Preparation method of halide perovskite thin film

Abstract

The invention discloses a preparation method of a halide perovskite thin film, which comprises the following steps of: dissolving monovalent cation acetate such as cesium / rubidium / formamidine acetate, divalent metal acetate such as lead / tin acetate and water-soluble acetate such as haloacetic acid by adopting water as a solvent, coating the solution on a substrate by adopting a spin coating, blade coating or spray coating manner, and drying to obtain the halide perovskite thin film. And heating and annealing to form the halide perovskite thin film. The prepared perovskite thin film can be applied to the fields of perovskite solar cells, photoelectric detectors and the like. Compared with a previously reported method for preparing the perovskite thin film through an aqueous solution, the method has the advantages that the step of synthesizing raw materials such as lead iodide, cesium iodide and iodoformamidine is omitted, and haloid acids such as hydriodic acid and hydrobromic acid are prevented from being used as halogen sources. Acetate is used as a raw material, water is used as a solvent, the preparation process is remarkably simplified, and the economic effect is huge.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic functional semiconductor materials and films, and in particular to a method for preparing a perovskite film for a perovskite optoelectronic device. Background Art

[0002] Halide perovskites (ABX3, where A is a monovalent cation such as formamidine, methylamine, or cesium, B is a divalent metal ion such as lead or tin, and X is a halide ion) have shown great application potential in the photovoltaic field due to their excellent optoelectronic properties. The key functional layer in perovskite optoelectronic devices, namely the perovskite thin film layer, is generally prepared by dissolving a halide precursor in a polar organic solvent such as DMF, DMSO, or NMP and then coating it. The halide precursor is usually synthesized by high-temperature reaction of a high-purity metal source obtained by metallurgy with a halogen element. As the scale of the perovskite industry gradually expands, the existing thin film preparation process using a large amount of polar organic solvents will face huge cost and environmental safety pressures. At the same time, higher requirements are placed on the crystal quality, purity, cost, and overall green and clean process of the large-scale preparation of precursors. The development of new technologies for perovskite thin film deposition is of great necessity and urgency.

[0003] The preparation of halide perovskites in aqueous solution is considered to be a low-cost and clean technology. At present, the preparation technology based on aqueous solution is mainly divided into two categories: 1) After the halide microcrystals are synthesized in aqueous solution, they are dissolved and coated with organic solvents to form a film. The use of organic solvents is still inevitable, and the synthesis process requires the use of a large amount of hydrohalic acid (such as hydroiodic acid, hydrobromic acid); 2) After the metal salt is dissolved in the aqueous solution, a thin film containing the metal salt is first deposited, and then the thin film is contacted with an organic solvent containing a monovalent cationic halide to react to obtain a halide perovskite film. The preparation process inevitably uses an organic solvent, and it is still necessary to pre-synthesize expensive monovalent cationic halides. In summary, the existing technology only partially uses water as a solvent, and does not completely replace the organic solvent with water, and the cost of raw materials is still relatively high. Summary of the Invention

[0004] The purpose of the present invention is to propose a method for preparing halide perovskite thin films using a full aqueous solution, while avoiding the use of strong acids such as hydrohalic acid and polar organic solvents, to obtain high-quality perovskite films with a simplified process.

[0005] The present invention comprises the following steps:

[0006] A: A monovalent cation acetate and a divalent metal acetate are mixed and dissolved in deionized water and stirred until clear to obtain a solution i; a halogenated acetic acid is dissolved in deionized water and stirred until clear to obtain a solution ii; wherein the monovalent cation acetate is one or more of formamidine acetate [CH4N2(CH3COOH)], cesium acetate [Cs(CH3COOH)], and rubidium acetate [Rb(CH3COOH)], and the divalent metal acetate is one or more of lead acetate [Pb(CH3COO)2] and stannous acetate [Sn(CH3COO)2];

[0007] B: Prepare a clean substrate, apply a certain amount of solution i on the substrate, and then bake at 30-90°C to obtain a prefabricated film containing lead and / or tin and rubidium and / or cesium and / or formamidine;

[0008] C: coating a certain amount of solution ii on the prefabricated film obtained in step B, and then baking at a high temperature of 100-300° C. to obtain a solid film;

[0009] D: Add a certain amount of water and / or alcohol organic matter to the film prepared in step C to rinse the film, and finally obtain a pure halide perovskite film.

[0010] Preferably, in step A, the halogenated acetic acid is one or more of iodoacetic acid (C2H3IO2), diiodoacetic acid (C2H2I2O2), triiodoacetic acid (C2HI3O2), bromoacetic acid (C2H3BrO2), dibromoacetic acid (C2H2Br2O2), tribromoacetic acid (C2HBr3O2), chloroacetic acid (C2H3ClO2), dichloroacetic acid (C2H2Cl2O2), and trichloroacetic acid (C2HCl3O2).

[0011] Preferably, in step A, the molar ratio of monovalent cation acetate to divalent metal acetate in the solution i is 1:1 to 1.1:1.

[0012] Preferably, in step A, the concentration of solution i is 0.5 mol / L to 5 mol / L, and the concentration of solution ii is 3 times that of solution i, that is, 1.5 mol / L to 15 mol / L.

[0013] Preferably, in step B, the substrate is any one of a silicon wafer, ITO or FTO glass, a metal foil, and a polymer flexible conductive substrate.

[0014] Preferably, in step B, the coating method is spin coating, spray coating, blade coating or slit coating.

[0015] Preferably, in step B, the baking time is 5-30 minutes.

[0016] Preferably, in step C, the coating method is spin coating, spray coating, blade coating or slit coating.

[0017] Preferably, in step C, the high-temperature baking time is 10-30 minutes.

[0018] Preferably, in step D, the alcohol organic compound is one or more of methanol, ethanol, isopropanol, and n-butanol.

[0019] The technical principles adopted in the present invention are as follows:

[0020] 1. Monovalent cation acetates such as cesium acetate and formamidine acetate and divalent metal acetates such as lead acetate and stannous acetate all have high solubility in water. At the same time, monovalent cation acetates and divalent metal acetates can be co-soluble in water without precipitation. Therefore, the solution prepared in step A can be coated in step B. After baking, the solvent water is evaporated, and the two salts are supersaturated and crystallized in the aqueous solution to form a prefabricated film;

[0021] 2. In step C, halogen is introduced into the prefabricated membrane, also using halogenated acetic acid. In the presence of water, the halogen ions react with the monovalent cations and divalent metal ions in the prefabricated membrane to form perovskite, while leaving acetic acid;

[0022] 3. In step D, the film is rinsed with water or an alcohol solvent. Due to the high solubility of the solvent in acetic acid, the residual acetic acid on the surface can be removed to obtain a pure halide perovskite film.

[0023] Compared with the existing perovskite film preparation technology, the present invention has the following advantages: the raw materials are abundant and easy to obtain, the preparation process is short, the economic and environmental effects are high, and a green and low-cost aqueous solution is used as a solvent to prepare the perovskite film. The solution system is green and has huge environmental and economic effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The flow chart of preparing halide perovskite thin films and the microscopic morphology of the films are shown in the following figure:

[0025] Figure 2 (a) morphology of the FAPbI3 perovskite film prepared in Example 1, (b) distribution of iodine in the FAPbI3 perovskite film, (c) distribution of lead in the FAPbI3 perovskite film;

[0026] Figure 3 is the X-ray diffraction pattern of the FAPbI3 perovskite film prepared in Example 1;

[0027] Figure 4 This is the photoluminescence spectrum of the FAPbI3 perovskite film prepared in Example 1. DETAILED DESCRIPTION

[0028] Example 1: Preparation of Formamidinium Lead Iodide (FAPbI3) Perovskite Film

[0029] The monovalent cation acetate is selected as formamidine acetate, the divalent metal acetate is selected as lead acetate, the molar ratio of formamidine acetate and lead acetate is 1:1, and the concentration of lead ions and formamidine ions (FA) is 2 mol / L. + ) aqueous solution i, and then stir it thoroughly at room temperature until the solution is clear. Next, iodoacetic acid is selected as the halogenated acetic acid, and an aqueous solution ii with a concentration of 6 mol / L is prepared, and stirred at room temperature until it is clear. Take a clean glass substrate, use a pipette or dropper to drop solution i on the glass substrate, and quickly spread the liquid film by spin coating. Then heat the substrate, control the temperature to 60°C, and keep it for 20 minutes. Heat the solution i to dry and crystallize to obtain a prefabricated film. Then take a solution ii equal to solution i and drop it on the dry prefabricated film, and still use spin coating to quickly spread solution ii. At this time, a light yellow film can be observed to form on the substrate. The film is then placed at 120°C and heated for 15 minutes. It can be observed that the film turns black, and the FAPbI3 perovskite mineral phase appears at this time. Finally, the film is rinsed with flowing ethanol to obtain a pure FAPbI3 perovskite film. The surface micromorphology of the obtained FAPbI3 perovskite film and the distribution of iodine / lead elements therein are shown as follows Figure 2 As shown in Figure 1, larger grains can be observed on the film surface, and the measured iodine / lead atomic ratio is close to the stoichiometric ratio of FAPbI3 perovskite 3 / 1 (Table 1). Figure 3 ) shows that the obtained film is FAPbI3 perovskite phase. Photoluminescence spectrum ( Figure 4 ) shows that the obtained FAPbI3 perovskite film has obvious photoelectric effect.

[0030] Table 1 Ratio of iodine and lead in the FAPbI3 perovskite film prepared in Example 1

[0031]

[0032] Example 2: Preparation of CsPbBr3 perovskite film

[0033] The monovalent cation acetate used was cesium acetate, and the divalent metal acetate was lead acetate. A 3 mol / L aqueous solution (i) of cesium acetate and lead acetate was prepared at a molar ratio of 1:1. Bromoacetic acid was then stirred thoroughly at room temperature until the solution was clear. Next, a 9 mol / L aqueous solution (ii) of bromoacetic acid was stirred at room temperature until the solution was clear. Solution i was applied to a clean glass substrate using a doctor blade. The substrate was then heated at 60°C for 20 minutes to dry and crystallize solution i, resulting in a preformed film. An equal amount of solution ii was then applied to the dried preformed film using a doctor blade. An orange-yellow film was observed to form on the substrate. The film was then heated at 200°C for 30 minutes, at which point the film turned orange-yellow, indicating the appearance of the CsPbBr3 perovskite phase. Finally, the film was rinsed with running water to obtain a pure CsPbBr3 perovskite film.

[0034] Example 3: (Cs 0.1 FA 0.9 )Preparation of PbI2Br perovskite thin films

[0035] The monovalent cation acetate is a mixture of cesium acetate and formamidine acetate, and the divalent metal acetate is lead acetate. The molar ratio of cesium acetate, formamidine acetate and lead acetate is 0.1:0.9:1, and an aqueous solution i with a concentration of 2 mol / L is prepared. Then, it is stirred thoroughly at room temperature until the solution is clear. Next, the halogenated acetic acid is a mixture of iodoacetic acid and bromoacetic acid, and an aqueous solution ii with an iodine / bromine molar ratio of 2:1 and a concentration of 6 mol / L is prepared. It is stirred at room temperature until it is clear. Take a clean glass substrate and scrape solution i onto the glass substrate by blade coating. Then heat the substrate and control the temperature to 60°C for 20 minutes. Heat to dry and crystallize solution i to obtain a prefabricated film. Then take solution ii equal to solution i and apply it to the dried prefabricated film by blade coating. At this time, a yellow film can be observed to form on the substrate. Then, place the film at 150°C and heat for 20 minutes. It can be observed that the film turns brown. At this time, (Cs 0.1 FA 0.9 )PbI2Br perovskite phase. Finally, the film was rinsed with flowing isopropanol to obtain pure (Cs 0.1 FA 0.9 )PbI2Br perovskite thin film.

Claims

1. A method for preparing a halide perovskite thin film, characterized in that: The following steps are involved: A: a monovalent cation acetate and a divalent metal acetate are mixed and dissolved in deionized water and stirred until clear to obtain solution i; a halogenated acetic acid is dissolved in deionized water and stirred until clear to obtain solution ii; wherein the monovalent cation acetate is one or more of formamidine acetate, cesium acetate, and rubidium acetate, and the divalent metal acetate is one or more of lead acetate and stannous acetate; B: Prepare a clean substrate, apply a certain amount of solution i on the substrate, and then bake at 30-90°C to obtain a prefabricated film containing lead and / or tin and rubidium and / or cesium and / or formamidine; C: coating a certain amount of solution ii on the prefabricated film obtained in step B, and then baking at a high temperature of 100-300° C. to obtain a solid film; D: Add a certain amount of water and / or alcohol organic matter to the film prepared in step C to rinse the film, and finally obtain a pure halide perovskite film.

2. The method according to claim 1, wherein In step A, the halogenated acetic acid is one or more of iodoacetic acid, diiodoacetic acid, triiodoacetic acid, bromoacetic acid, dibromoacetic acid, tribromoacetic acid, chloroacetic acid, dichloroacetic acid, and trichloroacetic acid.

3. The method according to claim 1, wherein In step A, the molar ratio of monovalent cation acetate to divalent metal acetate in the solution i is 1:1 to 1.1:

1.

4. The method according to claim 1, wherein In step A, the concentration of solution i is 0.5 mol / L to 5 mol / L, and the concentration of solution ii is 3 times that of solution i, which is 1.5 mol / L to 15 mol / L.

5. The method according to claim 1, wherein In step B, the substrate is any one of a silicon wafer, ITO or FTO glass, a metal foil, and a polymer flexible conductive substrate.

6. The method according to claim 1, wherein In step B, the coating method is spin coating, spray coating, blade coating or slit coating.

7. The method according to claim 1, wherein In step B, the baking time is 5-30 minutes.

8. The method according to claim 1, wherein In step C, the coating method is spin coating, spray coating, blade coating or slit coating.

9. The method according to claim 1, wherein In step C, the high-temperature baking time is 10-30 minutes.

10. The method according to claim 1, wherein In step D, the alcohol organic compound is one or more of methanol, ethanol, isopropanol, and n-butanol.

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