A controllable steam atmosphere-assisted perovskite thin film crystallization method

Abstract

The present invention relates to the technical field of perovskite film preparation, and discloses a method for crystallizing a perovskite film assisted by a controllable vapor atmosphere, comprising the following steps: (1) introducing solvent volatile gas and antisolvent volatile gas into a closed processing chamber via a carrier gas to form a mixed atmosphere in the closed processing chamber; (2) placing the spin-coated perovskite film in the closed processing chamber and allowing it to stand in the mixed atmosphere for pre-crystallization; and (3) removing the pre-crystallized perovskite film for annealing. The present invention pre-crystallizes the perovskite film in a mixed atmosphere of solvent and antisolvent, thereby regulating crystal growth kinetics, improving crystal size distribution and crystal integrity, and effectively reducing defects and impurities.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite film preparation, and in particular to a perovskite film crystallization method assisted by a controllable steam atmosphere. Background Art

[0002] Perovskite thin films, due to their unique optoelectronic properties and structural tunability, have become important materials in the fields of new energy and optoelectronics. Currently, methods for preparing perovskite thin films primarily include step-by-step deposition and one-step deposition. The step-by-step deposition method involves first depositing lead halide on a substrate. Then, by immersing the lead halide film in an organic ammonium salt solution or spin-coating the organic ammonium salt solution onto the lead halide film, the lead halide reacts with the organic ammonium ions to form a perovskite precursor film, which is then annealed. The one-step deposition method involves directly depositing a mixed solution of lead halide and organic ammonium salt onto a substrate to form a perovskite precursor film. Finally, a thermal annealing treatment is performed to obtain a crystalline perovskite film. In the one-step deposition method, an organic solvent (i.e., an antisolvent) that does not dissolve the perovskite is typically added during spin-coating of the mixed solution of lead halide and organic ammonium salt to rapidly induce the formation of perovskite grains, forming seed crystals for perovskite crystal growth. This helps facilitate perovskite crystal growth during the subsequent thermal annealing process, resulting in a high-quality perovskite thin film. For example, patent CN108649121B discloses a method for preparing perovskite thin films by dynamic spin coating.

[0003] However, perovskite films produced using existing methods often contain a significant amount of non-perovskite impurities at the bottom interface. These impurities increase defects and heterogeneity in the crystal structure, easily inducing the formation of tiny voids or defective regions. These unevenly grown regions may scatter light, visually appearing as white spots or circles. The causes of impurity formation include: 1. Interface-induced impurity nucleation: During perovskite crystallization, ions require diffusion and mass transfer within the solution or precursor to reach the appropriate location for crystallization. At the buried interface, the interfacial energy difference between the substrate and the perovskite material may lower the nucleation energy barrier for certain non-perovskite phases, making them more susceptible to nucleation at the buried interface. 2. Ion diffusion and mass transfer limitations: Ion diffusion is hindered by the substrate, resulting in uneven ion distribution. This uneven distribution causes the ion concentration in some areas to deviate from the ratio required for a perfect perovskite phase, making the formation of non-perovskite impurities more likely. 3. Solvent evaporation: During solution-based preparation, solvent evaporation at the buried interface is relatively slow, resulting in a significant amount of solvent residue. These residual solvents may change the properties of the bottom solution, affect the crystallization behavior of the solute, and make some impurities unable to fully participate in the normal crystallization process, thereby forming an impurity phase at the bottom. 4. Downward crystallization process from top to bottom: On the surface of the liquid film, the surface energy is higher. According to nucleation theory, higher surface energy is conducive to reducing the energy barrier of nucleation, making it easier for crystal nuclei to form on the surface of the liquid film. At the same time, the solvent on the surface of the liquid film evaporates faster, causing the crystallization of the perovskite film to follow a top-down process. The crystallization process of the upper solution continuously consumes solutes, resulting in a vertical difference in the solute concentration inside the perovskite liquid film. This concentration difference may cause the solute composition at the bottom to deviate from the ideal stoichiometric ratio, thereby promoting the formation of an impurity phase at the bottom. Summary of the Invention

[0004] The present invention aims to overcome the problem of the presence of a large number of non-perovskite phase impurities at the bottom interface of perovskite films produced by methods in the prior art. A controllable steam atmosphere-assisted perovskite film crystallization method is provided. The perovskite film is pre-crystallized in a mixed atmosphere of solvent and anti-solvent, which can regulate the crystal growth kinetics, improve the size distribution and crystal integrity of the crystals, and effectively reduce defects and impurities.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A controllable steam atmosphere assisted perovskite thin film crystallization method comprises the following steps:

[0007] (1) The carrier gas passes through a first gas washing bottle provided with a solvent and a second gas washing bottle provided with an anti-solvent, and the solvent volatile gas and the anti-solvent volatile gas are introduced into a closed treatment chamber to form a mixed atmosphere in the treatment chamber; the solvent volatile gas is one of N,N-dimethylformamide, dimethyl sulfoxide, ethanol, and N-methylpyrrolidone; the anti-solvent volatile gas is one of chlorobenzene, ethyl acetate, and isopropanol; the carrier gas is nitrogen; the carrier gas flow rate ratio through the first gas washing bottle and the second gas washing bottle is 1:0~10;

[0008] (2) Placing the spin-coated perovskite film in a processing chamber for pre-crystallization in a mixed atmosphere;

[0009] (3) The pre-crystallized perovskite film is taken out and annealed.

[0010] The present invention pre-crystallizes the perovskite film in a mixed atmosphere formed by a solvent and an anti-solvent. When the mixed vapor contacts the perovskite liquid film, it dissolves part of the precursor or the already formed tiny crystals in the liquid film, forming a local supersaturated solution area. In the subsequent annealing process, these dissolved substances will recrystallize in more favorable positions, thereby improving the size distribution and crystal integrity of the crystals and reducing the influence of defects and impurities. In addition, the mixed vapor in the present invention can participate in the chemical reaction of the perovskite precursor and regulate the kinetic process of crystal growth: on the one hand, by adjusting the ratio of the solvent volatile gas and the anti-solvent volatile gas carried in the carrier, the reaction rate between the precursors is controlled, so that the reaction proceeds more orderly, which is conducive to the growth of the crystal; on the other hand, the gas atmosphere and temperature in the processing chamber will affect the rate of solvent volatilization in the liquid film, further regulating the crystallization rate.

[0011] Therefore, the method of the present invention can effectively reduce defects and impurities in perovskite films, producing high-quality perovskite films. Furthermore, the method of the present invention possesses significant flexibility, enabling precise control of the ratio of solvent to antisolvent in the atmosphere and the gas temperature, based on the specific components of the perovskite, to achieve optimal results. The method of the present invention has outstanding advantages in practical applications, is highly compatible with scale-up production requirements, and is perfectly compatible with large-scale production technologies, making it particularly suitable for processing large-area perovskite films.

[0012] Preferably, an additive is added to the solvent in the first scrubbing bottle in step (1), wherein the additive is one or more volatile alkylamines. The present invention can achieve the effect of a passivating agent by mixing the additive into the solvent and feeding it into the processing chamber via the airflow, based on the compositional differences of the perovskite, thereby exhibiting a high degree of adaptability.

[0013] Preferably, the volatile alkylamine is selected from one or more of methylamine, ethylamine, propylamine, n-butylamine, and n-hexylamine. The choice of the additive can be determined according to the specific components of the perovskite thin film. For example, for a perovskite thin film containing more iodide ions, methylamine can be preferentially selected as the additive to better play the passivation role.

[0014] Preferably, the concentration of the additive in the solvent is 0.1 - 10 mol / L.

[0015] Preferably, the first washing bottle or the second washing bottle is heated, and the heating temperature is 25 - 80 °C.

[0016] Preferably, the flow rate of the carrier gas passing through the first washing bottle is 100 - 1000 mL / min; the flow rate of the carrier gas passing through the second washing bottle is 0 - 1000 mL / min; the total volume of the carrier gas introduced into the treatment chamber is 1 - 50% of the volume of the treatment chamber.

[0017] Preferably, the temperature in the closed treatment chamber during pre-crystallization in step (2) is 25 - 150 °C. A temperature sensor is provided in the treatment chamber.

[0018] Preferably, during the pre-crystallization process in step (2), the flow rate of the carrier gas is monitored and recorded in real time through a gas flow meter to ensure the stability of the mixed atmosphere.

[0019] Preferably, the pre-crystallization time of the perovskite thin film in the mixed atmosphere in step (2) is 5 - 60 min.

[0020] Preferably, the molecular formula of the perovskite thin film in step (2) is Cs x FA y MA 1-x-y Pb(I 1-z Br z )3, where 0 < x < 1, 0 < y < 1, 0 ≤ z ≤ 1; the thickness of the perovskite thin film is 400 - 1200 nm.

[0021] Preferably, the annealing temperature in step (3) is 70 - 150 °C, and the annealing time is 5 - 60 minutes.

[0022] Therefore, the present invention has the following beneficial effects:

[0023] (1) Pre-crystallizing the perovskite thin film in the mixed atmosphere of the solvent and the anti-solvent can regulate the crystal growth kinetics, improve the crystal size distribution and crystallization integrity, and effectively reduce defects and impurities;

[0024] (2) It has significant flexibility and can accurately control the ratio of the solvent to the anti-solvent and the gas temperature in the atmosphere according to the specific components of the perovskite to achieve the best effect;

[0025] (3) According to the differences in the components of perovskite, the type of additive can be flexibly selected and its concentration can be precisely controlled. The additive is mixed into the solvent and fed into the processing chamber together with the air flow to achieve the role of passivation agent, showing a high degree of adaptability;

[0026] (4) It has outstanding advantages in practical applications, is highly consistent with the needs of scaled-up production, and is perfectly matched with large-scale production technology. It is particularly suitable for the processing of large-area perovskite films. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a SEM image of the perovskite film prepared in Example 2 of the present invention.

[0028] Figure 2 This is a physical picture of the perovskite film prepared in Comparative Example 2 of the present invention.

[0029] Figure 3 is a SEM image of the perovskite film prepared in Comparative Example 4 of the present invention.

[0030] Figure 4 This is a physical picture of the perovskite film prepared in Comparative Example 5 of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0033] Overall embodiment:

[0034] A controllable steam atmosphere assisted perovskite thin film crystallization method comprises the following steps:

[0035] (1) The carrier gas passes through a first gas washing bottle provided with a solvent and a second gas washing bottle provided with an anti-solvent, and the solvent volatile gas and the anti-solvent volatile gas are introduced into a closed treatment chamber to form a mixed atmosphere in the treatment chamber; the solvent volatile gas is one of N,N-dimethylformamide, dimethyl sulfoxide, ethanol, and N-methylpyrrolidone; the anti-solvent volatile gas is one of chlorobenzene, ethyl acetate, and isopropanol; the carrier gas is nitrogen; the carrier gas flow rate ratio through the first gas washing bottle and the second gas washing bottle is 1:0~10;

[0036] (2) Placing the spin-coated perovskite film in a processing chamber for pre-crystallization in a mixed atmosphere;

[0037] (3) The pre-crystallized perovskite film is taken out and annealed.

[0038] As a specific embodiment, an additive is further added to the solvent in the first washing bottle, and the additive is one or more of volatile alkylamines.

[0039] As a specific embodiment, the volatile alkylamine is selected from one or more of methylamine, ethylamine, propylamine, n-butylamine, and n-hexylamine.

[0040] As a specific embodiment, the concentration of the additive in the solvent is 0.1 - 10 mol / L.

[0041] As a specific embodiment, the first washing bottle or the second washing bottle is heated, and the heating temperature is 25 - 80 °C.

[0042] As a specific embodiment, the carrier gas flow rate through the first washing bottle is 100 - 1000 mL / min; the carrier gas flow rate through the second washing bottle is 0 - 1000 mL / min; the total volume of the carrier gas introduced into the treatment chamber is 1 - 50% of the volume of the treatment chamber.

[0043] As a specific embodiment, in step (2), the temperature in the closed treatment chamber during pre-crystallization is 25 - 150 °C.

[0044] As a specific embodiment, in step (2), the pre-crystallization time of the perovskite thin film in the mixed atmosphere is 5 - 60 min.

[0045] As a specific embodiment, the molecular formula of the perovskite thin film in step (2) is Cs x [[ID=**23**]]FA y [[ID=**25**]]MA 1-x- y Pb(I 1-z Br z )3, where 0 < x < 1, 0 < y < 1, 0 ≤ z ≤ 1; the thickness of the perovskite thin film is 400 - 1200 nm.

[0046] As a specific embodiment, the annealing temperature in step (3) is 70 - 150 °C, and the annealing time is 5 - 60 minutes.

[0047] Example 1:

[0048] A method for crystallizing a FA 0.85 Cs 0.05 MA 0.1 PbI3 perovskite thin film assisted by a controllable vapor atmosphere, the steps are as follows:

[0049] 注:原文中“FA”和“MA”未明确中文释义,直接保留英文。若有其他特殊要求或需要进一步解释,请随时告知。(1) Nitrogen was used as the carrier gas and the carrier gas was divided into two routes. One route passed through the first gas washing bottle containing the solvent DMF and carried the solvent volatilization gas into the closed treatment chamber (the treatment chamber size was: length × width × height = 50 cm × 50 cm × 50 cm, and a heating platform was provided in the treatment chamber); the other route was not connected. After 20 minutes of ventilation, the closed treatment chamber was evenly filled with mixed vapor.

[0050] The carrier gas flow rate through the first gas washing bottle is 0.2 L / min, and the heating temperature of the first gas washing bottle is 50°C;

[0051] The carrier gas flow rate through the second gas washing bottle is 0 L / min, and the second gas washing bottle is not heated;

[0052] (2) Spin-coated FA 0.85 Cs 0.05 MA 0.1 The PbI3 perovskite film was placed on a heating platform in a closed processing chamber, the heating temperature was controlled at 60°C, and it was allowed to stand in a mixed atmosphere for 5 minutes for pre-crystallization;

[0053] (3) The pre-crystallized perovskite film was taken out and annealed in a glove box to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100°C and the annealing time was 60 minutes.

[0054] Example 2:

[0055] A controllable steam atmosphere assisted FA 0.85 Cs 0.05 MA 0.1 The PbI3 perovskite thin film crystallization method comprises the following steps:

[0056] (1) Nitrogen was used as the carrier gas and the carrier gas was divided into two routes. One route passed through the first gas washing bottle containing a DMF solution containing 2 mol / L methylamine, carrying the solvent volatilization gas and the additive methylamine into the closed treatment chamber (the treatment chamber size was: length × width × height = 50 cm × 50 cm × 50 cm, and a heating platform was provided in the treatment chamber); the other route was not connected. After 20 minutes of ventilation, the closed treatment chamber was evenly filled with mixed vapors.

[0057] The carrier gas flow rate through the first gas washing bottle is 0.2 L / min, and the heating temperature of the first gas washing bottle is 50°C;

[0058] The carrier gas flow rate through the second gas washing bottle is 0 L / min, and the second gas washing bottle is not heated;

[0059] (2) Spin-coated FA 0.85 Cs 0.05 MA 0.1The PbI3 perovskite film was placed on a heating platform in a closed processing chamber, the heating temperature was controlled at 60°C, and it was allowed to stand in a mixed atmosphere for 5 minutes for pre-crystallization;

[0060] (3) The pre-crystallized perovskite film was taken out and annealed to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100°C and the annealing time was 60 minutes.

[0061] Example 3:

[0062] A controllable steam atmosphere-assisted FAPbI3 perovskite thin film crystallization method comprises the following steps:

[0063] (1) Nitrogen was used as the carrier gas and the carrier gas was divided into two paths. One path passed through the first washing bottle containing the solvent DMF and carried the solvent volatile gas into the closed treatment chamber (the treatment chamber size was: length × width × height = 50 cm × 50 cm × 50 cm, and a heating platform was provided in the treatment chamber); the other path passed through the second washing bottle containing the anti-solvent chlorobenzene (CB) and carried the anti-solvent volatile gas into the closed treatment chamber. After ventilation for 10 minutes, the closed treatment chamber was evenly filled with mixed vapor.

[0064] The carrier gas flow rate through the first gas washing bottle is 0.8 L / min, and the heating temperature of the first gas washing bottle is 50°C;

[0065] The carrier gas flow rate through the second gas washing bottle is 0.2 L / min, and the heating temperature of the second gas washing bottle is 50°C;

[0066] (2) Place the spin-coated FAPbI3 perovskite film on a heating table in a closed processing chamber, control the heating temperature to 60°C, and let it stand in a mixed atmosphere for 5 minutes for pre-crystallization;

[0067] (3) The pre-crystallized perovskite film was taken out and annealed to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100°C and the annealing time was 60 minutes. The SEM image of the obtained perovskite film is shown in the figure below. Figure 1 As shown in Figure 1 It can be seen from the figure that the perovskite film prepared by the method of the present invention has dense crystals.

[0068] Example 4:

[0069] A controllable steam atmosphere-assisted FAPbI3 perovskite thin film crystallization method comprises the following steps:

[0070] (1) Nitrogen was used as the carrier gas and the carrier gas was divided into two paths. One path passed through the first gas washing bottle containing the solvent DMF and carried the solvent volatilization gas into the closed treatment chamber (the treatment chamber size was: length × width × height = 50 cm × 50 cm × 50 cm, and a heating platform was provided in the treatment chamber); the other path was not connected. After 10 minutes of ventilation, the closed treatment chamber was evenly filled with mixed vapor.

[0071] The carrier gas flow rate through the first gas washing bottle is 0.8 L / min, and the heating temperature of the first gas washing bottle is 50°C;

[0072] The carrier gas flow rate through the second gas washing bottle is 0 L / min, and the second gas washing bottle is not heated;

[0073] (2) Place the spin-coated FAPbI3 perovskite film on a heating table in a closed processing chamber, control the heating temperature to 60°C, and let it stand in a mixed atmosphere for 5 minutes for pre-crystallization;

[0074] (3) The pre-crystallized perovskite film was taken out and annealed to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100°C and the annealing time was 60 minutes.

[0075] Comparative Example 1 (not pre-crystallized in a mixed atmosphere):

[0076] A FA 0.85 Cs 0.05 MA 0.1 The preparation method of PbI3 perovskite film is as follows: spin-coated FA 0.85 Cs 0.05 MA 0.1 The PbI3 perovskite film was directly annealed to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100° C. and the annealing time was 60 minutes.

[0077] Comparative Example 2 (FA 0.85 Cs 0.05 MA 0.1 PbI3 pre-crystallized only in anti-solvent atmosphere):

[0078] A controllable steam atmosphere assisted FA 0.85 Cs 0.05 MA 0.1 The PbI3 perovskite thin film crystallization method comprises the following steps:

[0079] (1) Using nitrogen as the carrier gas, the carrier gas is divided into two paths, one of which is not connected; the other path passes through a second gas washing bottle containing anti-solvent chlorobenzene, carrying the anti-solvent volatile gas into a closed treatment chamber (the treatment chamber size is: length × width × height = 50 cm × 50 cm × 50 cm, and a heating platform is provided in the treatment chamber); after ventilation for 20 minutes, the closed treatment chamber is evenly filled with mixed vapor;

[0080] The carrier gas flow rate through the first gas washing bottle is 0 L / min, and the first gas washing bottle is not heated;

[0081] The carrier gas flow rate through the second gas washing bottle is 0.2 L / min, and the heating temperature of the second gas washing bottle is 50°C;

[0082] (2) Spin-coated FA 0.85 Cs 0.05 MA 0.1 The PbI3 perovskite film was placed on a heating platform in a closed processing chamber, the heating temperature was controlled at 60°C, and it was allowed to stand in a mixed atmosphere for 5 minutes for pre-crystallization;

[0083] (3) The pre-crystallized perovskite film was taken out and annealed to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100°C and the annealing time was 60 minutes. The actual picture of the obtained perovskite film is shown in the figure below. Figure 2 As shown in Figure 2 It can be seen that the surface of the perovskite film pre-crystallized only in the anti-solvent atmosphere is rough and has a frosted feel.

[0084] Comparative Example 3 (FAPbI3 pre-crystallized only in anti-solvent atmosphere):

[0085] A controllable steam atmosphere-assisted FAPbI3 perovskite thin film crystallization method comprises the following steps:

[0086] (1) Using nitrogen as the carrier gas, the carrier gas is divided into two paths, one of which is not connected; the other path passes through a second gas washing bottle containing anti-solvent chlorobenzene (CB), carrying the anti-solvent volatile gas into a closed treatment chamber (the treatment chamber size is: length × width × height = 50 cm × 50 cm × 50 cm, and a heating platform is provided in the treatment chamber); after ventilation for 10 minutes, the closed treatment chamber is evenly filled with mixed vapor;

[0087] The carrier gas flow rate through the first gas washing bottle is 0 L / min, and the first gas washing bottle is not heated;

[0088] The carrier gas flow rate through the second gas washing bottle is 0.2 L / min, and the heating temperature of the second gas washing bottle is 50°C;

[0089] (2) Place the spin-coated FAPbI3 perovskite film on a heating table in a closed processing chamber, control the heating temperature to 60°C, and let it stand in a mixed atmosphere for 5 minutes for pre-crystallization;

[0090] (3) The pre-crystallized perovskite film was taken out and annealed to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100°C and the annealing time was 60 minutes.

[0091] Comparative Example 4 (improper solvent selection):

[0092] A controllable steam atmosphere-assisted FAPbI3 perovskite thin film crystallization method comprises the following steps:

[0093] (1) Nitrogen is used as the carrier gas and the carrier gas is divided into two paths. One path passes through the first washing bottle containing the solvent ethanol and carries the solvent volatile gas into the closed treatment chamber (the treatment chamber size is: length × width × height = 50 cm × 50 cm × 50 cm, and the treatment chamber is equipped with a heating platform); the other path passes through the second washing bottle containing the anti-solvent chlorobenzene and carries the anti-solvent volatile gas into the closed treatment chamber. After ventilation for 10 minutes, the closed treatment chamber is evenly filled with mixed vapor;

[0094] The carrier gas flow rate through the first gas washing bottle is 0.8 L / min, and the heating temperature of the first gas washing bottle is 50°C;

[0095] The carrier gas flow rate through the second gas washing bottle is 0.2 L / min, and the heating temperature of the second gas washing bottle is 50°C;

[0096] (2) Place the spin-coated FAPbI3 perovskite film on a heating table in a closed processing chamber, control the heating temperature to 60°C, and let it stand in a mixed atmosphere for 5 minutes for pre-crystallization;

[0097] (3) The pre-crystallized perovskite film was taken out and annealed to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100°C and the annealing time was 60 minutes.

[0098] Comparative Example 5 (improper anti-solvent selection):

[0099] A controllable steam atmosphere-assisted FAPbI3 perovskite thin film crystallization method comprises the following steps:

[0100] (1) Nitrogen is used as the carrier gas and the carrier gas is divided into two paths. One path passes through the first washing bottle containing the solvent DMF and carries the solvent volatile gas into the closed treatment chamber (the treatment chamber size is: length × width × height = 50 cm × 50 cm × 50 cm, and the treatment chamber is equipped with a heating platform); the other path passes through the second washing bottle containing the anti-solvent cyclohexane and carries the anti-solvent volatile gas into the closed treatment chamber. After ventilation for 10 minutes, the closed treatment chamber is evenly filled with mixed vapor.

[0101] The carrier gas flow rate through the first gas washing bottle is 0.8 L / min, and the heating temperature of the first gas washing bottle is 50°C;

[0102] The carrier gas flow rate through the second gas washing bottle is 0.2 L / min, and the heating temperature of the second gas washing bottle is 50°C;

[0103] (2) Place the spin-coated FAPbI3 perovskite film on a heating table in a closed processing chamber, control the heating temperature to 60°C, and let it stand in a mixed atmosphere for 5 minutes for pre-crystallization;

[0104] (3) The pre-crystallized perovskite film was taken out and annealed to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100°C and the annealing time was 60 minutes. The SEM image of the obtained perovskite film is shown in the figure below. Figure 3 As shown in Figure 3 It can be seen from the figure that when the antisolvent type is not selected properly, the perovskite film is uneven and has holes (the positions marked with red circles are holes).

[0105] Comparative Example 6 (Volatile Gas Concentration Too High):

[0106] A controllable steam atmosphere assisted FA 0.85 Cs 0.05 MA 0.1 The PbI3 perovskite thin film crystallization method comprises the following steps:

[0107] (1) Nitrogen was used as the carrier gas and the carrier gas was divided into two routes. One route passed through the first gas washing bottle containing the solvent DMF and carried the solvent volatilization gas into the closed treatment chamber (the treatment chamber size was: length × width × height = 50 cm × 50 cm × 50 cm, and a heating platform was provided in the treatment chamber); the other route was not connected. After 60 minutes of ventilation, the closed treatment chamber was evenly filled with mixed vapor.

[0108] The carrier gas flow rate through the first gas washing bottle is 1.5 L / min, and the heating temperature of the first gas washing bottle is 80°C;

[0109] The carrier gas flow rate through the second gas washing bottle is 0 L / min, and the second gas washing bottle is not heated;

[0110] (2) Spin-coated FA 0.85 Cs 0.05 MA 0.1 The PbI3 perovskite film was placed on a heating platform in a closed processing chamber, the heating temperature was controlled at 60°C, and it was allowed to stand in a mixed atmosphere for 5 minutes for pre-crystallization;

[0111] (3) The pre-crystallized perovskite film was taken out and annealed to obtain a perovskite film with a thickness of 600 nm; the annealing temperature was 100°C and the annealing time was 60 minutes. The actual picture of the obtained perovskite film is shown in the figure below. Figure 4 As shown in Figure 4 It can be seen from the figure that when the concentration of volatile gas is too high, the surface of the perovskite film is contaminated.

[0112] The perovskite films prepared in the above examples and comparative examples were applied to perovskite solar cells, and their cell efficiency was tested. The results are shown in Table 1.

[0113] Table 1: Perovskite film performance test results

[0114]

[0115] As can be seen from Table 1, in Examples 1-4, the perovskite films pre-crystallized in a mixed atmosphere of solvent and anti-solvent using the method of the present invention exhibited no white spots or white circles on the bottom surface. When applied to perovskite cells, the cell efficiency was improved by 1-3% compared to the perovskite film pre-crystallized without a mixed atmosphere in Comparative Example 1. Furthermore, in Example 2, methylamine was added to the DMF solvent, which volatilized along with the DMF. After treatment with methylamine-containing vapor, the efficiency of the prepared perovskite solar cell was further improved by 0.5-1%, compared to the perovskite cell treated without the methylamine additive (Example 1).

[0116] In Comparative Examples 2 and 3, pre-crystallization was performed only in an antisolvent atmosphere. The antisolvent accelerates the desolvation process of the perovskite precursor solution, resulting in rapid crystallization (small grains) in some areas due to excessive antisolvent extraction, while other areas experience delayed crystallization (large grains) due to residual solvent, forming a multi-scale mixed grain structure. The resulting perovskite film exhibits a whitening and matte appearance, which can lead to reduced efficiency when used in perovskite cells.

[0117] In Comparative Examples 4 and 5, the types of solvents and anti-solvents are improperly selected. Since the boiling point, volatility and interaction of the solvents and anti-solvents with the precursors will directly affect the crystallization process of the perovskite, if the types of solvents and anti-solvents are improperly selected, such as using a solvent that does not match the perovskite precursor, resulting in insufficient solubility, or the anti-solvent cannot effectively reduce the solubility of the solvent for the precursor, it will be difficult to form the local supersaturated solution region described in the present invention, and effective regulation of crystal growth cannot be achieved, resulting in uneven crystal size distribution, poor crystal integrity, increased defects and impurities in the film, and unevenly sized grains and porous structures, which in turn lead to a decrease in the efficiency of the perovskite battery.

[0118] In Comparative Example 6, the concentration of volatile gas in the processing chamber reaches a high level. When the vapor contacts the inner wall of the chamber with a lower temperature, condensation is formed. The dripping of the condensation causes the film to be contaminated, thereby reducing the battery efficiency.

Claims

1. A method for crystallizing a perovskite thin film assisted by a controlled steam atmosphere, characterized in that the steps include: (1) The carrier gas passes through a first gas washing bottle provided with a solvent and a second gas washing bottle provided with an anti-solvent, and the solvent volatile gas and the anti-solvent volatile gas are introduced into a closed treatment chamber to form a mixed atmosphere in the treatment chamber; the solvent volatile gas is one of N,N-dimethylformamide, dimethyl sulfoxide, ethanol, and N-methylpyrrolidone; the anti-solvent volatile gas is one of chlorobenzene, ethyl acetate, and isopropanol; the carrier gas is nitrogen; the carrier gas flow rate ratio through the first gas washing bottle and the second gas washing bottle is 1:0~10; (2) Placing the spin-coated perovskite film in a processing chamber for pre-crystallization in a mixed atmosphere; (3) The pre-crystallized perovskite film is taken out and annealed.

2. The method for crystallizing perovskite thin films assisted by a controlled steam atmosphere according to claim 1, wherein: In step (1), an additive is added to the solvent in the first gas washing bottle, wherein the additive is a volatile alkylamine.

3. The controlled steam atmosphere assisted perovskite thin film crystallization method according to claim 2, characterized in that: The volatile alkylamine is selected from one or more of methylamine, ethylamine, propylamine, n-butylamine and n-hexylamine.

4. The method for crystallizing a perovskite thin film assisted by a controlled steam atmosphere according to claim 2 or 3, wherein: The concentration of the additive in the solvent is 0.1~10mol / L.

5. The method for perovskite thin film crystallization assisted by controlled steam atmosphere according to claim 4, characterized in that: Heat the first washing bottle or the second washing bottle at a temperature of 25-80°C.

6. The controlled steam atmosphere assisted perovskite thin film crystallization method according to claim 1, characterized in that: The carrier gas flow rate through the first gas washing bottle is 100~1000 mL / min; the carrier gas flow rate through the second gas washing bottle is 0~1000 mL / min; the total volume of the carrier gas introduced into the processing chamber is 1~50% of the processing chamber volume.

7. The method for perovskite thin film crystallization assisted by controlled steam atmosphere according to claim 1, wherein: During the pre-crystallization in step (2), the temperature in the closed treatment chamber is 25-150°C.

8. The method for crystallizing a perovskite thin film assisted by a controlled steam atmosphere according to claim 1 or 7, wherein: In step (2), the pre-crystallization time of the perovskite film in the mixed atmosphere is 5 to 60 minutes.

9. The method for perovskite thin film crystallization assisted by controlled steam atmosphere according to claim 1, wherein: The molecular formula of the perovskite thin film described in step (2) is Cs x FA y MA 1-x-y Pb(I 1-z Br z )3, where 0 < x < 1, 0 < y < 1, 0 ≤ z ≤ 1; the thickness of the perovskite thin film is 400 - 1200 nm.

10. The method for crystallizing perovskite thin films assisted by a controlled steam atmosphere according to claim 1, wherein: The annealing temperature in step (3) is 70-150° C., and the annealing time is 5-60 minutes.

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