Preparation method of back contact battery

Abstract

The invention relates to a preparation method of a back contact battery, which comprises the following steps of: after a tunneling layer, a doping layer and a mask are formed each time, firstly removing the mask on the front surface and the side surface by adopting a hydrofluoric acid solution, and then etching the exposed tunneling layer and the doping layer by adopting alkali liquor, so as to remove winding plating. The purpose of removing the winding plating can be achieved by adopting a combined process of acid etching and alkali etching, so that the use of nitric acid and concentrated sulfuric acid can be avoided, and hydrofluoric acid is mainly used in the process flow. The chemical property of hydrofluoric acid is relatively mild, and the corrosivity on the tunneling layer and the doping layer on the back is far smaller than that of nitric acid or concentrated sulfuric acid. Therefore, chemical damage to the functional film layers of the first conductive region and the second conductive region can be reduced to the greatest extent in the process of removing the winding plating, and the integrity and the electrical property of the functional film layers are ensured, so that the quality of the battery can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a method for preparing a back-contact cell. Background Technology

[0002] Back-contact solar cells, as a novel type of solar cell structure, offer numerous advantages, including high photoelectric conversion efficiency. However, during the fabrication of back-contact solar cells, the presence of multiple film layers inevitably occurs. This layering typically requires etching with a mixed acid solution of nitric acid, concentrated sulfuric acid, and hydrofluoric acid to remove the coating. However, the use of multiple acids, especially nitric acid and concentrated sulfuric acid, is not only environmentally unfriendly but may also damage the film structure on the back of the fabricated cell, thus impairing the cell's quality. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for preparing a back-contact battery that can improve battery quality in order to address the above problems.

[0004] A method for preparing a back-contact battery includes the following steps:

[0005] A substrate is provided, the back side of which has a first conductive region, a second conductive region, and an isolation region located between the first conductive region and the second conductive region;

[0006] A first tunneling layer, a first doped layer, and a first mask are sequentially formed on the surface of the substrate through a first high-temperature process.

[0007] The first acid etching is performed using hydrofluoric acid solution to remove the first mask located on the front and side surfaces of the substrate, and the first patterning process is performed on the back surface of the substrate using laser etching to remove the first mask located in the second conductive region and the isolation region.

[0008] The first tunneling layer and the first doped layer are removed by a first alkaline etching process.

[0009] A second high-temperature process is used to sequentially form a second tunneling layer, a second doped layer, and a second mask on the surface of the substrate.

[0010] A second acid etching process is performed using hydrofluoric acid solution to remove the second mask located on the front and side surfaces of the substrate, and a second patterning process is performed on the back surface of the substrate using laser etching to remove the second mask located in the first conductive region and the isolation region.

[0011] The exposed second tunneling layer and second doped layer are removed by a second alkaline etching.

[0012] A texturing process is used to form a texturing light-trapping structure in the exposed area of ​​the substrate, and a hydrofluoric acid solution is used to clean away the first mask located in the first conductive area and the second mask located in the second conductive area.

[0013] In one embodiment, in the first high-temperature process and the second high-temperature process, the front surfaces of the two substrates are facing each other and stacked, and a plating area distributed along the edge and a non-plating area located in the middle of the plating area are formed on the front surface of each substrate. The first tunneling layer, the first doped layer, the first mask, the second tunneling layer, the second doped layer and the second mask formed on the front surface of the substrate are all located in the plating area.

[0014] In one embodiment, in the steps of performing a first etching with hydrofluoric acid solution and a second etching with hydrofluoric acid solution, the substrate is placed in a chain etching machine. The surface of the etching tank of the chain etching machine is covered with multiple rollers, and the rollers are partially immersed in the hydrofluoric acid solution. The front of the substrate faces the rollers and can enter the etching tank sequentially under the drive of the rollers.

[0015] In one embodiment, in the first acid etching step using a hydrofluoric acid solution, the temperature of the hydrofluoric acid solution is 10°C-20°C, the volume fraction of hydrofluoric acid in the hydrofluoric acid solution is 40%-60%, and the process time of the first acid etching is 100S-200S.

[0016] In one embodiment, the first acid etching process takes 60-80 seconds.

[0017] In one embodiment, in the step of performing a second acid etching using a hydrofluoric acid solution, the volume fraction of hydrofluoric acid in the hydrofluoric acid solution is 30%-50%, and the process time of the second acid etching is 80S-150S.

[0018] In one embodiment, in the step of removing the exposed first tunneling layer and the first doped layer by a first alkaline etching, the alkaline etching solution used is a mixture of sodium hydroxide and water, and the volume fraction of the sodium hydroxide is 6%-14%. The process time of the first alkaline etching is 150-200 seconds, and the temperature of the alkaline etching solution is 75°C-85°C.

[0019] In one embodiment, in the step of removing the exposed second tunneling layer and the second doped layer by a second alkaline etching, the alkaline etching solution used is a mixture of sodium hydroxide, alkaline etching additive and water.

[0020] In one embodiment, the volume fraction of sodium hydroxide is 2%-4%, the volume fraction of alkaline etching additive is 0.8%-1.2%, the process duration of the second alkaline etching is 120S-180S, and the temperature of the alkaline etching solution is 60℃-70℃.

[0021] In one embodiment, the step further includes: forming a passivation layer on the surface of the substrate and forming metal electrodes in the first conductive region and the second conductive region.

[0022] The aforementioned method for fabricating a back-contact battery involves removing the front and side masks using hydrofluoric acid solution after each formation of the tunneling layer, doped layer, and mask. Then, an alkaline solution is used to etch away the exposed tunneling and doped layers, thus removing the wrap-around plating. Since this combination of acid and alkaline etching achieves the removal of the wrap-around plating, the use of nitric acid and concentrated sulfuric acid can be avoided. The primary acid used in the process is hydrofluoric acid. Hydrofluoric acid has relatively mild chemical properties, and its corrosiveness to the back-side tunneling and doped layers is far less than that of nitric acid or concentrated sulfuric acid. Therefore, the removal of the wrap-around plating minimizes chemical damage to the functional films in the first and second conductive regions, ensuring the integrity of the functional films and their electrical performance, thereby effectively improving battery quality. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart of the preparation method of the back contact battery in a preferred embodiment of the present invention;

[0025] Figures 2 to 14 for Figure 1 The diagram shows a scenario illustrating the process of fabricating a back-contact battery. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0029] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0030] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0031] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0032] Please see Figures 1 to 14 The method for preparing the back contact battery in the preferred embodiment of the present invention includes steps S10 to S80.

[0033] Step S10: A substrate 100 is provided, the back side of which has a first conductive region, a second conductive region, and an isolation region located between the first conductive region and the second conductive region.

[0034] The substrate 100 is a semiconductor material, which can be formed by doping in a silicon wafer. Depending on the doping type, the substrate 100 can be classified as N-type or P-type. Specifically, the substrate 100 has a front side, a back side, and a side side, with the side side connecting the front and back sides. The front side of the substrate 100 refers to the side facing upwards in practical applications, while the back side refers to the side facing downwards. The first conductive region, the second conductive region, and the isolation region are all located on the back side of the substrate 100. During the use of the fabricated back-contact battery, the front side of the substrate 100 faces the direction of light.

[0035] More specifically, the first and second conductive regions are generally arranged alternately in an interdigitated pattern along a direction parallel to the back surface of the substrate 100, while the isolation region is used to separate the first and second conductive regions. The first and second conductive regions have opposite conductivity types and different doping characteristics. For example, if the substrate 100 is N-type, the first conductive region is P-type doped, while the second conductive region is N-type doped; if the substrate 100 is P-type, the first conductive region is N-type doped, while the second conductive region is P-type doped.

[0036] Both the first and second conductive regions can form tunneling layers and doped layers, thus serving as the two electrodes of the solar cell. The isolation region, however, does not form tunneling layers or doped layers, and therefore cannot conduct electricity to separate the two electrodes. For example, if the first conductive region is P-type doped and the second conductive region is N-type doped, the positive and negative electrodes of the back contact cell will ultimately be formed on the first and second conductive regions, respectively. Conversely, if the first conductive region is N-type doped and the second conductive region is P-type doped, the negative and positive electrodes of the back contact cell will ultimately be formed on the first and second conductive regions, respectively.

[0037] In step S20, a first tunneling layer 200, a first doped layer 300, and a first mask 400 are sequentially formed on the surface of the substrate 100 through a first high-temperature process.

[0038] Specifically, a low-pressure chemical vapor deposition (LPCVD) process is generally used to sequentially form a first tunneling layer 200 and a first doped layer 300 on the surface of the substrate 100, as shown in [reference needed]. Figure 2 Next, after a high-temperature doping process, a first mask 400 is formed outside the first doped layer 300, as shown in the figure. Figure 3 The first mask 400 is typically boron-doped silicon dioxide (BSG). Silicon dioxide is chemically stable, especially reacting slowly with alkalis. Furthermore, the thickness of the first mask 400 is generally 45 nm to 75 nm.

[0039] The first tunneling layer 200, the first doped layer 300, and the first mask 400 are formed not only on the back side of the substrate 100, but also deposited around the sides and front side of the substrate 100. Depending on the process, the distribution area of ​​each film layer on the front side of the substrate 100 also varies.

[0040] Please refer to the following: Figure 2 and Figure 3 Specifically, in this embodiment, during the first high-temperature process, the front surfaces of the two substrates 100 are facing each other and stacked, and a plating area distributed along the edge and a non-plating area located in the middle of the plating area are formed on the front surface of each substrate 100. The first tunneling layer 200, the first doped layer 300 and the first mask 400 formed on the front surface of the substrate 100 are all located in the plating area.

[0041] The first high-temperature process employs a "double-insertion" method, where two substrates 100 are stacked and placed into appropriate equipment for simultaneous film formation. Although the two substrates 100 are spatially stacked, they are not completely flush, leaving gaps at their edges for film growth, thus creating a wrap-around coating. Therefore, a wrap-around coating area and a non-wrap-around coating area are formed on the front side of each substrate 100. The wrap-around coating area is located at the edge of the substrate 100, while the non-wrap-around coating area is located in the center of the substrate 100.

[0042] The "double insertion" method can save costs and improve production efficiency. Furthermore, when performing the first high-temperature process using the "double insertion" method, the first tunneling layer 200, the first doped layer 300, and the first mask 400 will not completely cover the front side of the substrate 100, thereby significantly reducing the area of ​​the wrap-around coating layer. This can also improve efficiency and save solution during the subsequent removal of the wrap-around coating.

[0043] It should be noted that in other embodiments, the first high-temperature process can also be performed using a "single insertion" method, that is, the single-layer substrate 100 is directly placed into the corresponding equipment for film formation. In this way, the first tunneling layer 200, the first doped layer 300, and the first mask 400 will completely cover the front side of the substrate 100.

[0044] In step S30, a first acid etching is performed using hydrofluoric acid solution to remove the first mask 400 located on the front and side surfaces of the substrate 100, and a first patterning process is performed on the back surface of the substrate 100 using laser etching to remove the first mask 400 located in the second conductive area and the isolation area.

[0045] Hydrofluoric acid solution can react with the first mask 400, but it does not readily react with the first doped layer 300. Therefore, when the front and side surfaces of the substrate 100 come into contact with the hydrofluoric acid solution, the corresponding portion of the first mask 400 can be removed, exposing the first doped layer 300. Figure 4 In this way, the first mask 400, which is coated around the front and sides of the substrate 100, can be removed.

[0046] Specifically, in this embodiment, in the first acid etching step using hydrofluoric acid solution, the substrate 100 is placed in a chain etching machine (not shown). The surface of the etching tank of the chain etching machine is covered with multiple rollers, and the rollers are partially immersed in the hydrofluoric acid solution. The front of the substrate 100 faces the rollers and can enter the etching tank sequentially under the drive of the rollers.

[0047] During the first acid etching process, the front side of the substrate 100 faces downwards, thus directly contacting the hydrofluoric acid solution in the etching tank. The hydrofluoric acid solution can also be adsorbed onto the sides of the substrate 100 through capillary action. Therefore, during the roller transport process, portions of the first mask 400 located on the front and sides of the substrate 100 can be removed. This ensures uniform acid etching. Furthermore, the back side of the substrate 100 faces upwards and is covered with a water film to protect the back film structure. This ensures that the first mask 400 on the back side of the substrate 100 remains intact after the first acid etching. After the first acid etching, the substrate 100 generally needs to be washed and dried to remove residual acid and moisture.

[0048] Furthermore, in this embodiment, in the step of performing the first acid etching using a hydrofluoric acid solution, the temperature of the hydrofluoric acid solution is 10°C-20°C, the volume fraction of hydrofluoric acid in the hydrofluoric acid solution is 40%-60%, and the process time of the first acid etching is 100S-200S. More preferably, the process time of the first acid etching is 60S-80S.

[0049] After the first acid etching is completed, a laser can be used to etch the first mask 400 retained on the back side of the substrate 100 according to a preset trajectory, and remove the first mask 400 located in the second conductive region and the isolation region, see... Figure 5 In this way, the first doped layer 300 located in the second conductive region and the isolation region will also be exposed, while the first doped layer 300 and the first tunneling layer 200 located in the first conductive region can continue to be covered by the first mask 400.

[0050] Step S40: Remove the exposed first tunneling layer 200 and first doped layer 300 by a first alkaline etching.

[0051] Specifically, the exposed first tunneling layer 200 and first doped layer 300 refer to the first tunneling layer 200 and first doped layer 300 located in the second conductive region and isolation region on the front, side, and back sides of the substrate 100. Since the alkaline solution does not readily react with the first mask 400, the first tunneling layer 200 and first doped layer 300 located in the first conductive region will remain intact under the protection of the remaining first mask 400. After the first alkaline etching, the second conductive region and isolation region on the front, side, and back sides of the substrate 100 will also be exposed, see... Figure 6 .

[0052] After the first tunneling layer 200 and the first doped layer 300 on the front and side surfaces of the substrate 100 are etched with an alkaline solution, the first tunneling layer 200 and the first doped layer 300 that are coated around the front and side surfaces of the substrate 100 can be removed. In other words, the coating of the first tunneling layer 200 and the first doped layer 300 is removed in two steps, along with the coating of the first mask 400, using a combination of acid etching and alkaline etching. Furthermore, the acid etching process uses a single acid solution, eliminating the need for nitric acid and concentrated sulfuric acid; the main acid used in the process is hydrofluoric acid. Importantly, hydrofluoric acid has relatively mild chemical properties, minimizing chemical damage to the first tunneling layer 200 and the first doped layer 300 during the removal of the coating.

[0053] Optionally, in this embodiment, in the step of removing the exposed first tunneling layer 200 and first doped layer 300 by the first alkaline etching, the alkaline etching solution used is a mixture of sodium hydroxide and water, and the volume fraction of sodium hydroxide is 6%-14%. The process time of the first alkaline etching is 150S-200S, and the temperature of the alkaline etching solution is 75℃-85℃.

[0054] Alkaline etching involves immersing the entire substrate 100 in a bath containing an alkaline etching solution. A mixture of sodium hydroxide and water is effective for etching the first tunneling layer 200 and the first doped layer 300, but relatively mild on the first mask 400. Therefore, the decomposition of the first mask 400 located in the first conductive region is weaker during alkaline etching. Typically, after the first alkaline etching, the remaining thickness of the first mask 400 in the first conductive region is approximately 10 nm to 40 nm.

[0055] In step S50, a second tunneling layer 500, a second doped layer 600, and a second mask 700 are sequentially formed on the surface of the substrate 100 through a second high-temperature process.

[0056] The second high-temperature process is largely the same as the first high-temperature process. Generally, a low-pressure chemical vapor deposition process is used to sequentially form the second tunneling layer 500 and the second doped layer 600. Then, a high-temperature doping advance process is used to form the second mask 700 outside the second doped layer 600. The second mask 700 can be made of the same material as the first mask 400, but the doping elements and density differ, and its thickness is generally 55nm-65nm. The materials of the second tunneling layer 500 and the second doped layer 600 differ from those of the first tunneling layer 200 and the first doped layer 300.

[0057] Similar to the first high-temperature process, the second tunneling layer 500, the second doped layer 600, and the second mask 700 are not only formed on the back side of the substrate 100, but also deposited around to the sides and front side of the substrate 100. Furthermore, as... Figure 7 and Figure 8 As shown, on the back side of the substrate 100, since the first conductive region is still covered by the first tunneling layer 200, the first doped layer 300 and the first mask 400, the second tunneling layer 500, the second doped layer 600 and the second mask 700 located in the first conductive region will be formed sequentially on the surface of the first mask 400.

[0058] Similarly, specifically in this embodiment, in the second high-temperature process, the front surfaces of the two substrates 100 are facing each other and stacked. The second tunneling layer 500, the second doped layer 600, and the second mask 700 formed on the front surface of the substrates 100 are all located in the wrap-around plating area. That is, the second high-temperature process also adopts a "double-insertion" method. In this way, the second tunneling layer 500, the second doped layer 600, and the second mask 700 will not completely cover the front surface of the substrates 100, thereby improving production efficiency and saving solution in the subsequent removal of the wrap-around plating.

[0059] In step S60, a second acid etching is performed using hydrofluoric acid solution to remove the second mask 700 located on the front and side surfaces of the substrate 100, and a second patterning process is performed on the back surface of the substrate 100 using laser etching to remove the second mask 700 located in the first conductive area and the isolation area.

[0060] Similarly, the hydrofluoric acid solution can react with the second mask 700, but it does not readily react with the second doped layer 600. Therefore, when the front and side surfaces of the substrate 100 come into contact with the hydrofluoric acid solution, the corresponding portion of the second mask 700 can be removed, exposing the second doped layer 600. Figure 9 After the second acid etching is completed, a laser can be used to etch the second mask 700 retained on the back side of the substrate 100 according to a preset trajectory, and remove the second mask 700 located in the first conductive region and the isolation region, see... Figure 10 In this way, the second doped layer 600 located in the first conductive region and the isolation region will also be exposed, while the second doped layer 600 located in the second conductive region and the second tunneling layer 500 can continue to be covered by the second mask 700.

[0061] The process flow for the second acid etching is roughly the same as that for the first acid etching. Specifically, in this embodiment, in the step of using hydrofluoric acid solution for the second acid etching, the substrate 100 is placed in a chain etching machine. The surface of the etching tank of the chain etching machine is covered with multiple rollers, and the rollers are partially immersed in the hydrofluoric acid solution. The front of the substrate 100 faces the rollers and can enter the etching tank sequentially under the drive of the rollers.

[0062] More specifically, in this embodiment, in the step of performing the second acid etching using a hydrofluoric acid solution, the volume fraction of hydrofluoric acid in the hydrofluoric acid solution is 30%-50%, and the process time of the second acid etching is 80S-150S.

[0063] Step S70: Remove the exposed second tunneling layer 500 and second doped layer 600 by a second alkaline etching.

[0064] Specifically, the exposed second tunneling layer 500 and second doped layer 600 refer to the second tunneling layer 500 and second doped layer 600 located in the first conductive region and isolation region on the front, side, and back of the substrate 100. Since the alkaline solution does not readily react with the second mask 700, the second tunneling layer 500 and second doped layer 600 located in the second conductive region will remain intact under the protection of the remaining second mask 700. See Figure 11 As can be seen, after the second alkaline etching, the isolation areas on the front, side and back of the substrate 100 will be exposed, and the first mask 400 located in the first conductive area will also be exposed.

[0065] The process flow for the second alkaline etching is largely the same as that for the first alkaline etching, the difference being the composition of the alkaline etching solution. Optionally, in this embodiment, in the step of removing the exposed second tunneling layer 500 and second doped layer 600 by the second alkaline etching, the alkaline etching solution used is a mixture of sodium hydroxide, alkaline etching additive, and water.

[0066] Sodium hydroxide solution exhibits superior etching performance on the second tunneling layer 500 and the second doped layer 600, but is relatively milder on the second mask 700. Furthermore, the main component of the alkaline etching additive is a protective agent for the second mask, resulting in weaker decomposition of the second mask 700 during alkaline etching. Typically, after the second alkaline etching, the remaining thickness of the second mask 700 in the second conductive region is approximately 10 nm to 40 nm.

[0067] Furthermore, in this embodiment, in the second alkaline etching process, the volume fraction of sodium hydroxide in the alkaline etching solution is 2%-4%, and the volume fraction of the alkaline etching additive is 0.8%-1.2%. The process duration of the second alkaline etching is 120S-180S, and the temperature of the alkaline etching solution is 60℃-70℃.

[0068] Similarly, the plating around the second tunneling layer 500 and the second doped layer 600, as well as the plating around the second mask 700, are also removed in two steps, using a combination of acid etching and alkaline etching. Since the acid etching process uses a single acid solution, hydrofluoric acid, without the need for nitric acid or concentrated sulfuric acid, chemical damage to the second tunneling layer 500 and the second doped layer 600 in the second conductive region can be minimized during the plating removal process.

[0069] In step S80, a texturing process is used to form a texturing light-trapping structure in the exposed area of ​​the substrate 100, and a hydrofluoric acid solution is used to clean away the first mask 400 located in the first conductive region and the second mask 700 located in the second conductive region.

[0070] like Figure 12 As shown, after the second alkaline etching, the exposed areas of the substrate 100 include its front, side, and back isolation regions. In other words, the textured light-trapping structure formed by texturing is distributed across the front, side, and isolation regions of the substrate 100. This textured light-trapping structure enhances the overall light-trapping effect of the back-contact cell, thereby contributing to improved conversion efficiency.

[0071] Specifically, the texturing solution used in the alkaline texturing process is generally a mixture of sodium hydroxide, alkaline texturing additive, and water. The main component of the texturing additive is a texturing agent, with a volume fraction of sodium hydroxide of 0.8%-1.2% and a volume fraction of alkaline texturing additive of 0.5%-1.0%. The process duration of the alkaline texturing process is 450-600 seconds, and the process temperature is 65℃-80℃.

[0072] During the texturing process, the first tunneling layer 200 and the first doped layer 300 located in the first conductive region continue to be covered by the residual first mask 400, while the second tunneling layer 500 and the second doped layer 600 located in the second conductive region continue to be covered by the residual second mask 700. Therefore, it can effectively prevent the texturing solution from contacting the first tunneling layer 200, the first doped layer 300, the second tunneling layer 500, and the second doped layer 600, thereby better protecting the above functional film layers to avoid corrosion of the above functional film layers by the texturing solution.

[0073] After texturing is completed, the substrate 100 is rinsed and then placed in an acid pickling tank containing hydrofluoric acid to remove the remaining first mask 400 and second mask 700. This exposes the first doped layer 300 of the first conductive region and the second doped layer 600 of the second conductive region, which facilitates the extraction of the two electrodes of the back contact battery in subsequent processes.

[0074] In addition, such as Figure 13 and Figure 14 As shown, in this embodiment, the method for preparing the back contact battery further includes the steps of: forming a passivation layer 800 on the surface of the substrate 100, and forming metal electrodes 900 in the first conductive region and the second conductive region.

[0075] The passivation layer 800 generally serves to protect and reduce reflection, which helps to further improve the conversion efficiency. The metal electrode 900, according to the pattern of the first conductive area and the second conductive area, can lead out the two poles of the back contact battery, thereby obtaining a complete back contact battery.

[0076] The aforementioned method for fabricating a back-contact battery involves removing the front and side masks using hydrofluoric acid solution after each formation of the tunneling layer, doped layer, and mask. Then, an alkaline solution is used to etch away the exposed tunneling and doped layers, thus removing the wrap-around plating. Since this combination of acid and alkaline etching achieves the removal of the wrap-around plating, the use of nitric acid and concentrated sulfuric acid can be avoided. The primary acid used in the process is hydrofluoric acid. Hydrofluoric acid has relatively mild chemical properties, and its corrosiveness to the back-side tunneling and doped layers is far less than that of nitric acid or concentrated sulfuric acid. Therefore, the removal of the wrap-around plating minimizes chemical damage to the functional films in the first and second conductive regions, ensuring the integrity of the functional films and their electrical performance, thereby effectively improving battery quality.

[0077] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a back contact battery, characterized in that, Including the following steps: A substrate is provided, the back side of which has a first conductive region, a second conductive region, and an isolation region located between the first conductive region and the second conductive region; A first tunneling layer, a first doped layer, and a first mask are sequentially formed on the surface of the substrate through a first high-temperature process. The first acid etching is performed using hydrofluoric acid solution to remove the first mask located on the front and side surfaces of the substrate, and the first patterning process is performed on the back surface of the substrate using laser etching to remove the first mask located in the second conductive region and the isolation region. The first tunneling layer and the first doped layer are removed by a first alkaline etching process. A second high-temperature process is used to sequentially form a second tunneling layer, a second doped layer, and a second mask on the surface of the substrate. A second acid etching process is performed using hydrofluoric acid solution to remove the second mask located on the front and side surfaces of the substrate, and a second patterning process is performed on the back surface of the substrate using laser etching to remove the second mask located in the first conductive region and the isolation region. The exposed second tunneling layer and second doped layer are removed by a second alkaline etching. A texturing process is used to form a texturing light-trapping structure in the exposed area of ​​the substrate, and a hydrofluoric acid solution is used to clean away the first mask located in the first conductive area and the second mask located in the second conductive area.

2. The method for preparing a back contact battery according to claim 1, characterized in that, In the first high-temperature process and the second high-temperature process, the front sides of the two substrates are facing each other and stacked, and a plating area distributed along the edge and a non-plating area located in the middle of the plating area are formed on the front side of each substrate. The first tunneling layer, the first doped layer, the first mask, the second tunneling layer, the second doped layer and the second mask formed on the front side of the substrate are all located in the plating area.

3. The method for preparing a back contact battery according to claim 1, characterized in that, In the steps of performing the first etching and the second etching using hydrofluoric acid solution, the substrate is placed in a chain etching machine. The surface of the etching tank of the chain etching machine is covered with multiple rollers, and the rollers are partially immersed in the hydrofluoric acid solution. The front of the substrate faces the rollers and can enter the etching tank sequentially under the drive of the rollers.

4. The method for preparing a back contact battery according to claim 1, characterized in that, In the first acid etching step using hydrofluoric acid solution, the temperature of the hydrofluoric acid solution is 10℃-20℃, the volume fraction of hydrofluoric acid in the hydrofluoric acid solution is 40%-60%, and the process time of the first acid etching is 100S-200S.

5. The method for preparing a back contact battery according to claim 4, characterized in that, The first acid etching process takes 60-80 seconds.

6. The method for preparing a back contact battery according to claim 1, characterized in that, In the second acid etching step using a hydrofluoric acid solution, the volume fraction of hydrofluoric acid in the hydrofluoric acid solution is 30%-50%, and the process time for the second acid etching is 80S-150S.

7. The method for preparing a back contact battery according to claim 1, characterized in that, In the step of removing the exposed first tunneling layer and the first doped layer by the first alkaline etching, the alkaline etching solution used is a mixture of sodium hydroxide and water, and the volume fraction of sodium hydroxide is 6%-14%. The process time of the first alkaline etching is 150-200 seconds, and the temperature of the alkaline etching solution is 75°C-85°C.

8. The method for preparing a back contact battery according to claim 1, characterized in that, In the step of removing the exposed second tunneling layer and second doped layer by a second alkaline etching, the alkaline etching solution used is a mixture of sodium hydroxide, alkaline etching additive and water.

9. The method for preparing a back contact battery according to claim 8, characterized in that, The volume fraction of sodium hydroxide is 2%-4%, the volume fraction of alkaline etching additive is 0.8%-1.2%, the process duration of the second alkaline etching is 120S-180S, and the temperature of the alkaline etching solution is 60℃-70℃.

10. The method for preparing a back contact battery according to any one of claims 1 to 9, characterized in that, It also includes the steps of: forming a passivation layer on the surface of the substrate and forming metal electrodes in the first conductive region and the second conductive region.

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