Solar cell and preparation method thereof

Abstract

The invention provides a solar cell and a preparation method thereof, and the preparation method comprises the steps: carrying out the grooving of a substrate, and forming a grooving region; the position of the slotting area is the same as the position of a subsequently prepared metal grid line; sequentially preparing a functional layer and a dielectric layer on the slotted substrate; etching the dielectric layer to expose the functional layer; wherein the etching position is the same as the position of the subsequently prepared metal grid line; and a metal grid line is electroplated after the dielectric layer is etched. According to the invention, the width of the metal grid line is kept in a required range, the shading of the grid line is reduced, the condition of poor pulling-out force of the grid line is improved to a certain extent, and the performance of the solar cell is improved.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of solar cell preparation, and in particular to a solar cell and a preparation method thereof. Background Art

[0002] Solar cells or photovoltaic cells (PV) are components that convert solar energy into electrical energy. When sunlight shines on the semiconductor material on the surface of the solar cell, the semiconductor material absorbs the energy of the photons, allowing the electrons in the semiconductor atoms to obtain enough energy to be excited from the covalent bonds to form free electrons. These free electrons separate under the action of the PN junction electric field to form current, which can drive the load to work. The production process of solar cells mainly includes steps such as cleaning, texturing, diffusion, etching, coating, screen printing and sintering. These steps work together to process the substrate into a solar cell with photoelectric conversion function.

[0003] With the development of photovoltaic technology, the photoelectric conversion efficiency of solar cells has gradually increased and the cost has gradually decreased. However, due to the high price of silver paste used in the screen printing process, the cost of silver paste accounts for about 40% of the non-silicon cost of the battery, making the cost of solar cells high. One way is to replace the silver in the metallization process with cheap metals such as copper through electroplating, chemical plating and other technologies, making electroplating and chemical plating technologies a new way to achieve cost reduction.

[0004] Most solar cell metallization is achieved through screen printing. The screen printing process first prints the slurry onto the cell in a certain pattern. Then, the effective ingredients in the slurry corrode and burn through the surface dielectric material at high temperature, thereby connecting to the conductive substrate on the top to achieve current extraction. However, the slurry used for screen printing has a high silver content, so the cost is relatively high. Electroplating metallization has attracted much attention because it uses relatively cheap metals such as copper and nickel to prepare metal grid lines, which can significantly reduce costs. The process is generally to first partially remove the dielectric layer on the surface of the cell by laser etching or masking, exposing the conductive substrate at the bottom, and then prepare the metal grid lines on the exposed substrate.

[0005] Since the dielectric layer on the surface of the solar cell is relatively thin (nanometer level), the surface depth of the dielectric layer removed is relatively low. On the one hand, this will cause epitaxial growth of the metal grid lines during the electroplating process, increase the width of the metal grid lines, increase the shading of the grid lines, and adversely affect the performance of the cell. On the other hand, since the contact area between the metal grid lines and the cell substrate is relatively small, the metal grid line pull-off force will be poor. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a solar cell and a preparation method thereof, so that the width of the metal grid line is kept within the required range, the grid line shading is reduced, and the poor grid line pull-off force is improved to a certain extent, thereby improving the performance of the solar cell.

[0007] To solve the above technical problems, in the first aspect, the present invention provides a method for preparing a solar cell, comprising: performing a grooving process on a substrate to form a grooved area, wherein the position of the grooved area is the same as the position of a metal grid line prepared subsequently; sequentially preparing a functional layer and a dielectric layer on the grooved substrate; etching the dielectric layer to expose the functional layer, wherein the etching position is the same as the position of the metal grid line prepared subsequently; and electroplating the metal grid line after etching the dielectric layer.

[0008] Optionally, before the substrate is subjected to the grooving process to form the grooving area, the method further includes: cleaning the substrate to be grooved.

[0009] Optionally, the width of the grooved area is slightly wider than the width of the metal gate line to be prepared.

[0010] Optionally, performing a groove process on the substrate to form the grooved area includes: performing a groove process on the substrate using a laser etching process or a chemical etching groove process to form the grooved area.

[0011] Optionally, etching the dielectric layer to expose the functional layer includes: etching the dielectric layer using a laser etching process or a mask etching process to expose the functional layer.

[0012] Optionally, the thickness of the functional layer in the grooved area is the same as that in the non-grooved area.

[0013] Optionally, during the etching process of the dielectric layer, the depth of the groove formed by etching is 5 to 15 μm, and the width of the groove is 15 to 30 μm.

[0014] Optionally, before electroplating the metal gate line, the method further includes: preparing a seed layer in the groove formed by etching.

[0015] In a second aspect, the present invention provides a solar cell, comprising a substrate, a functional layer, a dielectric layer and a metal grid line; the substrate has a groove area, and the groove area is at the same position as the metal grid line; the functional layer is located on the surface of the substrate; the dielectric layer is located on the surface of the functional layer; the metal grid line is located in the groove on the dielectric layer and is conductively connected to the functional layer, wherein the groove position is the same as the groove area position.

[0016] Optionally, the solar cell is prepared by the solar cell preparation method described in the first aspect.

[0017] Compared with the prior art, the present invention has the following advantages: the solar cell preparation process is improved, firstly, the substrate is grooved to form a grooved area, the position of the grooved area is the same as the position of the metal grid line prepared subsequently, and then the functional layer and the dielectric layer are prepared in sequence on the grooved substrate, and then the dielectric layer is etched to expose the functional layer, wherein the etching position is the same as the position of the metal grid line prepared subsequently, and finally the metal grid line is electroplated after the dielectric layer is etched, so as to keep the width of the metal grid line within the required range, reduce the grid line shading, and also improve the situation of poor grid line pull-off force to a certain extent, thereby improving the performance of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0019] Figure 1 It is a schematic diagram of a process of preparing a solar cell according to an embodiment of the present invention;

[0020] Figure 2 It is a schematic diagram of the battery structure at each stage based on the traditional solar cell preparation method;

[0021] Figure 3 This is a schematic diagram of the battery structure at each stage of the solar cell preparation method according to an embodiment of the present invention;

[0022] Figure 4 It is a schematic diagram of the structure of the groove before electroplating the metal grid line in one embodiment of the present invention.

[0023] Figure 2 S1 to S5 represent the steps of a conventional solar cell preparation method. Figure 3 P1 to P6 represent the steps of a method for preparing a solar cell according to an embodiment of the present invention.

[0024] Figure 4 Middle: 100 - substrate, 200 - functional layer, 300 - dielectric layer, 110 - grooved area, 310 - groove. DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0026] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0027] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0028] Figure 1 is a schematic diagram of a process for preparing a solar cell according to an embodiment of the present invention, with reference to Figure 1 As shown, method 100 includes: S110, performing a groove process on the substrate to form a groove area, wherein the position of the groove area is the same as the position of the metal gate line prepared subsequently; S120, sequentially preparing a functional layer and a dielectric layer on the substrate after the groove process; S130, etching the dielectric layer to expose the functional layer; wherein the etching position is the same as the position of the metal gate line prepared subsequently; S140, electroplating the metal gate line after etching the dielectric layer.

[0029] In the traditional solar cell manufacturing process, the metal grid line is located at the position of the groove on the dielectric layer, but the depth of the groove depends only on the depth of etching (grooving, film opening or patterning) of the dielectric layer. Figure 2 As shown, the solar cell preparation method mainly includes: S1, providing a substrate, generally a silicon substrate; S2, preparing a functional layer on the substrate, and a functional layer is prepared on the upper and lower surfaces of the substrate in the figure; S3, preparing a dielectric layer on the functional layer; S4, etching the dielectric layer to form a groove, which is used for subsequent electroplating of metal grid lines; S5, electroplating the metal grid lines at the groove position. It can be seen that in the preparation process of the above solar cell, the depth of the groove is only determined by the depth of the dielectric layer after etching. Therefore, the depth of the electroplated metal grid line in the groove is also the depth of the groove. Since the dielectric layer on the surface of the solar cell is relatively thin (nanometer level), the depth of the groove formed by removing the dielectric layer is relatively low. On the one hand, the low groove depth will cause the epitaxial growth of the metal grid line during the electroplating process, increase the width of the metal grid line, and further increase the shading of the metal grid line, which has an adverse effect on the performance of the solar cell; on the other hand, since the contact area between the metal grid line and the substrate of the solar cell is relatively small, the metal grid line pull-off force will be poor, which is not conducive to the structural stability of the solar cell.

[0030] In this embodiment, in order to increase the electroplating depth of the metal gate line, the method of this embodiment pre-grooves the substrate to form a grooved area before preparing the functional layer and the dielectric layer, and the position of the grooved area is the same as the position where the metal gate line is subsequently formed. Therefore, the depth of the formed metal gate line not only includes the depth formed by etching the dielectric layer, but also includes the depth of the grooved area formed by pre-grooving the substrate, thereby inhibiting the epitaxial growth of the metal gate line beyond the groove width range and improving the pull-off force of the metal gate line.

[0031] Exemplary, reference Figure 3 As shown, the solar cell preparation method mainly includes: P1, providing a substrate, generally a silicon substrate; P2, grooving the substrate to form a grooved area, the location of the grooved area is the same as the location of the metal grid line prepared later, and the upper and lower surfaces of the substrate are grooved in the figure; P3, sequentially preparing functional layers on the grooved substrate; P4, preparing a dielectric layer on the functional layer. It can be seen that since the substrate surface has a grooved area, even if the functional layer and the dielectric layer are prepared on the substrate, the grooved area on the substrate can still be shown on the surface of the intermediate product;

[0032] P5. Etch the dielectric layer to expose the functional layer. At this time, the groove depth (i.e., the subsequent metal grid line depth) includes not only the depth formed by etching the dielectric layer, but also the depth of the grooved area pre-grooved on the substrate, which is deeper than the conventional groove depth; P6. Electroplate the metal grid line after etching the dielectric layer. It can be seen that the solar cell prepared by the method of this embodiment has the following advantages: First, since the groove depth is deep enough, the epitaxial growth of the metal grid line beyond the groove width range during the electroplating process can be significantly suppressed, so that the width of the metal grid line is maintained within the required range, the metal grid line shading is reduced, and the performance of the solar cell is improved; second, since the contact area between the metal grid line and the sidewall dielectric layer is increased, the metal grid line pull-off force can also be improved to a certain extent, thereby improving the structural stability of the solar cell.

[0033] Figure 4 is a schematic diagram of the structure of the groove before the metal grid line is electroplated in one embodiment of the present invention, referring to Figure 4 As shown in the figure, a functional layer 200 and a dielectric layer 300 are provided on a substrate 100, wherein the substrate 100 is grooved before the functional layer 200 is prepared to form a grooved area 110. As can be seen from the figure, the depth of the grooved area 110 is the part below the dotted line in the figure, and the height is h. This part height can make the depth of the metal grid line electroplated later deeper.

[0034] In one example, before the substrate is subjected to a groove processing to form a grooved area, the method of this embodiment further includes cleaning the substrate to be grooved.

[0035] In this embodiment, cleaning the substrate is an important step in the preparation process of solar cells, which can improve product quality. There are various ways to clean the substrate, which are mainly determined by the material of the substrate, the type of contaminants and the requirements of the manufacturing process. Common cleaning methods include alkaline solution cleaning and acidic solution cleaning. Among them, alkaline solution cleaning uses an alkaline solution, such as a mixture of ammonia, hydrogen peroxide and water for cleaning, which effectively removes organic contaminants or particles through oxidation and etching reactions; acidic solution cleaning uses an acidic solution, such as a mixture of hydrochloric acid, hydrogen peroxide and water for cleaning, which can dissolve metal impurities, form a complexing agent, and desorb metal impurities from the surface of the substrate. Through the substrate cleaning process, pollutants such as particulate matter, organic matter, and metal impurities on the surface of the substrate can be removed to ensure the cleanliness of the substrate surface, provide good substrate conditions for the subsequent preparation process, and ensure the smooth progress of the preparation process.

[0036] In one example, the width of the slotted area is slightly wider than the width of the metal grid line. During the battery manufacturing process, there will be certain process tolerances due to equipment accuracy, material properties, etc. In order to ensure that the metal grid line can be completely covered in the predetermined area, the width of the slotted area needs to be slightly larger than the width of the metal grid line to accommodate these possible deviations. In addition, by increasing the width of the slotted area, the alignment tolerance can be improved, reducing problems such as metal grid line breakage or short circuit caused by alignment deviation.

[0037] In one example, the substrate is grooved to form the grooved area by using a laser groove process or a chemical etching groove process to form the grooved area.

[0038] Laser grooving is the process of processing the substrate using the high energy density characteristics of the laser beam. When the laser beam is irradiated to the surface of the substrate, the substrate surface absorbs the laser energy and rapidly heats up. When the temperature reaches the melting point or boiling point of the substrate, the substrate material will melt, ablate or evaporate, thereby partially removing the substrate material and forming a groove structure. Laser grooving has extremely high precision and can accurately control the shape, size and depth of the grooves to adapt to different solar cell structures and performance requirements. This precise control capability helps to optimize the solar cell structure and improve the overall performance of the solar cell. In addition, during the laser grooving process, the high temperature of the laser beam can remove defects and impurities on the surface of the substrate, making the substrate purer.

[0039] Compared with the laser grooving process, the advantage of the chemical etching grooving process is that the chemical etching grooving uses low-cost chemical reagents, such as acid and alkaline solutions, and its initial investment cost and operating cost are lower than high-end equipment such as laser grooving. In addition, the chemical etching reaction speed is fast, and a large number of substrates can be grooved in a short time, thereby improving production efficiency. The chemical etching grooving process is suitable for various types of solar cell materials, such as monocrystalline silicon, polycrystalline silicon, amorphous silicon, etc. It has a wide range of applicability, and can also achieve complex groove structures and precise size control by changing the mask pattern and etching conditions.

[0040] In one example, etching the dielectric layer to expose the functional layer may involve etching the dielectric layer using a laser etching process or a mask etching process to expose the functional layer.

[0041] In this embodiment, not only laser grooving or chemical etching grooving can be used to groove the substrate, but also laser etching or mask etching can be used to etch the dielectric layer. The advantages of laser grooving and mask etching are not described here.

[0042] In one example, the thickness of the functional layer is the same in the grooved area and the non-grooved area. In this embodiment, since the thickness of the functional layer is the same in the grooved area and the non-grooved area, after the functional layer is prepared, the depth of the surface groove of the corresponding intermediate product is the same as the depth of the grooved area of ​​the substrate, and the depth formed by the pre-grooving treatment of the substrate can be fully utilized, which is beneficial to the subsequent electroplating of the metal grid line and the depth of the metal grid line embedded in the dielectric layer. The method of this embodiment increases the depth of the metal grid line area by performing a groove treatment in the metal grid line area according to certain requirements. After removing the dielectric layer, during the growth of the metal grid line in the grid line area, due to the limitation of the side wall of the groove area, the metal grid line will only grow upward, thereby avoiding the epitaxial growth of the metal grid line beyond the width of the groove; at the same time, due to the increase in the contact area between the metal grid line and the side wall, it has a certain effect on improving the pull-off force of the metal grid line.

[0043] In one example, during the etching of the dielectric layer, the depth of the groove formed by etching is 5 to 15 μm, and the width of the groove is 15 to 30 μm.

[0044] In one example, before electroplating the metal gate lines, the method of this embodiment further includes preparing a seed layer in the groove formed by etching.

[0045] In this embodiment, the seed layer is a very thin metal film deposited on a specific surface, and its main function is to serve as a base layer for subsequent electroplating, deposition and other processes to improve the adhesion, conductivity and other properties between the plating layer and the base layer. The seed layer can significantly enhance the bonding force between the subsequent plating layer and the base layer, prevent the plating layer from falling off or peeling off, and it usually has good conductivity, can serve as a channel for current transmission, and improve the conductivity of the entire structure.

[0046] The preparation process of the seed layer includes physical vapor deposition (PVD), chemical vapor deposition (CVD), sputtering and evaporation. Among them, the sputtering method is widely used due to its advantages of high deposition efficiency and good film quality. In the solar cell manufacturing of this embodiment, in order to form a conductive channel or a grid line structure, a seed layer needs to be prepared, and then the required metal grid lines are formed on the seed layer by electroplating or deposition process.

[0047] In the solar cell preparation method of the present embodiment, a substrate is first grooved to form a grooved area, the position of the grooved area is the same as the position of the metal grid line prepared subsequently, and then a functional layer and a dielectric layer are sequentially prepared on the grooved substrate, and the dielectric layer is etched to expose the functional layer, wherein the etching position is the same as the position of the metal grid line prepared subsequently, and finally the metal grid line is electroplated after etching the dielectric layer, so as to keep the width of the metal grid line within the required range, reduce the grid line shading, and also improve the situation of poor grid line pull-off force to a certain extent, thereby improving the performance of the solar cell.

[0048] Another embodiment of the present invention provides a solar cell, including a substrate, a functional layer, a dielectric layer and a metal grid line; the substrate has a groove area, and the groove area is at the same position as the metal grid line; the functional layer is located on the surface of the substrate; the dielectric layer is located on the surface of the functional layer; the metal grid line is located in the groove on the dielectric layer and is conductively connected to the functional layer, wherein the position of the groove is the same as the position of the groove area.

[0049] In this embodiment, since the groove area on the substrate is the same as the metal grid line area finally formed, the depth of the metal grid line (groove depth) includes not only the depth formed by etching the dielectric layer, but also the depth of the groove area formed by pre-grooving on the substrate. The advantages brought about by this are: first, since the groove depth is deep enough, the epitaxial growth of the metal grid line beyond the groove width range during the electroplating process can be significantly suppressed, so that the width of the metal grid line is maintained within the required range, the metal grid line shading is reduced, and the performance of the solar cell is improved; second, since the contact area between the metal grid line and the sidewall dielectric layer is increased, the metal grid line pull-off force can also be improved to a certain extent, thereby improving the structural stability of the solar cell.

[0050] In one example, the solar cell of this embodiment can be prepared by the solar cell preparation method of the aforementioned embodiment. The relevant preparation method can refer to the aforementioned embodiment and will not be described in detail here.

[0051] The depth of the metal grid line of the solar cell of this embodiment includes not only the depth formed by etching the dielectric layer, but also the depth of the groove area formed by pre-grooving on the substrate, which is deeper than the conventional groove depth, so that the width of the metal grid line is maintained within the required range, reducing grid line shading; in addition, it also improves the poor pull-off force of the metal grid line to a certain extent, thereby improving the stability of the solar cell structure.

[0052] The basic concepts have been described above. Obviously, for those skilled in the art, the above invention disclosure is only used as an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0053] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0054] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this application, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0055] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A method for preparing a solar cell, characterized in that: include: Performing a groove process on the substrate to form a groove area; the location of the groove area is the same as the location of the metal grid line prepared subsequently; Sequentially preparing a functional layer and a dielectric layer on the grooved substrate; Etching the dielectric layer to expose the functional layer; The etching position is the same as the position of the metal gate line prepared later; The metal gate line is electroplated after etching the dielectric layer.

2. The method for preparing a solar cell according to claim 1, wherein: The method further comprises: cleaning the substrate to be grooved before forming the grooved area.

3. The method for preparing a solar cell according to claim 1, wherein: The width of the grooved area is slightly wider than the width of the metal gate line to be prepared.

4. The method for preparing a solar cell according to claim 1, wherein: Performing a groove process on the substrate to form a grooved area includes: performing a groove process on the substrate using a laser etching process or a chemical etching groove process to form the grooved area.

5. The method for preparing a solar cell according to claim 1, wherein: Etching the dielectric layer to expose the functional layer includes: etching the dielectric layer using a laser etching process or a mask etching process to expose the functional layer.

6. The method for preparing a solar cell according to claim 1, wherein: The thickness of the functional layer in the grooved area is the same as that in the non-grooved area.

7. The method for preparing a solar cell according to claim 1, wherein: During the etching of the dielectric layer, the depth of the groove formed by etching is 5 to 15 μm, and the width of the groove is 15 to 30 μm.

8. The method for preparing a solar cell according to claim 1, wherein: Before electroplating the metal grid lines, the method further includes: preparing a seed layer in the grooves formed by etching.

9. A solar cell, characterized in that: The invention comprises a substrate, a functional layer, a dielectric layer and a metal gate line; the substrate has a groove area, and the groove area is at the same position as the metal gate line; the functional layer is located on the surface of the substrate; the dielectric layer is located on the surface of the functional layer; the metal gate line is located in a groove on the dielectric layer and is conductively connected to the functional layer, wherein the groove is at the same position as the groove area.

10. The solar cell according to claim 9, characterized in that The solar cell is prepared by the solar cell preparation method according to any one of claims 1 to 8.

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