A kind of formamidine hydroiodide and its preparation method and application

Abstract

The present invention relates to a formamidine hydroiodide and a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing an ethanol solution of formamidine acetate and a hydroiodic acid solution, reacting, and obtaining a crude formamidine hydroiodide product; (2) mixing the crude formamidine hydroiodide product in step (1) with an azeotropic solvent, and performing at least three groups of reduced pressure distillation and solvent recovery operations to obtain formamidine hydroiodide. When the formamidine hydroiodide formed by the preparation method of the present invention has a high yield, high purity, low water content, and is suitable for process amplification; the obtained formamidine hydroiodide is used for perovskite solar cells, and the cell efficiency, open circuit voltage, current density and fill factor of the cell are higher.

Description

Technical Field

[0001] The invention relates to the technical field of perovskite solar cells, and in particular to formamidine hydroiodide and a preparation method and application thereof. Background Art

[0002] Perovskite solar cells are the next generation photovoltaic technology that has great potential for industrialization.

[0003] CN112133837A discloses a method for preparing a perovskite crystal film, which includes the following steps: S1, preparing a lead iodide film; S2, dissolving a mixture containing formamidine hydroiodide in an organic solvent, adding deionized water, mixing evenly, and then dripping it onto the surface of the film obtained in step S1, coating it after standing for a period of time, and annealing it in an inert atmosphere to obtain a perovskite crystal film. The method disclosed can effectively improve the crystallization conversion of the perovskite crystal film and effectively increase the size of the grains.

[0004] Formamidinium-based perovskite solar cells can be used as the main component of the active layer of perovskite solar cells due to their suitable band gap and good stability. Among them, formamidinium hydroiodide is the main precursor material for the preparation of formamidinium-based perovskite solar cells, and a stable amplification process is urgently needed to meet the needs of high quality and high yield.

[0005] CN111153808A discloses a method for purifying methylamine hydroiodide and formamidine hydroiodide raw materials, wherein a strong reducing agent is added to a solution of methylamine hydroiodide or formamidine hydroiodide, and the elemental iodine in the raw materials of methylamine hydroiodide and formamidine hydroiodide is reduced to an iodide ion compound, and the raw material solution after the reaction is cleaned and filtered multiple times using an alcohol solution and ether, respectively, to avoid the mixing of elemental iodine, thereby obtaining high-purity raw material crystals. The disclosed method effectively removes elemental iodine in the raw material, greatly reduces the elemental iodine residue in the raw material, and improves the purity of the raw material.

[0006] The existing synthesis methods of formamidine hydroiodide mainly continue the laboratory-level preparation methods, among which the most common method is to prepare formamidine hydroiodide by reacting formamidine acetate and hydroiodic acid (for example, Energy Environ. Sci., 2014, 7, 982-988, J. Mater. Chem. A, 2015, 3, 9171-9178). However, this method achieves product purification at the laboratory level by washing with a large amount of ether, which is not suitable for process scale-up and improving product yield.

[0007] In summary, it is crucial to develop a preparation method for formamidine hydroiodide that is suitable for process scale-up and improves product purity and production efficiency. Summary of the invention

[0008] In view of the deficiencies in the prior art, the object of the present invention is to provide a formamidine hydroiodide and a preparation method and application thereof. When the formamidine hydroiodide formed by the preparation method has a high yield, high purity and low water content, the formed formamidine hydroiodide is used for perovskite solar cells, and the cell efficiency, open circuit voltage, current density and fill factor of the cell are suitable for process amplification.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing formamidine hydroiodide, the preparation method comprising the following steps:

[0011] (1) mixing an ethanol solution of formamidine acetate and a hydroiodic acid solution, reacting them to obtain a crude formamidine hydroiodide product;

[0012] (2) The crude formamidine hydroiodide product in step (1) is mixed with an azeotropic solvent, and at least three (e.g., four, five, six, etc.) reduced pressure distillations and solvent recovery operations are performed to obtain formamidine hydroiodide.

[0013] In the present invention, the reaction formula of step (1) is as follows:

[0014]

[0015] In the prior art, the preparation of the crude product of formamidine hydroiodide can also be carried out by the above method, but in the subsequent process, the solvent ethanol and water, and the by-product acetic acid are removed by reduced pressure rotary evaporation. In theory, removing acetic acid can make the reaction proceed in the forward direction and improve the product yield and purity; However, in the actual operation process, due to the high boiling point of the generated acetic acid, it becomes difficult to remove after dissolving the product. In the subsequent process of optionally using a solvent such as ether for cleaning, since acetic acid dissolves a large amount of products and has a large polarity, it causes it to be miscible with the solvent, and even if it is repeated many times, a good cleaning effect cannot be achieved; In addition, acetic acid fails to completely remove and affects the purity of the product, and some hydroiodic acid can volatilize or be oxidized in a free form, increasing the difficulty of cleaning. In the subsequent optional drying process, since acetic acid is not removed, the occurrence of situations such as product hardening will also occur.

[0016] In the present invention, the preparation method avoids a high-temperature distillation environment by applying an azeotropic system, and quickly removes water and ethanol added during the reaction, as well as byproducts such as acetic acid and ethyl acetate generated by the reaction, especially acetic acid, by adding an azeotropic solvent, thereby accelerating the distillation rate, facilitating the forward reaction, improving the purity and yield of the product, and being suitable for process scale-up.

[0017] Preferably, in step (1), in the ethanol solution of formamidine acetate, based on the volume of ethanol as 100 mL, the mass of formamidine acetate is 10-50 g, for example, 15 g, 20 g, 25 g, 30 g, 35 g, 40 g, 45 g, etc., more preferably 30 g.

[0018] Preferably, the mass concentration of the hydroiodic acid solution is 40%-60%, such as 45%, 50%, 55%, 60%, etc., and more preferably 57%.

[0019] Preferably, in step (2), the azeotropic solvent comprises any one of benzene, toluene, xylene, n-heptane, n-octane, cyclohexane or carbon tetrachloride, or a combination of at least two thereof, wherein typical but non-limiting combinations include: a combination of benzene and toluene, a combination of toluene, n-heptane, n-octane and cyclohexane, a combination of n-octane, cyclohexane and carbon tetrachloride, etc., and toluene and / or n-heptane are further preferred.

[0020] In the present invention, the above-mentioned solvents are preferred because the azeotropic solvent avoids the high-temperature distillation environment, accelerates the distillation rate, and introduces the product from a protic solvent environment that is prone to decomposition and oxidation into a non-protic weakly polar solvent environment, thereby improving the quality and yield of the product and simplifying the production method.

[0021] Preferably, the operations of reduced pressure distillation and solvent recovery include a first group of operations, a second group of operations and a third group of operations.

[0022] Preferably, in the first group of operations, the second group of operations and the third group of operations, the temperature of the reduced pressure distillation is increased sequentially.

[0023] In the present invention, after adding the azeotropic solvent, the product can be quickly evaporated to dryness at a relatively low temperature (for example, the temperature of the reduced pressure distillation can be controlled at 35-65° C.) through ternary azeotropy or binary azeotropy, especially to remove acetic acid, promote the forward reaction of formamidine hydroiodide, and improve the reaction yield.

[0024] In the present invention, the temperature and vacuum degree of the reduced pressure distillation in the first group of operations and the second group of operations can be adjusted within an appropriate range, with the purpose of achieving stepwise distillation and complete removal of water, ethanol and acetic acid.

[0025] Preferably, in the first set of operations, the temperature of the reduced pressure distillation is 35-45°C, such as 36°C, 38°C, 40°C, 42°C, 44°C, etc., and more preferably 40°C.

[0026] In the present invention, the main purpose of the first group of operations is to quickly remove water. Therefore, an azeotropic solvent with a relatively large proportion of water and a relatively low azeotropic point is preferably used, and toluene is preferred.

[0027] Preferably, the recovered solvent specifically comprises a mixed solvent obtained by cooling and extracting the reduced pressure distillation, and taking the upper layer solvent.

[0028] In the present invention, by adding the azeotropic solvent, the solvent recovered after co-evaporation is separated into layers after cooling, and the added azeotropic solvent can be extracted and separated into liquids for easy recovery and reuse.

[0029] Preferably, the first group of operations also includes adding the obtained upper layer solvent again to the remaining product after the reduced pressure distillation, and continuing the reduced pressure distillation and solvent recovery operations at least once (for example, twice, three times, four times, five times, six times, etc.) until there is no visible condensation reflux at the set temperature.

[0030] In the present invention, the amount of the azeotropic solvent added in the first group of operations is related to the water content in the ethanol and hydroiodic acid solutions used in the reaction process. Generally speaking, under a certain reduced pressure distillation temperature and vacuum degree, and under the conditions that the amount of water and ethanol to be removed in the system and the amount of acetic acid as a byproduct obtained theoretically are certain, the amount of the azeotropic solvent added can be determined according to the type of the selected azeotropic solvent.

[0031] For example, taking the azeotropic solvent toluene as an example, the mass ratio of the ternary azeotropic solvent water: ethanol: toluene is about 1:3:4. The mixed solvent is separated into layers after cooling, wherein the ratio of water: ethanol: toluene in the upper layer solvent is about 1:5:27. The upper layer solvent can be separated and reused.

[0032] Preferably, in step (1), in the ethanol solution of formamidine acetate, based on the volume of ethanol being 100 mL and the mass of formamidine acetate being 10-50 g (e.g., 15 g, 20 g, 25 g, 30 g, 35 g, 40 g, 45 g, etc.), and the mass concentration of the hydroiodic acid solution being 40%-60% (e.g., 45%, 50%, 55%, etc.), the amount of toluene, the azeotropic solvent, added in the first group of operations is 60-150 mL (e.g., 80 mL, 100 mL, 120 mL, 140 mL, etc.).

[0033] For example, taking the azeotropic solvent n-heptane as an example, the mass ratio of the ternary azeotropic solvent water: ethanol: n-heptane is about 1:5:10. The mixed solvent is layered after cooling, wherein the ratio of water: ethanol: n-heptane in the upper layer solvent is about 1:25:500. The upper layer solvent can be separated and reused.

[0034] Preferably, the second set of operations also includes adding the obtained upper layer solvent again to the remaining product after the reduced pressure distillation, and continuing the reduced pressure distillation and solvent recovery operations at least once (for example, twice, three times, four times, five times, six times, etc.) until the azeotropic solvent is cooled and no longer stratified.

[0035] Preferably, in step (1), in the ethanol solution of formamidine acetate, based on the volume of ethanol being 100 mL and the mass of formamidine acetate being 10-50 g (e.g., 15 g, 20 g, 25 g, 30 g, 35 g, 40 g, 45 g, etc.), and the mass concentration of the hydroiodic acid solution being 40%-60% (e.g., 45%, 50%, 55%, etc.), the amount of n-heptane added as the azeotropic solvent in the first group of operations is 150-200 mL (e.g., 160 mL, 170 mL, 180 mL, 190 mL, etc.).

[0036] Preferably, in the second set of operations, an azeotropic solvent is added into the system before the reduced pressure distillation.

[0037] Preferably, the azeotropic solvent comprises the upper layer solvent obtained in the first set of operations.

[0038] In the present invention, the main purpose of the second group of operations is to remove acetic acid. Therefore, a weakly polar solvent is selected to reduce the solubility of the product formamidine hydroiodide in acetic acid; and preferably, an azeotropic solvent with a larger proportion of acetic acid and a lower azeotropic point is selected, preferably toluene and / or n-heptane.

[0039] In the present invention, the azeotropic solvent in the second set of operations can be selected from the upper layer solvent recovered in the first set of operations, or can be selected from the newly added azeotropic solvent required.

[0040] Illustratively, the azeotropic solvents in the first group of operations and the second group of operations may be different, but considering the consistency of the two-step azeotropic process, it is preferred to use the same one, or the same combination.

[0041] Preferably, in the second set of operations, the temperature of the reduced pressure distillation is 45-55°C, such as 46°C, 48°C, 50°C, 52°C, 54°C, etc.

[0042] Preferably, the recovered solvent specifically comprises a mixed solvent obtained by cooling and extracting the reduced pressure distillation, and taking the upper layer solvent.

[0043] Taking the azeotropic solvent toluene as an example, the ratio of the binary azeotropic solvent acetic acid: toluene is about 3:7. Sodium hydroxide solution can be added to react and then the upper toluene solvent can be separated and recovered for reuse.

[0044] Taking the azeotropic solvent n-heptane as an example, the ratio of the binary azeotropic solvent acetic acid:n-heptane is about 3:7. Sodium hydroxide solution can be added to react and then the upper n-heptane solvent can be separated and recovered for reuse.

[0045] Preferably, the extraction solution comprises an aqueous sodium hydroxide solution.

[0046] Preferably, the concentration of the sodium hydroxide aqueous solution is 0.05-0.2M / L, for example, 0.06M / L, 0.08M / L, 0.1M / L, 0.12M / L, 0.14M / L, 0.16M / L, 0.18M / L, etc.

[0047] Preferably, the second set of operations also includes adding the obtained upper layer solvent again to the remaining product after the reduced pressure distillation, and continuing the reduced pressure distillation and solvent recovery operations at least once (for example, twice, three times, four times, five times, six times, etc.) until there is no visible condensation reflux at the set temperature.

[0048] Preferably, in the third group of operations, an azeotropic solvent is added into the system before the reduced pressure distillation.

[0049] Preferably, the azeotropic solvent includes the upper layer solvent obtained in the first set of operations and / or the upper layer solvent obtained in the second set of operations.

[0050] Preferably, in the third set of operations, the temperature of the reduced pressure distillation is 55-65°C, for example, 56°C, 58°C, 60°C, 62°C, 64°C, etc.

[0051] Preferably, the recovered solvent specifically comprises a mixed solvent obtained by cooling and extracting the reduced pressure distillation, and taking the upper layer solvent.

[0052] Preferably, the third group of operations also includes adding the obtained upper layer solvent again to the remaining product after the reduced pressure distillation, and continuing the reduced pressure distillation and solvent recovery operations at least once (for example, twice, three times, four times, five times, six times, etc.) until there is no visible condensation reflux.

[0053] Preferably, the extraction solution comprises an aqueous sodium hydroxide solution.

[0054] Preferably, the concentration of the sodium hydroxide aqueous solution is 0.05-0.2M / L, for example, 0.06M / L, 0.08M / L, 0.1M / L, 0.12M / L, 0.14M / L, 0.16M / L, 0.18M / L, etc.

[0055] Preferably, the vacuum degree of the reduced pressure distillation is 5-15 mbar, for example, 6 mbar, 8 mbar, 10 mbar, 12 mbar, 14 mbar, etc.

[0056] Preferably, in step (2), after the last set of vacuum distillation and solvent recovery operations are completed, the product of the vacuum distillation is further cleaned and dried.

[0057] In the present invention, by adding an azeotropic solvent, the distillation purification temperature can be lowered (in the prior art, the normal distillation temperature is about 90°C or even close to 100°C, and the distillation is incomplete, while the distillation temperature in the present invention can be lowered to within 65°C), the oxidation and volatilization of hydroiodic acid can be inhibited, the product purity can be improved, the number of cleaning times can be reduced, and the amount of cleaning solvent used can be reduced.

[0058] Preferably, the cleaning solvent comprises diethyl ether.

[0059] Preferably, the cleaning is performed 1-3 times, for example, once, twice, three times, etc.

[0060] Preferably, the amount of the cleaning solvent added is 10-30 mL, such as 15 mL, 20 mL, 25 mL, etc.

[0061] As a preferred technical solution, the preparation method comprises the following steps:

[0062] (1) mixing an ethanol solution of formamidine acetate and a hydroiodic acid solution, reacting them to obtain a crude formamidine hydroiodide product;

[0063] (2) adding an azeotropic solvent to the crude formamidine hydroiodide product, setting the water bath temperature to 35-45° C., the vacuum degree to 5-15 mbar, and performing reduced pressure distillation until no condensation reflux is visible at this temperature;

[0064] (3) After cooling, the mixed solvent is extracted and separated to obtain the upper layer solvent to achieve solvent recovery;

[0065] Optionally, the obtained upper layer solvent is added again to the remaining product after the reduced pressure distillation, and the reduced pressure distillation and solvent recovery are continued at 35-45° C. and a vacuum degree of 5-15 mbar, and the above operation is performed at least once;

[0066] (4) adding the recovered upper layer solvent and / or the added azeotropic solvent to the residual product after the reduced pressure distillation in step (2) or (3), setting the water bath temperature to 45-55° C., the water bath temperature is higher than the water bath temperature in step (2) or (3), the vacuum degree is 5-15 mbar, and performing reduced pressure distillation until no condensation reflux is visible at this temperature;

[0067] (5) After cooling, extracting and separating the recovered mixed solvent to obtain the upper layer solvent to achieve solvent recovery;

[0068] Optionally, the obtained upper layer solvent is added again to the remaining product after the reduced pressure distillation, and the reduced pressure distillation and solvent recovery are continued at 45-55° C. and a vacuum degree of 5-15 mbar, and the above operation is performed at least once;

[0069] (6) adding the recovered upper layer solvent and / or the added azeotropic solvent to the residual product after the reduced pressure distillation in step (4) or (5), setting the water bath temperature to 55-65° C., which is higher than the water bath temperature in step (4) or (5), and the vacuum degree to 5-15 mbar, and performing reduced pressure distillation until no condensation reflux is visible at this temperature;

[0070] (7) After cooling, extracting and separating the recovered mixed solvent to obtain the upper layer solvent to achieve solvent recovery;

[0071] Optionally, the obtained upper layer solvent is added again to the remaining product after the reduced pressure distillation, and the reduced pressure distillation and solvent recovery are continued at 55-65° C. and a vacuum degree of 5-15 mbar, and the above operation is performed at least once;

[0072] (8) washing and drying the reduced pressure distillation product obtained in step (6) or (7) to obtain the formamidine hydroiodide.

[0073] Preferably, in steps (5) and (7), the extraction and separation process comprises: adding sodium hydroxide solution to the recovered mixed solvent for extraction and separation.

[0074] In a second aspect, the present invention provides formamidine hydroiodide, which is obtained by the preparation method described in the first aspect.

[0075] In a third aspect, the present invention provides a perovskite solar cell, wherein the perovskite solar cell comprises the formamidine hydroiodide described in the second aspect.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] (1) In the present invention, when the formamidine hydroiodide formed by the preparation method, the product has high yield, high purity and low water content. The obtained formamidine hydroiodide is used for perovskite solar cells, and the battery efficiency, open circuit voltage, current density and fill factor of the battery are higher.

[0078] (2) In the present invention, when the formamidine hydroiodide formed by the preparation method, the yield of the product is above 90%, the purity is above 99.9%, the water content is less than 10 mg / kg, and when the formamidine hydroiodide is used in a perovskite solar cell, the cell efficiency is above 15.9%, the open circuit voltage is above 1.04 V, and the current density is above 22.53 mA / cm 2 Above, the filling factor is above 69.6%.

[0079] (3) In the prior art method for preparing formamidine hydroiodide, the boiling points of water and by-product acetic acid increase because a large amount of formamidine hydroiodide is dissolved. As the distillation process proceeds, the concentration gradually increases and the boiling point becomes higher and higher. It is necessary to use a water bath temperature close to 100° C. in combination with a high vacuum to remove the formamidine hydroiodide. Even so, the whole process is slow and it is difficult to completely remove the formamidine hydroiodide. During the long distillation process and at high temperature, the product will undergo side reactions such as decomposition and oxidation.

[0080] In the present invention, by using the azeotropic system, a high-temperature distillation environment is avoided, the distillation speed is accelerated, the use of cleaning solvents is reduced, the quality and yield of the product are improved, the production method is simplified, and it is suitable for process amplification. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 is a comparison chart of the NMR results of the formamidine hydroiodide described in Example 1 and Comparative Example 1;

[0082] Figure 2 is a comparison chart of the filling factor results of the formamidine hydroiodide described in Example 1 and Comparative Example 1;

[0083] Figure 3 is a comparison chart of the battery efficiency results of the formamidine hydroiodide described in Example 1 and Comparative Example 1;

[0084] Figure 4 It is a comparison chart of the open circuit voltage results of the formamidine hydroiodide described in Example 1 and Comparative Example 1;

[0085] Figure 5 It is a comparison chart of the short-circuit current results of the formamidine hydroiodide described in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0086] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0087] Example 1

[0088] This embodiment provides a method for preparing formamidine hydroiodide, the preparation method comprising the following steps:

[0089] (1) Dissolve 15 g of formamidine acetate in 50 mL of ethanol, add 21 mL of 57% hydroiodic acid solution at 0° C., and react for 2 hours to obtain a crude product of formamidine hydroiodide;

[0090] (2) adding 50 mL of toluene solvent to the crude formamidine hydroiodide product, setting the water bath temperature to 40° C., adjusting the vacuum degree to 10 mbar, and performing reduced pressure distillation until no visible condensation reflux is observed at this temperature, and the mass ratio of water: ethanol: toluene in the distilled solvent is approximately 1:3:4;

[0091] (3) After cooling, the upper layer solvent is obtained, and the upper layer solvent contains water: ethanol: toluene in a ratio of about 1:5:27, and the obtained upper layer solvent is added again to the remaining product after the vacuum distillation, and the vacuum distillation is continued at a water bath temperature of 40° C. and a vacuum degree of 10 mbar until no condensation reflux is visible at this temperature;

[0092] (4) Repeat step (3) twice;

[0093] (5) cooling the upper layer solvent recovered in step (4), extracting and separating the liquid using 50 mL of 0.1 M / L sodium hydroxide aqueous solution to obtain the upper layer solvent;

[0094] (6) adding the upper layer solvent recovered in step (5) to the remaining product after distillation again, raising the water bath temperature to 50° C., adjusting the vacuum degree to 10 mbar, and continuing the reduced pressure distillation until no condensation reflux is visible at this temperature, and the solvent recovered by the reduced pressure distillation contains acetic acid:toluene in a ratio of about 3:7;

[0095] After cooling, the mixture was extracted with 50 mL of 0.1 M / L sodium hydroxide aqueous solution to obtain the upper solvent layer;

[0096] (7) Repeat step (6) twice;

[0097] (8) adding the upper layer solvent recovered in step (7) to the remaining product after distillation again, raising the water bath temperature to 60° C., adjusting the vacuum degree to 10 mbar, and continuing the reduced pressure distillation until no condensation reflux is visible at this temperature;

[0098] (9) The product obtained by the reduced pressure distillation in step (8) is washed three times with 20 mL of ether and dried to obtain the formamidine hydroiodide.

[0099] Example 2

[0100] This embodiment provides a method for preparing formamidine hydroiodide, the preparation method comprising the following steps:

[0101] (1) Dissolve 15 g of formamidine acetate in 50 mL of ethanol, add 21 mL of 57% hydroiodic acid solution at 0° C., and react for 2 hours to obtain a crude product of formamidine hydroiodide;

[0102] (2) adding 75 mL of n-heptane solvent to the crude formamidine hydroiodide product, setting the water bath temperature to 40° C., and adjusting the vacuum degree to 10 mbar until no condensation reflux is visible at this temperature, and the mass ratio of water: ethanol: n-heptane in the solvent removed by distillation is approximately 1:5:10;

[0103] (3) After cooling, extracting and separating the liquid to obtain the upper solvent, the upper solvent containing water: ethanol: n-heptane in a ratio of about 1:25:500, adding the obtained upper solvent to the remaining product after distillation again, and continuing the reduced pressure distillation at a water bath temperature of 40° C. and a vacuum degree of 10 mbar until no condensation reflux is visible at this temperature;

[0104] (4) Repeat step (3) twice;

[0105] (5) cooling the upper layer solvent recovered in step (4), extracting and separating the liquid using 50 mL of 0.1 M / L sodium hydroxide aqueous solution to obtain the upper layer solvent;

[0106] (6) adding the upper layer solvent recovered in step (5) to the remaining product after distillation again, raising the water bath temperature to 50° C., adjusting the vacuum degree to 10 mbar, and continuing the reduced pressure distillation until no condensation reflux is visible at this temperature, and the solvent recovered by the reduced pressure distillation contains acetic acid:n-heptane in a ratio of about 3:7;

[0107] After cooling, the mixture was extracted with 50 mL of 0.1 M / L sodium hydroxide aqueous solution to obtain the upper solvent layer;

[0108] (7) Repeat step (6) twice;

[0109] (8) adding the upper layer solvent recovered in step (7) to the remaining product after distillation again, raising the water bath temperature to 60° C., adjusting the vacuum degree to 10 mbar, and continuing the reduced pressure distillation until no condensation reflux is visible at this temperature;

[0110] (9) The product obtained by the reduced pressure distillation in step (8) is washed three times with 20 mL of ether and dried to obtain the formamidine hydroiodide.

[0111] Example 3

[0112] This embodiment provides a method for preparing formamidine hydroiodide, the preparation method comprising the following steps:

[0113] (1) Dissolve 5 g of formamidine acetate in 50 mL of ethanol, add 7 mL of 80% hydroiodic acid solution at 0° C., and react for 3 hours to obtain a crude product of formamidine hydroiodide;

[0114] (2) adding 30 mL of cyclohexane and 30 mL of benzene to the crude product of formamidine hydroiodide, setting the water bath temperature to 35° C. and the vacuum degree to 15 mbar, and performing reduced pressure distillation until no condensation reflux is visible at this temperature, and the mass ratio of water: ethanol: cyclohexane and benzene in the solvent removed by distillation is approximately 2:5:20:20;

[0115] (3) After cooling, the mixed solvent is extracted and separated to obtain the upper layer solvent to achieve solvent recovery;

[0116] The obtained upper layer solvent is added again to the remaining product after the vacuum distillation, and the vacuum distillation and solvent recovery are continued at 35° C. and a vacuum degree of 15 mbar, and the above operation is performed twice;

[0117] (4) adding the recovered upper layer solvent to the residual product after the reduced pressure distillation in step (3), setting the water bath temperature to 45° C. and the vacuum degree to 15 mbar, and performing reduced pressure distillation until no condensation reflux is visible at this temperature;

[0118] (5) After cooling, extract the separated liquid with 50 mL of 0.1 M / L sodium hydroxide aqueous solution to obtain the upper layer solvent to recover the solvent;

[0119] The obtained upper layer solvent is added again to the residual product after the vacuum distillation, and the vacuum distillation and solvent recovery are continued at 45° C. and a vacuum degree of 15 mbar. The solvent recovered by the vacuum distillation contains acetic acid: cyclohexane: benzene in a ratio of about 1:25:25, and the above operation is performed twice;

[0120] (6) adding the recovered upper layer solvent to the residual product after the reduced pressure distillation in step (5), setting the water bath temperature to 55° C. and the vacuum degree to 15 mbar, and performing reduced pressure distillation until no condensation reflux is visible at this temperature;

[0121] (7) The reduced pressure distillation product obtained in step (6) is washed three times with 10 mL of ether and dried to obtain the formamidine hydroiodide.

[0122] Comparative Example 1

[0123] This comparative example provides a method for preparing formamidine hydroiodide, which is carried out according to the document J. Mater. Chem. A, 2015, 3, 9171-9178, and specifically comprises the following steps:

[0124] (1) Dissolve 15 g of formamidine acetate in 50 mL of ethanol, add 21 mL of 57% hydroiodic acid solution at 0° C., and react for 2 hours to obtain a crude product of formamidine hydroiodide;

[0125] (2) removing the solvent from the crude formamidine hydroiodide product obtained in step (1) by rotary evaporation at 50° C. for 1 h;

[0126] (3) the product obtained in step (2) was washed with ethanol by stirring for 30 minutes and then filtered;

[0127] (4) The product obtained in step (3) was washed three times with 100 mL of ether and dried at 60° C. in a vacuum environment for 24 hours to obtain the formamidine hydroiodide.

[0128] Performance Testing

[0129] 1. The formamidine hydroiodide obtained by the preparation methods described in Examples 1-3 and Comparative Example 1 was tested as follows:

[0130] (1) Yield: calculated based on the ratio of actual product quality to theoretical yield;

[0131] (2) Purity: calculated based on NMR spectrum;

[0132] (3) Water content: determined according to the Karl Fischer water content test method;

[0133] 2. The formamidine hydroiodide obtained by the preparation method described in Examples 1-3 and Comparative Example 1 was applied to the perovskite solar cell for testing. Under the AM1.5 standard spectrum, six cells were used in each test to test IV at the same time every day for three consecutive days to obtain the fill factor, cell efficiency, open circuit voltage and current density of the cell.

[0134] The test results are summarized in Table 1 and Figures 1 to 5 middle.

[0135] Table 1

[0136]

[0137]

[0138] In the table, “~” means “approximately equal to”.

[0139] From the analysis of the data in Table 1, it can be seen that when the formamidine hydroiodide formed by the preparation method of the present invention has a high yield, high purity, and low water content, the obtained formamidine hydroiodide is used for perovskite solar cells, and the battery efficiency, open circuit voltage, current density, and fill factor of the battery are better; when the formamidine hydroiodide formed by the preparation method of the present invention has a yield of more than 90%, a purity of more than 99.9%, and a water content of less than 10 mg / kg, the formed formamidine hydroiodide is used for perovskite solar cells, and the battery efficiency is more than 15.9%, the open circuit voltage is more than 1.04 V, and the current density is 22.53 mA / cm 2 Above, the filling factor is above 69.6%.

[0140] Analysis of Comparative Example 1 and Example 1 shows that the performance of Comparative Example 1 is not as good as that of Example 1. The specific results are compared in Tables 1 and Figures 1 to 5 are reflected in; for example, Figure 1 In Example 1, there is no peak of acetate (residual formamidine acetate) in the range of 1.0-2.0 ppm; the effect of the bimodal fractal is better in the range of 8.5-9.0 ppm, indicating that the water content is less; Figure 2 , Figure 3 , Figure 4 and Figure 5 The battery efficiency, open circuit voltage, current density and fill factor of the two batteries were compared, and Example 1 performed better, which proved that the formamidine hydroiodic acid prepared by the preparation method of the present invention has better performance.

[0141] The applicant declares that the present invention illustrates the detailed method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing formamidine hydroiodide, characterized in that: The preparation method comprises the following steps: (1) mixing an ethanol solution of formamidine acetate and a hydroiodic acid solution, reacting them to obtain a crude formamidine hydroiodide product; (2) mixing the crude formamidine hydroiodide product in step (1) with an azeotropic solvent, and performing at least three sets of reduced pressure distillation and solvent recovery operations to obtain formamidine hydroiodide; The operation of the reduced pressure distillation and solvent recovery includes a first group of operations, a second group of operations and a third group of operations; in the first group of operations, the second group of operations and the third group of operations, the temperature of the reduced pressure distillation is increased successively.

2. The preparation method according to claim 1, characterized in that: In step (2), the azeotropic solvent includes any one of benzene, toluene, xylene, n-heptane, n-octane, cyclohexane or carbon tetrachloride, or a combination of at least two thereof.

3. The preparation method according to claim 1, characterized in that: In the first set of operations, the temperature of the reduced pressure distillation is 35-45°C.

4. The preparation method according to claim 1, characterized in that: In the first group of operations, the solvent recovery specifically includes cooling and extracting the mixed solvent obtained by vacuum distillation, and taking the upper layer of solvent.

5. The preparation method according to claim 4, characterized in that: The first set of operations also includes adding the obtained upper layer solvent to the remaining product after the reduced pressure distillation, and continuing the reduced pressure distillation and solvent recovery operations until there is no visible condensation reflux at the set temperature.

6. The preparation method according to claim 1, characterized in that: In the second group of operations, an azeotropic solvent is added into the system before the reduced pressure distillation.

7. The preparation method according to claim 6, characterized in that: The azeotropic solvent includes the upper layer solvent obtained in the first set of operations.

8. The preparation method according to claim 1, characterized in that: In the second set of operations, the temperature of the reduced pressure distillation is 45-55°C.

9. The preparation method according to claim 1, characterized in that: In the second group of operations, the solvent recovery specifically includes cooling and extracting the mixed solvent obtained by vacuum distillation, and taking the upper layer of solvent.

10. The preparation method according to claim 9, characterized in that: The second set of operations also includes adding the obtained upper layer solvent to the remaining product after the reduced pressure distillation, and continuing to perform at least one reduced pressure distillation and solvent recovery operation until there is no visible condensation reflux at the set temperature.

11. The preparation method according to claim 1, characterized in that: In the third group of operations, an azeotropic solvent is added into the system before the reduced pressure distillation.

12. The preparation method according to claim 11, characterized in that: The azeotropic solvent includes the upper layer solvent obtained in the first set of operations and / or the upper layer solvent obtained in the second set of operations.

13. The preparation method according to claim 1, characterized in that: In the third set of operations, the temperature of the reduced pressure distillation is 55-65°C.

14. The preparation method according to claim 1, characterized in that: In the third group of operations, the solvent recovery specifically includes cooling and extracting the mixed solvent obtained by vacuum distillation, and taking the upper layer of solvent.

15. The preparation method according to claim 14, characterized in that: The third group of operations also includes adding the obtained upper layer solvent to the remaining product after the reduced pressure distillation, and continuing to perform at least one reduced pressure distillation and solvent recovery operation until there is no visible condensation reflux.

16. The preparation method according to any one of claims 4, 9 and 14, characterized in that: The extraction solution includes an aqueous sodium hydroxide solution.

17. The preparation method according to claim 16, characterized in that: The concentration of the sodium hydroxide aqueous solution is 0.05-0.2M / L.

18. The preparation method according to claim 1, characterized in that: The vacuum degree of the reduced pressure distillation is 5-15 mbar.

19. The preparation method according to claim 1, characterized in that: In step (2), after the last set of vacuum distillation and solvent recovery operations are completed, the process further includes washing and drying the vacuum distillation product.

20. The preparation method according to claim 19, characterized in that: The cleaning solvent includes diethyl ether.

21. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: (1) mixing an ethanol solution of formamidine acetate and a hydroiodic acid solution, reacting them to obtain a crude formamidine hydroiodide product; (2) adding an azeotropic solvent to the crude formamidine hydroiodide product, setting the water bath temperature to 35-45° C., the vacuum degree to 5-15 mbar, and performing reduced pressure distillation until no condensation reflux is visible at this temperature; (3) After cooling, the mixed solvent is extracted and separated to obtain the upper layer solvent to achieve solvent recovery; The obtained upper layer solvent is added again to the remaining product after the reduced pressure distillation, and the reduced pressure distillation and solvent recovery are continued at 35-45° C. and a vacuum degree of 5-15 mbar, and the above operation is performed at least once; (4) adding the recovered upper layer solvent and / or the added azeotropic solvent to the residual product after the reduced pressure distillation in step (2) or (3), setting the water bath temperature to 45-55° C., the water bath temperature is higher than the water bath temperature in step (2) or (3), the vacuum degree is 5-15 mbar, and performing reduced pressure distillation until no condensation reflux is visible at this temperature; (5) After cooling, the mixed solvent is extracted and separated to obtain the upper layer solvent to achieve solvent recovery; The obtained upper layer solvent is added again to the remaining product after the reduced pressure distillation, and the reduced pressure distillation and solvent recovery are continued at 45-55° C. and a vacuum degree of 5-15 mbar, and the above operation is performed at least once; (6) adding the recovered upper layer solvent and / or the added azeotropic solvent to the residual product after the reduced pressure distillation in step (4) or (5), setting the water bath temperature to 55-65° C., which is higher than the water bath temperature in step (4) or (5), and the vacuum degree to 5-15 mbar, and performing reduced pressure distillation until no condensation reflux is visible at this temperature; (7) After cooling, extracting and separating the obtained mixed solvent to obtain the upper layer solvent to achieve solvent recovery; The obtained upper layer solvent is added again to the remaining product after the reduced pressure distillation, and the reduced pressure distillation and solvent recovery are continued at 55-65° C. and a vacuum degree of 5-15 mbar, and the above operation is performed at least once; (8) washing and drying the reduced pressure distillation product obtained in step (6) or (7) to obtain the formamidine hydroiodide.

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