A perovskite thin film and a preparation method of a solar cell thereof

Abstract

The present application relates to a perovskite thin film, containing perovskite crystals with a structure of ABX3 type, the perovskite crystals being formed by a precursor BX2 material and a precursor AX material in sequence and reacting with each other, and the precursor BX2 material further containing a main solvent, an ionic liquid-containing additive A1R, a second additive and a solution containing anions R ‑ The present application also discloses a solar cell using the perovskite thin film, and a preparation method of the perovskite thin film and the solar cell. The present application adds the ionic liquid-containing additive and the second additive to stabilize the vertical directional growth of the mesoporous structure of lead halide, controls the growth of the perovskite crystals so that the lead halide forms a mesoporous, directional growth thin film morphology, which is more conducive to the diffusion and reaction crystallization of organic / inorganic halide vapor.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of perovskite solar technology, and particularly relates to a perovskite thin film and a preparation method of a perovskite solar cell. BACKGROUND

[0002] A solar cell is a photoelectric conversion device that converts solar energy into electrical energy by using the photovoltaic effect of a semiconductor. To date, solar power generation has become the most important renewable energy source in addition to hydroelectric power generation and wind power generation. The semiconductors currently used in commercialization include single-crystal silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, copper indium gallium selenide, and the like, but most of them have high energy consumption and high cost.

[0003] In recent years, a perovskite solar cell has attracted widespread attention. The perovskite solar cell uses an organic metal halide as a light absorption layer. The perovskite has a cubic octahedral structure of ABX3 type, as shown in FIG. 1. The thin film solar cell prepared from such a material has a simple process, low production cost, stability, and high conversion rate. Since 2009, the photoelectric conversion efficiency has increased from 3.8% to more than 23%, which is higher than that of a commercial crystalline silicon solar cell and has a greater cost advantage.

[0004] Various perovskite solar cell thin film forming processes can be divided into two categories: solution method and gas phase method. The solution method is simple to operate, but the thin film uniformity and repeatability are poor, which affects the efficiency of the cell. The gas phase method includes double-source co-evaporation method, gas phase assisted solution method, chemical vapor deposition (CVD), vapor transport deposition (VTD), and the like. The gas phase method such as the gas phase assisted solution method, the chemical vapor deposition (CVD), and the vapor transport deposition (VTD) is more suitable for industrialization. Through the above methods, a uniform, large grain size, and large area perovskite thin film can be prepared. The most important thing in the above methods is the transport and reaction crystallization of organic / inorganic halide vapor in the lead halide thin film. However, the lead halide prepared by general vacuum evaporation or solution method is relatively dense, and it is difficult for organic / inorganic halide vapor to enter the inside of the thin film, especially the bottom layer of the thin film, which to some extent restricts the crystallization quality of the perovskite crystal and the film forming thickness of the perovskite crystal, making it difficult to further improve the conversion efficiency and stability of the solar cell.

[0005] In addition, generally, the I-Pb-I ionic bond is strong in the layered structure of lead iodide, and the van der Waals force between adjacent layers is weak. Due to the large volume of FA and other cations, it is difficult to insert them into the layered structure of lead iodide. However, FA and other cations have a high affinity for PbI2, and easily interact with PbI2 at the edges of the crystal to form a low-barrier δ-phase perovskite, thereby affecting the efficiency and stability of the cell. 2+

[0006] ​For the two-step methods of preparing perovskite films, such as gas-assisted solution method, chemical vapor deposition (CVD), vapor transport deposition (VTD), and ambient reactive deposition, lead halide is formed into a mesoporous, directionally grown film morphology through crystal control, which is more conducive to the diffusion and reaction crystallization of organic / inorganic halide vapor.

[0007] Although lead halide prepared using ionic liquids as solvents can form mesoporous structures and grow vertically, the I-Pb-I ionic bond is stronger in the layered structure of lead iodide. Meanwhile, vapor-phase methods for preparing perovskite thin films, such as vapor-assisted solution deposition, chemical vapor deposition (CVD), and vapor transport deposition (VTD), require high reaction temperatures, low atmospheric pressures, and relatively long reaction times. As the reaction proceeds, the ionic liquid gradually evaporates. When AX has not completely reacted with the lead halide, but the ionic liquid has largely evaporated, the structure of the lead halide film tends to collapse, making it difficult for the remaining ionic liquid to fully evaporate. Furthermore, the changes in the lead halide structure make it difficult for AX to enter the lead halide interior, making the reaction difficult to proceed.

[0008] In addition, if ionic liquids are used purely to dissolve lead halide, in actual large-area preparation processes such as scraping and slit coating, the ionic liquids easily absorb water, resulting in a short storage time of the solution and high requirements for the production environment. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method for preparing a perovskite film and a solar cell thereof. The perovskite film is a vertically oriented mesoporous film, which not only improves the photoelectric conversion efficiency but also greatly improves the stability of the perovskite solar cell.

[0010] The present invention is achieved by providing a perovskite film, wherein the perovskite film contains perovskite crystals with a molecular formula of ABX3 type structure, wherein the perovskite crystals are formed by the precursor BX2 material and the precursor AX material forming films in sequence and reacting with each other, wherein the precursor BX2 material also contains a main solvent, an ionic liquid additive A1R, a second additive, and an anion R - A solution in which

[0011] A is an amino group, an amidine group or any monovalent cation in the base group,

[0012] B is any divalent cation of lead, tin, tungsten, copper, zinc, gallium, germanium, arsenic, selenium, rhodium, palladium, silver, cadmium, indium, antimony, osmium, iridium, platinum, gold, mercury, thallium, bismuth, or polonium,

[0013] X is at least one monovalent anion selected from iodine, bromine, chlorine, astatine, thiocyanate, and acetate,

[0014] The main solvent is any one of an amide solvent, a sulfone / sulfoxide solvent, an ester solvent, a hydrocarbon, a halogenated hydrocarbon solvent, an alcohol solvent, a ketone solvent, an ether solvent, an aromatic hydrocarbon solvent that can dissolve the precursor BX2 material,

[0015] A1 is an amine group-containing monovalent cation,

[0016] R is a carboxyl group-containing monovalent organic anion,

[0017] The second additive is an organic polymer additive or a sulfur-containing small molecule additive, the organic polymer additive is a branched or heterochain polymer, and the sulfur-containing small molecule additive is an organic salt or an inorganic salt containing a sulfur structure C1R', wherein C1 is any one of an amine group, an amidine group, and an alkali group monovalent cation, R' is any one of a fluorine ion, an iodine ion, a bromine ion, a chlorine ion, a mosure ion, a thiocyanate ion, and an acetate ion monovalent anion, or the sulfur-containing small molecule additive is a sulfur-containing cyclic small molecule, the sulfur-containing cyclic small molecule is a 3-6 membered ring or includes 1-3 ring units, and sulfur can be in the ring or can exist in a side chain group.

[0018] The present application is achieved in this way, and provides a preparation method of the perovskite thin film as described above, comprising the following steps:

[0019] Step one, preparation of a precursor mixed solution: the precursor BX2 material, the ion-containing additive A1R liquid, and the second additive are dissolved in a main solvent, and are fully stirred; then a solution containing an anion R - is added, and is fully stirred for use;

[0020] Step two, a thin film containing the precursor mixed solution is prepared by using any one of a spin coating, a blade coating, a slot die continuous coating, a spraying, and a printing processing mode, is annealed at 80-120 DEG C for 1-5 min, and a vertically oriented growth and stable precursor BX2 thin film is obtained;

[0021] Step three, the prepared precursor BX2 thin film is placed in a vapor deposition forming cavity, a precursor AX material is used as an evaporation source, the heating temperature of the precursor AX material is controlled, the precursor BX2 thin film is placed in an atmosphere of the precursor AX material, and the gas molecules of the precursor AX material and the molecules of the precursor BX2 material react to generate a perovskite crystal.

[0022] The present application is achieved in this way, and provides a solar cell, wherein the solar cell contains the perovskite thin film as described above, or contains the perovskite thin film prepared by using the preparation method of the perovskite thin film as described above.

[0023] The present application is achieved in this way, and provides a preparation method of the solar cell as described above, and contains the preparation method of the perovskite thin film as described above.

[0024] Compared with the prior art, the perovskite film and the method for preparing the solar cell thereof of the present invention have the following characteristics:

[0025] 1. By adding ionic liquid as an additive, the crystal growth of crystalline lead halide is controlled so that the lead halide forms a mesoporous, directional growth film morphology, which is more conducive to the diffusion and reaction crystallization of organic / inorganic halide vapor.

[0026] 2. Use a second additive to stabilize the vertically oriented growth of the mesoporous structure of the lead halide. This type of second additive will not enter the perovskite lattice, but will exist in the lead halide crystal. The second additive can be an organic polymer additive or a sulfur-containing small molecule additive. The organic polymer additive will not enter the crystal lattice but will exist at the grain boundary. Due to the skeleton structure of the organic polymer, the lead halide crystal structure will not change under high reaction temperature and low pressure environment, thus ensuring the smooth progress of the reaction. When adding sulfur-containing small molecule additives to the precursor solution, sulfur and Pb 2+ There is a strong interaction between them, but they will not enter the crystal lattice. The sulfur-containing small molecule additives interspersed at the grain boundaries help to stabilize the vertical directional growth of the lead halide structure, and also ensure the volatilization of the ionic liquid and the diffusion of the precursor AX during the reaction, and the normal progress of the reaction.

[0027] 3. If ionic liquid is used to dissolve lead halide, in the actual large-area preparation process such as blade coating and slit coating, the ionic liquid easily absorbs water, resulting in a short storage time of the solution and high requirements for the production environment. However, the present invention uses ionic liquid A1R as an additive and adds an excess of anion R to the mixed solution of the precursor BX2 material. - , helps stabilize the solution, and at the same time prevents the combination of lead halide film and water during large-area preparation processes such as blade coating and slit coating, which is beneficial to large-area production and device stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1a This is a SEM electron microscopic image of the perovskite crystal surface of the perovskite film prepared in the present invention; Figure 1b This is a cross-sectional image of the perovskite film prepared in the present invention;

[0029] Figure 2 This is a surface SEM electron micrograph of the perovskite film prepared in the present invention;

[0030] Figure 3 This is a performance test curve of the solar cell prepared in Example 1 of the present invention;

[0031] Figure 4 This is the heating aging test curve of the solar cell prepared in Inventive Example 1. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] A preferred embodiment of the perovskite film of the present invention comprises a perovskite crystal having a molecular formula of ABX3 type structure, wherein the perovskite crystal is formed by forming a precursor BX2 material and a precursor AX material into films in sequence and reacting with each other, wherein the precursor BX2 material further comprises a main solvent, an ionic liquid additive A1R, a second additive and an anion R - A solution in which

[0034] A is an amino group, an amidine group or any monovalent cation in the base group,

[0035] B is any divalent cation of lead, tin, tungsten, copper, zinc, gallium, germanium, arsenic, selenium, rhodium, palladium, silver, cadmium, indium, antimony, osmium, iridium, platinum, gold, mercury, thallium, bismuth, or polonium,

[0036] X is at least one monovalent anion selected from the group consisting of iodine, bromine, chlorine, astatine, thiocyanate, and acetate.

[0037] The main solvent is any one of amide solvents, sulfone / sulfoxide solvents, ester solvents, hydrocarbons, halogenated hydrocarbon solvents, alcohol solvents, ketone solvents, ether solvents, and aromatic hydrocarbon solvents that can dissolve the precursor BX2 material.

[0038] A1 is a monovalent cation containing an amine group, preferably a methylamine ion.

[0039] R is a monovalent organic anion containing a carboxyl group, preferably a formate ion or an acetate ion.

[0040] The second additive is an organic polymer additive or a sulfur-containing small molecule additive, the organic polymer additive is a branched or heterochain polymer, the sulfur-containing small molecule additive is a sulfur-containing organic salt or inorganic salt with a structure of C1R', wherein C1 is any monovalent cation of an amine group, an amidine group, or an alkali group, and R' is any monovalent anion of fluorine, iodine, bromine, chlorine, astatine, thiocyanate, or acetate, or the sulfur-containing small molecule additive is a sulfur-containing cyclic small molecule, wherein the sulfur-containing cyclic small molecule is a 3-6 membered ring, or includes 1-3 cyclic units, and the sulfur can be in the ring or present in the side chain group.

[0041] The second additive is used to stabilize the vertically oriented growth mesoporous structure of the precursor BX2 material (such as lead halide), overcoming the defects of the prior art.

[0042] The organic polymer additive is at least one of polysiloxane derivatives, polymethyl methacrylate, polystyrene, polyethylene glycol, polypropylene glycol, polyvinyl pyrrolidone, polylactic acid, polyvinyl alcohol, polyacrylic acid, polyurethane, polyethylene imine, polyacrylthiamine, polystyrene sulfonic acid, polyvinyl pyrrolidone, polyvinyl butyral resin, and fluorine-based polymers.

[0043] The concentration of the precursor BX2 material is 0.5 mol / L to 2 mol / L. The amount of the ionic additive A1R added is 40% to 200% of the molar amount of the precursor BX2 material. - The amount of solution added is 20% to 200% of the molar amount of the ionic additive A1R liquid. - The solution increases the anion R - concentration to improve the water resistance and stability of the precursor solution.

[0044] The amount of the organic polymer additive added is 0-5 mg / mL, and its molecular weight range is 200-100,000. The amount of the sulfur-containing additive added is 0-5% of the molar weight of the precursor BX2 material. The perovskite film is prepared using the following process:

[0045] First, a solution method is used to prepare a precursor BX2 material, an ion additive A1R, a second additive and an anion R - of film.

[0046] Secondly, a thin film containing a precursor AX material is prepared on the prepared thin film containing a precursor BX2 material by a vapor phase method, and perovskite crystals are formed after the bonding surfaces of the precursor BX2 material and the precursor AX material react with each other.

[0047] The present invention also discloses a method for preparing the perovskite film as described above, comprising the following steps:

[0048] Step 1: Prepare the precursor mixed solution: Dissolve the precursor BX2 material, the ion additive A1R liquid, and the second additive in the main solvent and stir thoroughly; then add the anion R - Stir the solution thoroughly for later use.

[0049] Step 2: Prepare a film containing the precursor mixed solution by any one of spin coating, blade coating, slit continuous coating, spraying, and printing, and anneal at 80°C to 120°C for 1min to 5min to obtain a vertically oriented and stable precursor BX2 film.

[0050] Step 3: Place the prepared precursor BX2 film in a vapor deposition molding cavity, use the precursor AX material as an evaporation source, control the heating temperature of the precursor AX material, and place the precursor BX2 film in the atmosphere of the precursor AX material. The gas molecules of the precursor AX material react with the molecules of the precursor BX2 material to form perovskite crystals.

[0051] Step 4: Rinse with isopropyl alcohol (IPA), blow dry with nitrogen (N2), and then anneal to obtain a perovskite film.

[0052] The present invention further discloses a solar cell, wherein the solar cell comprises the above-mentioned perovskite film, or comprises a perovskite film prepared by the above-mentioned method for preparing the perovskite film.

[0053] The present invention also discloses a method for preparing the solar cell as described above, which is characterized in that it includes the method for preparing the perovskite film as described above.

[0054] The method for preparing the solar cell of the present invention is further described below with reference to specific examples.

[0055] Example 1

[0056] The first method for preparing a solar cell of the present invention comprises the following steps:

[0057] (11) A 5 cm × 5 cm piece of transparent conductive glass was cleaned with detergent, deionized water, acetone, and isopropyl alcohol ultrasonically for 30 min each, then dried with N2 and treated in a UVO-zone for 10 min.

[0058] (12) Prepare 10nm~30nm NiO on the transparent conductive layer by solution method x hole transport layer;

[0059] (13) Preparation of lead halide precursor solution: 0.461 g of PbI2, 77.08 mg of methylamine formate, and 1.25 mg of 2-methylthiopyridine were dissolved in 1 mL of DMF and stirred thoroughly; then 0.086 g of formic acid was added and stirred thoroughly for use.

[0060] (14) Prepare lead halide thin films by spin coating and anneal at 80℃~120℃ for 1min~5min.

[0061] (15) Place the prepared PbI2 film substrate in the film forming chamber and control the air pressure at 10 -8 Pa~10 5 Pa, heat FAI, make FAI vapor react with PbI2 film, prepare FAPbI3 perovskite film, and anneal at 130℃~170℃ for 0~30min.

[0062] (16) Depositing an electron transport layer C60 on the FAPbI3 perovskite film with a thickness of 5nm~40nm;

[0063] (17) Electrode Ag was deposited by vacuum evaporation.

[0064] Example 2

[0065] The second method for preparing a solar cell of the present invention comprises the following steps:

[0066] (21) A 5 cm × 5 cm transparent conductive glass was cleaned with detergent, deionized water, acetone, and isopropyl alcohol ultrasonically for 30 min each, then dried with N2 and treated in a UVO-zone for 10 min;

[0067] (22) A 10 nm to 30 nm SnO2 electron transport layer was prepared on the transparent conductive layer by a solution method.

[0068] (23) Prepare the lead halide precursor solution: dissolve 0.461 g of PbI2, 77.08 mg of methylamine formate, and 1 mg of PMMA in 1 mL of DMF and stir thoroughly; then add 0.086 g of formic acid and stir thoroughly for use.

[0069] (24) Prepare lead halide thin films by blade coating and anneal at 80°C~120°C for 1 min to 5 min.

[0070] (25) Place the prepared PbI2 film substrate in the film forming chamber and control the air pressure at 10 -8 Pa~10 5 Pa, heat FAI, make FAI vapor react with PbI2 film, prepare FAPbI3 perovskite film, and anneal at 130℃~170℃ for 5min~30min.

[0071] (26) Depositing a hole transport layer PTAA on the FAPbI3 perovskite film with a thickness of 5 nm to 20 nm;

[0072] (27) Electrode Ag was deposited by vacuum evaporation.

[0073] The solar cell prepared in Example 1 was tested and the results were shown in Figures 1 to Figure 4 The test results are shown.

[0074] like Figure 1a As shown in FIG, a SEM electron micrograph of the perovskite film of the solar cell prepared by the present invention shows that the perovskite crystals are in an ordered porous shape.

[0075] exist Figure 1bThe micro holes are longitudinally distributed in the perovskite thin film from the cross section, and the surface and internal morphology of the lead halide form diffusion channels of organic / inorganic halide vapor, which helps the reaction and crystallization of the lead halide and the organic / inorganic halide vapor.

[0076] As shown in Figure 2 and Figure 3 , the prepared perovskite thin film is uniform and dense, the surface is relatively flat, and the efficiency reaches 18.23%.

[0077] As shown in Figure 4 , the prepared perovskite thin film is not easy to change from black to yellow, which greatly improves the stability of the perovskite solar cell, and the attenuation rate is less than 5% after heating aging for 1000 hours at 85℃.

[0078] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A perovskite film, comprising perovskite crystals having an ABX3 structure, wherein the perovskite crystals are formed by sequentially forming a film of a precursor BX2 material and a precursor AX material and reacting with each other, wherein: The precursor BX2 material also includes a main solvent, an ionic liquid additive A1R, a second additive and an anion R - A solution in which A is an amino group, an amidine group or any monovalent cation in the base group, B is any divalent cation of lead, tin, tungsten, copper, zinc, gallium, germanium, arsenic, selenium, rhodium, palladium, silver, cadmium, indium, antimony, osmium, iridium, platinum, gold, mercury, thallium, bismuth, or polonium, X is at least one monovalent anion selected from iodine, bromine, chlorine, astatine, thiocyanate, and acetate, The main solvent is any one of amide solvents, sulfone / sulfoxide solvents, ester solvents, hydrocarbons, halogenated hydrocarbon solvents, alcohol solvents, ketone solvents, ether solvents, and aromatic hydrocarbon solvents that can dissolve the precursor BX2 material. A1 is a monovalent cation containing an amine group, R is a monovalent organic anion containing a carboxyl group, The second additive is an organic polymer additive or a sulfur-containing small molecule additive, the organic polymer additive is a branched or heterochain polymer, the sulfur-containing small molecule additive is a sulfur-containing organic salt or inorganic salt having a structure of C1R', wherein C1 is any one of a monovalent cation of an amine group, an amidine group, and an alkali group, and R' is any one of a monovalent anion of fluorine, iodine, bromine, chlorine, astatine, thiocyanate, and acetate, or the sulfur-containing small molecule additive is a sulfur-containing cyclic small molecule, wherein the sulfur-containing cyclic small molecule is a 3-6 membered ring, or includes 1-3 cyclic units, and the sulfur may be in the ring or in a side chain group; The organic polymer additive is at least one of polysiloxane derivatives, polymethyl methacrylate, polystyrene, polyethylene glycol, polypropylene glycol, polyvinyl pyrrolidone, polylactic acid, polyvinyl alcohol, polyacrylic acid, polyurethane, polyethylene imine, polyacrylthiamine, polystyrene sulfonic acid, polyvinyl pyrrolidone, polyvinyl butyral resin, and fluorine-based polymers.

2. The perovskite film according to claim 1, wherein The concentration of the precursor BX2 material is 0.5 mol / L to 2 mol / L, and the added amount of the ionic liquid additive A1R is 40% to 200% of the molar amount of the precursor BX2 material.

3. The perovskite film according to claim 2, wherein in, A1 is a methylamine ion, and R is a formate ion or an acetate ion.

4. The perovskite film according to claim 2, wherein The anion-containing R - The amount of the solution added is 20% to 200% of the molar amount of the ionic liquid additive A1R liquid.

5. The perovskite film according to claim 2, wherein The addition amount of the organic polymer additive is 1-5 mg / mL, and the addition amount of the sulfur-containing small molecule additive is 1-5% of the molar amount of the precursor BX2 material.

6. The perovskite film according to claim 1, wherein The perovskite film is prepared by the following process: First, a solution method is used to prepare a precursor BX2 material and an ionic liquid additive A1R, a second additive and an anion R - film; Secondly, a thin film containing a precursor AX material is prepared on the prepared thin film containing a precursor BX2 material by a vapor phase method, and perovskite crystals are formed after the bonding surfaces of the precursor BX2 material and the precursor AX material react with each other.

7. A method for preparing a perovskite thin film according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: Prepare the precursor mixed solution: Dissolve the precursor BX2 material, the ionic liquid additive A1R liquid, and the second additive in the main solvent and stir thoroughly; then add the anion R - The solution was stirred thoroughly for use; Step 2: Prepare a film containing the precursor mixed solution by any one of spin coating, blade coating, slit continuous coating, spraying, and printing, and anneal at 80° C. to 120° C. for 1 min to 5 min to obtain a vertically oriented and stable precursor BX2 film; Step 3: Place the prepared precursor BX2 film in a vapor deposition molding cavity, use the precursor AX material as an evaporation source, control the heating temperature of the precursor AX material, and place the precursor BX2 film in the atmosphere of the precursor AX material. The gas molecules of the precursor AX material react with the molecules of the precursor BX2 material to form perovskite crystals.

8. The method for preparing a perovskite thin film according to claim 7, wherein: Also includes step four: Step 4: Rinse with isopropyl alcohol, dry with nitrogen, and then anneal to obtain a perovskite film.

9. A solar cell, characterized in that: The solar cell includes the perovskite thin film according to any one of claims 1 to 6, or includes a perovskite thin film prepared by the method for preparing a perovskite thin film according to claim 7 or 8.

10. A method for preparing a solar cell according to claim 9, characterized in that: The invention comprises a method for preparing a perovskite film as claimed in claim 7 or 8.

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