An air knife with a long-short lip structure and a method for preparing a perovskite thin film using the air knife

Abstract

The present invention discloses a gas knife with a long and short lip structure and a method for preparing a perovskite thin film by using the gas knife, belonging to the field of thin film preparation for solar cells. By setting a reasonable difference between the long and short lips of the gas knife and arranging a cutting structure with a certain angle at the top of the long lip, the air flow flows out from the air outlet of the gas knife and generates a flow towards the short lip at the top of the long lip of the gas knife, forming a diffused air flow with a certain angle. After the diffused air flow acts on the liquid film on the substrate, a wider range of strong wind field regions will be formed. After the liquid film is quickly dried, a thin film with high crystallization quality can be obtained. When preparing the thin film, the present invention further reduces the action range of the weak wind field during the drying process of the thin film by adjusting the distance between the gas knife and the liquid film on the substrate and increasing the deflection angle of the diffused air flow relative to the liquid film on the substrate, thereby obtaining a uniform and dense perovskite thin film.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of solar cell thin films, and particularly relates to a long and short lip structure air knife and a method for preparing perovskite thin films by using the air knife. Background Art

[0002] In the photovoltaic field, perovskite solar cells using organic-metal halides with a perovskite structure as light absorption materials have attracted wide attention in the photovoltaic community. In recent years, the conversion efficiency of perovskite solar cells has been significantly improved. Currently, under laboratory conditions, the efficiency of small-area (0.1 cm 2 ) perovskite solar cells has reached 26.1%, while the efficiency of large-area (>1 cm 2 ) perovskite solar cells has exceeded 22%. The perovskite thin film is the basic material for photoelectric conversion in perovskite solar cells and is also the key and core part of the battery. To achieve a stable and efficient perovskite solar cell, the key lies in obtaining a uniform, dense and high-quality perovskite thin film. Currently, solution methods are mainly used to prepare large-area perovskite thin films. Although the solution method is relatively simple to operate, it often fails to effectively control the uniformity and crystallinity of the thin film. Traditional techniques prepare thin films by allowing the perovskite precursor solution to dry naturally, but this method is difficult to achieve good control over the crystallization characteristics of the thin film, so a uniform and dense perovskite thin film cannot be obtained. To improve this problem, various improvements and optimizations are being carried out to obtain higher-quality perovskite thin films. Assisted drying of the liquid film by an air knife can control the rapid crystallization of the liquid film to a certain extent. When an ordinary air knife blows on the liquid film on the substrate, it will generate two parts: a weak wind field and a strong wind field. The strong wind field part is the wind field that enables the liquid film to crystallize efficiently and with high quality. If the intensity of this part is too small, it cannot meet the conditions for efficient and high-quality crystallization of the liquid film. If the intensity is too large, it will cause physical damage to the liquid film. There is a weak wind field before the strong wind field acts on the liquid film, which will cause low-quality crystallization of the liquid film. If the range of this weak wind field part is too large, it will affect the overall uniformity and density of the entire thin film, and further affect the overall uniformity and photoelectric performance of the solar cell. Summary of the Invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a high-performance long and short lip air knife structure and its control method applicable to the field of perovskite thin film scraping. By correcting the difference between the long and short lips of the long and short lip air knife structure, cutting the top of the long lip, and controlling the distance between the air knife and the substrate and the deflection angle of the air knife, on the premise that the overall intensity of the strong wind field that ensures efficient and high-quality crystallization of the thin film is 1.5 m / s to 5.5 m / s, the action range of the weak wind field is fully reduced, and the quality of the perovskite thin film is improved.

[0004] According to one aspect of the present invention, the present invention first provides an air knife with a long and short lip structure. The air knife includes an air knife body. On the upper and lower sides of one end of the air knife body, a long knife lip and a short knife lip are respectively arranged. The air knife body, the long knife lip and the short knife lip enclose an air knife cavity. An air outlet is formed between the long knife lip and the short knife lip. The top of the long knife lip has a cutting structure, and the lip difference between the long knife lip and the short knife lip is 2 - 6 mm.

[0005] Further, the lip difference between the long knife lip and the short knife lip is 4 mm.

[0006] According to an embodiment of the present invention, the cutting angle of the cutting structure at the top of the long knife lip is 45 - 75 degrees.

[0007] According to an embodiment of the present invention, in addition to the cutting structure, the top of the long knife lip also has a cutting remaining structure, and the cutting remaining length of the cutting remaining structure is 0.25 - 1.25 mm.

[0008] According to another aspect of the present invention, the present invention also provides a method for preparing a perovskite thin film using the above air knife, including the following steps:

[0009] S1: Coating a perovskite solution on the surface of a substrate to form a perovskite liquid film, and placing the perovskite liquid film under the air knife in a non-contact manner;

[0010] S2: Passing an air flow into the air blowing channel in the air knife, so that the air flow first moves along the walls of the long and short lips of the air knife after coming out of the air outlet, generating a diffused air flow in the direction of the short lip at the top of the long lip. The diffused air flow dries the perovskite liquid film as the air knife moves, and a perovskite thin film is obtained after drying.

[0011] According to an embodiment of the present invention, in step S1, the perovskite precursor solution is coated on the surface of the substrate by one of spin coating, brushing or slot-die coating.

[0012] According to an embodiment of the present invention, in step S2, when the diffused air flow dries the perovskite liquid film as the air knife moves, the air knife is offset axially relative to the substrate, and the deflection angle of the air knife relative to the substrate is gradually increased, so that the action point of the air knife on the substrate is offset. The deflection angle is 5 - 30°, which can further reduce the action range of the weak wind field on the premise of ensuring the strong wind field intensity range.

[0013] According to an embodiment of the present invention, the deflection angle is 5 - 25°.

[0014] According to an embodiment of the present invention, in step S1, the distance between the air knife and the substrate is maintained at 0.1 mm - 0.3 mm.

[0015] According to an embodiment of the present invention, the deflection shaft of the air knife is driven to drive the air knife to deflect, so as to increase the deflection angle of the air knife relative to the substrate.

[0016] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following technical advantages are mainly possessed:

[0017] (1) Firstly, through the improvement of the overall structure of the air knife, the present invention can reduce the weak air flow field range generated during the blowing process from 11 mm to 2.52 mm on the premise of ensuring that the intensity and action range of the characteristic strong air flow field meet the requirements of efficient and high-speed drying of the thin film.

[0018] (2) The present invention can further reduce the action range of the weak air flow field to 1 mm by implementing deflection control on the high-performance long and short lip air knife of the structure and adjusting the air supply distance between it and the substrate during the thin film drying process, thereby greatly improving the crystallization quality and compactness of the thin film. Description of the Drawings

[0019] Figure 1 Schematic diagram of the internal structure and top structure of the air knife.

[0020] Figure 2 Schematic diagram of the top structure of the air knife in the simulation software.

[0021] Figure 3 Schematic diagram of the strong and weak air flow fields formed at the top of the air knife.

[0022] Figure 4 Simulation diagram of the action range of the strong and weak air flow fields in the substrate varying with the difference between the long and short lips in Examples 1-2

[0023] Figure 5 Variation of the strong and weak air flow fields with the reserved length of the long lip top of the air knife in Examples 1 and 3

[0024] Figure 6 Variation of the strong and weak air flow fields with the distance between the top of the air knife and the substrate in Example 4

[0025] Figure 7 Variation of the strong and weak air flow fields with the deflection angle of the air knife in Example 5

[0026] Figure 8 Data diagram of the action range of the strong and weak air flow fields in the substrate varying with the difference between the long and short lips in Examples 1-2

[0027] Figure 9 Variation of the action range of the weak air flow field in the substrate with the reserved length of the long lip top of the air knife in Example 2

[0028] Figure 10 Variation of the action range of the strong and weak air flow fields in the substrate with the distance between the top of the air knife and the substrate in Example 4

[0029] Figure 11 For Example 5, the variation of the action range of the strong and weak wind fields on the substrate with the deflection angle of the air knife

[0030] Figure 12 SEM image of the thin film prepared in Example 1.

[0031] Figure 13 SEM image of the thin film prepared in Example 3a.

[0032] Figure 14 SEM image of the thin film prepared in Example 5c.

[0033] The reference numerals are as follows: 1. Difference in length between the long and short lips of the air knife, 2. Horizontal substrate, 3. Cutting angle of the top of the long lip of the air knife, 4. Retained length area after cutting the top of the long lip, 5. Deflection angle of the air knife, 6. Air outlet of the air knife, 7. Distance between the top of the long lip of the air knife and the substrate, 8. Weak wind field action area, 9. Strong wind field action area. Detailed implementation manners

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be 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 used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The top structure of the air knife is as shown in Figure 1 and Figure 2 shown, where 1 is the difference in length between the long and short lips of the air knife, 2 is the horizontal substrate, 3 is the cutting angle of the top of the long lip of the air knife, 4 is the retained area after cutting the top of the long lip, 5 is the deflection angle of the air knife, 6 is the air outlet of the air knife, and 7 is the distance between the top of the long lip of the air knife and the substrate.

[0036] The basic distribution of the airflow field formed by the air knife with this structure at the substrate is as shown in Figure 3 shown, where the gray part 8 is the weak wind field action area and the black part 9 is the strong wind field action area.

[0037] In the improvement of the high-performance air knife structure with long and short lips, by setting a certain length of difference in length between the long and short lips at both ends of the air outlet of the air knife, the airflow first moves along the difference in length between the long and short lips and adheres to the wall after coming out of the air outlet, and a diffused airflow at a certain angle in the direction of the short lip is generated at the top of the long lip, thereby increasing the action range of the strong wind field. The following are specific examples:

[0038] Example 1

[0039] This embodiment first provides an air knife with a long and short lip structure. The air knife includes an air knife body. At the upper and lower sides of one end of the air knife body, a long knife lip and a short knife lip are respectively arranged. The air knife body, the long knife lip and the short knife lip enclose an air knife cavity. An air outlet is formed between the long knife lip and the short knife lip. The lip difference between the long knife lip and the short knife lip is 2 mm. The top of the long knife lip has a cutting structure and a cutting remainder structure. The cutting angle of the cutting structure is 45°, and the cutting remainder structure has a cutting remainder length of 0.25 mm.

[0040] When preparing the thin film, first apply the perovskite solution on the surface of the horizontal substrate to form a perovskite liquid film, ensuring that the thickness of the perovskite liquid film is ≤ 5000 nm. Then, use a horizontal bracket to fix this structured air knife above the horizontal substrate, and introduce high-pressure nitrogen into the internal chamber of the air knife. After the nitrogen gas flow comes out of the air outlet of the air knife, it first moves along the walls of the long and short lips of the air knife, generating a diffusion air flow in the direction of the short lip at the top of the long lip. This diffusion air flow collides with the liquid film on the substrate and dries the entire perovskite liquid film as the air knife continuously moves. After drying, a perovskite thin film is obtained. The morphology of the perovskite thin film prepared in this Example 1 is as Figure 12 shown. The surface of the perovskite thin film is flat and smooth, and the grain sizes are basically uniform and dense and compact.

[0041] Example 2

[0042] Example 2a: Different from Example 1, the lip difference between the long knife lip and the short knife lip is 4 mm.

[0043] Example 2b: Different from Example 1, the lip difference between the long knife lip and the short knife lip is 6 mm.

[0044] Figure 4 It is a simulation diagram of the change of the strong and weak wind field ranges with the lip difference in Examples 1 - 2.

[0045] When the lip difference is 4 mm, on the premise of ensuring that the action range of the strong wind field is 5.8 mm, the weak wind field range can be attenuated from 11.5 mm to 10.2 mm, as Figure 8 shown. When the lip difference is less than 2 mm or greater than 6 mm, the range of the strong wind field is too small, which is not conducive to the uniformity of the thin film and the crystallization process.

[0046] Example 3

[0047] Example 3a: Different from Example 1, the cutting angle at the top of the long knife lip is 60°, and the cutting remainder length is 0.75 mm.

[0048] Example 3b: Different from Example 1, the cutting angle at the top of the long knife lip is 75°, and the cutting remainder length is 1.25 mm.

[0049] As Figure 5As shown, after continuously increasing the remaining length of the long lip top cutting, the action range of the strong wind field remains basically unchanged; when the remaining length reaches 0.75 mm, on the premise of ensuring that the action range of the strong wind field is 5.66 mm, the action range of the weak wind field can be attenuated from 5.8 mm to 2.52 mm, as Figure 9 shown.

[0050] The morphology of the perovskite thin film prepared in Example 3a is as Figure 13 shown. The surface of the perovskite thin film is flat and smooth, the grain size is basically uniform and dense and compact, and the overall flatness is good.

[0051] Example 4

[0052] Example 4a: Different from Example 3a, the distance between the air knife and the substrate is reduced to 0.1 mm to control the blocking effect of the lip difference area on the wind field and reduce the action range of the weak wind field.

[0053] Example 4b: Different from Example 3a, the distance between the air knife and the substrate is increased to 0.3 mm.

[0054] As Figure 6 , Figure 10 shown, when the distance between the air knife and the substrate is further increased on the basis of 0.3 mm, the action range of the strong wind field gradually becomes smaller, and the action range of the weak wind field will continue to increase. Therefore, when the distance between the air knife and the substrate is less than 0.1 mm and greater than 0.3 mm, the action ranges of the strong and weak wind fields are not ideal, and 0.2 mm is the best distance.

[0055] Example 5

[0056] Example 5 is different from Example 3a in that during the drying process of the thin film, by gradually increasing the deflection angle of the air knife, the action point of the air knife on the substrate thin film is offset, and on the premise of slightly weakening the intensity range of the strong wind field, the action range of the weak wind field is continuously weakened.

[0057] Among them, the deflection angles of Examples 5a - 5c are 5°, 15°, and 25° respectively, as Figure 7 shown.

[0058] When the deflection angle further reaches 30°, the reduction of the action range of the weak wind field is still remarkable, as Figure 11 shown, but when it is greater than 30°, the action ranges of both the strong and weak wind fields decrease too fast, which is not conducive to the formation of the thin film. The morphology of the perovskite thin film prepared in Example 5c is as Figure 14 shown. The surface of the perovskite thin film is flat and smooth, the grain size is basically uniform and dense and compact, and the overall flatness is good.

[0059] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An air knife with a long and short lip structure, characterized in that, The air knife includes an air knife body. On the upper and lower sides of one end of the air knife body, a long knife lip and a short knife lip are respectively arranged. The air knife body, the long knife lip and the short knife lip enclose an air knife cavity. An air outlet is formed between the long knife lip and the short knife lip. The top of the long knife lip has a cutting structure. The lip difference between the long knife lip and the short knife lip is 2 - 6 mm; the cutting angle of the cutting structure at the top of the long knife lip is 45 - 75 degrees; in addition to the cutting structure, the top of the long knife lip also has a cutting remaining structure, and the cutting remaining structure has a cutting remaining length of 0.25 - 1.25 mm.

2. The lip structure air knife according to claim 1, characterized in that, The lip difference between the long knife lip and the short knife lip is 4 mm.

3. A method for preparing a perovskite thin film by using the air knife with the long and short lip structure according to claim 1 or 2, comprising the following steps: S1: Coating a perovskite solution on the surface of a substrate to form a perovskite liquid film, and placing the perovskite liquid film under the air knife without contact; S2: Introducing an air flow into the air blowing channel in the air knife, so that the air flow first moves along the walls of the long and short lips of the air knife after coming out of the air outlet, and a diffused air flow is generated in the direction of the short lip at the top of the long lip. The diffused air flow dries the perovskite liquid film as the air knife moves, and a perovskite thin film is obtained after drying.

4. The method according to claim 3, wherein In step S1, the perovskite precursor solution is coated on the surface of the substrate by one of the methods of doctor blade coating, brush coating or spin coating.

5. The method according to claim 3, characterized in that, In step S2, when the diffused air flow dries the perovskite liquid film as the air knife moves, the air knife is offset axially relative to the substrate, and the deflection angle of the air knife relative to the substrate is gradually increased, so that the action point of the air knife on the substrate is offset, and the deflection angle is 5 - 30°.

6. The method according to claim 5, wherein The deflection angle is 5 - 25°.

7. The method according to claim 3, characterized in that In step S1, the distance between the air knife and the substrate is maintained at 0.1 mm - 0.3 mm.

8. The method according to any one of claims 3-7, characterized in that, The air knife is driven to deflect by driving the deflection shaft of the air knife to increase the deflection angle of the air knife relative to the substrate.

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