Drying treatment method of perovskite wet film

Abstract

The invention discloses a drying treatment method of a perovskite thin film, which comprises the following steps: in the process of technological processing and technological transmission of the perovskite thin film, controlling volatilization of a protective solvent in which hydrogen sulfide gas is dissolved, so that a protective solvent gas atmosphere is formed in technological equipment and a transmission passage. According to the invention, by controlling the volatilization of the protective solvent, a protective solvent gas atmosphere is formed in the equipment and the passage, and the unfavorable drying of the perovskite wet film is effectively prevented or delayed, so that the stability, the film forming uniformity and the process yield of the battery are improved. The combined gas of the protective solvent gas and the nitrogen N2 gas is input into the vacuum drying furnace at low flow, so that the organic solvent in the wet film can be rapidly extracted, and the compact perovskite film with high quality and no pinholes can be obtained. And the crystallized perovskite thin film can be prevented from being eroded by water vapor in air during transmission, so that the conversion efficiency of the perovskite solar cell is improved, and the service life of the perovskite solar cell is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and in particular to a drying treatment method for a perovskite film in a perovskite solar cell. Background Art

[0002] In the wet preparation of perovskite solar cells, a perovskite solution prepared by an organic solvent needs to be coated on the substrate to form a perovskite wet film, which becomes a perovskite dry film after vacuum drying, annealing and crystallization, and then sent to the evaporation equipment to evaporate other functional layers. Therefore, the coating / vacuum drying / crystallization process is a key link in forming a high-quality perovskite film light-absorbing layer. Since the coating / vacuum drying / crystallization process links are connected together and the process flow time is relatively long. In the various process processes of preparing perovskite solar cells in the prior art, unreasonable volatilization and drying of organic solvents in the perovskite wet film, untimely extraction and removal of organic solvents, or erosion of the perovskite film by water vapor in the air after crystallization, and other process defects will seriously affect the stability of the performance of perovskite solar cells.

[0003] When preparing a wet film of perovskite solution by slit coating or doctor blade coating, the evaporation rate of the organic solvent on the surface of the perovskite wet film is greater than the condensation rate of the organic solvent vapor above its surface, that is, the organic solvent on the surface of the perovskite wet film is constantly evaporating. During the coating and transportation process, the perovskite wet film is inevitably dried in advance, and a large amount of uncrystallized non-perovskite phase is introduced into the yellow dry film, which will adversely affect the conversion efficiency and service life of the perovskite battery.

[0004] When large-area perovskite coatings are applied in batches, due to the influence of the size of the substrate itself (such as a specification of 1200mm*600mm), the organic solvent in the wet film at the starting point of coating will evaporate before the organic solvent in the wet film at the end point of coating, resulting in inconsistent organic solvent concentrations in the wet film at both ends of coating, and ion migration occurs, which ultimately leads to uneven thickness of the perovskite dry film.

[0005] After the coating process is completed, the perovskite wet film will be dried and crystallized as soon as possible. However, since the coating process time is generally shorter than the drying and crystallization process, part of the perovskite wet film will remain in the buffer chamber waiting for drying and crystallization. During the waiting process, the organic solvent in the perovskite wet film in the buffer chamber will inevitably continue to evaporate, which is not conducive to inducing the perovskite wet film to reach a supersaturated state for directional nucleation, resulting in differences in the crystallinity of the subsequent perovskite film.

[0006] During the vacuum drying process, the organic solvent in the wet perovskite film is difficult to extract quickly, and it will remain in the dry perovskite film, causing defects, which is not conducive to obtaining high-quality, pinhole-free and dense perovskite films. After crystallization, the perovskite film is easily corroded by water vapor in the air, affecting the stability of the perovskite battery.

[0007] Therefore, how to overcome the defects in the process of preparing perovskite solar cells with the prior art, such as unreasonable volatilization and drying of organic solvents in the perovskite wet film, untimely extraction and removal of organic solvents, or erosion of the perovskite film by water vapor in the air after crystallization, is a problem that needs to be solved in this field. Summary of the invention

[0008] The present invention aims to solve the technical problems in the prior art of preparing perovskite solar cells, that is, the organic solvent in the perovskite wet film is not evaporated and dried reasonably, the organic solvent is not extracted and removed in time, or the perovskite film is corroded by water vapor in the air after crystallization. A drying method for a perovskite film in a perovskite solar cell is provided.

[0009] The present invention provides a method for drying a perovskite film, comprising the following steps:

[0010] During the process of processing and transmission of perovskite thin films, the volatilization of the protective solvent dissolved with hydrogen sulfide gas is controlled to form a protective solvent gas atmosphere in the equipment of each process and in the transmission corridor.

[0011] Preferably, the protective solvent is an organic solvent DMF (N,N-dimethylformamide) in which hydrogen sulfide (H2S) gas is dissolved, with a purity of 99.99%, and a volume ratio of H2S / DMF of 0.01 mM / L.

[0012] Preferably, the protective solvent gas atmosphere is arranged in coating equipment-aisle-buffer chamber-aisle-vacuum drying furnace-aisle-annealing furnace-aisle.

[0013] Preferably, in the process of coating equipment-aisle-buffer chamber-aisle, the protective solvent gas is first input and the concentration of the protective solvent gas is increased so that the volatilization rate of the organic solvent on the surface of the perovskite wet film is equal to the condensation rate of the organic solvent vapor in the air, and then the coating process is started.

[0014] Preferably, when the volatilization rate of the organic solvent on the surface of the perovskite wet film is equal to the condensation rate of the vapor of the organic solvent in the air, the pressure inside the device no longer increases and stabilizes at a fixed value, and the vapor of the organic solvent reaches a saturated vapor pressure at a certain temperature. The calculation formula of the saturated vapor pressure is the following Clausius-Clapeyron equation:

[0015]

[0016] Where P is the saturated vapor pressure, T is the temperature in Kelvin, L is the heat of vaporization in J / Kg,

[0017] △V is the volume change between gas and liquid.

[0018] Preferably, the saturated vapor pressure of the organic solvent vapor increases with increasing temperature, and the relationship between the saturated vapor pressure and temperature conforms to the following Clausius-Clapeyron equation:

[0019]

[0020] Where △vapHm is the molar heat of vaporization of the liquid, which is a constant within the temperature range.

[0021] Preferably, in the vacuum drying furnace, the combined gas of the protective solvent gas and nitrogen N2 gas is input at a flow rate of 20 μL / min.

[0022] Preferably, the combined gas is composed of 5% protective solvent gas and 95% nitrogen N2 gas in a volume ratio.

[0023] Preferably, the temperature is adjusted to heat the protective solvent to make it evaporate slowly, and the protective solvent gas is input into the aisle from the vacuum drying furnace to the annealing furnace, inside the annealing furnace, and into the aisle from the annealing furnace to the evaporation equipment.

[0024] The present invention controls the volatilization of DMF-protective solvent in which a certain amount of hydrogen sulfide (H2S) gas is dissolved during a series of process treatments and process transmission of the perovskite film of the perovskite solar cell, so that a stable protective solvent gas atmosphere is formed in each process equipment and in the transmission corridor, and defects in the passivated perovskite interface are prevented, so as to improve the quality of the perovskite film. That is, in the process of coating equipment-corridor-buffer chamber-corridor, the protective solvent gas is first input, and the concentration of the protective solvent gas is continuously increased, so that the volatilization rate of the organic solvent on the surface of the perovskite wet film is equal to the condensation rate of the organic solvent vapor in the air, that is, the saturated vapor pressure of the vapor is achieved by regulating the protective solvent solvent atmosphere, so that the organic solvent vapor and the organic solvent liquid reach a phase equilibrium state, effectively overcoming the defect of premature drying of the organic solvent in the perovskite wet film, avoiding the problem of inconsistent organic solvent concentration of the wet film at both ends of the coating, migration of ions, and uneven thickness of the perovskite dry film. It is conducive to inducing the perovskite wet film to reach a supersaturated state of directional nucleation, so that the crystallinity of the perovskite film is consistent. In the process of vacuum drying, the combination of protective solvent gas and nitrogen N2 gas is input at a low flow rate to quickly extract the organic solvent in the wet perovskite film, which is conducive to obtaining high-quality, pinhole-free and dense perovskite film. It can also prevent the perovskite film after crystallization from being corroded by water vapor in the air during transmission, thereby improving the stability, conversion efficiency and service life of perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of a wet perovskite film of the present invention that is not in a protective solvent atmosphere after coating;

[0026] Figure 2 It is a schematic diagram of a perovskite wet film in a protective solvent atmosphere after coating in the prior art;

[0027] Figure 3 A schematic diagram of a perovskite dry film after vacuum drying in the prior art;

[0028] Figure 4 It is a schematic diagram of the perovskite dry film after vacuum drying by introducing the combined gas of the present invention;

[0029] Figure 5 The prior art is a SEM image of a perovskite film processed in a protective solvent atmosphere;

[0030] Figure 6 This is a SEM image of the perovskite film processed in a protective solvent atmosphere of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and do not constitute a limitation to the present invention.

[0032] Due to the defects in the prior art of preparing perovskite solar cells, such as unreasonable volatilization and drying of organic solvents in the perovskite wet film, untimely extraction and removal of organic solvents, or corrosion of the perovskite film by water vapor in the air after crystallization, the performance of perovskite solar cells is seriously affected.

[0033] In order to solve the above problems, the present invention proposes a drying method for a perovskite film of a perovskite solar cell, comprising the following steps:

[0034] During the process of processing and transmission of perovskite thin films, the volatilization of the protective solvent dissolved with hydrogen sulfide gas is controlled, so that a protective solvent gas atmosphere is formed in the equipment of each process and in the transmission corridor, thereby improving the stability, conversion efficiency and service life of the perovskite solar cell.

[0035] The protective solvent is an organic solvent DMF (N,N-dimethylformamide) dissolved with hydrogen sulfide (H2S) gas, with a purity of 99.99% and a volume ratio of H2S / DMF of 0.01 mM / L. That is, the protective solvent is mainly an organic solvent.

[0036] The present invention sets a control device with a heating device and a cover plate in the processing equipment of the perovskite film and the process transmission corridor, and produces a protective solvent gas atmosphere for the drying process of the perovskite film by heating the protective solvent contained in the control device and volatilizing it. For example, in the following process flow:

[0037] Coating equipment - aisle - buffer room - aisle - vacuum drying furnace - aisle - annealing furnace - in the aisle.

[0038] In order to solve the problems that arise in the process of coating equipment-aisle-buffer room-aisle, the protective solvent in the control device is heated and volatilized, and the protective solvent gas is pre-input into the closed coating equipment, buffer room and transmission channel to create a protective solvent gas atmosphere in the closed working space, and the concentration of the protective solvent gas in the air of the coating equipment is continuously increased, so that the vapor pressure on the surface of the perovskite wet film can be increased, the gas pressure inside the coating equipment is increased, and the condensation rate of the solvent on the surface of the perovskite wet film is increased, which can effectively reduce the volatilization rate of the wet film. The volatilization rate of the protective solvent gas is manipulated by the control device, so that the volatilization rate of the organic solvent on the surface of the perovskite wet film is equal to the condensation rate of the organic solvent vapor in the closed space, that is, the organic solvent atmosphere in the air inside the coating equipment and the volatilization of the organic solvent on the surface of the perovskite wet film are in a state of equilibrium, and then the coating and transmission processing are started.

[0039] When the volatilization rate of the organic solvent on the surface of the perovskite wet film is equal to the condensation rate of the vapor of the organic solvent in the air, the pressure inside the device no longer increases and stabilizes at a fixed value. The vapor of the organic solvent reaches the saturated vapor pressure at a certain temperature. The calculation formula of the saturated vapor pressure is the following Clausius-Clapeyron equation:

[0040]

[0041] Where P is the saturated vapor pressure, T is the temperature in Kelvin, L is the heat of vaporization in J / Kg,

[0042] △V is the volume change between gas and liquid. This equation can be used to simply calculate the saturated vapor pressure of the solvent.

[0043] The results of testing the control device to manipulate the protective solvent gas atmosphere to reach saturated vapor pressure at different temperatures are as follows: Before coating the perovskite coating, check whether the coating equipment is sealed intact, and first open the cover of the control device filled with the protective solvent. At this time, the high-precision instrument set in the coating equipment shows a temperature of 20°C and a pressure of P (平衡前) The heating temperature of the control device is adjusted to 50°C to accelerate the volatilization rate of the protective solvent in the control device, so that the vapor pressure in the device continues to increase, and the pressure reading continues to increase. Finally, the pressure reading in the coating device no longer changes, the closed system is in a state of equilibrium, and the vapor pressure of the organic solvent reaches the saturated vapor pressure. The pressure reading P (平衡后) The display shows 101.681KPa. At this time, the perovskite wet film was applied. After the coating was completed, it was left to stand for five minutes. The perovskite wet film did not change color or dry prematurely, and the pressure reading was almost unchanged. Figure 1 The figure shows the perovskite wet film of the present invention after coating in a protective solvent gas atmosphere. Figure 2 The figure shows a perovskite wet film coated without a protective solvent gas atmosphere, and the wet film has obvious color change. Figure 1 and Figure 2 The difference in the perovskite wet film state is intuitively shown.

[0044] The test results show that the control device is operated in advance so that the protective solvent gas atmosphere in the coating equipment is in a dynamic equilibrium with the perovskite wet film coating, that is, the evaporation rate of the organic solvent on the surface of the perovskite wet film is equal to the condensation rate of the organic solvent. The saturated vapor pressure of the protective solvent at 20 degrees Celsius is theoretically 0.34KPa calculated according to the above Clausius-Clapeyron equation. The saturated vapor pressure P of the protective solvent obtained in this test is (饱和) The actual value in the coating equipment is the pressure indication after equilibrium P (平衡后) 101.681 minus the pressure reading P before the control device opens the cover (平衡前) 101.333, the actual value of the saturation pressure of the protective solvent is: P (饱和) =P (平衡后) -P (平衡前) =101.681-101.333=0.348KPa. The theoretical value is close to the actual value, the △P between the two is 0.008KPa, and the relative difference is 2.35%.

[0045] The saturated vapor pressure of the organic solvent vapor increases with increasing temperature, and the relationship between the saturated vapor pressure and temperature conforms to the following Clausius-Clapeyron equation:

[0046]

[0047] Where △vapHm is the molar heat of vaporization of the liquid, which is a constant within the temperature range.

[0048] By using the control device to release the protective solvent gas, the saturated vapor pressure of the organic solvent at different temperatures inside the coating equipment can be measured, and the organic solvent volatilization of the perovskite wet film in the coating equipment is induced at different temperatures to reach a state of equilibrium with the organic solvent atmosphere. The results of the saturated vapor pressure of the protective solvent at different temperatures in the coating equipment are shown in Table 1:

[0049] Table 1

[0050]

[0051] In the actual mass-produced perovskite components, some perovskite wet films will wait for drying and crystallization in the buffer chamber after coating. The control device manipulates the organic solvent atmosphere inside the buffer chamber to reach the saturated vapor pressure to prevent the perovskite wet film from drying out prematurely, thereby improving the production yield of the entire perovskite line, promoting the connection between the coating / drying / crystallization process sections, and ensuring the uniformity and stability of the perovskite dry film coating.

[0052] The test results of the control device are as follows: Before opening the control device cover in the buffer room, check whether the air tightness inside the buffer room is intact. At this time, the instrument in the buffer room shows a temperature of 25°C and a pressure indication of P (平衡前) The vapor pressure on the perovskite wet film will continue to rise. Observe the pressure changes in the buffer chamber. If the pressure rises and remains at a fixed value for three minutes, it reaches the saturated vapor pressure. At this time, the evaporation rate of the organic solvent on the surface of the perovskite wet film in the buffer chamber is equal to its condensation rate, that is, it is in a phase change equilibrium state. Close the cover. At this time, the pressure reading P in the buffer chamber is (平衡后) The display shows 99.887KPa, and the saturated vapor pressure of the organic solvent is measured to be 0.488KPa. At this time, open the door of the buffer chamber, input the perovskite wet film component, and then close the door. Since the internal pressure of the buffer chamber is greater than the external pressure when the door is opened, part of the solvent gas escapes, the pressure decreases, and the pressure reading is 99.754KPa. Open the cover of the control device again, set the temperature to 40°C, accelerate the volatilization of the solvent in the control device, delay the escape of solvent molecules on the surface of the perovskite wet film, increase the pressure of the gas system in the buffer chamber, and observe the pressure changes in the buffer chamber. If the pressure rises and remains at a fixed value for three minutes, it means that the saturated vapor pressure is reached again. Close the cover, and the pressure reading P is now (平衡后) Displays 99.912KPa.

[0053] When vacuum drying is used to extract organic solvents from the perovskite wet film, some commonly used organic polar solvents, such as DMF (N,N-dimethylformamide), NMP (N-methylpyrrolidone), DMSO (dimethyl sulfoxide), etc., are difficult to remove quickly. In particular, DMSO will remain in the perovskite dry film to a large extent, resulting in volume collapse and introduction of defects during the subsequent annealing process.

[0054] In order to solve the above problems, the present invention proposes a method of using a low-flow protective gas to assist in accelerating the extraction rate of organic solvents in perovskite wet films during vacuum drying. The protective gas is a combination of the protective solvent gas and nitrogen N2 gas provided by the present invention. The combined gas is a combination of 5% protective solvent gas and 95% N2 gas in a volume ratio. Among them, the 5% protective solvent gas is obtained by evaporating the protective solvent therein by a heating control device. The remaining 95% N2 is the commonly used backfill drying gas inside the vacuum drying furnace VCD. The 5% protective solvent gas is a gas that plays the main function of accelerating the solvent extraction rate and passivation.

[0055] During the vacuum drying process, a protective gas is introduced into the vacuum drying furnace at a flow rate of 20 μL / min to increase the extraction rate of the organic solvent in the perovskite wet film and reduce the residual solvent in the perovskite dry film. During processing, the control device heats the protective solvent inside to volatilize it, and the gas atmosphere of the volatilized protective solvent will produce a thermal runaway effect, which accelerates the gas microflow through the temperature gradient drive, generates a temperature difference between the exhaust channels, and thus accelerates the vacuum process to reduce the residual organic solvent in the perovskite dry film. Figure 4 The perovskite dry film shown in FIG. has a smooth and flat film surface. The perovskite dry film comparative example using the prior art vacuum drying process, such as Figure 3 As shown, the surface of the perovskite dry film is rough and foggy. The results show that the present invention can accelerate the solvent extraction rate and is conducive to obtaining a beautiful and smooth perovskite dry film.

[0056] In the aisle-annealing furnace-aisle treatment process after the vacuum drying furnace, the perovskite film will inevitably be corroded and degraded by water vapor in the air and converted into a yellow phase of optically inert δ-FAPbI3. In order to solve the problem, a control device is installed in the aisle and annealing furnace. The control device is provided with a heating device and a cover to control the volatilization rate of the protective solvent therein. That is, the cover of the control device is opened, and the heating temperature is adjusted to 30°C, so that the protective solvent evaporates slowly. By controlling the input of protective solvent gas into the aisle and annealing furnace, the defects of the perovskite film can be repaired and passivated, and the invasion of water vapor into the perovskite film can be weakened. The protective solvent gas atmosphere contains a small amount of H2S gas volatilized from the protective solvent, which can repair the defects on the surface of the perovskite film and passivate the undercoordinated Pb 2+ ions, the reaction process is as follows:

[0057] H2S+Pb + PbS+2H

[0058] Since a trace amount of H2S gas in the air in the passage and the annealing furnace reacts with PbI2 remaining on the surface of the perovskite film, a moisture-resistant PbS film is generated, thereby preventing moisture in the air from further corroding the internal perovskite film.

[0059] The perovskite film that entered the evaporation equipment after annealing and crystallization was analyzed by scanning electron microscopy (SEM) for film morphology, crystallinity and grain size of the perovskite film. Figure 6 As shown in Figure 2, the surface of the perovskite film in the protective solvent gas atmosphere is dense and pinhole-free. Figure 5 As shown, in the comparative example - prior art, the perovskite film treated in the atmosphere without the protective solvent gas provided by the present invention has pinholes on the surface of the perovskite film. The results show that the drying treatment method proposed by the present invention can improve the crystallization quality of the perovskite film and reduce the short-circuit current density damage caused by pinholes.

[0060] After annealing and crystallization, the perovskite dry film will be immediately sent to the evaporation equipment to evaporate other functional layers. When the evaporation equipment is running, the internal state is high vacuum, and the perovskite film will no longer be corroded by water vapor. When the evaporation is completed, the surface of the perovskite is also covered with a functional layer, which enhances the surface stability of the product and does not require the protection of the organic solvent gas atmosphere.

[0061] In addition, the above-mentioned coating / vacuum drying / annealing crystallization and transmission channel and other major process engineering, all use the protective solvent provided by the present invention. The protective solvent is a DMF organic solution dissolved with 0.01mM / L H2S gas, with a purity of 99.99%. It can be reused to reduce costs.

[0062] The thickness of the perovskite dry film dried by the prior art (control group) and the thickness of the perovskite dry film dried in a protective solvent gas atmosphere (optimized group) of the present invention are tested and compared.

[0063] The film thickness data of the control group and the optimized group of the perovskite dry film measured by ellipsometer under the same film thickness standard and coating parameters are all taken at average distances, with a total of 31 positions.

[0064] As shown in Table 2, the film thickness test record of the perovskite dry film treated by the existing technology is shown in Table 2. The measured average film thickness of the control group is 499nm, which is quite different from the parameter setting film thickness of 600nm, while the measured average film thickness of the optimization group is 592nm, which is slightly different from the parameter setting film thickness of 600nm, which indicates that the product yield is higher in the protective solvent gas atmosphere.

[0065] Table 2

[0066]

[0067] As shown in Table 3, the film thickness test record of the perovskite dry film dried in the protective solvent gas atmosphere of the present invention is shown. The film thickness of the control group at the coating starting point is 423nm and the film thickness at the coating end point is 570nm, with a large difference of 147nm in thickness, and the uniformity of the entire film is 16%. The film thickness of the optimized group at the coating starting point is 575nm and the film thickness at the coating end point is 614nm, with a small difference of 39nm in thickness, and the uniformity of the entire film is 4%. This is conducive to forming a better interface contact between the perovskite film and other functional layers to reduce interface defects, thereby obtaining a more stable perovskite film quality and increasing the stability of the device.

[0068] Table 3

[0069]

[0070] The present invention controls the volatilization of the protective solvent dissolved with hydrogen sulfide gas during the process of the process processing and process transmission of the perovskite film, so that the protective solvent gas atmosphere is formed in the equipment of each process and in the transmission corridor, effectively preventing or delaying the unfavorable drying of the perovskite wet film, thereby improving the stability, film formation uniformity and process yield of the perovskite solar cell. The combined gas of the protective solvent gas and nitrogen N2 gas is input into the vacuum drying furnace at a low flow rate, and the organic solvent in the perovskite wet film can be quickly extracted, which is conducive to obtaining a high-quality, pinhole-free and dense perovskite film. It can also avoid the perovskite film after crystallization from being eroded by water vapor in the air during transmission, thereby improving the conversion efficiency and service life of the perovskite solar cell.

[0071] The above description is only a specific implementation of the present invention. It should be pointed out that any modification, equivalent substitution and change made within the spirit and framework of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for drying a perovskite film, comprising the following steps: During the process of processing and transmission of perovskite thin films, the volatilization of the protective solvent dissolved with hydrogen sulfide gas is controlled to form a protective solvent gas atmosphere in the equipment of each process and in the transmission corridor.

2. The drying method according to claim 1, characterized in that: The protective solvent is an organic solvent N,N-dimethylformamide dissolved with hydrogen sulfide gas, with a purity of 99.99%, and a volume ratio of H2S / DMF of 0.01 mM / L.

3. The drying method according to claim 2, characterized in that: The protective solvent gas atmosphere is arranged in the coating equipment-aisle-buffer chamber-aisle-vacuum drying furnace-aisle-annealing furnace-aisle.

4. The drying method according to claim 3, characterized in that: In the process of coating equipment-aisle-buffer chamber-aisle, the protective solvent gas is first input and the concentration of the protective solvent gas is increased so that the volatilization rate of the organic solvent on the surface of the perovskite wet film is equal to the condensation rate of the organic solvent vapor in the air, and then the coating process is started.

5. The drying method according to claim 4, characterized in that: When the volatilization rate of the organic solvent on the surface of the perovskite wet film is equal to the condensation rate of the vapor of the organic solvent in the air, the pressure inside the device no longer increases and stabilizes at a fixed value. The vapor of the organic solvent reaches the saturated vapor pressure at a certain temperature. The calculation formula of the saturated vapor pressure is the following Clausius-Clapeyron equation: Where P is the saturated vapor pressure, T is the temperature in Kelvin, L is the heat of vaporization in J / Kg, △V is the volume change between gas and liquid.

6. The drying method according to claim 4, characterized in that: The saturated vapor pressure of the organic solvent vapor increases with increasing temperature, and the relationship between the saturated vapor pressure and temperature conforms to the following Clausius-Clapeyron equation: Where △vapHm is the molar heat of vaporization of the liquid, which is a constant within the temperature range.

7. The drying method according to claim 3, characterized in that: In the vacuum drying oven, the combined gas of the protective solvent gas and nitrogen N2 gas was input at a flow rate of 20 μL / min.

8. The drying method according to claim 7, characterized in that: The combined gas is composed of 5% protective solvent gas and 95% nitrogen N2 gas in a volume ratio.

9. The drying method according to claim 3, characterized in that: The temperature is adjusted to heat the protective solvent to make it volatilize slowly, and the protective solvent gas is input into the aisle from the vacuum drying furnace to the annealing furnace, inside the annealing furnace, and from the aisle from the annealing furnace to the evaporation equipment.

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