Laminated solar cell and preparation method thereof

Abstract

The invention relates to the technical field of solar cells, and discloses a laminated solar cell and a preparation method thereof. The preparation method comprises: forming a bottom cell; forming an intermediate layer on one side surface of the bottom cell; performing texturing on the surface of one side, deviating from the bottom battery, of the middle layer to form a nanoscale microstructure; and forming a top cell on the nanoscale microstructure on one side, deviating from the bottom cell, of the middle layer, wherein the thickness of the top cell is greater than the height of the nanoscale microstructure. According to the preparation method of the laminated solar cell, the middle layer is arranged between the bottom cell and the top cell, the nanoscale microstructure is formed on the surface of the side, relatively away from the bottom cell, of the middle layer, and the height of the nanoscale microstructure is smaller than the thickness of the top cell, so that the reliable connection performance between the top cell and the bottom cell can be ensured, and the reliability of the laminated solar cell is improved. And the overall light absorption capability of the bottom cell and the laminated solar cell is also improved, so that the photoelectric conversion efficiency of the laminated solar cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly relates to a tandem solar cell and a preparation method thereof. Background Art

[0002] A tandem solar cell includes absorption layers with different bandgaps. The absorption layer with a relatively wide bandgap is placed in the area close to the front surface of the tandem solar cell to preferentially absorb short-wavelength light with high energy; while the absorption layer with a relatively narrow bandgap is located on the back surface to absorb long-wavelength light with low energy. This structure can effectively utilize the photon energy in different wavelength bands, promote the critical wavelength to extend towards the long-wave direction, thereby significantly improving the spectral absorption range and conversion efficiency. Moreover, by dividing the absorption spectrum into two main regions, the thermal loss in the process of generating electron-hole pairs can be effectively reduced. Therefore, the above structure has gradually become the research focus in the field of solar cells.

[0003] Regarding the bottom cell that absorbs long-wavelength light in a tandem solar cell, in recent years, the Tunnel Oxide Passivated Contact (hereinafter referred to as TOPCon) cell with a higher market share has been widely concerned. TOPCon cells usually use single-crystalline silicon materials with a bandgap of about 1.12 eV to absorb the visible light and ultraviolet parts in sunlight. Usually, wet chemical texturing is performed on the surface of TOPCon cells using an alkaline solution to form a Figure 1 textured surface structure 100 in the form of a pyramid with a height between 1.0 μm and 1.5 μm as shown, and an antireflection film is applied on its surface to further enhance the light trapping ability.

[0004] However, since the preparation of a tandem solar cell also requires forming an intermediate layer 2 and a top cell 3 including functional layers such as an electron transport layer, a hole transport layer, and a perovskite absorption layer on the TOPCon cell. According to the actual design requirements, the total thickness of the intermediate layer 2 and the top cell 3 is usually less than the height of the textured surface structure 100 formed by texturing, as Figure 2 shown. Therefore, when forming a perovskite top cell on the surface of the textured TOPCon cell, the textured surface structure 100 will cause a significant reduction in the surface adhesion between the perovskite top cell and the TOPCon cell, thereby affecting the long-term stability of the cell. In response to this situation, in related technologies, the textured surface structure 100 can be turned downward so that the smooth surface of the TOPCon cell is in contact with the perovskite top cell. Although this method can improve the adhesion and stability to some extent, it will also increase the surface reflectivity, instead reducing the light absorption ability of the TOPCon cell, and ultimately limiting the photoelectric conversion efficiency of the tandem solar cell. Summary of the Invention

[0005] In view of this, the present invention provides a tandem solar cell and a preparation method thereof to solve the problem that it is difficult for existing tandem solar cells to balance stability and light conversion efficiency.

[0006] In a first aspect, the present invention provides a preparation method of a tandem solar cell, comprising:

[0007] Forming a bottom cell;

[0008] Forming an intermediate layer on one surface of the bottom cell;

[0009] Texturing one surface of the intermediate layer facing away from the bottom cell to form nanostructured microstructures;

[0010] Forming a top cell on the nanostructured microstructures on one side of the intermediate layer facing away from the bottom cell, wherein the thickness of the top cell is greater than the height of the nanostructured microstructures.

[0011] Beneficial effects: In the preparation method of the tandem solar cell of the present invention, an intermediate layer is provided between the bottom cell and the top cell, and nanostructured microstructures are formed on one surface of the intermediate layer relatively far from the bottom cell, and the height of the nanostructured microstructures is less than the thickness of the top cell, which can not only ensure the reliable connection performance between the top cell and the bottom cell, but also improve the light absorption capacity of the bottom cell and the overall tandem solar cell, thereby improving the photoelectric conversion efficiency of the tandem solar cell.

[0012] In an optional embodiment, atmospheric pressure plasma technology is used to texture one surface of the intermediate layer facing away from the bottom cell.

[0013] Beneficial effects: The present invention uses atmospheric pressure plasma technology to texture the intermediate layer, which can avoid the corrosion and deformation problems that the chemical solution in wet etching may cause to the intermediate layer material, ensure the formation of an intermediate layer with a good surface morphology of nanostructured microstructures, and at the same time ensure the consistency and controllability of the surface morphology and optical properties of the intermediate layer. In addition, using atmospheric pressure plasma technology to form surface texturing can flexibly adjust the depth or size of texturing, which can be achieved from the nanoscale (at least a few nanometers) to the microscale (at most a few micrometers). This free adjustment ability provides better flexibility for designing and optimizing the surface morphology of the intermediate layer to meet different optical and electronic performance requirements. And the external quantum efficiency value of the intermediate layer after surface texturing is significantly higher than that of the untextured intermediate layer, that is, surface texturing of the intermediate layer can effectively enhance the light absorption capacity of the battery, and thus significantly improve the photoelectric conversion performance and power generation efficiency of the tandem solar cell.

[0014] In an optional embodiment, using atmospheric pressure plasma technology to texture one surface of the intermediate layer facing away from the bottom cell includes:

[0015] Turning on the atmospheric pressure plasma equipment;

[0016] A bottom cell with an intermediate layer will be formed and placed in an atmospheric pressure plasma device for texturing in a continuous moving manner.

[0017] Beneficial effects: Before performing texturing treatment on the surface of the intermediate layer using the atmospheric pressure plasma technology, first turn on the atmospheric pressure plasma device to ensure that the continuous conveying structure and the plasma medium injection reach a stable state. The bottom cell with the intermediate layer, through the synergistic effect with the continuous conveying structure at the bottom of the atmospheric pressure plasma device, realizes etching on the surface material of the intermediate layer through plasma under non-contact conditions, forming uniform microstructures with a nanoscale size, avoiding the situation of deformation or damage to the internal structure of the intermediate layer caused by chemical solution erosion of the material. The process steps of texturing the surface of the intermediate layer using the atmospheric pressure plasma technology can be integrated into the equipment through a continuous propulsion In-Line process. Simply put, it is a way in which multiple samples are continuously fed into the equipment one by one while the specific texturing process is carried out synchronously. This process significantly simplifies the equipment composition compared to the vacuum plasma method, does not require a complex vacuum system, thus reducing the equipment cost, and the continuous production capacity of the atmospheric pressure plasma device can also improve the manufacturing efficiency and meet the requirements of large-scale production.

[0018] In an optional implementation manner, the moving speed range of the bottom cell with the intermediate layer is 1 mm / sec to 100 mm / sec.

[0019] Beneficial effects: Avoid the problem that the etching depth on the surface of the intermediate layer is insufficient due to too fast a speed, resulting in some surfaces not being etched, and the uniformity and consistency of the surface morphology of the intermediate layer are poor; and avoid the problem that the surface of the intermediate layer is over-etched due to too slow a speed, and even etched to the surface of the bottom cell, resulting in partial loss of the intermediate layer, making it difficult to ensure the connection reliability of the top cell on the bottom cell.

[0020] In an optional implementation manner, the spacing distance between the plasma injection port of the atmospheric pressure plasma device and the surface of the intermediate layer facing away from the bottom cell is 1 mm to 10 mm.

[0021] Beneficial effects: Avoid the problem that the plasma cannot effectively reach the surface of the intermediate layer to achieve etching and the etching uniformity is difficult to guarantee due to too large a spacing distance; and avoid the problem of over-etching due to too small a spacing, which affects the performance of the intermediate layer and the connection reliability of the top cell and the bottom cell.

[0022] In an optional implementation manner, in the step of texturing the surface of the intermediate layer facing away from the bottom cell, the texturing medium used includes one or more of argon, helium, ammonia, sulfur hexafluoride, oxygen, and hydrogen.

[0023] Beneficial effects: When performing the texturing process, the texturing medium configured is a mixed gas plasma, which helps to control the etching height of the nanostructured microstructure on the surface of the intermediate layer and form a uniform nanostructured microstructure.

[0024] In an alternative embodiment, in the step of texturing the surface of the intermediate layer facing away from the bottom cell, the frequency range of the texturing medium ejected by the atmospheric pressure plasma device is 10 kHz to 400 kHz, and the power range is 0.1 kW to 2 kW.

[0025] Beneficial effects: Controlling the frequency of the ejected texturing medium between 10 kHz and 400 kHz, that is, the atmospheric pressure plasma device is in a low-frequency state during texturing, helps to avoid waste of the texturing medium when continuously pushing the bottom cell with the intermediate layer into the atmospheric pressure plasma device, and can also ensure appropriate etching of the surface of the intermediate layer. Controlling the power of the ejected texturing medium between 0.1 kW and 2 kW can, on the one hand, avoid excessive etching of the surface of the intermediate layer due to too high power, and on the other hand, can also avoid the problem of insufficient etching, and finally form an intermediate layer surface with uniform etching depth and good surface morphology.

[0026] In an alternative embodiment, after texturing the surface of the intermediate layer facing away from the bottom cell and before forming the top cell on the nanostructured microstructure on the side of the intermediate layer facing away from the bottom cell, it further includes: surface treatment of the side surface of the intermediate layer with nanostructured microstructure.

[0027] Beneficial effects: After the texturing step on the surface of the intermediate layer is completed, surface defect treatment is performed on this side surface to reduce possible surface damage during the texturing process and alleviate the defects formed in the intermediate layer.

[0028] In an alternative embodiment, the surface treatment of the side surface of the intermediate layer with nanostructured microstructure includes: surface treatment of the side surface of the intermediate layer with nanostructured microstructure by an atmospheric pressure plasma device; the surface treatment medium includes hydrogen plasma, the flow rate range of the hydrogen plasma is 0.1 liter to 1 liter, the treatment time range is: 5 seconds to 30 seconds, and the power range of the surface treatment is 0.1 kW to 2 kW.

[0029] Beneficial effects: The surface treatment step after texturing is completed using the same equipment as the texturing process to ensure that the continuously moving intermediate layer after texturing can immediately complete the surface defect treatment thereafter. The atmospheric pressure plasma equipment continuously completes texturing and surface treatment, improving process continuity and preparation efficiency. The surface defect treatment is completed using hydrogen plasma without introducing new impurities additionally, ensuring the surface cleanliness of the intermediate layer; controlling the flow rate of hydrogen plasma between 0.1 L and 1 L, the treatment time between 5 s and 30 s, and the power of surface treatment between 0.1 kW and 2 kW to ensure the sufficiency of surface defect treatment without damaging the internal structure of the intermediate layer and ensuring the surface defect treatment effect of the intermediate layer.

[0030] In an alternative embodiment, the thickness range of the intermediate layer is 10 nm to 100 nm; the height range of the nanostructured microstructures is 10 nm to 100 nm.

[0031] Beneficial effects: Ensure that nanostructured microstructures are formed on the surface of the intermediate layer, avoiding damage to the bottom cell. And compared with the top cell with a thickness between 1 μm and 1.5 μm, the thickness of the nanostructured microstructures formed on the intermediate layer is much smaller than the thickness of the top cell, which can ensure the firm fixation of the top cell on the bottom cell.

[0032] In an alternative embodiment, the bottom cell includes a tunnel oxide layer passivated contact cell; the intermediate layer includes an indium tin oxide thin film; the top cell includes a perovskite cell, and the perovskite cell includes a first carrier transport layer, a perovskite absorption layer, and a second carrier transport layer, and the first carrier transport layer is disposed close to the intermediate layer.

[0033] Beneficial effects: The bottom cell includes a tunnel oxide layer passivated contact cell, which has a low cost and excellent optical conversion performance; the intermediate layer includes an indium tin oxide thin film, which has good light transmittance and electrical conductivity; the top cell includes a perovskite cell, and the wide bandgap helps to absorb high-energy short-wavelength light, ensuring the photoelectric conversion efficiency of the tandem solar cell.

[0034] In a second aspect, the present invention further provides a tandem solar cell, including: a bottom cell, an intermediate layer, and a top cell, the intermediate layer is disposed on one surface of the bottom cell, and the side of the intermediate layer facing away from the bottom cell has nanostructured microstructures; the top cell is disposed on the nanostructured microstructures on the side of the intermediate layer facing away from the bottom cell, and the thickness of the top cell is greater than the height of the nanostructured microstructures.

[0035] Beneficial effects: In the tandem solar cell of the present invention, an intermediate layer is provided between the bottom cell and the top cell, and nanostructured microstructures are formed on the surface of the intermediate layer relatively far from the bottom cell, and the height of the nanostructured microstructures is less than the thickness of the top cell. This can not only ensure the reliable connection performance between the top cell and the bottom cell, but also improve the light absorption capacity of the bottom cell and the overall tandem solar cell, thereby effectively improving the photoelectric conversion efficiency of the tandem solar cell. Description of the Drawings

[0036] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the related art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the related art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 is a schematic structural diagram of a bottom cell after wet chemical texturing in the related art;

[0038] Figure 2 is a schematic structural diagram of a tandem solar cell including a bottom cell after wet chemical texturing in the related art;

[0039] Figure 3 is a schematic flow diagram of the preparation method of the tandem solar cell according to the embodiment of the present invention;

[0040] Figure 4 is a schematic structural diagram of a tandem solar cell according to an embodiment of the present invention;

[0041] Figure 5 is another schematic structural diagram of a tandem solar cell according to an embodiment of the present invention;

[0042] Figure 6 is the surface morphology of the intermediate layer textured by atmospheric pressure plasma technology according to the embodiment of the present invention;

[0043] Figure 7 is a comparative schematic diagram of the external quantum efficiency curve of the intermediate layer textured by atmospheric pressure plasma technology and the external quantum efficiency curve of the intermediate layer not textured by atmospheric pressure plasma technology according to the embodiment of the present invention.

[0044] Description of the Reference Numerals:

[0045] 100, Textured surface structure;

[0046] 1, Bottom cell; 2, Intermediate layer; 21, Nanoscale microstructures; 3, Top cell; 31, First carrier transport layer; 32, Perovskite absorption layer; 33, Second carrier transport layer. Detailed implementation manners

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention rather than all structures are shown in the accompanying drawings. In the following description, the description of well-known structures and technologies is omitted to avoid unnecessarily confusing the concepts of the present invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and for the purpose of clear expression, some details are enlarged, and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are only exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs. In the context of the present invention, when a layer / component is referred to as being "on" another layer / component, the layer / component can be directly on the other layer / component, or there can be an intermediate layer / component between them. Additionally, if a layer / component is "on" another layer / component in one orientation, then when the orientation is reversed, the layer / component can be "under" the other layer / component.

[0048] Based on the different connection forms and sub-cell positions of single-junction cells, tandem solar cells can generally be divided into two-terminal tandem cells and four-terminal tandem cells. Specifically, two-terminal tandem cells connect two sub-cells in series through a tunneling junction, and only two electrodes, a front electrode and a back electrode, are required for the whole cell; while the sub-cells in four-terminal tandem cells are electrically independent of each other, and independent electrodes are configured on the front and back of each sub-cell. This structural design gives four-terminal tandem cells greater flexibility in terms of electrical performance optimization and independent regulation, but it also increases the structural complexity and manufacturing cost.

[0049] Regarding the tandem solar cells in related technologies, compared with conventional silicon heterojunction cells, the Tunnel Oxide Passivated Contact (hereinafter referred to as TOPCon) cells exhibit a relatively low open-circuit voltage (VOC) and a relatively high short-circuit current density (JSC). However, due to its advantage of lower production cost, and the disadvantages of its voltage and current performance are not significant, it is considered more suitable as the bottom cell for absorbing long-wavelength light in tandem solar cells. TOPCon cells usually use an alkaline solution for wet texturing on their surfaces to form, such as Figure 1The pyramidal textured structure 100 with a height between 1.0 μm and 1.5 μm as shown has a surface reflectivity of approximately 10% - 15% in the visible and infrared bands, and an antireflection film is applied to its surface to further enhance the light trapping ability. The design purpose of the pyramidal texture is to extend the optical path of light inside the battery, reduce the surface reflectivity, and thus improve the light absorption efficiency of the silicon-based material.

[0050] However, referring to Figure 2 , when fabricating the tandem perovskite / TOPCon solar cell, an intermediate layer 2 and a top cell 3 including functional layers such as an electron transport layer (ETL), a hole transport layer (HTL), and a perovskite absorption layer 32 also need to be formed on the TOPCon cell. According to the actual design requirements, the total thickness of the intermediate layer 2 and the top cell 3 is usually less than the height of the textured structure 100 formed by texturing. Specifically, the thickness of the intermediate layer 2 is about 10 nm - 50 nm, the thickness of the ETL or HTL is about 10 nm - 100 nm, and the thickness of the perovskite absorption layer 32 is 300 nm - 600 nm, and the total layer thickness is only 330 nm - 850 nm. Therefore, when depositing the perovskite top cell 3 on a TOPCon cell with a textured structure 200 height greater than 1 μm, as Figure 2 shown. Therefore, when forming the perovskite top cell 3 on the surface of the textured TOPCon cell, the textured structure 100 will cause a significant reduction in the surface adhesion between the perovskite absorption layer 32 and the TOPCon cell, thus affecting the long-term stability of the cell. In response to this situation, in the related art, the textured structure 100 is turned downward so that the smooth surface of the TOPCon cell contacts the perovskite top cell 3. However, although this method improves the adhesion and stability to some extent, it also increases the surface reflectivity, instead reducing the light absorption ability of the TOPCon cell and ultimately limiting the light conversion efficiency of the tandem solar cell.

[0051] Therefore, as Figures 3 to 7 shown, this embodiment provides a method for fabricating a tandem solar cell, Figure 1 which is a schematic flow diagram of the fabrication method. The fabrication method includes the following steps:

[0052] Step S301, forming the bottom cell 1.

[0053] Exemplarily, the bottom cell 1 of this embodiment is preferably a tunnel oxide passivated contact cell (hereinafter referred to as TOPCon cell) to obtain a bottom cell 1 of a tandem solar cell with low cost and excellent power generation performance. The conventional fabrication process is used to fabricate the TOPCon cell as the bottom cell 1. Since the fabrication process is relatively mature, the specific details are not elaborated here. Of course, other types of cell structures are not excluded as the bottom cell 1 as long as they can meet the application requirements of the tandem solar cell.

[0054] Step S302: Form an intermediate layer 2 on one side surface of the bottom cell 1.

[0055] Exemplarily, the intermediate layer 2 in this embodiment is selected as a transparent conductive film to facilitate the connection between the bottom cell 1 and the top cell 3. Specifically, on one side surface of the prepared TOPCon cell, the intermediate layer 2 can be formed by using one of methods such as magnetron sputtering, evaporation coating, and atomic layer deposition (ALD for short).

[0056] Step S303: Texturize the side surface of the intermediate layer 2 facing away from the bottom cell 1 to form microstructures 21 of nanoscale size.

[0057] Perform a texturing process on the side surface of the intermediate layer 2 that does not contact the bottom cell 1 to form microstructures 21 of nanoscale size on the intermediate layer 2. Compared with the traditional method of directly texturing the surface of the bottom cell 1 using a wet process to form a micron-scale textured surface structure 100, texturing the intermediate layer 2 in this embodiment can obtain a smaller nanoscale surface structure. Texturing the intermediate layer 2 to form microstructures 21 of nanoscale size can not only achieve a good light absorption effect of the bottom cell 1 but also ensure the connection reliability of the top cell 3 on the surface of the bottom cell 1, ultimately ensuring the photoelectric conversion efficiency of the tandem solar cell.

[0058] Step S304: Form a top cell 3 on the microstructures 21 of nanoscale size on the side of the intermediate layer 2 facing away from the bottom cell 1, and the thickness of the top cell 3 is greater than the height of the microstructures 21 of nanoscale size.

[0059] Exemplarily, the top cell 3 in this embodiment is selected as a perovskite thin-film battery including an electron transport layer (ETL for short) or a hole transport layer (HTL for short) and a perovskite absorber layer 32. The thickness of the perovskite thin-film battery is generally between 0.1 μm and 0.15 μm. The height of the microstructures 21 of nanoscale size formed on the intermediate layer 2 in this embodiment is much smaller than this thickness. Therefore, good adhesion performance between the perovskite thin-film battery and the TOPCon cell can be achieved. At the same time, the microstructures 21 of nanoscale size can also ensure the light absorption ability of the bottom cell 1, ultimately resulting in an integrated perovskite / TOPCon tandem solar cell with high photoelectric conversion efficiency.

[0060] In summary, in the method for manufacturing the stacked solar cell of this embodiment, an intermediate layer 2 is provided between the bottom cell 1 and the top cell 3, and nanostructured microstructures 21 are formed on the surface of the intermediate layer 2 on the side relatively far from the bottom cell 1, and the height of the nanostructured microstructures 21 is less than the thickness of the top cell 3, which can not only ensure the reliable connection performance between the top cell 3 and the bottom cell 1, but also improve the light absorption capacity of the bottom cell 1 and the overall stacked solar cell, thereby improving the photoelectric conversion efficiency of the stacked solar cell.

[0061] Of course, the bottom cell 1 of this embodiment can be a TOPCon cell with smooth flat surfaces on both sides, such as Figure 4 shown; it can also be a TOPCon cell with a conventional textured surface 100 on the side facing away from the intermediate layer 2, that is, a TOPCon cell after traditional wet texturing on one surface and then inversion is selected as the bottom cell 1 in this embodiment, and then an intermediate layer 2 is formed on the other surface of the TOPCon cell for re-texturing to form an intermediate layer 2 with nanostructured microstructures 21, such as Figure 5 shown.

[0062] Specifically, in this embodiment, atmospheric pressure plasma technology is used to texture the surface of the intermediate layer 2 on the side facing away from the bottom cell 1.

[0063] In this embodiment, atmospheric pressure plasma technology is used to texture the surface of the intermediate layer 2 to form the surface morphology of the intermediate layer 2 as shown in the scanning electron microscope image in Figure 6 shown. The image clearly shows the nanostructured pyramid-shaped surface microstructures. By this method, the technical shortcoming that the traditional wet texturing process of crystalline silicon solar cells cannot be applied to the intermediate layer 2 can be made up. First, for example, the thickness limitation problem. The thickness of the intermediate layer 2 in the stacked solar cell is usually 10 nm to 100 nm, specifically depending on the material type and design requirements; while the depth of the textured surface 100 formed by the traditional wet texturing process is about 1 μm, far exceeding the thickness range of the intermediate layer 2. Therefore, if the wet process is applied to the intermediate layer 2, over-etching will occur, and precise nanostructuring cannot be achieved, which is not suitable for the requirements of thin-layer composite materials. Secondly, there is the problem of the influence of chemical solutions. The wet process requires the use of alkaline or acidic solutions for etching. However, when the intermediate layer 2 is immersed in the chemical solution, its basic structure is extremely prone to deformation, and this deformation will damage the electron transport and optical properties of the intermediate layer 2, significantly reducing the light absorption capacity and easily leading to a decrease in the photoelectric conversion efficiency of the stacked solar cell.

[0064] In summary, in this embodiment, atmospheric pressure plasma technology is used to texture the intermediate layer 2, which can avoid the corrosion and deformation problems that chemical solutions may cause to the material of the intermediate layer 2 in wet etching, and ensure the formation as in Figure 6The intermediate layer 2 with a microstructure 21 surface topography of good nanoscale size is shown, while also ensuring the consistency and controllability of the surface topography and optical properties of the intermediate layer 2. In addition, using atmospheric pressure plasma technology to form surface texturing allows for flexible adjustment of the texturing depth or size, which can be achieved from the nanoscale (at least a few nanometers) to the microscale (up to a few micrometers). This free adjustment ability provides better flexibility for designing and optimizing the surface topography of the intermediate layer 2 to meet different optical and electronic performance requirements. Figure 7 Figure shows a comparative schematic diagram of the external quantum efficiency (EQE) curve (curve a) of the intermediate layer 2 with surface texturing using atmospheric pressure plasma technology and the external quantum efficiency curve (curve b) of the intermediate layer 2 without surface texturing, which is very Figure 7 It can be obtained that the external quantum efficiency value of the intermediate layer 2 after surface texturing is significantly higher than that of the intermediate layer 2 without texturing, that is, surface texturing of the intermediate layer 2 can effectively enhance the light absorption ability of the battery, thereby significantly improving the photoelectric conversion performance and power generation efficiency of the tandem solar cell.

[0065] Further, the step S303 of texturing the surface of the intermediate layer 2 facing away from the bottom cell 1 using the atmospheric pressure plasma technology includes:

[0066] Step S3031, turn on the atmospheric pressure plasma device.

[0067] Exemplarily, the atmospheric pressure plasma device of this embodiment has at least one chamber. A plasma jet port is provided at the top of the chamber, and a continuous conveying structure such as a conveyor belt is provided at the bottom of the chamber for driving the bottom cell 1 with the intermediate layer 2 to move continuously in the chamber. Before performing the texturing treatment on the surface of the intermediate layer 2 using the atmospheric pressure plasma technology, first turn on the atmospheric pressure plasma device to ensure that the continuous conveying structure and the plasma medium jet reach a stable state.

[0068] Step S3032, place the bottom cell 1 with the intermediate layer 2 in the atmospheric pressure plasma device in a continuous moving manner for texturing.

[0069] The bottom cell 1 with the intermediate layer 2 is etched through the interaction of plasma with the surface material of the intermediate layer 2 under non-contact conditions by cooperating with the continuous conveying structure at the bottom of the atmospheric pressure plasma device, forming uniform nanostructured microstructures 21 with a nanoscale size, avoiding the deformation or damage of the internal structure of the intermediate layer 2 caused by chemical solution erosion of the material. The process steps of texturing the surface of the intermediate layer 2 by the atmospheric pressure plasma technology can be integrated into the equipment through the continuous propulsion In-Line process. Simply put, it is a method in which multiple samples are continuously fed into the equipment one by one while the specific texturing process is carried out synchronously. This process significantly simplifies the equipment composition compared to the vacuum plasma method, does not require a complex vacuum system, thereby reducing the equipment cost, and the continuous production capacity of the atmospheric pressure plasma device can also improve the manufacturing efficiency and meet the requirements of large-scale production.

[0070] Reference Figure 4 , in this embodiment, the moving speed range of the bottom cell 1 with the intermediate layer 2 relative to the atmospheric pressure plasma device is 1 mm / sec to 100 mm / sec. If the speed is too fast, it may lead to insufficient etching depth on the surface of the intermediate layer 2, and there may be a situation where some surfaces are not etched, resulting in poor uniformity and consistency of the surface morphology of the intermediate layer 2; if the speed is too slow, it may lead to excessive etching on the surface of the intermediate layer 2, and even etching to the surface of the bottom cell 1, resulting in partial loss of the intermediate layer 2, making it difficult to ensure the connection reliability of the top cell 3 on the bottom cell 1.

[0071] Furthermore, in this embodiment, the spacing distance between the plasma jet orifice of the atmospheric pressure plasma device and the surface of the intermediate layer 2 facing away from the bottom cell 1 is set to be 1 mm to 10 mm. If the spacing distance is too large, it may lead to the plasma being unable to effectively reach the surface of the intermediate layer 2 to achieve etching, and it is also difficult to ensure the etching uniformity; if the spacing is too small, there will be a problem of over-etching, affecting the performance of the intermediate layer 2 and the connection reliability of the top cell 3 and the bottom cell 1.

[0072] In one embodiment, when texturing is carried out by the atmospheric pressure plasma device, the temperature of the bottom cell 1 and the atmospheric pressure plasma device is controlled between 50 and 150 °C to ensure the material properties of the bottom cell 1 and the intermediate layer 2.

[0073] In this embodiment, in the step S303 of texturing the surface of the intermediate layer 2 facing away from the bottom cell 1, the texturing medium used includes one or more of argon, helium, ammonia, sulfur hexafluoride, oxygen, and hydrogen.

[0074] That is, the texturing medium configured during the texturing process is a mixed gas plasma, which helps to control the etching height of the nanostructured microstructures 21 with a nanoscale size on the surface of the intermediate layer 2, forming uniform and consistent nanostructured microstructures 21.

[0075] In step S303 of texturing the surface of the middle layer 2 facing away from the bottom cell 1 based on the above solution, the frequency range of the texturing medium ejected by the atmospheric pressure plasma device is 10 kHz to 400 kHz, and the power range is 0.1 kW to 2 kW.

[0076] Controlling the frequency of ejecting the texturing medium between 10 kHz and 400 kHz, that is, the atmospheric pressure plasma device is in a low-frequency state during texturing, helps to avoid waste of the texturing medium when the bottom cell 1 with the middle layer 2 formed is continuously pushed into the atmospheric pressure plasma device, and can also ensure appropriate etching of the surface of the middle layer 2. Controlling the power of ejecting the texturing medium between 0.1 kW and 2 kW can, on the one hand, avoid excessive etching of the surface of the middle layer 2 due to too high power, and on the other hand, can also avoid the problem of insufficient etching, and finally on the surface of the middle layer 2 with uniform etching depth and good surface morphology.

[0077] In one embodiment, in the above method for preparing a stacked solar cell, after step S303 of texturing the surface of the middle layer 2 facing away from the bottom cell 1 and before step S304 of forming the top cell 3 on the nanostructured microstructure 21 on the side of the middle layer 2 facing away from the bottom cell 1, it further includes: surface treatment of the side surface of the middle layer 2 having the nanostructured microstructure 21.

[0078] After the texturing step is completed on the surface of the middle layer 2, surface defect treatment is performed on this side surface to reduce possible surface damage during the texturing process and relieve the defects formed in the middle layer 2.

[0079] Specifically, the above surface treatment of the side surface of the middle layer 2 having the nanostructured microstructure 21 includes: surface treatment of the side surface of the middle layer 2 having the nanostructured microstructure 21 by an atmospheric pressure plasma device. The surface treatment medium during surface treatment includes hydrogen plasma, the flow rate range of hydrogen plasma is 0.1 liter to 1 liter, the treatment time range is: 5 seconds to 30 seconds, and the power range of surface treatment is 0.1 kW to 2 kW.

[0080] That is, the surface treatment step after texturing is completed using the same equipment as the texturing process. Exemplarily, the top of the chamber of the atmospheric pressure plasma device includes a plurality of plasma ejection ports, including a texturing plasma ejection port and a surface treatment plasma ejection port. The surface treatment plasma ejection port and the texturing plasma ejection port have a certain distance interval to ensure that the continuously moving middle layer 2 can complete surface defect treatment immediately after texturing is completed. The atmospheric pressure plasma device continuously completes texturing and surface treatment, improving process continuity and preparation efficiency.

[0081] The surface defect treatment is completed by using hydrogen plasma without introducing new impurities additionally, ensuring the surface cleanliness of the intermediate layer 2; controlling the flow rate of hydrogen plasma between 0.1 L and 1 L, the treatment time between 5 s and 30 s, and the surface treatment power between 0.1 kW and 2 kW, ensuring the sufficiency of surface defect treatment without damaging the internal structure of the intermediate layer 2 and ensuring the surface defect treatment effect of the intermediate layer 2.

[0082] In one embodiment, the thickness range of the above-mentioned intermediate layer 2 is 10 nm to 100 nm, and the height range of the nanostructured microstructures 21 is 10 nm to 100 nm, so that the nanostructured microstructures 21 are formed on the surface of the intermediate layer 2 to avoid damaging the bottom cell 1. And compared with the top cell 3 with a thickness between 1 μm and 1.5 μm, the thickness of the nanostructured microstructures 21 formed on the intermediate layer 2 is much smaller than the thickness of the top cell 3, which can ensure the firm fixation of the top cell 3 on the bottom cell 1.

[0083] In the tandem solar cell of this embodiment, the bottom cell 1 includes a tunnel oxide layer passivated contact cell, which has a low cost and excellent optical conversion performance; the intermediate layer 2 includes an indium tin oxide thin film, which has good light transmission performance and electrical conductivity; the top cell 3 includes a perovskite cell, and the perovskite cell includes a first carrier transport layer 31, a perovskite absorption layer 32, and a second carrier transport layer 33, and the first carrier transport layer 31 is disposed close to the intermediate layer 2. Among the first carrier transport layer 31 and the second carrier transport layer 33, one of them is an electron transport layer and the other is a hole transport layer.

[0084] Reference Figure 4 and Figure 5 Referring to

[0085] In the tandem solar cell of this embodiment, an intermediate layer 2 is disposed between the bottom cell 1 and the top cell 3, nanostructured microstructures 21 are formed on the surface of the intermediate layer 2 relatively far from the bottom cell 1, and the height of the nanostructured microstructures 21 is less than the thickness of the top cell 3, which can not only ensure the reliable connection performance between the top cell 3 and the bottom cell 1, but also improve the light absorption capacity of the bottom cell 1 and the overall tandem solar cell, thereby improving the photoelectric conversion efficiency of the tandem solar cell.

[0086] The further functional descriptions of the above-mentioned layer structures are the same as those in the corresponding embodiments described above, and will not be elaborated here.

[0087] In the above description, technical details such as the layout and etching of each layer are not described in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. with the desired shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not exactly the same as the methods described above. In addition, although the embodiments are described separately above, this does not mean that the measures in each embodiment cannot be used in combination advantageously.

[0088] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A method for preparing a stacked solar cell, characterized in that: include: forming a bottom battery; forming an intermediate layer on a surface of one side of the bottom battery; Texturing a surface of the intermediate layer on one side facing away from the bottom battery to form a nano-scale microstructure; A top cell is formed on the nanoscale microstructure on a side of the intermediate layer facing away from the bottom cell, and a thickness of the top cell is greater than a height of the nanoscale microstructure.

2. The method for preparing a stacked solar cell according to claim 1, characterized in that: The atmospheric pressure plasma technology is used to texturize the surface of the middle layer on one side away from the bottom battery.

3. The method for preparing a stacked solar cell according to claim 2, characterized in that: The step of using atmospheric pressure plasma technology to texturize the surface of the middle layer facing away from the bottom battery comprises: Turn on the atmospheric pressure plasma equipment; The bottom battery formed with the middle layer is placed in the atmospheric pressure plasma equipment in a continuously moving manner for texturing.

4. The method for preparing a stacked solar cell according to claim 3, characterized in that: The bottom cell formed with the intermediate layer has a moving speed ranging from 1 mm / sec to 100 mm / sec.

5. The method for preparing a stacked solar cell according to claim 4, characterized in that: The distance between the plasma jet port of the atmospheric pressure plasma equipment and the surface of the middle layer facing away from the bottom battery is 1 mm to 10 mm.

6. The method for preparing a stacked solar cell according to claim 5, characterized in that: In the step of texturing the surface of the intermediate layer facing away from the bottom cell, the texturing medium used includes one or more of argon, helium, ammonia, sulfur hexafluoride, oxygen and hydrogen.

7. The method for preparing a stacked solar cell according to claim 6, characterized in that: In the step of texturing the surface of the side of the intermediate layer facing away from the bottom battery, the atmospheric pressure plasma equipment sprays the texturing medium at a frequency ranging from 10 kHz to 400 kHz and a power ranging from 0.1 kW to 2 kW.

8. The method for preparing a tandem solar cell according to any one of claims 1 to 7, characterized in that: After texturing the surface of the side of the intermediate layer away from the bottom battery and before forming a top battery on the nano-scale microstructure on the side of the intermediate layer away from the bottom battery, the method further includes: The surface of one side of the intermediate layer having the nanoscale microstructure is surface treated.

9. The method for preparing a stacked solar cell according to claim 8, characterized in that: The surface treatment of one side of the intermediate layer having a nano-scale microstructure comprises: The surface of one side of the intermediate layer having a nanoscale microstructure is surface treated by an atmospheric pressure plasma device; the surface treatment medium includes hydrogen plasma, the flow rate of the hydrogen plasma ranges from 0.1 liter to 1 liter, the treatment time ranges from 5 seconds to 30 seconds, and the power range of the surface treatment is 0.1kW to 2kW.

10. The method for preparing a stacked solar cell according to claim 9, characterized in that: The thickness of the intermediate layer ranges from 10 nm to 100 nm; the height of the nano-scale microstructure ranges from 10 nm to 100 nm.

11. The method for preparing a stacked solar cell according to claim 1, characterized in that: The bottom cell comprises a tunneling oxide layer passivation contact cell; the middle layer comprises a tin-doped indium oxide film; the top cell comprises a perovskite cell, the perovskite cell comprises a first carrier transport layer, a perovskite absorption layer and a second carrier transport layer, and the first carrier transport layer is arranged close to the middle layer.

12. A stacked solar cell, characterized in that: include: Bottom battery; An intermediate layer is disposed on a side surface of the bottom battery; The side of the intermediate layer facing away from the bottom cell has a nanoscale microstructure; The top battery is arranged on the nanoscale microstructure on the side of the middle layer away from the bottom battery; the thickness of the top battery is greater than the height of the nanoscale microstructure.

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