Preparation method of perovskite single crystal based on binary solvent system

Abstract

The invention provides a binary solvent system-based perovskite single crystal preparation method, which comprises: S1, mixing a perovskite precursor mixture and a binary solvent system, and carrying out heating stirring to obtain a clear saturated solution; the binary solvent system is composed of one of aniline or aniline homologues and alkylamine; the alkylamine is a derivative of ammonia in which one or more hydrogen atoms in an ammonia molecule are substituted by an organic group; wherein in the binary solvent system, the mass percentage content of the amine organic matter is 1%-50%; and S2, filtering the clear saturated solution, adding the filtered clear saturated solution into a single crystal growth container, and heating to obtain the perovskite single crystal. According to the technical scheme, the perovskite single crystal prepared by the inverse temperature crystallization method is low in nucleation rate, low in surface defect density and free of solvent residues on the surface.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite optoelectronic materials, and particularly to a method for preparing perovskite single crystals based on a binary solvent system. Background Art

[0002] In recent years, organic-inorganic hybrid perovskites have attracted much attention in the fields of photovoltaics, light-emitting diodes, detectors, and lasers due to their low cost and excellent physical properties, such as high absorption coefficient, long carrier lifetime, and high carrier mobility. However, the commercialization process of perovskite optoelectronic devices is restricted by the operating stability of the devices. Currently, most perovskite optoelectronic devices are prepared from perovskite polycrystalline thin films. A large number of uncoordinated ions are enriched at the grain boundaries of the polycrystalline thin films, which are easily eroded by water and oxygen in the environment. During the operation of the devices, ion migration is likely to form defects, thereby inducing perovskite degradation and a decline in the performance of optoelectronic devices until they fail.

[0003] Perovskite single crystals have no grain boundaries and have lower defect state density, higher carrier diffusion length, and better environmental stability, which makes them a substitute material for polycrystalline perovskites. Among the many methods for preparing perovskite single crystals, the solution inverse temperature crystallization method is highly regarded for its fast growth rate, high yield, and simple operation. However, the perovskite precursor solvents suitable for inverse temperature crystallization growth are very limited. For example, in the prior art, perovskite single crystals prepared using γ-butyrolactone solvent are known. In this technique, since the inverse temperature crystallization method drives the rapid precipitation of solutes through a temperature gradient, this process may lead to an excessively fast growth rate on the crystal surface. Under high-speed growth conditions, surface atoms / molecules are difficult to arrange fully and orderly, and it is easy to form uncoordinated ions (such as Pb 2+ dangling bonds) or lattice distortion, thereby increasing the surface defect density. In addition, when the single crystal is taken out of the high-temperature solvent, the rapid volatilization of the residual solvent on the single crystal surface may cause local composition segregation or microcracks on the crystal surface. Moreover, the surface of perovskite single crystals is usually terminated with a PbI2 or MAI layer. Due to the volatility of MA + (methylammonium ion), the surface is prone to form a metastable structure rich in lead iodide due to the loss of MA + . Such regions with stoichiometric imbalance are prone to become defect sites. Research shows that the surface defect density of single crystals (10 13 -10 15 cm -3 ) is approximately 5 times that of their interior. The prior art has problems such as high surface defect state density of the obtained perovskite single crystals, surface solvent residue, high nucleation rate, and difficulty in preparing perovskite single crystal thin films with a high surface-to-thickness ratio.

[0004] These problems limit the widespread use of perovskite single crystals and are not conducive to the commercialization of perovskite optoelectronic devices. Therefore, it is urgent to study a new type of perovskite precursor solution with inverse temperature crystallinity, which can be used to prepare high-quality perovskite single crystals without solvent residues and with a low nucleation rate. Summary of the Invention

[0005] In view of the above technical problems, the present invention discloses a method for preparing perovskite single crystals based on a binary solvent system. The binary solvent system used has inverse temperature crystallinity and a low nucleation rate, and can be used to prepare large-area, high-quality perovskite single crystals without solvent residues on the surface. Secondly, by adjusting the type of amine organic compound in the binary solvent, the controllable preparation of perovskite single crystals can be realized.

[0006] For this, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing perovskite single crystals based on a binary solvent system, comprising the following steps:

[0008] Step S1, mixing a perovskite precursor mixture with a binary solvent system, heating and stirring to obtain a clear saturated solution;

[0009] The binary solvent system consists of one of aniline or aniline homologues and an alkylamine; the alkylamine is a derivative of ammonia in which one or more hydrogen atoms in ammonia molecules are replaced by organic groups; in the binary solvent system, the mass percentage content of the alkylamine is 1%-50%; the aniline homologues refer to a series of organic compounds obtained by adding or changing substituents on the basis of aniline; the dosage of the alkylamine is determined according to the amount of the perovskite precursor mixture dissolved in the binary solvent system to obtain a clear saturated solution;

[0010] Step S2, after filtering the clear saturated solution, adding it to a single crystal growth container and heating to obtain perovskite single crystals. Among them, the single crystal growth container adopts a single crystal growth container of the prior art, which can include a beaker, a flask, and a confined space constructed by stacking two glass slides.

[0011] The binary solvent system adopted in this technical solution has inverse temperature crystallinity for the perovskite precursor. The solubility of perovskite in this solvent will first increase and then decrease with the increase of temperature. This property can be used for inverse temperature crystallization. Specifically, this method utilizes the difference in the solubility of amine organic compounds in the perovskite precursor and the multifunctionality of their branched chains. By mixing different amine organic compound solutions to form a binary solvent, the prepared perovskite single crystals have high quality, high yield, low nucleation rate, no solvent residues, and controllable crystal planes and morphologies.

[0012] As a further improvement of the present invention, the mass percentage content of the alkylamine is 4% to 15%.

[0013] As a further improvement of the present invention, the aniline homolog is p-toluidine, p-chloroaniline, p-isopropylaniline, o-nitroaniline or m-ethoxyaniline.

[0014] As a further improvement of the present invention, the alkylamine is diethylamine, n-butylamine, pentylamine, heptylamine, octylamine, oleylamine, phenethylamine, cyclopentylamine or cyclohexylamine.

[0015] As a further improvement of the present invention, the perovskite precursor mixture is composed of two or more compounds of AX and BX2 that can form a perovskite structure. The AX includes at least one of MAI, MABr, MACl, FAI, FABr, FACl, CsI, CsBr, CsCl, and the BX includes at least one of PbI2, PbBr2, PbCl2, SnI2, SnBr2, SnCl2.

[0016] As a further improvement of the present invention, the mixing of the perovskite precursor mixture with the binary solvent system includes: mixing one of aniline or an aniline homolog with the perovskite precursor mixture to form a slurry, and then adding an appropriate amount of alkylamine and heating and stirring to obtain a clear saturated solution; the addition amount of the alkylamine is determined according to the amount of the clear saturated solution obtained by stirring. The mass of AX and BX2 is not greater than the maximum solubility of the perovskite precursor solute in the binary solvent.

[0017] As a further improvement of the present invention, the temperature of the heating and stirring in step S1 is the temperature T corresponding to the maximum solubility of the perovskite precursor mixture in the binary solvent system. max .

[0018] As a further improvement of the present invention, in step S2, the starting temperature of the heating is between room temperature and T max , and the heating rate is 1 °C / 10 min - 1 °C / 4 h; the ending temperature of the heating is between T max and the minimum temperature T corresponding to the solubility decrease of the perovskite precursor solute in the binary solvent system. min between.

[0019] The present invention also discloses a binary solvent system for the preparation of perovskite single crystals, which is composed of one of aniline or an aniline homolog and an alkylamine; the alkylamine is a derivative of ammonia in which one or more hydrogen atoms in the ammonia molecule are replaced by organic groups; in the binary solvent system, the mass percentage content of the alkylamine is 1% - 50%. The dosage of the alkylamine is determined according to the amount of the clear saturated solution obtained by dissolving the perovskite precursor mixture in the binary solvent system. Further, the mass percentage content of the alkylamine is 4% - 15%.

[0020] As a further improvement of the present invention, the aniline homolog is p-toluidine, p-chloroaniline, p-isopropylaniline, o-nitroaniline or m-ethoxyaniline.

[0021] As a further improvement of the present invention, the alkylamine is diethylamine, n-butylamine, pentylamine, heptylamine, octylamine, oleylamine, phenethylamine, cyclopentylamine or cyclohexylamine.

[0022] The present invention also discloses a perovskite precursor solution, which includes a perovskite precursor mixture and a solvent. The solvent is the binary solvent system for preparing perovskite single crystals as described above. The perovskite precursor mixture is composed of two or more compounds of AX and BX2 that can form a perovskite structure. The AX includes at least one of MAI, MABr, MACl, FAI, FABr, FACl, CsI, CsBr, CsCl, and the BX includes at least one of PbI2, PbBr2, PbCl2, SnI2, SnBr2, SnCl2.

[0023] The present invention also discloses the use of a binary mixed solvent system in the preparation of perovskite materials. The binary mixed solvent system consists of one of aniline or an aniline homolog and an alkylamine. The alkylamine is a derivative of ammonia in which one or more hydrogen atoms in the ammonia molecule are replaced by organic groups. In the binary solvent system, the mass percentage content of the alkylamine is 1% - 50%. The dosage of the alkylamine is determined according to the amount of the perovskite precursor mixture dissolved in the binary solvent system to obtain a clear saturated solution. Further, the mass percentage content of the alkylamine is 4% - 15%.

[0024] As a further improvement of the present invention, the aniline homolog is p-toluidine, p-chloroaniline, p-isopropylaniline, o-nitroaniline or m-ethoxyaniline.

[0025] As a further improvement of the present invention, the alkylamine is diethylamine, n-butylamine, pentylamine, heptylamine, octylamine, oleylamine, phenethylamine, cyclopentylamine or cyclohexylamine.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] First, the technical solution of the present invention provides a novel binary solvent system with inverse temperature crystallization property of perovskite precursor, which broadens the types of solvents for preparing perovskite single crystals by inverse temperature crystallization method. This binary solvent system has inverse temperature crystallization property and low nucleation rate, and can prepare large-area high-quality (low surface defect density) perovskite single crystals without solvent residue on the surface. Secondly, by adjusting the types of amine organic compounds in the binary solvent, various properties such as crystal plane, morphology, crystallization temperature and yield of perovskite single crystals can be finely adjusted.

[0028] Second, the preparation method of the technical solution of the present invention is simple. Single crystals can be prepared in different containers, large single crystals and single crystal thin films can be prepared, and various optoelectronic devices can also be prepared in combination with other processes, which has universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the solubility change curve of MAPbI3 in different binary solvent systems with temperature in Examples 1-4 of the present invention. The solubility of perovskite first increases and then decreases with the increase of temperature, so inverse temperature crystallization can be carried out.

[0030] Figure 2 It is the picture of MAPbI3 perovskite single crystals prepared by different binary solvent systems in Examples 1-4 of the present invention; among them, (a)-(d) are the physical pictures of MAPbI3 perovskite single crystals prepared in 3 ml-glass bottles in Examples 1-4 respectively, and (e)-(h) are the physical pictures of MAPbI3 perovskite single crystals prepared in the confined space constructed by glass slides in Examples 1-4 respectively.

[0031] Figure 3 It is the XRD spectrum diagram measured for MAPbI3 perovskite single crystals prepared by different binary solvent systems in Examples 1-4 of the present invention; Figures (a)-(d) are the XRD spectrum diagrams of MAPbI3 perovskite single crystals prepared in Examples 1-4 respectively.

[0032] Figure 4 It is the rocking curve spectrum diagram measured for MAPbI3 perovskite single crystals prepared by different binary solvent systems in Examples 1-4 of the present invention; Figures (a)-(d) are the rocking curve spectrum diagrams of MAPbI3 perovskite single crystals prepared in Examples 1-4 respectively.

[0033] Figure 5 It is the defect state density spectrum diagram measured for MAPbI3 perovskite single crystals prepared by different binary solvent systems in Examples 1-4 of the present invention; Figures (a)-(d) are the defect state density spectrum diagrams of MAPbI3 perovskite single crystals prepared in Examples 1-4 respectively.

[0034] Figure 6 It is the physical picture of the MAPbI3 perovskite single crystal obtained in Comparative Example 3 of the present invention, where (a) is the physical picture placed in the container and (b) is the physical picture of the MAPbI3 perovskite single crystal.

[0035] Figure 7 It is the test result of the spatial size defect state density of the MAPbI3 perovskite single crystals prepared in Examples 1-4 and Comparative Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] The following further details the preferred embodiments of the present invention.

[0037] Example 1

[0038] Preparation of MAPbI3 perovskite single crystals using an aniline (AN)-diethylamine (DA) binary solvent system: Weigh 230 mg of PbI2 and 79 mg of MAI, add a solvent composed of 0.5 mL of AN and 25 μL of DA, stir at 60 °C until clear to prepare a MAPbI3 perovskite precursor solution. Filter the solution through a 0.45 μm organic filter head and inject it into a 3 mL glass bottle or a confined space constructed by glass slides. After sealing, place it on a heating stage, start heating from 60 °C at a rate of 1 °C / 15 min to 110 °C, which takes a total of 12.5 h. Finally, take out the single crystals and perform XRD, rocking curve, and space charge limited current method-defect state density tests.

[0039] Example 2

[0040] Preparation of MAPbI3 perovskite single crystals using an aniline (AN)-n-butylamine (BA) binary solvent system: Weigh 230 mg of PbI2 and 79 mg of MAI, add a solvent composed of 0.5 mL of AN and 24 μL of BA, stir at 60 °C until clear to prepare a MAPbI3 perovskite precursor solution. Filter the solution through a 0.45 μm organic filter head and inject it into a 3 mL glass bottle or a confined space constructed by glass slides. After sealing, place it on a heating stage, start heating from 60 °C at a rate of 1 °C / 30 min to 110 °C, which takes a total of 25 h. Finally, take out the single crystals and perform XRD, rocking curve, and space charge limited current method-defect state density tests.

[0041] Example 3

[0042] Preparation of MAPbI3 perovskite single crystals using an aniline (AN)-heptylamine (HA) binary solvent system: Weigh 230 mg of PbI2 and 79 mg of MAI, add a solvent composed of 0.5 mL of AN and 30 μL of HA, stir at 60 °C until clear to prepare a MAPbI3 perovskite precursor solution. Filter the solution through a 0.45 μm organic filter head and inject it into a 3 mL glass bottle or a confined space constructed by glass slides. After sealing, place it on a heating stage, start heating from 60 °C at a rate of 1 °C / 30 min to 110 °C, which takes a total of 25 h. Finally, take out the single crystals and perform XRD, rocking curve, and space charge limited current method-defect state density tests.

[0043] Example 4

[0044] Preparation of MAPbI3 perovskite single crystals using an aniline (AN)-oleylamine (OLA) binary solvent system: Weigh 230 mg of PbI2 and 79 mg of MAI, add a solvent composed of 0.5 mL of AN and 82 μL of OLA, stir at 60 °C until clear, and prepare a MAPbI3 perovskite precursor solution. Filter the solution through a 0.45 μm organic filter head and inject it into a 3 mL glass bottle or a confined space constructed by glass slides. After sealing, place it on a heating stage, start heating from 60 °C at a rate of 1 °C every 30 minutes until 110 °C, which takes a total of 25 hours. Finally, take out the single crystals and perform XRD, rocking curve, and space charge limited current method - defect state density tests.

[0045] The solubility change curves of MAPbI3 in different binary solvent systems for Examples 1 to 4 with temperature are as Figure 1 shown. It can be seen that the solubility of the perovskite first increases and then decreases with increasing temperature, so inverse temperature crystallization can be carried out. That is, as the solvent temperature increases, the solubility of the perovskite solute decreases, thereby precipitating single crystals.

[0046] In Examples 1 to 4, the pictures of MAPbI3 perovskite single crystals prepared in different binary solvent systems in glass bottles or in the confined space of glass slides are as Figure 2 shown. It can be seen that as the alkyl chain of the alkylamine molecule in the binary solvent changes, the morphology of the perovskite single crystal also changes. By calculation, the surface / thickness ratios of the MAPbI3 perovskite single crystals prepared in Examples 1 to 4 are 79.87 mm, 27.11 mm, 112.55 mm, and 62.94 mm, respectively.

[0047] In Examples 1 to 4, the XRD spectra of MAPbI3 perovskite single crystals prepared in different binary solvent systems are as Figure 3 shown. It can be seen that as the alkyl chain of the alkylamine molecule in the binary solvent changes, the exposed crystal plane of the perovskite single crystal changes from the (100) crystal plane to the (110) crystal plane.

[0048] In Examples 1 to 4, the rocking curve spectra of MAPbI3 perovskite single crystals prepared in different binary solvent systems are as Figure 4 shown, where the smaller full width at half maximum of the rocking curve indicates a very high quality of the perovskite single crystal.

[0049] In Examples 1 to 4, the defect state density spectra of MAPbI3 perovskite single crystals prepared in different binary solvent systems are as Figure 5 shown. It can be seen that the lower defect state density indicates a very high quality of the perovskite single crystal.

[0050] In Examples 1 to 4, the process of single crystal nucleation and growth is a long-term, continuous, and slow process, generally lasting 12 - 25 hours.

[0051] As can be seen from the above embodiments, the binary solvent can regulate the growth process of MAPbI3 perovskite single crystals. Moreover, the alkylamine adsorbed on the surface of the single crystal will endow the perovskite single crystal with solventophobicity, so that when it is taken out of the high-temperature solvent, the instantaneously cooled solvent will not dissolve the surface, or the solvent will remain on the surface, but will directly flow away quickly from the surface of the single crystal.

[0052] Comparative Example 1

[0053] On the basis of Example 1, only aniline was used as the solvent. It was found that the solubility of aniline in the perovskite precursor solute was very low, only 0.02 M, and the 1 M perovskite precursor solute showed a slurry state in aniline. And the perovskite does not have inverse temperature crystallinity in aniline and no single crystals will precipitate even at a high temperature of 180 °C. However, the binary solvent system of aniline-alkylamine used in Examples 1 to 4 can dissolve 1 M of the precursor solute, and single crystals can precipitate at about 100 °C.

[0054] Comparative Example 2

[0055] On the basis of Example 1, only alkylamine was used as the solvent. Diethylamine, n-butylamine, heptylamine, and oleylamine were used for experiments respectively. The perovskite precursor mixtures of Examples 1 to 4 were added into diethylamine, n-butylamine, heptylamine, and oleylamine respectively. These alkylamines have a high solubility in the perovskite precursor mixture, greater than 2 M, but do not have inverse temperature crystallinity.

[0056] Comparative Example 3

[0057] To prepare MAPbI3 perovskite single crystals using the commonly used GBL (γ-butyrolactone) solvent system, the following steps are included:

[0058] Weigh 230 mg of PbI2 and 79 mg of MAI, add 1 mL of GBL solvent, stir at 60 °C until clear to prepare a MAPbI3 perovskite precursor solution. Filter the solution through a 0.45 μm organic filter head and inject it into a 3 ml glass bottle or the confined space constructed by glass slides. After sealing, place it on a heating table, start heating from 60 °C at a rate of 1 °C / 30 min to 110 °C, and finally take out the single crystal for calculation of the surface / thickness ratio and testing of the density of spatial size defect states by the driving-level capacitance method (DLCP).

[0059] The physical diagram of the MAPbI3 single crystal obtained in this comparative example is as Figure 6 shown. It was calculated that the surface / thickness ratio of the MAPbI3 single crystal prepared by this method was 13.35 mm, which was much lower than the surface / thickness ratios of the MAPbI3 perovskite single crystals obtained in Examples 1 to 4 (79.87 mm, 27.11 mm, 112.55 mm, and 62.94 mm for Examples 1 to 4 respectively).

[0060] The space - size defect state density of the MAPbI3 perovskite single crystals prepared in Examples 1 - 4 and Comparative Example 3 was measured by the driving - level capacitance method, and the comparison results are as Figure 7 shown. It can be seen from this figure that the surface defect density of the single crystal prepared with the GBL solution in Comparative Example 3 is 9.12×10 15 cm -3 , the surface defect density of the MAPbI3 perovskite single crystal prepared with the AN - DA solution in Example 1 is 2.91×10 12 cm -3 , the surface defect density of the MAPbI3 perovskite single crystal prepared with the AN - BA solution in Example 2 is 2.94×10 12 cm -3 , the surface defect density of the MAPbI3 perovskite single crystal prepared with the AN - HA solution in Example 3 is 1.16×10 10 cm -3 , and the surface defect density of the MAPbI3 perovskite single crystal prepared with the AN - OLA solution in Example 4 is 1.58×10 12 cm -3 . By comparison, Examples 1 - 4 have lower surface defect densities.

[0061] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for preparing a perovskite single crystal based on a binary solvent system, characterized in that: The steps include: Step S1, mixing the perovskite precursor mixture with a binary solvent system, heating and stirring, to obtain a clear saturated solution; the binary solvent system is composed of aniline or one of aniline homologues and alkylamine; wherein the mass percentage content of the alkylamine in the binary solvent system is 1%-50%; Step S2, filtering the clarified saturated solution, adding it into a single crystal growth container, and heating it to obtain a perovskite single crystal.

2. The method for preparing a perovskite single crystal based on a binary solvent system according to claim 1, characterized in that: The aniline homologue is p-toluidine, p-chloroaniline, p-isopropylaniline, o-nitroaniline or m-ethoxyaniline, and the alkylamine is diethylamine, n-butylamine, pentylamine, heptylamine, octylamine, oleylamine, phenylethylamine, cyclopentylamine or cyclohexylamine.

3. The method for preparing a perovskite single crystal based on a binary solvent system according to claim 2, characterized in that: The perovskite precursor mixture is composed of two or more compounds AX and BX2 that can construct a perovskite structure, wherein the AX includes at least one of MAI, MABr, MACl, FAI, FABr, FACl, CsI, CsBr, and CsCl, and the BX includes at least one of PbI2, PbBr2, PbCl2, SnI2, SnBr2, and SnCl2; The step S1 of mixing the perovskite precursor mixture with the binary solvent system comprises: mixing aniline or one of the aniline homologues with the perovskite precursor mixture into a slurry, adding an alkylamine, heating and stirring to obtain a clear saturated solution; The amount of the alkylamine added is determined based on the amount of a clear saturated solution obtained by stirring.

4. The method for preparing a perovskite single crystal based on a binary solvent system according to claim 3, characterized in that: The heating and stirring temperature in step S1 is the temperature T corresponding to the maximum solubility of the perovskite precursor mixture in the binary solvent system. max .

5. The method for preparing a perovskite single crystal based on a binary solvent system according to claim 3, characterized in that: In step S2, the starting temperature of the heating is room temperature and T max The heating rate is 1°C / 10min-1°C / 4h; the termination temperature of the heating is T max The temperature T corresponding to the minimum value after the solubility of the perovskite precursor solute in the binary solvent system decreases min between.

6. A binary solvent system for preparing perovskite single crystals, characterized in that: The invention is composed of aniline or one of aniline homologues and alkylamine; wherein in the binary solvent system, the mass percentage content of the alkylamine is 1%-50%.

7. The binary solvent system for preparing perovskite single crystals according to claim 6, characterized in that: The aniline homologue is p-toluidine, p-chloroaniline, p-isopropylaniline, o-nitroaniline or m-ethoxyaniline, and the alkylamine is diethylamine, n-butylamine, pentylamine, heptylamine, octylamine, oleylamine, phenylethylamine, cyclopentylamine or cyclohexylamine.

8. A perovskite precursor solution, comprising a perovskite precursor mixture and a solvent, characterized in that: The solvent is a binary solvent system for preparing perovskite single crystals as described in claim 6, and the perovskite precursor mixture is composed of two or more compounds AX and BX2 that can construct a perovskite structure, wherein the AX includes at least one of MAI, MABr, MACl, FAI, FABr, FACl, CsI, CsBr, and CsCl, and the BX includes at least one of PbI2, PbBr2, PbCl2, SnI2, SnBr2, and SnCl2.

9. Use of a binary mixed solvent system in the preparation of perovskite materials, characterized in that: The binary mixed solvent system consists of aniline or one of aniline homologues and alkylamine; the alkylamine is an ammonia derivative in which one or more hydrogen atoms in the ammonia molecule are replaced by an organic group; wherein the mass percentage content of the alkylamine in the binary solvent system is 1%-50%.

10. Use of the binary mixed solvent system according to claim 9 in preparing perovskite materials, characterized in that: The aniline homologue is p-toluidine, p-chloroaniline, p-isopropylaniline, o-nitroaniline or m-ethoxyaniline, and the alkylamine is diethylamine, n-butylamine, pentylamine, heptylamine, octylamine, oleylamine, phenylethylamine, cyclopentylamine or cyclohexylamine.

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