PbI₂In a molar ratio of 1: stirring for 1.5h to obtain black powder, wherein the black powder is MAPbI₃Perovskite crystallites.

Comparative example 4

Preparation of perovskite microcrystal (MAPbI)₃) The procedure (2) and the reagents, parameters and the like used in the respective steps were the same as in example 5, except that: and (3) changing the microwave heating mode in the step (2) into a direct heating method, wherein the direct heating method adopts a heating table for heating, the heating temperature in the direct heating method is 100 ℃, and the heating time is 40 min.

Comparative example 5

Efficient preparation of perovskite microcrystal (MAPbI) by microwave method₃) The procedure (2) and the reagents, parameters and the like used in the respective steps were the same as in example 5, except that: replacing Propylene Carbonate (PC) in the step (1) with butyrolactone (GBL) as a solvent.

Comparative example 6

Preparation of perovskite microcrystal (MAPbI)₃) The steps and reagents, parameters and the like involved in the steps are the same as those in comparative example 4, except that: replacing Propylene Carbonate (PC) in the step (1) with butyrolactone (GBL) as a solvent.

Effect verification:

to show the universality of perovskite crystallites prepared by the present invention, as shown in FIG. 2, the present application prepares a plurality of alloy crystallites (e.g., FA) by adjusting the molar ratio of MAI to FAI in examples 1-2_0.75MA_0.25PbI₃、FA_0.25MA_0.75PbI₃Etc.), wherein the perovskite crystallites obtained in example 1 are FA_0.75MA_0.25PbI₃Example 2 the perovskite crystallites obtained were FA_0.25MA_0.75PbI₃As shown in the X-ray diffraction results of FIG. 2, it is proved that all the products obtained by the methods of examples 1-2 are high-purity microcrystals without impurities.

The effect comparison was made by combining example 4 and comparative example 1, as shown in FIG. 3, according to the polarity of the solvent and the coordination ability (the smaller the number of donor of the solvent, the lower the Pb²⁺More difficult to coordinate, low crystallization temperature, easier to crystallize and precipitate, and easier to protect the crystal surface), and the selection of a proper solvent system is of great importance to the quality of the perovskite microcrystal.

As shown in fig. 4(a), in comparative example 1, conventional butyrolactone (GBL) was used as a solvent, and since it has a large number of donors and a high crystallization temperature, it is easily coordinated with lead iodide, and has a high solubility to perovskite. Therefore, in the crystallization process, when the temperature is reduced and the solubility is rapidly increased, the mother liquor can severely etch the crystal surface. Therefore, the crystal surface obtained in comparative example 1 was in a wrinkled state and had no metallic luster.

As shown in fig. 4(b), in example 4, Propylene Carbonate (PC) is selected as the solvent, and since the donor number is small, it is difficult to coordinate with lead iodide, perovskite can be precipitated at a lower temperature, and the problem of etching the crystal surface by the mother solution due to temperature drop during the crystallization filtration process can be greatly avoided, so as to maintain the good metallic luster of the crystal surface.

As shown in fig. 5, the perovskite crystallites obtained by example 4 and comparative example 1 were MAPbI₃The X-ray diffraction result proves that all the products obtained by the method in the example 4 are high-purity impurity-free microcrystals, which shows that the perovskite microcrystals obtained by using the Propylene Carbonate (PC) as a solvent have high purity.

The superiority of the methods of examples 1 to 4 can be verified by comparing the effects of example 4 and comparative examples 2 to 3, and as shown in fig. 6(a) and (b), the X-ray diffraction obtained by the conventional milling method of comparative example 2 and the stirring method of comparative example 3 is powdery and does not have any metallic luster. As shown in fig. 7, the X-ray diffraction characterization indicated that neither the conventional milling method of comparative example 2 nor the stirring method of comparative example 3 resulted in a pure phase of the powder, with impurities present. In contrast, MAPbI prepared by the method of example 4₃Pure phase, no impurities, and high diffraction peak intensity, indicating MAPbI prepared by the method of example 4₃The microcrystal has higher crystallinity and better quality.

Comparing the effects with those of example 5 and comparative examples 4 to 6, it is possible to show the superiority of the Propylene Carbonate (PC) solvent selected in examples 1 to 5, and to compare the yields of the conventional direct heating method of comparative examples 4 and 6 with the microwave heating method of example 5 and comparative example 5, and the results are shown in table 2 below:

TABLE 2 preparation of MAPbI by microwave and direct heating methods under treatment with different solvents₃Experimental results of (2)

As can be seen from table 2, the microwave heating of examples 5 and comparative examples 5 was higher in yield than the direct heating of comparative examples 4 and 6, and the microwave heating required shorter time for synthesizing perovskite crystallites than the direct heating, and the yield was higher, regardless of whether butyrolactone (GBL) or Propylene Carbonate (PC) was used as a solvent.

In addition, the yield of the microcrystals prepared in example 5 and comparative example 4 by microwave heating using Propylene Carbonate (PC) as a solvent was 10 times higher than that of the microcrystals prepared in comparative example 4 and comparative example 6 by microwave heating using butyrolactone (GBL) as a solvent. In comparative example 6, when butyrolactone (GBL) was used as the solvent, the product could not be obtained after direct heating for 40min, indicating that the Propylene Carbonate (PC) solvent optimally selected in examples 1-5 is more suitable for rapid, mass synthesis of high quality perovskite crystallites.

Comparing the effects of the embodiment 3 and the embodiment 6, as shown in fig. 8, the diffraction peak of the perovskite microcrystal obtained by gradient temperature control in the embodiment 6 is stronger than that of the microcrystal powder obtained by direct microwave heating at 100 ℃ in the comparison 2, which shows that the embodiment 6 reduces the nucleation number by gradient temperature rise to make the crystal size larger and obtain the perovskite microcrystal with higher crystallinity, that is, the quality of the perovskite microcrystal product is obviously improved by the gradient temperature rise heating mode.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.