Solar cell and preparation method thereof

Abstract

The invention provides a solar cell and a preparation method thereof, and belongs to the technical field of photovoltaic cells, the solar cell comprises a cell piece, a passivation film layer is arranged on the front side and / or the back side of the cell piece, and the thickness of the passivation film layer has a thickness difference in the middle area and the edge area of the cell piece. Passivation film layers with gradually changing thicknesses are adopted on the front face and / or the back face of the cell. When the film thickness of the middle area of the cell is smaller than that of the edge area, the utilization rate of incident light of the middle area of the cell can be increased while the passivation effect of the edge area of the cell is enhanced. When the light source mainly irradiates the edge area of the battery, the illumination quantity of the middle area is small, and the change trend that the thickness of the passivation film layer of the middle area is larger than that of the edge area is adopted, so that the high incident light utilization rate of the edge and the optimal passivation effect of the middle area are guaranteed, and the photoelectric conversion efficiency of the whole battery is improved.

Description

Technical Field

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

[0002] The incident light utilization rate and surface recombination are two important factors affecting the photoelectric conversion efficiency of solar cells. When the thickness of the passivation film layer increases, the chemical passivation and field passivation effects usually increase accordingly, which can better reduce the surface recombination rate of carriers and improve the cell efficiency. However, at the same time, the passivation film layer will absorb a certain amount of incident light, thereby reducing the proportion of incident light entering the cell substrate, resulting in optical losses. The thicker the passivation film layer, the higher the proportion of incident light absorbed and the greater the optical losses.

[0003] Currently, the thickness of the entire surface passivation film layer on the solar cell is uniform from the middle region to the edge region. However, due to uneven surface recombination efficiency and uneven light intensity during the production, testing, or use of the solar cell, this design of the passivation film layer with uniform thickness will affect the photoelectric conversion efficiency of the cell.

[0004] Therefore, the current design method of the passivation film layer with uniform thickness does not fully stimulate the photoelectric conversion efficiency of the photovoltaic cell, and the photoelectric conversion efficiency of the cell still needs to be improved. Summary of the Invention

[0005] An embodiment of the present invention provides a solar cell and a preparation method thereof, aiming to improve the photoelectric conversion efficiency of the photovoltaic cell.

[0006] In a first aspect, to achieve the above object, the technical solution adopted by the present invention is: providing a solar cell, including: a cell sheet, a passivation film layer is provided on the front and / or back of the cell sheet, and there is a thickness difference between the middle region and the edge region of the cell sheet in the thickness of the passivation film layer.

[0007] In combination with the first aspect, in some feasible embodiments, the thickness of the passivation film layer gradually increases from the middle region to the edge region; or the thickness of the passivation film layer gradually decreases from the middle region to the edge region of the cell sheet.

[0008] In combination with the first aspect, in some feasible embodiments, the outermost side of the edge region has a section with a uniform edge thickness.

[0009] In combination with the first aspect, in some feasible embodiments, the passivation film layer is a field passivation film layer and / or a non-field passivation film layer.

[0010] In combination with the first aspect, in some feasible embodiments, when the passivation film layer includes a field passivation film layer and a field-free passivation film layer, the thickness of the field passivation film layer gradually increases from the middle region to the edge region, and the thickness of the field-free passivation film layer gradually decreases from the middle region to the edge region to form a flat surface; or the thickness of the field passivation film layer gradually decreases from the middle region to the edge region, and the thickness of the field-free passivation film layer gradually increases from the middle region to the edge region to form a flat surface.

[0011] In a second aspect, the present invention also provides a preparation method for preparing the solar cell, and the method includes: Placing the bracket on the tray, placing the battery cell on the bracket, and forming a gap between the battery cell and the tray; Using chemical vapor deposition, the gas flow enters the gap from around the bracket, and a passivation film layer is deposited on the lower surface of the battery cell; The thickness of the formed passivation film layer gradually increases from the middle region to the edge region.

[0012] In combination with the second aspect, in some feasible embodiments, the bracket includes at least four columns, the four columns support at the four corners of the battery cell, and connecting rods are arranged between the four columns to connect the four columns together.

[0013] In a third aspect, the present invention also provides a preparation method for preparing the solar cell, and the method includes: Manufacturing a housing with a central air inlet hole at the top; Placing the battery cell on the tray, covering the housing on the battery cell, so that a sealed cavity with only the central air inlet hole is formed between the housing and the tray; Using chemical vapor deposition, the gas flow enters the sealed cavity from the central air inlet hole, and the central air inlet hole is directly opposite to the middle region of the battery cell; The thickness of the formed passivation film layer gradually decreases from the middle region to the edge region.

[0014] In combination with the third aspect, in some feasible embodiments, the housing includes a side enclosure and a top baffle arranged on the side enclosure, and the central air inlet hole is arranged in the middle of the top baffle; The side enclosure surrounds the periphery of the battery cell, and the top baffle is located above the battery cell, so that the housing and the tray form a sealed cavity with only the central air inlet hole.

[0015] In combination with the third aspect, in some feasible embodiments, the top baffle is parallel to the tray; alternatively, the top baffle is in the shape of a frustum of a pyramid with an upwardly inclined surface, so that the included angle formed between the top baffle and the tray is an acute angle.

[0016] Compared with the prior art, the solar cell and its manufacturing method provided by the present invention have the beneficial effects that: the passivation film layer has a good passivation effect, can effectively reduce the surface recombination rate of the battery, thereby increasing the battery efficiency. However, when the passivation film layer is relatively thick, it will absorb part of the incident light, resulting in optical loss and reducing the utilization rate of the incident light. By using a passivation film layer with a thickness difference, by appropriately increasing the thickness of the passivation film layer in the edge region or appropriately reducing the thickness of the passivation film layer in the edge region, it has practical significance for improving the overall efficiency of the battery.

[0017] In this application, a passivation film layer with a gradually changing thickness is used on the front and / or back of the battery. When the film thickness in the middle region of the battery is less than that in the edge region, while enhancing the passivation effect in the edge region of the battery, the utilization rate of the incident light in the middle region of the battery can be increased. When the light source mainly irradiates the edge region of the battery, the amount of light in the middle region is less. Then, a changing trend where the thickness of the passivation film layer in the middle region is greater than that in the edge region is adopted to ensure a high utilization rate of the incident light at the edge and the best passivation effect in the middle region, thereby improving the photoelectric conversion efficiency of the overall battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of the passivation film layer on the solar cell provided by the embodiment of the present invention, where the thickness of the passivation film layer increases from the middle region to the edge region (the thickness of the passivation film layer is zero in the middle region of the battery cell); Figure 2 It is a schematic structural diagram of the passivation film layer on the solar cell provided by the embodiment of the present invention, where the thickness of the passivation film layer increases from the middle region to the edge region (the thickness of the passivation film layer is not zero in the middle region of the battery cell); Figure 3 It is a schematic structural diagram of the field passivation film layer on the solar cell provided by the embodiment of the present invention, where the thickness of the field passivation film layer increases from the middle region to the edge region, and the thickness of the non-field passivation film layer decreases from the middle region to the edge region; Figure 4 It is a schematic structural diagram of the preparation of a thick passivation film layer in the edge region and a thin passivation film layer in the middle region provided by the embodiment of the present invention; Figure 5 It is a schematic structural diagram of the preparation of a thin passivation film layer in the edge region and a thick passivation film layer in the middle region provided by the embodiment of the present invention Figure 1 ; Figure 6 It is a schematic structural diagram of the preparation of a thin passivation film layer in the edge region and a thick passivation film layer in the middle region provided by the embodiment of the present invention Figure 2 ; Description of the reference numerals in the drawings: 1. Solar cell; 11. Intermediate region; 12. Edge region; 2. Passivation film layer; 21. Uniform edge thickness region; 22. Field passivation film layer; 23. Non-field passivation film layer; 3. Tray; 4. Column; 5. Side enclosure; 6. Top baffle; 61. Central air inlet. Detailed implementation manners

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, 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.

[0020] The passivation film layer has a good passivation effect and can effectively reduce the surface recombination rate of the battery, thereby increasing the battery efficiency. However, when the passivation film layer is relatively thick, it will absorb part of the incident light, resulting in optical loss and reducing the utilization rate of the incident light.

[0021] The utilization rate of incident light and surface recombination are two important factors affecting the photoelectric conversion efficiency of the battery. When the thickness of the field passivation film layer increases, the chemical passivation and field passivation effects usually increase accordingly, which can better reduce the surface recombination rate of carriers and improve the battery efficiency. However, at the same time, the passivation film layer will absorb a certain amount of incident light, thereby reducing the proportion of incident light entering the battery substrate and causing optical loss. The thicker the passivation film layer, the higher the proportion of incident light absorbed and the greater the optical loss. Therefore, appropriately increasing or reducing the thickness of the passivation film layer in the edge region has practical significance for improving the overall efficiency of the battery.

[0022] Please refer to Figures 1 to 6 , and now the solar cell with the passivation film layer 2 having a gradually changing thickness provided by the present invention will be described. The solar cell with the passivation film layer 2 having a gradually changing thickness includes: a solar cell 1, and a passivation film layer 2 is provided on the front and / or back of the solar cell 1, and there is a thickness difference between the intermediate region 11 and the edge region 12 of the solar cell 1 in the thickness of the passivation film layer 2.

[0023] This application includes the cases where the passivation film layer 2 is provided on the front of the solar cell 1, the passivation film layer 2 is provided on both the front and the back, and the passivation film layer 2 is only provided on the back; among them, mainly refers to the passivation film layer 2 on the light-receiving surface, and the passivation film layer 2 with such a thickness change needs to be adopted.

[0024] Through the passivation film layer 2 with a thickness difference, by appropriately increasing the thickness of the passivation film layer 2 in the edge region 12 or appropriately reducing the thickness of the passivation film layer 2 in the edge region 12, this application has practical significance for improving the overall efficiency of the battery.

[0025] In this application, a passivation film layer 2 with a gradually changing thickness is used on the front and / or back of the battery cell 1. When the film thickness in the middle region 11 of the battery is less than that in the edge region 12, the passivation effect in the edge region 12 of the battery can be enhanced while increasing the utilization rate of incident light in the middle region 11 of the battery. However, in a certain application scenario, if the light source mainly irradiates the edge region 12 of the battery and the amount of light in the middle region 11 is less, then the changing trend that the thickness of the passivation film layer 2 in the middle region 11 is greater than that in the edge region 12 is adopted to ensure a high utilization rate of incident light at the edge and the best passivation effect in the middle region 11, thereby improving the photoelectric conversion efficiency of the overall battery.

[0026] The design concept of this application uses the difference in the thickness of the passivation film layer 2 between the middle region 11 and the edge region 12 to improve the photoelectric conversion efficiency of the battery. The specific application scenarios are as follows: Generally, the gradually changing trend that the thickness of the passivation film layer 2 in the edge region 12 is greater than that in the middle region 11 is adopted. Because generally, it is considered that the passivation effect in the edge region 12 of the battery is more important than the utilization rate of incident light, and the utilization rate of incident light in the middle region 11 is more important than the passivation effect. For example, after making a solar cell into a photovoltaic module and conducting electrical tests, black edges caused by insufficient passivation effect in the edge region 12 of the battery are often seen. Therefore, in the production of the passivation film layer 2, the thickness of the passivation film layer 2 in the edge region 12 should be greater than that in the middle region 11.

[0027] For another example, during the cutting process of the battery substrate and the production process of the battery, the surface recombination rate in the edge region 12 of the battery is more likely to be greater than that in the middle region 11 due to process reasons. Therefore, appropriately increasing the thickness of the passivation film layer 2 in the edge region 12 has practical significance for improving the overall efficiency of the battery; while the utilization rate of incident light in the middle region 11 of the battery is relatively more important, and appropriately reducing the thickness of the passivation film layer 2 in the middle region 11 can improve the utilization rate of incident light in the middle region 11.

[0028] This application also protects the gradually changing trend that the thickness of the passivation film layer 2 in the edge region 12 is thin and the thickness of the passivation film layer 2 in the middle region 11 is thick.

[0029] For example, during the production process, there are more defects or impurities in the middle region 11. Therefore, the passivation effect in the middle region 11 is more important, and thus it is necessary to increase the thickness of the passivation film in the middle region 11. However, this will reduce the utilization rate of incident light. Therefore, the thickness of the passivation film in the edge region 12 is reduced to make up for the loss of incident light in the middle region 11 by increasing the utilization rate of incident light in the edge region 12.

[0030] For another example: in the scenario where the amount of light incident on the surface of the battery is uneven and the light source irradiates more on the edge region 12 of the battery cell 1, the probability that the middle region 11 of the battery is blocked is greater, and the changing trend that the thickness of the passivation film layer 2 in the edge region 12 is less than that in the middle region 11 should also be adopted.

[0031] For ease of understanding, the following analyzes the influence of the thickness of the passivation film layer 2 on the utilization rate of incident light: The utilization rate of incident light is directly related to the thickness of the passivation film layer 2. The incident light irradiating the surface of the battery needs to pass through the passivation film layer 2 on the surface of the battery before reaching the monocrystalline silicon substrate of the battery. Only after reaching the monocrystalline silicon substrate of the battery can the incident light induce electron-hole pairs in the substrate, thereby forming a photocurrent and converting light energy into electrical energy. Therefore, the larger the proportion of light incident on the monocrystalline silicon substrate, the higher the utilization rate of the incident light, and the corresponding higher the photoelectric conversion efficiency. However, the passivation film layer 2 covering the monocrystalline silicon substrate on the surface of the battery will absorb a part of the photons when the incident light passes through. The photons absorbed by the passivation film layer 2 cannot be used to generate free electron-hole pairs, but are consumed in the lattice vibration of the passivation film layer 2 material and converted into heat energy. That is, the incident light absorbed by the passivation film layer 2 cannot be used to convert electrical energy, which is a useless absorption and is also called parasitic absorption. Parasitic absorption is an important factor in reducing the utilization rate of incident light and causing optical losses. Parasitic absorption is related to the thickness of the passivation film layer 2. The thicker the passivation film layer 2, the more incident light is absorbed. Reducing the thickness of the passivation film layer 2 can effectively reduce the optical losses caused by parasitic absorption and improve the utilization rate of incident light. However, at the same time, the thickness of the passivation film layer will also affect its passivation effect. An overly thin passivation film cannot form stable chemical passivation and field passivation effects.

[0032] Therefore, in the present application, according to different application scenarios or the personalized characteristics of the battery, a thickness difference exists between the middle region 11 and the edge region 12 of the passivation film layer 2 on the battery chip 1. By thickening or thinning the edge region 12 and correspondingly thinning or thickening the middle region 11, the efficiency of the battery is improved.

[0033] In some embodiments, the thickness difference between the edge region 12 and the middle region 11 ≤ 100 nm.

[0034] In some embodiments, referring to Figure 1 , the thickness of the passivation film layer 2 gradually increases from the middle region 11 to the edge region 12. Moreover, the thickness of the passivation film layer 2 in the middle region 11 can be zero, that is, the passivation film layer 2 can only exist in the edge region 12.

[0035] Example 1: There is an aluminum oxide layer with a gradually changing thickness in the edge region 12 on the back of the battery, and there is no aluminum oxide layer in the middle region 11. The aluminum oxide layer in the edge region 12 covers one-third of the area of the battery chip 1. In the edge region 12, the thickness of the aluminum oxide layer near the outermost edge of the battery is greater than 5 nm, and in the direction from the outermost edge of the battery to the middle region 11 of the battery, the thickness of the aluminum oxide gradually decreases to 0 nm. The meaning of gradually decreasing is that the overall change trend of the thickness is decreasing. As Figure 1As shown, the alumina layer in the outermost edge region 12 may have a uniform edge thickness region 21, and then the thickness gradually decreases to zero. There is no alumina layer in the middle region 11.

[0036] Example 2: On the front side of the battery, there is a silicon nitride layer covering from the edge region 12 to the middle region 11, and the overall thickness of the silicon nitride layer decreases. The thickness of the silicon nitride film layer in the middle region 11 is not zero, as Figure 2 shown.

[0037] For the case where the thickness of the passivation film layer 2 increases from the middle region 11 to the edge region 12, the shape of the passivation film layer 2 on the solar cell substrate is a concave spherical surface, or an inverted conical shape, or an inverted frustum shape.

[0038] For the case where the thickness of the passivation film layer 2 gradually thins from the middle region 11 to the edge region 12 of the cell 1, the shape of the passivation film layer 2 on the solar cell substrate is a convex spherical surface, or a regular conical shape, or a regular frustum shape.

[0039] In some embodiments, the outermost side of the edge region 12 has a uniform edge thickness region 21.

[0040] In some embodiments, the passivation film layer 2 is a field passivation film layer 22 and / or a non-field passivation film layer 23.

[0041] In some embodiments, as Figure 3 shown, when the passivation film layer 2 includes a field passivation film layer 22 and a non-field passivation film layer 23, the thickness of the field passivation film layer 22 gradually increases from the middle region 11 to the edge region 12, and the thickness of the non-field passivation film layer 23 gradually decreases from the middle region 11 to the edge region 12 to form a flat surface.

[0042] Example 3: As Figure 3 shown, the thickness of the alumina field passivation layer on the front side of the battery gradually decreases from the edge region 12 to the middle region 11. The thickness of the other passivation layer or antireflection layer with non-field passivation effect gradually increases from the edge region 12 to the middle region 11 to form a flat upper surface of the battery.

[0043] The field passivation film involved in this application has positive or negative fixed charges by itself, and the absolute value of the fixed charge density ≥ 1×10 10 cm -2 .

[0044] Optionally, the thickness of the field passivation film layer 22 gradually thins from the middle region 11 to the edge region 12, and the thickness of the non-field passivation film layer 23 gradually thickens from the middle region 11 to the edge region 12 to form a flat surface.

[0045] In some embodiments, the field-free passivation film layer 23 is one or a combination of an aluminum oxide film layer, a silicon nitride film layer, and a silicon oxide film layer. For example, the field-free passivation film layer 23 may include a stacked aluminum oxide film layer, a silicon nitride film layer, and a silicon oxide film layer, and may also include a stacked amorphous silicon film layer and a polycrystalline silicon film layer.

[0046] In some embodiments, the field passivation film layer 22 is one or a combination of an aluminum oxide film layer, a silicon nitride film layer, and a silicon oxide film layer.

[0047] The passivation film layer 2 provided in this application further includes hydrogen atoms, and the hydrogen atom content also gradually changes with the change in the thickness of the passivation film layer 2. The higher the hydrogen atom content at the position where the passivation film layer 2 is thicker.

[0048] Hydrogen atom content: By using a reaction gas containing hydrogen elements, it is possible to incorporate hydrogen atoms into the passivation film layer 2. The common reaction gases for silicon nitride and aluminum oxide passivation film layers 2 both contain hydrogen elements. The role of hydrogen in the passivation film layer 2 is very important. Hydrogen atoms can combine with the dangling bonds on the surface of the crystalline silicon substrate to achieve the passivation of dangling bonds. The dangling bonds existing on the surface of the crystalline silicon substrate are important defect types. Appropriately increasing the hydrogen content in the passivation film layer 2 can increase the content of hydrogen atoms reaching the surface of the crystalline silicon substrate and passivating the dangling bonds, thereby reducing the dangling bond defect density and improving the passivation quality. The thicker the passivation film layer 2, the larger the volume of the passivation film layer 2 per unit area, the higher the total hydrogen content per unit area. After the battery undergoes a high-temperature process, the more hydrogen atoms move from the passivation film layer 2 to the surface of the crystalline silicon substrate, and the better the passivation quality.

[0049] Furthermore, the surface texture size below the passivation film layer 2 provided in this application gradually changes synchronously with the change in the thickness of the passivation film layer 2. That is, the surface texture size below the thicker region of the passivation film layer 2 is also larger. The surface texture shape includes a pyramid shape or a polished tower base shape, and the surface texture size refers to the height of the pyramid or the height of the center point of the polished tower base.

[0050] Purpose of the gradually changing surface texture: When the surface texture size is large, it will affect the deposition quality of the passivation film layer 2 deposited on the surface texture. When depositing a thinner passivation film layer 2 on a surface texture with a large size, it may occur that the peak position of the surface texture is exposed and the passivation film layer 2 fails to successfully cover the peak, or it may also occur that the passivation film layer 2 at the peak is rubbed off when the battery wafers 1 are stacked, thus affecting the passivation effect. Therefore, in the region where the passivation film layer 2 is thinner, the surface texture size can be appropriately reduced to improve the deposition quality of the passivation film layer 2. In the region where the passivation film layer 2 is thicker, appropriately increasing the surface texture size can reduce the total surface area of the surface texture, thereby reducing the surface recombination.

[0051] Controlling the gradually changing height of the textured surface: Both the concentration of the texturing solution and the reaction time can affect the size of the textured surface. A mask layer with uneven thickness is formed on the surface of the crystalline silicon substrate. When reacting with the texturing solution, in the areas where the mask layer is thicker, the solution needs to first etch the mask layer to contact the surface of the crystalline silicon substrate, thereby shortening the reaction time between the texturing solution and the substrate in the areas where the mask layer is thicker. The shorter the reaction time, the smaller the size of the textured surface.

[0052] Based on the same inventive concept, the present invention further provides a preparation method for preparing a solar cell with a passivation film layer 2 having a gradually changing thickness, and the method includes: Referring to Figure 4 , place the bracket on the tray 3, place the battery wafer 1 on the bracket, so that a gap is formed between the battery wafer 1 and the tray 3; Using chemical vapor deposition, the gas flow a enters the gap from the periphery of the bracket, and deposits the passivation film layer 2 on the lower surface of the battery wafer 1; The thickness of the formed passivation film layer 2 gradually increases from the middle region 11 to the edge region 12.

[0053] Combined with Figure 4 As shown, in some embodiments, the bracket includes at least four columns 4, the four columns 4 support the four corners of the battery wafer 1, and a connecting rod (not shown in the figure) is arranged between the four columns 4 to connect the four columns 4 together.

[0054] Referring to Figure 5 and Figure 6 , based on the same inventive concept, the present invention further provides a preparation method for preparing the solar cell with the passivation film layer 2 having a gradually changing thickness, and the method includes: Fabricate a housing with a central air inlet hole 61 at the top; Place the battery wafer 1 on the tray 3, cover the housing on the battery wafer 1, so that a sealed cavity with only the central air inlet hole 61 is formed between the housing and the tray 3; Using chemical vapor deposition, the gas flow b enters the sealed cavity from the central air inlet hole 61, and the central air inlet hole 61 is directly opposite to the middle region 11 of the battery wafer 1; The gas flow b can only enter from the central air inlet hole 61. The gas flow density is high in the middle region 11 of the battery wafer 1, while the gas flow density in the edge region 12 is low. The thickness of the formed passivation film layer 2 gradually thins from the middle region 11 to the edge region 12.

[0055] In some embodiments, referring to Figure 5 and Figure 6, the housing includes a side enclosure 5 and a top baffle 6 provided on the side enclosure 5. The central air inlet hole 61 is provided in the middle of the top baffle 6; the side enclosure 5 surrounds the periphery of the solar cell 1, and the top baffle 6 is located above the solar cell 1, so that the housing and the tray 3 form a sealed cavity with only the central air inlet hole 61. Among them, there is no air inlet hole in the side enclosure 5. Therefore, the air flow can only enter from the central air inlet hole 61. The air flow density is high in the middle area 11 of the solar cell 1, while the air flow density in the edge area 12 is low. Thus, the thickness of the passivation film layer 2 formed gradually thins from the middle area 11 to the edge area 12.

[0056] In some embodiments, the top baffle 6 is parallel to the tray 3, as Figure 5 shown; or, the top baffle 6 is a frustum of a pyramid with an upwardly inclined surface, so that the included angle formed between the top baffle 6 and the tray 3 is an acute angle, as Figure 6 shown.

[0057] The preparation process of the solar cell with the passivation film layer 2 having a gradually changing thickness provided by this application is as follows: When depositing the passivation film layer 2 by chemical vapor deposition methods such as PECVD or LPCVD, the gas source is usually located above the solar cell 1. The solar cell 1 is placed on the tray 3. The gas undergoes a chemical reaction on the upper surface of the solar cell 1 to form the passivation film layer 2, and the lower surface of the cell does not contact the reaction gas, thereby realizing the deposition of a passivation film layer 2 with a uniform thickness only on the upper surface of the solar cell 1.

[0058] PECVD: The full name of PECVD is Plasma Enhanced Chemical Vapor Deposition, which is a core technology for depositing thin film materials at low temperatures through plasma-assisted reactions.

[0059] LPCVD--Low Pressure Chemical Vapor Deposition, low pressure chemical vapor deposition method.

[0060] The preparation process of the passivation film layer 2 with a gradually changing thickness that is thick in the middle and thin at the edges is as follows: To form a passivation film layer 2 with a gradually changing thickness that is thick at the edges and thin in the middle, the tray 3 of the battery cell 1 can be modified. Four-corner columns 4 are placed between the four corners of the battery cell 1 and the tray 3 (there are only columns 4 at the four corners). The battery cell 1 is supported by the four columns 4, and a gap is formed between the battery cell 1 and the lower tray 3. The reaction gas can enter the gap below the battery cell 1 from between the columns 4 and contact the lower surface of the battery cell 1. Since the gas flow density at the edge of the lower surface is high and the gas flow density of the reaction gas contacted by the middle region 11 of the lower surface is low, a passivation film layer 2 with a gradually changing thickness that is thick in the edge region 12 and thin in the middle region 11 can be formed on the lower surface of the battery cell 1. By adjusting the height of the four columns 4, the gas flow density entering the gap below the battery cell 1 can be controlled, thereby controlling the trend of the gradually changing thickness of the passivation film layer 2 on the lower surface of the battery according to the experimental data. For the passivation film layer 2 with a uniform thickness formed on the upper surface of the battery during this process, it can be removed by a single-sided cleaning process.

[0061] Among them, the number of columns 4 can also be more. For example, one column 4 is also provided at the middle position of each of the four sides of the battery cell 1.

[0062] The preparation process of the passivation film layer 2 with a gradually changing thickness that is thin at the edges and thick in the middle is as follows: To form a passivation film layer 2 with a gradually changing thickness that is thin at the edges and thick in the middle, another modification method can be carried out on the tray 3 of the battery cell 1. A surrounding side enclosure 5 is provided between the battery cell 1 and the tray 3, and a top baffle 6 with a central air inlet hole 61 is provided on the side enclosure 5 to form a sealed cavity with only the central air inlet hole 61. The side enclosure 5 blocks the gas flow from the side, so that the gas flow can only enter from the central air inlet hole 61, and thus directly contacts the middle region 11 of the battery cell 1. Then, the gas flow density in the middle region 11 of the upper surface of the battery cell 1 is high, and the thickness of the passivation film layer 2 formed by the reaction of the gas in the middle region 11 of the battery cell 1 is also large. The density of the reaction gas contacted by the edge region 12 of the battery cell 1 is small, and the thickness of the passivation film layer 2 formed by the reaction is also thin, thereby forming a gradually changing trend of being thick in the center and thin at the edges.

[0063] According to the experimental data, by adjusting the height of the side enclosure 5, the size of the central air inlet hole 61 of the top baffle 6, and the angle between the top baffle 6 and the horizontal plane, the gas flow density on the upper surface of the battery cell 1 can be controlled, thereby controlling the trend of the gradually changing thickness. For example, Figure 5 the top baffle 6 is placed horizontally, while Figure 6 a top baffle 6 arranged at an angle with the horizontal plane is set.

[0064] The terms involved in this article are explained as follows: Fixed charge: The film layer formed by some materials will carry a certain amount of fixed charge due to its material properties. For example, the alumina film layer usually carries a negative fixed charge, and the silicon nitride film layer usually carries a positive fixed charge.

[0065] Field passivation: When the electron concentration and hole concentration on the battery surface are similar, the surface recombination rate is the highest. If the concentration of a certain type of carrier on the surface decreases, the surface recombination rate will be greatly reduced. The fixed charges in the field passivation film layer will repel the carriers of the same electric charge and attract the carriers of the opposite electric charge, thereby changing the surface carrier concentration and reducing the recombination probability of electrons and holes. This process is called field effect passivation.

[0066] Chemical passivation: The passivation film layer can saturate the dangling bonds and various defect states on the battery surface, reduce the interface defect density, and reduce the recombination centers in the forbidden band, which is the chemical passivation effect.

[0067] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A solar cell, characterized in that: include: A battery cell (1) is provided with a passivation film layer (2) on the front and / or back of the battery cell (1), and the thickness of the passivation film layer (2) differs between a middle region (11) of the battery cell (1) and an edge region (12) thereof.

2. The solar cell according to claim 1, wherein: The thickness of the passivation film layer (2) gradually increases from the middle area (11) to the edge area (12); or The thickness of the passivation film layer (2) gradually decreases from the middle area (11) to the edge area (12) of the battery cell (1).

3. The solar cell according to claim 1, wherein: The outermost side of the edge region (12) has a section of uniform edge thickness area (21).

4. The solar cell according to claim 1, wherein The passivation film layer (2) is a field passivation film layer (22) and / or a non-field passivation film layer (23).

5. The solar cell according to claim 4, characterized in that When the passivation film layer (2) comprises a field passivation film layer (22) and a non-field passivation film layer (23), the thickness of the field passivation film layer (22) gradually increases from the middle region (11) to the edge region (12), and the thickness of the non-field passivation film layer (23) gradually decreases from the middle region (11) to the edge region (12), so as to form a flat surface; or The thickness of the field passivation film layer (22) gradually decreases from the middle area (11) to the edge area (12), and the thickness of the non-field passivation film layer (23) gradually increases from the middle area (11) to the edge area (12), so as to form a flat surface.

6. A method for preparing a solar cell according to any one of claims 1 to 5, characterized in that: The method comprises: Placing a bracket on a tray (3), and placing a battery cell (1) on the bracket, so that a gap is formed between the battery cell (1) and the tray (3); By using a chemical vapor deposition method, an airflow enters the gap from around the support to deposit a passivation film layer (2) on the lower surface of the battery cell (1); The thickness of the formed passivation film layer (2) gradually increases from the middle area (11) to the edge area (12).

7. The preparation method according to claim 6, characterized in that: The support comprises at least four columns (4), the four columns (4) supporting the four corners of the battery sheet (1), and connecting rods are arranged between the four columns (4) to connect the four columns (4) together.

8. A method for preparing a solar cell according to any one of claims 1 to 5, characterized in that: The method comprises: Making a cover shell with a central air inlet hole (61) at the top; Placing the battery sheet (1) on a tray (3), and placing the cover shell on the battery sheet (1), so that a sealed cavity having only the central air inlet hole (61) is formed between the cover shell and the tray (3); By using a chemical vapor deposition method, an air flow enters the sealed cavity from the central air inlet hole (61), and the central air inlet hole (61) is directly opposite to the middle area (11) of the battery cell (1); The thickness of the formed passivation film layer (2) gradually decreases from the middle area (11) to the edge area (12).

9. The preparation method according to claim 8, characterized in that: The housing comprises a side baffle (5) and a top baffle (6) arranged on the side baffle (5), and the central air inlet (61) is arranged in the middle of the top baffle (6); The side baffles (5) are arranged around the periphery of the battery cell (1), and the top baffle (6) is located above the battery cell (1), so that the cover shell and the tray (3) form a sealed cavity with only the central air inlet hole (61).

10. The preparation method according to claim 9, characterized in that: The top baffle (6) is parallel to the tray (3); or, the top baffle (6) is in the shape of a quadrangular pyramid with an upwardly inclined surface, so that the angle formed between the top baffle (6) and the tray (3) is an acute angle.

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