A low-boiling ink, a method for preparing a perovskite film therefrom and photovoltaic applications thereof

Abstract

The application discloses a low-boiling-point ink, a method for preparing a perovskite film by using the low-boiling-point ink and photovoltaic application of the perovskite film. The application adopts a low-boiling-point solvent prepared by mixing multiple components to prepare a perovskite precursor ink. The ink does not need any post-treatment after film coating, and a room-temperature stable perovskite precursor film can be prepared by natural evaporation of the solvent. A high-quality perovskite film can be obtained after heat annealing of the precursor film. The crystallization rate and crystallization quality of the film can be accurately controlled by adjusting the low-boiling-point solvent components and constructing the precursor structure.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and in particular to a low-boiling-point ink, a method for preparing perovskite thin films therefrom, and their photovoltaic applications. Background Technology

[0002] The rapid depletion of traditional fossil fuels has forced humanity to seek new renewable energy sources. Photovoltaic technology, which converts sunlight into electricity, has become a promising alternative to fossil fuels. Perovskite photovoltaics have distinguished themselves among various photovoltaic technologies due to their rapidly improving photoelectric conversion efficiency and low-cost solution preparation. Perovskite thin films, as the active layer material in perovskite photovoltaics, directly affect the photoelectric conversion efficiency of the device. Depositing high-quality, large-area perovskite thin films using solution methods is a crucial part of the commercialization of perovskite materials.

[0003] Currently, precursor inks used for solution deposition of perovskite thin films primarily employ high-boiling-point aprotic solvents. Common solvents such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and γ-butyrolactone (GBL) are typically difficult to remove during film deposition. Residual solvents significantly slow down the nucleation rate and result in poor film morphology. This directly impacts the application of perovskite materials in photovoltaic technology.

[0004] Existing perovskite precursor inks often require post-treatment methods such as solvent removal, vacuum annealing, substrate heating, and air knife purging during the deposition process in order to quickly remove the solvent from the wet film formed by the ink.

[0005] These post-processing methods have limited control over the crystallization rate and quality of thin films, which restricts the high-throughput deposition of perovskite films and introduces additional post-processing costs. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a low-boiling-point ink, a method for preparing perovskite thin films therefrom, and its photovoltaic applications.

[0007] In a first aspect, the present invention provides a perovskite ink comprising perovskite and a multi-component mixed solvent system; wherein the multi-component mixed solvent system comprises solvent A, solvent B and cosolvent C;

[0008] Solvent A is selected from acetonitrile;

[0009] Solvent B is selected from one, two or more of the following: acetates (such as isopropyl acetate, propyl acetate, ethyl acetate, methyl acetate, etc.), alcohols (such as methanol, ethanol, propanol, isopropanol, n-butanol, etc.), aromatics (such as benzene, toluene, chlorobenzene, etc.), n-hexane, cyclohexanone, and tetrahydrofuran;

[0010] The cosolvent C is a Lewis base, wherein the Lewis base is selected from one, two, or more of the following: dimethyl sulfoxide, thionyl chloride, thiourea, urea, hydrazine hydrate, pyridine, pyrrole, pyrrolidine, piperidine, carbazole, imidazole, indole, histidine, tryptophan, 1,8-diazabicycloundec-7-ene, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, ethylenediamine, monopropylamine, diallylamine, monobutylamine, tert-butylamine, dibutylamine, aniline, N,N-diisopropylethylamine, or their hydrochlorides.

[0011] In some embodiments, the concentration of perovskite in the perovskite ink is 0.5-6 mol / L, preferably 1-2 mol / L.

[0012] In some embodiments, the volume ratio of solvent A to solvent B is 1:9-9:1, preferably 1:9-5:5, and even more preferably 8:2-9:1.

[0013] In some embodiments, solvent B is selected from one, two or more of isopropyl acetate, propyl acetate, ethyl acetate, methanol, ethanol, isopropanol, toluene, chlorobenzene, cyclohexane, cyclohexanone, and tetrahydrofuran, preferably isopropyl acetate.

[0014] And / or, the cosolvent C is a Lewis base, wherein the Lewis base is selected from one, two or more of monomethylamine, dimethylamine, diethylamine, dimethyl sulfoxide, thionyl chloride, N,N-diisopropylethylamine or their hydrochloride salts, preferably one, two or more of monomethylamine, dimethylamine, diethylamine or their hydrochloride salts.

[0015] In some embodiments, when cosolvent C is mixed with solvent A and solvent B, if cosolvent C is a gas, the gas is passed into the mixed solvent of solvent A and solvent B until saturation; if cosolvent C is a liquid, cosolvent C is mixed with the mixed solvent of solvent A and solvent B.

[0016] In some embodiments, the ratio of perovskite to co-solvent C is 1:1 to 1:4, preferably 1:1.2.

[0017] In some embodiments, the perovskite is selected from any one, two, or more of 1) and / or 2):

[0018] 1) Organic-inorganic hybrid perovskite single crystals or powders, such as MAPbI3, MAPb(I x Cl 1-x 3. MAPb(I) x Br 1-x 3. MAPb(I) x Br y Cl 1-x-y 3. MA x FA1-x PbI3, MA x FA 1-x Pb(I y Cl 1-y 3. MA x FA 1-x Pb(I y Br 1-y 3. MA x FA 1-x Pb(I y Br z Cl 1-y-z )3; where MA is a methylamine cation and FA is a formamidin cation; x = [0,1], y = [0,1], z = [0,1];

[0019] 2) A mixture of raw materials such as MAI, MABr, MACl, FAI, FABr, FACl, PbI2, PbBr2, and PbCl2 in an A:B:X ratio of 1:1:3 is formed into ABX3; in ABX3, A = MA and FA, B = Pb, and X = I, Br, and Cl; MA is a methylamine cation and FA is a formamidinium cation.

[0020] Secondly, the present invention provides a method for preparing the above-mentioned perovskite ink, comprising the following steps:

[0021] 1) Mix solvent A and solvent B, then add cosolvent C and mix thoroughly;

[0022] 2) Add perovskite and mix evenly to obtain the perovskite ink.

[0023] In some implementations, the instruments used to mix the ingredients evenly in step 1) and / or step 2) are vortex mixers and / or magnetic stirrers.

[0024] Thirdly, the present invention provides a method for preparing a perovskite thin film, comprising the following steps: providing the above-mentioned perovskite ink, performing a film-forming treatment on the above-mentioned perovskite ink on a substrate, and obtaining the perovskite thin film.

[0025] In some embodiments, the substrate is selected from silicon, silicon dioxide, soda-lime glass, borosilicate glass, quartz glass, indium tin oxide glass (ITO glass), polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyimide (PI) film, fluorine-doped tin oxide glass (FTO glass), ITO / PET, ITO / PEN, etc.

[0026] In some implementation schemes, the film-forming process is as follows:

[0027] 1) The above substrate is cleaned under ultraviolet light or oxygen plasma.

[0028] 2) Apply the above perovskite ink using any of the following methods: spin coating, doctor blade coating, spray coating, wire rod coating, slot coating, screen printing, etc., to form a wet film.

[0029] In some embodiments, the wet film yields a perovskite film, such as a high-quality perovskite film, after the solvent has naturally evaporated.

[0030] In some implementations, the solvent evaporation temperature is 20-40 degrees Celsius, preferably 25 degrees Celsius.

[0031] In some implementations, the resulting perovskite film can be further treated by thermal annealing to promote the crystallization of the perovskite film.

[0032] In some implementations, the heat annealing temperature is 50-150 degrees Celsius, preferably 100 degrees Celsius.

[0033] Fourthly, the present invention provides a perovskite thin film prepared by the above-described method for preparing perovskite thin films.

[0034] In some embodiments, the average grain size of the perovskite thin film is greater than or equal to 400 nm.

[0035] In some embodiments, the thickness of the perovskite film is 50-1000 nm.

[0036] Fifthly, the present invention provides a perovskite photovoltaic device, comprising the above-mentioned perovskite thin film, substrate, hole transport layer, electron transport layer and top electrode.

[0037] In some technical solutions, the substrate is selected from silicon, silicon dioxide, soda-lime glass, borosilicate glass, quartz glass, indium tin oxide glass (ITO glass), polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyimide (PI) film, fluorine-doped tin oxide glass (FTO glass), ITO / PET, ITO / PEN, etc.

[0038] And / or, the hole transport layer is selected from: poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT:PSS), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), poly(3-hexylthiophene-2,5-diyl) (P3HT), [N,N-di(4-methoxyphenyl)amino]spirodifluorene (Spiro-MeOTAD), phthalocyanine blue (CuPc), nickel oxide, molybdenum trioxide, cuprous iodide, etc.;

[0039] And / or, the electron transport layer is selected from: titanium dioxide, tin dioxide, fullerene, [6,6]-phenyl C 61 butyrate methyl ester (PC61BM), etc.;

[0040] And / or, the top electrode is selected from: gold, silver, copper, calcium, barium, chromium, etc.

[0041] Sixthly, the present invention provides a method for fabricating the above-mentioned perovskite photovoltaic device, comprising the following steps:

[0042] The selected layers are coated layer by layer according to the device structure of substrate / hole transport layer / the above-mentioned perovskite thin film / electron transport layer / top electrode or substrate / electron transport layer / the above-mentioned perovskite thin film / hole transport layer / top electrode, using methods such as spin coating, blade coating, spray coating, wire rod coating, slot coating, screen printing, chemical vapor deposition, and physical vapor deposition.

[0043] Beneficial effects

[0044] This invention employs a multi-component mixture of low-boiling-point solvents to formulate a perovskite precursor ink. This ink requires no post-treatment after coating; the room-temperature stable perovskite precursor film is prepared simply by the natural evaporation of the solvent. High-quality perovskite films are obtained by thermal annealing the precursor film. The crystallization rate and quality of the film can be precisely controlled by adjusting the low-boiling-point solvent components and constructing the precursor structure. Attached Figure Description

[0045] Figure 1 Perovskite inks with different boiling points were obtained by using solvent A in different volume ratios.

[0046] Figure 2 The morphology of perovskite films formed by ink obtained using a mixed solvent of isopropyl acetate and acetonitrile.

[0047] Figure 3 The perovskite intermediate phase is formed when a mixed solvent of isopropyl acetate and acetonitrile is used.

[0048] Figure 4 Grain size of perovskite thin films (scanning electron microscope image).

[0049] Figure 5 Current density-voltage curve of a solar cell. Detailed Implementation

[0050] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0051] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0052] Example 1: Preparation of Perovskite Ink

[0053] 1) Ten solvents B were mixed with acetonitrile in different proportions to obtain mixed solvents. The solvents B selected for mixing with acetonitrile were chosen from one of the following: isopropyl acetate, ethyl acetate, methanol, ethanol, isopropanol, toluene, chlorobenzene, n-hexane, cyclohexanone, and tetrahydrofuran. The mixing ratios of solvent B and acetonitrile were 1:9, 2:8, 3:7, 4:6, and 5:5. The volume of the mixed solvent was 0.5-1 mL.

[0054] 2) The selected co-solvent is diethylamine. Dissolve 1.2 mmol of diethylamine in the mixed solvent described in 1). After mixing thoroughly, add 1 mmol of MAPbI3 perovskite powder. Vortex mix for 5 min or stir with a magnetic stirrer for 10 min to obtain a homogeneous and clear perovskite ink. The prepared ink is as follows: Figure 1 As shown.

[0055] Example 2: Preparation of perovskite thin films

[0056] 1) Clean the surface of the soda-lime glass substrate under ultraviolet light or oxygen plasma.

[0057] 2) The perovskite ink in Example 1 is coated using any of the following methods: spin coating, doctor blade coating, spray coating, wire rod coating, slot coating, screen printing, etc., to form a wet film.

[0058] The wet film is subjected to thermal annealing at 150 degrees Celsius after the solvent evaporates naturally (at an environment of 25 degrees Celsius) to promote film crystallization.

[0059] In the ink of Example 1, the ink composed of isopropyl acetate and acetonitrile has a beneficial effect on the crystallization of perovskite films. For example... Figure 2 As shown, the perovskite film formed by the ink obtained when isopropyl acetate and acetonitrile are mixed in a ratio of 2:8 exhibits the best morphology.

[0060] Example 3: Grain size of perovskite thin films

[0061] When different perovskite inks from Example 1 are used, the resulting perovskite intermediate crystal phases also differ. By controlling the type and ratio of solvents, the perovskite intermediate crystal phase can be controlled, especially the grain size of the perovskite film, thereby further improving the quality of the obtained perovskite film.

[0062] For example, ink obtained by mixing isopropyl acetate and acetonitrile in a 2:8 ratio, using diethylamine as a co-solvent, and mixing MAPbI3 perovskite in a 1:1.2 ratio with a total concentration of 1.5 mol / L, can form a perovskite intermediate crystal phase composed of lead iodide, methylamine iodide, and methylamine. The structure is as follows... Figure 3 As shown. The formation of this intermediate crystalline phase significantly increases the grain size of the perovskite film, as indicated by scanning electron microscopy. Figure 4 As shown, the average grain size can reach over 400 nm.

[0063] Example 4

[0064] FTO glass was selected as the substrate. The substrate was cleaned in a UV-ozone cleaner for 30 minutes. Then, a 25 mg / mL aqueous solution of tin dioxide nanoparticles was spin-coated onto the substrate at 3000 rpm. The substrate was then annealed at 150°C for 30 minutes. After annealing and cooling to room temperature, a perovskite ink (1 mol / L) with acetonitrile-ethyl acetate (6:4 volume ratio) and a diethylamine to MAPbI3 perovskite molar ratio of 1.2:1 was spin-coated onto the tin dioxide at 6000 rpm and annealed at 100°C for 15 minutes. After cooling to room temperature, a 20 mg / mL P3HT chlorobenzene solution was spin-coated onto the perovskite layer at 3000 rpm. Finally, 100 nm of gold was deposited on the P3HT layer using physical vapor deposition to obtain the desired perovskite solar cell.

[0065] Example 5

[0066] ITO glass was selected as the substrate. The substrate was cleaned in oxygen plasma for 200 seconds. Then, a 20 mg / mL aqueous solution of nickel oxide nanoparticles was coated onto the substrate using a slot coating method at a coating speed of 10 mm / s. The substrate was then annealed at 150°C for 30 minutes. After annealing and cooling to room temperature, perovskite ink (MAPbI3, 2 mol / L perovskite) saturated with acetonitrile-isopropyl acetate (9:1 volume ratio) and methylamine gas dissolved in the mixed solvent was coated onto the nickel oxide substrate using a slot coating method at a coating speed of 15 mm / s. The substrate was then annealed at 100°C for 15 minutes. After cooling to room temperature, a 20 mg / mL PC61BM chlorobenzene solution was coated onto the perovskite layer using a slot coating method at a coating speed of 10 mm / s. Finally, 100 nm copper was deposited on the PC61BM layer using physical vapor deposition to obtain the desired perovskite solar cell.

[0067] The current density-voltage curve of the obtained solar cell is as follows: Figure 5As shown, the photoelectric conversion efficiency of the solar cell was 21.15% after using a mixed solvent of acetonitrile and isopropyl acetate. Compared with solar cells using acetonitrile, acetonitrile-ethanol, acetonitrile-tetrahydrofuran, acetonitrile-cyclohexane, and acetonitrile-isopropanol as solvents, the photoelectric conversion efficiency of the solar cell was significantly improved after using the acetonitrile-isopropyl acetate mixed solvent ink.

[0068] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A perovskite ink, comprising perovskite and a multi-component mixed solvent system; wherein, The multi-component mixed solvent system includes solvent A, solvent B, and cosolvent C; Solvent A is selected from acetonitrile; Solvent B is selected from isopropyl acetate; The cosolvent C is a Lewis base, wherein the Lewis base is selected from monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, ethylenediamine, monopropylamine, monobutylamine, tert-butylamine, dibutylamine or its hydrochloride salt; The volume ratio of solvent A to solvent B is 8:2-9:1; The ratio of perovskite to co-solvent C is 1:1 to 1:4; The perovskite is selected from the ABX3 mixture formed by combining MAI, MABr, MACl, FAI, FABr, PbI2, PbBr2, and PbCl2 raw materials with A:B:X = 1:1:3; in ABX3, A = MA and FA, B = Pb, and X = I, Br, and Cl; MA is a methylamine cation, and FA is a formamidinium cation.

2. The perovskite ink according to claim 1, characterized in that, The concentration of perovskite is 0.5-6 mol / L.

3. The perovskite ink according to claim 2, characterized in that, The concentration of perovskite is 1-2 mol / L.

4. The perovskite ink according to any one of claims 1-3, characterized in that, The cosolvent C is a Lewis base, which is selected from one, two or more of monomethylamine, dimethylamine, diethylamine or their hydrochloride salts; And / or, the ratio of perovskite to co-solvent C is 1:1.

2.

5. A method for preparing the perovskite ink according to any one of claims 1-4, comprising the following steps: 1) Mix solvent A and solvent B, then add cosolvent C and mix thoroughly; 2) Add perovskite and mix evenly to obtain the perovskite ink.

6. A method for preparing a perovskite thin film, comprising the following steps: The perovskite ink according to any one of claims 1-4 is provided, and the perovskite ink is subjected to a film-forming treatment on a substrate to obtain the perovskite thin film.

7. The preparation method according to claim 6, characterized in that, The film-forming process is as follows: 1) Clean the substrate surface under ultraviolet light or oxygen plasma. 2) The perovskite ink is coated using any one of the following methods: spin coating, doctor blade coating, spray coating, wire rod coating, slot coating, or screen printing to form a wet film.

8. The preparation method according to claim 7, characterized in that, The wet film can be obtained as a perovskite thin film after the solvent evaporates naturally. And / or, the resulting perovskite film may be further treated using a thermal annealing method.

9. The preparation method according to claim 8, characterized in that, The solvent's natural evaporation temperature is 20-40 degrees Celsius. And / or, the heat annealing temperature is 50-150 degrees Celsius.

10. A perovskite thin film prepared by the preparation method according to any one of claims 6-9.

11. The perovskite thin film according to claim 10, characterized in that, The average grain size of the perovskite thin film is greater than or equal to 400 nm; And / or, the thickness of the perovskite film is 50-1000 nm.

12. A perovskite photovoltaic device comprising the perovskite thin film, substrate, hole transport layer, electron transport layer, and top electrode as described in any one of claims 10-11.

13. The perovskite photovoltaic device according to claim 12, characterized in that, The substrate is selected from silicon, silicon dioxide, soda-lime glass, borosilicate glass, indium tin oxide glass, polyethylene terephthalate film, polyethylene naphthalate film, polyimide film, fluorine-doped tin oxide glass, ITO / PET, and ITO / PEN. And / or, the hole transport layer is selected from: poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene / polystyrene sulfonate), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly(3-hexylthiophene-2,5-diyl), [N,N-bis(4-methoxyphenyl)amino]spirodifluorene, phthalocyanine blue, nickel oxide, molybdenum trioxide, and cuprous iodide; And / or, the electron transport layer is selected from: titanium dioxide, tin dioxide, fullerene, and methyl [6,6]-phenyl-C61-butyrate; And / or, the top electrode is selected from: gold, silver, copper, calcium, barium, chromium.

14. The perovskite photovoltaic device according to claim 12, characterized in that, The substrate is made of quartz glass.

15. A method for fabricating a perovskite photovoltaic device according to any one of claims 12-14, comprising the following steps: The selected layers are coated layer by layer according to the device structure of substrate / hole transport layer / perovskite film / electron transport layer / top electrode or substrate / electron transport layer / perovskite film / hole transport layer / top electrode, using spin coating, blade coating, spray coating, wire rod coating, slot coating, screen printing, chemical vapor deposition, or physical vapor deposition methods.

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