Bis(trifluoromethanesulfonyl)imide formamidine compound structure, preparation method and application thereof

Abstract

The present invention provides a bis(trifluoromethanesulfonyl)imide formamidine compound and a preparation method thereof. The chemical formula of the compound is C3H5F6N3O4S2 or (CF3SO2)2NNH2=CHNH2, the molecular weight is 325.2g / mol, and the general structural formula of the compound is shown as follows (the same compound, four different structural expressions). There are two preparation methods, both of which can react completely within 20 minutes at room temperature. The compound is a white crystal or powder and does not contain active alkali metal elements such as Li contained in inorganic bis(trifluoromethanesulfonyl)imide salts such as commonly used solar cell charge transport layer additives (LiTSFI, NaTSFI, KTSFI, AgTSFI). + 、Na + , K + 、Ag + , with advantages such as chemical inertness, environmental friendliness, abundant raw materials, adjustable size, good crystallinity, and high mobility. This preparation method is simple, convenient, and reproducible, which is conducive to large-scale industrial preparation and can be used as a charge transport layer material in solar cells.

Description

Technical Field

[0001] The present invention relates to a bis(trifluoromethanesulfonyl)imide formamidine compound structure, a preparation method and an application thereof. Background Art

[0002] Bistrifluoromethanesulfonimide (TSFI) salt compounds are a class of excellent charge transport layer additives for solar cells. - The special chemical structure of the cations has high electrochemical stability and conductivity; and the cations are mostly active alkali metals such as Li + 、Na + , K + 、Ag + Etc., there are moisture absorption and instability: Compared with known inorganic bis(trifluoromethanesulfonyl)imide salts such as LiTSFI, NaTSFI, KTSFI, and AgTSFI, the present invention's bis(trifluoromethanesulfonyl)imide formamidine compound (FATSFI) based on formamidine (FA) cation has not been reported, and it has the advantages of 1) improving charge extraction from the photovoltaic layer; 2) stabilizing the photovoltaic layer interface; 3) enhancing charge transfer performance; 4) inhibiting water and oxygen corrosion; 5) improving high-temperature stability; 6) improving photoelectric conversion efficiency. Therefore, the development of a bis(trifluoromethanesulfonyl)imide formamidine compound with chemical inertness, high reproducibility, simple synthesis, environmental friendliness, and high mobility to achieve solar cells with high photoelectric conversion efficiency is an urgent market demand and also of great significance to the field of this technology. It is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0003] The present invention provides a bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) compound, characterized by a chemical formula of C3H5F6N3O4S2 or (CF3SO2)2NNH2=CHNH2, a molecular weight of 325.2 g / mol, and a chemical structure as shown in the attached figure. Figure 1 As shown (the same compound, four different structural expressions).

[0004] The specific technical scheme is as follows: The preparation method of bis(trifluoromethanesulfonyl)imide formamidine comprises the following steps:

[0005] Bistrifluoromethanesulfonyl imide (CAS No. 82113-65-3) and formamidine acetate (CAS No. 3473-63-0) are dissolved in a solvent respectively, and the two solutions are slowly mixed under stirring at room temperature. When the two raw materials are mixed in an equal stoichiometric ratio (molar ratio of 1:1), the reaction is terminated. The solvent and the by-product acetic acid in the reaction solution are completely distilled off by vacuum distillation to obtain the target crude product. After recrystallization and vacuum drying, bistrifluoromethanesulfonyl imide formamidine with a purity of up to 99.9% is prepared.

[0006] Silver bis(trifluoromethanesulfonyl imide) (CAS No. 189114-61-2) and formamidine halide are dissolved in solvents respectively, and the two solutions are slowly mixed under stirring at room temperature. The reaction is terminated when the two raw materials are mixed in an equal stoichiometric ratio (molar ratio of 1:1). The by-product silver halide precipitate obtained by the reaction is filtered out, and the filtrate is evaporated to dryness by vacuum distillation to obtain the target crude product. After recrystallization and vacuum drying, bis(trifluoromethanesulfonyl imide formamidine halide) with a purity of up to 99.9% is prepared.

[0007] As a preferred embodiment, the formamidine halide described in

[0006] is formamidine chloride (CAS No. 6313-33-3), formamidine bromide (CAS No. 146958-06-7), or formamidine iodide (CAS No. 879643-71-7).

[0008] As a preferred embodiment, in the method for preparing bis(trifluoromethanesulfonyl)imide formamidine described in

[0005] , the solvent is a solvent with a low boiling point below 180°C and miscible with the by-product acetic acid, such as water, alcohols, ketones, ethers, lipids, benzene, etc.

[0009] As a preferred embodiment, in the method for preparing bis(trifluoromethanesulfonyl)imide formamidine described in

[0006] , the solvent is a solvent that does not dissolve the silver halide precipitate, such as water, alcohols, ketones, ethers, lipids, benzene, etc.

[0010] As a preferred embodiment, in the method for preparing bis(trifluoromethanesulfonyl)imide formamidine described in

[0005] , the amounts of trifluoromethanesulfonyl imide and formamidine acetate are in an equal stoichiometric ratio (molar ratio of 1:1) to ensure that only the target product and the by-product acetic acid are produced after the reaction, and to ensure that all solvents and by-products can be evaporated by vacuum distillation, thereby improving the yield.

[0011] As a preferred embodiment, in the method for preparing bis(trifluoromethanesulfonyl)imide formamidine described in

[0006] , the amounts of bis(trifluoromethanesulfonyl)imide silver and formamidine halide are used in an equal stoichiometric ratio (molar ratio of 1:1) to ensure that only the target product and the by-product silver halide are precipitated after the reaction, and to ensure that all by-products can be removed by filtration, thereby improving the yield.

[0012] As a preferred embodiment, the preparation method of bis(trifluoromethanesulfonyl)imide formamidine described in

[0005] has the following reaction formula:

[0013]

[0014] As a preferred embodiment, the preparation method of bis(trifluoromethanesulfonyl)imide formamidine described in

[0006] has the following reaction formula:

[0015]

[0016] In one embodiment, the formamidine bis(trifluoromethanesulfonyl)imide (FATSFI) is a single crystal or powder.

[0017] The above-mentioned bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) does not contain active alkali metal elements and has the advantages of being chemically inert, environmentally friendly, having abundant raw materials, adjustable size, good crystallinity, and high mobility.

[0018] The present invention also provides the use of the bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) in the preparation of solar cells.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention discloses a bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) and its preparation method and application. The bis(trifluoromethanesulfonyl)imide salt does not contain active alkali metal elements such as Li contained in inorganic bis(trifluoromethanesulfonyl)imide salts such as common solar cell charge transport layer additives (LiTSFI, NaTSFI, KTSFI, AgTSFI). + 、Na + , K + 、Ag + , with advantages such as chemical inertness, environmental friendliness, abundant raw materials, adjustable size, good crystallinity, and high mobility. This preparation method is simple, convenient, and reproducible, which is conducive to large-scale industrial preparation and can be used as a charge transport layer material in solar cells.

[0021] Therefore, after a large number of experiments, the inventors selected the bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) with 2,2″,7,7″-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) and 4-tert-butylpyridine (t-BP), doped and mixed them in proportion, and applied them as charge transport layer materials in solar cells.

[0022] In one embodiment, the molar ratio of bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) to 2,2″,7,7″-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) is 1:0.1 to 1:100; the molar ratio of bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) to 4-tert-butylpyridine (t-BP) is 1:0.1 to 1:10. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the general structural formula of the bis(trifluoromethanesulfonyl)imide formamidine (FATSFI for short) compound of the present invention (the same compound has four different structural expressions).

[0024] Figure 2 is the purified FATFSI of Example 3 of the present invention 1 H NMR (DMSO) spectrum.

[0025] Figure 3 is the purified FATFSI of Example 3 of the present invention 19 F NMR (DMSO) spectrum.

[0026] Figure 4 is the purified FATSFI of Example 3 of the present invention 13 C NMR (DMSO) spectrum.

[0027] Figure 5 This is the differential scanning calorimetry (DSC) test curve of the purified FATSFI in Example 3 of the present invention.

[0028] Figure 6 This is a thermogravimetric analyzer (TGA) test curve of the purified FATSFI in Example 3 of the present invention.

[0029] Figure 7 3. It is a scanning electron microscope (SEM) photograph of the top surface of the solar cell before and after coating FATSFI as the charge transport layer material according to Example 4 of the present invention.

[0030] Figure 8 1 is a scanning electron microscope (SEM) photograph of a cross section of a solar cell before and after coating with FATSFI as a charge transport layer material according to Example 4 of the present invention.

[0031] Figure 9 This is a charge mobility curve measured by the space charge limited current method (SCLC) using FATSFI of Example 4 of the present invention as a charge transport layer material.

[0032] Figure 10 It is the work function of FATSFI in Example 4 of the present invention as the charge transport layer material measured by ultraviolet photoelectron spectroscopy (UPS).

[0033] Figure 11 This is the voltage-current (JV) curve measured for the solar cell using FATSFI as the charge transport layer material according to Example 4 of the present invention. DETAILED DESCRIPTION

[0034] The essential features and advantages of the present invention are further described below with reference to examples, but the present invention is not limited to the examples listed.

[0035] Example 1

[0036] Synthesis of bis(trifluoromethanesulfonyl)imide formamidine.

[0037] In a reactor equipped with an agitator, 281 g (1 mol, 99% purity) of bistrifluoromethanesulfonyl imide (CAS No. 82113-65-3) and 500 mL of anhydrous ethanol were added. After the raw materials were completely dissolved, the reaction temperature was maintained at room temperature (25±10°C). 104 g (1 mol, 99% purity) of formamidine acetate (CAS No. 3473-63-0) dissolved in 100 mL of anhydrous ethanol solution was slowly added to the reactor. The reaction was stirred at room temperature for 1 hour to complete the reaction. After the reaction, the ethanol solvent and the byproduct acetic acid in the solution were completely removed by vacuum distillation, and the crude bistrifluoromethanesulfonyl imide formamidine product was obtained by vacuum drying at 60°C as white crystals with a yield of not less than 95%.

[0038] Example 2

[0039] Synthesis of bis(trifluoromethanesulfonyl)imide formamidine.

[0040] In a reactor equipped with an agitator, 38.8 g (0.1 mol, 99% purity) of silver bis(trifluoromethanesulfonyl imide) (CAS No. 189114-61-2) and 200 mL of anhydrous ethanol were added. After the raw materials were completely dissolved, the reaction temperature was maintained at room temperature (25±10°C). 50 mL of anhydrous ethanol solution containing 17.2 g (0.1 mol, 99% purity) of formamidine iodide (CAS No. 879643-71-7) was slowly added to the reactor. The reaction was stirred at room temperature for 1 hour to complete the reaction. The silver iodide precipitate produced by the reaction was filtered to remove the silver iodide precipitate, and the ethanol solvent in the filtrate was completely distilled off under reduced pressure. The crude bis(trifluoromethanesulfonyl imide) formamidine product was obtained as white crystals at a yield of not less than 95%.

[0041] Table 1 Effect of different raw material stoichiometric ratios on the purity and yield of bis(trifluoromethanesulfonyl)imide formamidine

[0042]

[0043] Example 3

[0044] Purification of Bis(trifluoromethanesulfonyl)imide Formamidine

[0045] The crude product of bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) obtained above was dissolved in an appropriately treated anhydrous polar solvent, and then anhydrous dichloromethane was slowly added dropwise to the solution under stirring until a small amount of crystals precipitated. After being stored in a refrigerator at -20°C for 24 hours, pure white needle-shaped FATSFI crystals were obtained by filtration. After testing, the purity of the product after two recrystallization treatments can reach 99.9%.

[0046] like Figure 2 Shown is the purified FATSFI 1 H NMR (DMSO) spectrum; Figure 3 Shown is the purified FATSFI 19 FNMR (DMSO) spectrum; such as Figure 4 Shown is the purified FATSFI of Example 3 of the present invention. 13 C NMR (DMSO) spectrum.

[0047] 1 H NMR (DMSO) δ: 8.81 (4H, 2×NH2), 7.80 (1H, CH)

[0048] 19 F NMR (DMSO) δ: -78.63 (6F, 2×CF3)

[0049] 13 C NMR (DMSO) δ: 156.68 (1C, CH), 124.35~114.75 (2C, 2×CF3)

[0050] like Figure 5 This is the differential scanning calorimetry (DSC) test curve of the purified FATSFI of Example 3 of the present invention.

[0051] T m =79.8℃, T c =55.9℃

[0052] like Figure 6 This is the thermogravimetric analyzer (TGA) test curve of the purified FATSFI of Example 3 of the present invention.

[0053] T d =326℃

[0054] The present invention also provides the use of the bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) in the preparation of solar cells.

[0055] Example 4

[0056] Application of bis(trifluoromethanesulfonyl)imide formamidine (FATSFI) in the preparation of solar cells.

[0057] 7 mg of bis(trifluoromethanesulfonyl)imide formamidine (FATSFI), 28 mg of 4-tert-butylpyridine (t-BP), and 90 mg of 2,2″,7,7″-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) were dissolved in 1 mL of chlorobenzene to obtain a FATSFI-based charge transport layer material solution.

[0058] The FATSFI-based charge transport layer material solution obtained above was spin-coated on the photovoltaic layer to form a thin film at a rotation speed of 4000 rpm, an acceleration of 2000 rpm, and a spin time of 30 seconds.

[0059] like Figure 7 Shown are scanning electron microscope (SEM) photos of the top surface of the solar cell before and after coating with FATSFI as the charge transport layer material in Example 4 of the present invention. The photos show that the original photovoltaic layer is completely covered after coating with the FATSFI-based charge transport layer.

[0060] like Figure 8 Shown are cross-sectional scanning electron microscope (SEM) photographs of a solar cell before and after coating with FATSFI as a charge transport layer material according to Example 4 of the present invention. The photograph shows that the thickness of the FATSFI-based charge transport layer after coating is approximately 100 to 150 nm.

[0061] like Figure 9 The charge mobility curve of FATSFI as the charge transport layer material in Example 4 of the present invention is measured by the space charge limited current method (SCLC). The transfer rate of the charge transport layer based on FATSFI is calculated to be 5.66×10 -4 cm 2 v -1 s -1 .

[0062] like Figure 10 The figure shows the work function of FATSFI in Example 4 of the present invention as a charge transport layer material measured by ultraviolet photoelectron spectroscopy (UPS), and it can be calculated that WF=4.85eV and VBM=0.33eV.

[0063] like Figure 11The voltage-current (JV) curve of the solar cell with FATSFI as the charge transport layer material according to Example 4 of the present invention is shown. The positive scan open circuit voltage is 1.179 V and the short circuit current is 25.27 mA / cm 2 , fill factor is 80.40%, conversion efficiency is 23.96%; reverse scan open circuit voltage is 1.184V, short circuit current is 25.28mA / cm 2 , the fill factor is 82.47%, and the conversion efficiency is 24.68%.

[0064] It should be noted that the above preferred embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit and essence of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. Application of a bis(trifluoromethanesulfonyl imide) formamidine compound in the preparation of solar cells. The structural formula of the bis(trifluoromethanesulfonyl imide) formamidine compound is shown below:

Images