Solar cell manufacturing method and solar cell

Abstract

The present application relates to a method for preparing a solar cell and a solar cell. The solar cell includes a substrate, wherein the first surface of the substrate has a plurality of first regions and a plurality of second regions distributed in an alternating manner, the second region including a first sub-region and a second sub-region distributed along a first direction; the first region is provided with a tunneling oxide layer and a first doped conductive layer. The preparation method includes: providing a substrate, sequentially preparing a tunneling oxide layer, a first doped conductive layer, and a dielectric layer on the first surface; patterning the second region using a first laser, sequentially modifying the dielectric layer within the plurality of first sub-regions into a loose structure along the first direction; patterning the second region using a second laser, sequentially modifying the dielectric layer within the plurality of second sub-regions into a loose structure along the first direction; and removing the modified dielectric layer, first doped conductive layer, and tunneling oxide layer within the second region. This preparation method can reduce surface defects on the cell and improve the cell's conversion efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of solar cell production, and in particular to a method for preparing a solar cell and a solar cell. Background Art

[0002] The back of the TOPCon cell is equipped with a passivation contact structure consisting of a tunneling oxide layer and a first doped conductive layer. An excessively thick first doped conductive layer will cause parasitic absorption of infrared light on the back of the silicon wafer, resulting in low electron mobility and heavy carrier recombination losses. This will lead to a series of problems such as poor long-wave response and low bifaciality of silicon solar cells, thus restricting further improvement of solar cell conversion efficiency.

[0003] In existing technology, laser patterning is typically used to modify the oxide layer on the non-metallic surface of the back of a TOPCon cell. This modified oxide layer and the passivation contact structure within the non-metallic area are then cleaned and removed to reduce parasitic absorption in the non-metallic area. However, due to the limitations of laser technology, the width of existing lasers is very small, and the oxide layer within the same non-metallic area requires two lasers to be processed. However, the oxide layer in the area treated by the two lasers will form a denser oxide due to secondary melting in a short period of time. This makes it impossible to completely clean the passivation contact structure in this area during subsequent cleaning steps, thereby affecting the photovoltaic conversion efficiency of the solar cell. Summary of the Invention

[0004] In view of this, the present application provides a method for preparing a solar cell and a solar cell, so as to solve the problem in the prior art that defects in the laser patterning process step result in low photoelectric conversion efficiency of the solar cell.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a solar cell, wherein the solar cell includes a substrate, the substrate having a first surface, the first surface having a plurality of first regions and a plurality of second regions staggered along a first direction, the second region including a first sub-region and a second sub-region distributed along the first direction, the first sub-region and the second sub-region having an overlapping region in the first direction; along the thickness direction of the substrate toward a direction away from the substrate, the first region is sequentially provided with a tunneling oxide layer, a first doped conductive layer and a dielectric layer; the preparation method includes: providing a substrate, sequentially preparing the tunneling oxide layer, the first doped conductive layer and the dielectric layer on the first surface; using a first laser to perform patterning on the second region, the first laser sequentially modifying the dielectric layer in the first sub-region of the plurality of second regions into a loose structure along the first direction; using a second laser to perform patterning on the second region, the second laser sequentially modifying the dielectric layer in the second sub-region of the plurality of second regions into a loose structure along the first direction; removing the modified dielectric layer, the first doped conductive layer and the tunneling oxide layer in the second region; the first direction is perpendicular to the thickness direction of the substrate.

[0006] In one possible implementation, when removing the modified dielectric layer, the first doped conductive layer and the tunneling oxide layer in the second region, the preparation method specifically includes: a first alkaline washing to remove the modified dielectric layer and part of the first doped conductive layer in the second region; water washing; and a second alkaline washing to remove the remaining first doped conductive layer and tunneling oxide layer in the second region.

[0007] In one possible implementation, the first alkaline washing uses a NaOH solution with a concentration of 3% to 3.5% and a treatment time of 100s to 200s; and / or, the second alkaline washing uses a NaOH solution with a concentration of 2.9% to 3.1% and a treatment time of 100s to 200s.

[0008] In a possible implementation, the power of the first laser is 50W to 55W; and / or the power of the second laser is 50W to 55W.

[0009] In a possible implementation, the frequency of the first laser is 500 kHz to 600 kHz; and / or the frequency of the second laser is 500 kHz to 600 kHz.

[0010] In a possible implementation, the scanning speed of the first laser is 55,000 mm / s to 60,000 mm / s; and / or the scanning speed of the second laser is 55,000 mm / s to 60,000 mm / s.

[0011] In a possible implementation, a size of the first laser spot in the first direction is 100 μm to 500 μm; and / or a size of the second laser spot in the first direction is 100 μm to 500 μm.

[0012] In a possible implementation manner, a size of the overlapping area in the first direction is 100 μm to 200 μm.

[0013] In one possible implementation, when the second area is patterned using a first laser, the scanning path of the first laser is S-shaped; and / or, when the second area is patterned using a second laser, the scanning path of the second laser is S-shaped.

[0014] In second aspect, an embodiment of the present application provides a solar cell, which is manufactured using the above-described method for preparing a solar cell, and the solar cell includes at least: a substrate having a first surface, the first surface having a plurality of first regions and a plurality of second regions staggered along a first direction; a tunneling oxide layer arranged in the first region; and a first doped conductive layer arranged on a side surface of the tunneling oxide layer away from the substrate.

[0015] In the present application, a first laser can sequentially modify the dielectric layer within multiple first sub-regions along a first direction into a loose structure. The modified dielectric layer can react with a subsequent cleaning solution, thereby facilitating the removal of the dielectric layer, first doped conductive layer, and tunneling oxide layer within the first sub-region. A second laser can sequentially modify the dielectric layer within multiple second sub-regions along the first direction into a loose structure. The modified dielectric layer can react with a cleaning solution, thereby facilitating the removal of the dielectric layer, first doped conductive layer, and tunneling oxide layer within the second sub-region. The first and second sub-regions need to overlap to ensure that the dielectric layer within the second region is modified by the laser treatment, thereby avoiding the situation in which the first doped conductive layer and tunneling oxide layer in the area covered by the unmodified dielectric layer cannot react with the cleaning solution due to the presence of unmodified dielectric layer in subsequent steps. Furthermore, in this embodiment, the first laser is first used to treat the multiple first sub-regions along the first direction, and then the second laser is used to treat the multiple second sub-regions along the first direction, so that there is an interval between the treatment times of the first sub-regions and the second sub-regions within the same second region. When the second sub-region is processed by the second laser, the dielectric layer in the first sub-region located in the same second region as the second sub-region has completed cooling, thereby preventing the dielectric layer in the overlapping area of ​​the first sub-region and the second sub-region in the same second region from undergoing secondary melting in a short period of time to form a denser oxide, thereby ensuring that the dielectric layer, the first doped conductive layer and the tunnel oxide layer in the second region can all react with the cleaning solution in subsequent steps and be completely removed, thereby reducing defects on the first surface and facilitating improved photoelectric conversion efficiency of the solar cell.

[0016] It should be understood that the foregoing general description and the following detailed description are merely illustrative and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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 use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 A schematic diagram of the cross-sectional structure of a solar cell provided in this application;

[0019] Figure 2 for Figure 1 A schematic structural diagram of the backlight side of the solar cell in the first embodiment;

[0020] Figure 3 for Figure 2A magnified view of the local structure in

[0021] Figure 4 for Figure 1 A schematic structural diagram of the backlight surface of the solar cell in the second embodiment;

[0022] Figure 5 for Figure 4 A magnified view of the local structure in

[0023] Figure 6 A flow chart of the method for preparing a solar cell provided in this application;

[0024] Figure 7 This is a schematic structural diagram of the process for preparing a solar cell provided in this application when a dielectric layer is formed;

[0025] Figure 8 This is a schematic structural diagram of the first laser treatment in the method for preparing a solar cell provided in this application;

[0026] Figure 9 This is a schematic structural diagram of the second laser treatment in the method for preparing a solar cell provided in this application;

[0027] Figure 10 A flow chart of the method for preparing a solar cell provided in this application;

[0028] Figure 11 for Figure 10 Schematic diagram of the process flow corresponding to the preparation method;

[0029] Figure 12 A schematic diagram of the scanning paths of the first laser and the second laser in the first solar cell structure;

[0030] Figure 13 A schematic diagram of the scanning paths of the first laser and the second laser in the second solar cell structure;

[0031] Figure 14 A flow chart of the method for preparing a solar cell provided in this application;

[0032] Figure 15 for Figure 14 Schematic diagram of the process flow corresponding to the preparation method;

[0033] Figure 16 A flow chart of the method for preparing a solar cell provided in this application;

[0034] Figure 17 for Figure 16 Schematic diagram of the process flow corresponding to the preparation method.

[0035] Reference numerals:

[0036] 1-base;

[0037] 1a-first surface;

[0038] 1b-second surface;

[0039] 11-First area;

[0040] 12-Second area;

[0041] 121-first sub-area;

[0042] 122-second sub-area;

[0043] 2- tunneling oxide layer;

[0044] 3-first doped conductive layer;

[0045] 4- dielectric layer;

[0046] 5- first electrode;

[0047] 51-first main grid;

[0048] 52-first secondary grid;

[0049] 61-first anti-reflection layer;

[0050] 62-first passivation layer;

[0051] 7-second doped conductive layer;

[0052] 81- second anti-reflection layer;

[0053] 82- second passivation layer;

[0054] 9-Second electrode. DETAILED DESCRIPTION

[0055] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0056] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0057] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0058] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. Furthermore, the character " / " in this document generally indicates an "or" relationship between the associated objects.

[0059] The embodiment of the present application provides a solar cell, such as Figure 1 As shown, the solar cell is a TOPCon cell, comprising a substrate 1, which can be an N-type substrate or a P-type substrate. The N-type substrate 1 can be a silicon substrate doped with an N-type element, and the N-type element can specifically be one or a combination of pentavalent elements such as phosphorus, arsenic, or antimony. The P-type substrate 1 can be a silicon substrate doped with a P-type element, and the P-type element can specifically be one or a combination of trivalent elements such as boron, indium, or gallium. The structure of the solar cell is described below using the substrate 1 as an N-type substrate as an example. The substrate 1 includes a first surface 1a and a second surface 1b that are relatively distributed along its thickness direction Z. The first surface 1a is specifically the backlight side of the substrate 1, that is, the surface that is not directly exposed to sunlight, and the second surface 1b is specifically the light-facing side of the substrate 1, that is, the surface that can be directly exposed to sunlight. Both the first surface 1a and the second surface 1b can receive sunlight and convert light energy into electrical energy.

[0060] like Figure 1 As shown, the first surface 1a has a first region 11 and a second region 12 that are staggered along a first direction X, and the first direction X is perpendicular to the thickness direction Z of the substrate 1. The first region 11 is specifically a metallized region, and the second region is specifically a non-metallized region. Along the thickness direction Z of the substrate 1 toward the direction away from the substrate 1, a tunneling oxide layer 2 and a first doped conductive layer 3 are sequentially arranged in the first region 11. The tunneling oxide layer 2 and the first doped conductive layer 3 form a passivation contact structure. The tunneling oxide layer 2 may include at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, amorphous silicon, and polycrystalline silicon, and can chemically passivate the first surface 1a, thereby reducing the recombination center at the contact surface between the tunneling oxide layer 2 and the substrate 1, thereby reducing the recombination rate of carriers at the contact surface between the substrate 1 and the tunneling oxide layer 2. The first doped conductive layer 3 may include at least one of N-type doped amorphous silicon, N-type doped polycrystalline silicon, N-type doped microcrystalline silicon and N-type doped silicon carbide, and is used to form a field passivation layer, which can reduce the minority carrier concentration and realize the selective transmission of majority carriers, thereby reducing the carrier recombination rate.

[0061] Along the thickness direction Z of the substrate 1, a first passivation layer 62 is further provided on the surface of the first doped conductive layer 3 away from the tunneling oxide layer 2, and a first anti-reflection layer 61 is further provided on the surface of the first passivation layer 62 away from the first doped conductive layer 3. The surface of the second region 12 is also provided with a first passivation layer 62 and a first anti-reflection layer 61 stacked along the thickness direction Z of the substrate 1. The first anti-reflection layer 61 in the first region 11 and the first anti-reflection layer 61 in the second region 12 can be a single unitary structure, and the first passivation layer 62 in the first region 11 and the first passivation layer 62 in the second region 12 can be a single unitary structure. The first anti-reflection layer 61 utilizes thin-film interference to reduce light reflection and increase the incidence of light incident on the first surface 1a. Specifically, it can be a silicon oxide layer or an aluminum oxide layer. The first passivation layer 62 may include at least one of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide and aluminum oxide, which can play a good passivation role, enhance the carrier concentration of the first surface 1a, and improve the short-circuit current and open-circuit voltage of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0062] The first region 11 is also provided with a first electrode 5, which specifically serves as the negative electrode of the solar cell. At least a portion of the structure of the first electrode 5 can penetrate the first anti-reflection layer 61 and the first passivation layer 62 to form an electrical connection with the first doped conductive layer 3. The passivation contact structure formed by the first electrode 5, the tunneling oxide layer 2, and the doped conductive layer 2 is only provided within the first region 11. This can reduce metal contact recombination between the passivation contact structure and the first electrode 5, thereby improving the first electrode 5's ability to collect carriers.

[0063] like Figure 1 As shown, along the thickness direction Z of the substrate 1, in a direction away from the substrate 1, the second surface 1b of the solar cell is sequentially provided with a second doped conductive layer 7, a second passivation layer 82, and a second anti-reflection layer 81. The second doped conductive layer 7 may include at least one of P-type doped amorphous silicon, P-type doped polycrystalline silicon, P-type doped microcrystalline silicon, and P-type doped silicon carbide, and is used to form a field passivation layer, which can reduce the concentration of minority carriers and achieve selective transmission of majority carriers, thereby reducing the carrier recombination rate. The second anti-reflection layer 81 uses thin film interference to reduce light reflection and increase the incidence rate of light incident on the second surface 1b. Specifically, it can be a silicon oxide layer or an aluminum oxide layer. The second passivation layer 82 may include at least one of silicon oxide, silicon nitride, silicon oxynitride, titanium oxide, and aluminum oxide, and can provide a good passivation effect, enhance the carrier concentration of the second surface 1b, and increase the short-circuit current and open-circuit voltage of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0064] The second surface 1 b is further provided with a second electrode 9 , which is specifically the positive electrode of the solar cell. At least a portion of the second electrode 9 can penetrate the second anti-reflection layer 81 and the second passivation layer 82 to form an electrical connection with the second doped conductive layer 7 .

[0065] In a specific embodiment, the solar cell can be a main grid cell, the first electrode 5 includes a first main grid 51 and a first fine grid 52, the first main grid 51 and the first fine grid 52 together constitute the negative electrode of the solar cell. The second electrode 9 includes a second main grid and a second fine grid, the second main grid and the second fine grid together constitute the positive electrode of the solar cell. Figure 2 As shown, when the solar cell is a busbar cell, the first fine grid 52 extends along the first direction X, and the first busbar 51 extends along the second direction Y. The first direction X and the second direction Y are perpendicular to each other, and the first direction X and the second direction Y are respectively perpendicular to the thickness direction Z of the substrate 1. Figure 3 As shown, when the solar cell is a busbar cell, the first regions 11 and the second regions 12 are alternately arranged not only in the first direction X but also in the second direction Y.

[0066] In another specific embodiment, the solar cell may also be a busbar-less cell. In this case, the first electrode 5 only includes the first fine grid 52, which is the negative electrode of the solar cell. The second electrode 9 only includes the second fine grid, which is the positive electrode of the solar cell. Figure 4 As shown, when the solar cell is a busbar-less cell, a plurality of first fine grids 52 are spaced apart along the first direction X, and the first fine grids 52 extend along the second direction Y, as shown in FIG. Figure 5 As shown, when the solar cell is a busbar-less cell, the first regions 11 and the second regions 12 are alternately arranged only in the first direction X.

[0067] It should be noted that Figure 2-Figure 4 The number of the first main grid 51 and the second fine grid 52 is only for illustration and does not represent the actual number in the solar cell structure. This embodiment does not limit the specific number of the first main grid 51 and the second fine grid 52.

[0068] The present application also provides a method for preparing a solar cell, which is used to prepare the solar cell described above. Figure 6 As shown, the preparation method comprises:

[0069] Step S1: providing a substrate 1, and sequentially preparing a tunneling oxide layer 2, a first doped conductive layer 3 and a dielectric layer 4 on a first surface 1a of the substrate 1.

[0070] like Figure 7As shown, in this step, a deposition process can be used to form a tunneling oxide layer 2 on the first surface 1a of the substrate 1. A deposition process can also be used to form a first doped conductive layer 3 on the back side of the tunneling oxide layer 2. A deposition process can also be used to form a dielectric layer 4 on the back side of the first doped conductive layer 3. The dielectric layer 4 can include at least one of silicon oxide, silicon nitride, aluminum oxide, or silicon oxynitride. When the doping element in the first doped conductive layer 3 is phosphorus, the dielectric layer 4 can be a phosphosilicate glass layer. In this embodiment, the dielectric layer 4 is described as a phosphosilicate glass layer.

[0071] Among them, the deposition process can specifically be an atomic layer deposition process or a vapor deposition process. This embodiment can adopt plasma enhanced chemical vapor deposition technology, which has a fast deposition rate and good thickness and composition uniformity of the formed structural layer, which is beneficial to improving the stability and preparation efficiency of the passivation contact structure composed of the tunneling oxide layer 2 and the first doped conductive layer 3.

[0072] Step S2: patterning the second region 12 with a first laser. The first laser modifies the dielectric layer 4 in the first sub-regions 121 of the plurality of second regions 12 into a loose structure in sequence along the first direction X.

[0073] Step S3: patterning the second region 12 with a second laser. The second laser modifies the dielectric layer 4 in the second sub-regions 122 of the plurality of second regions 12 into a loose structure in sequence along the first direction X.

[0074] In steps S2 and S3 above, the first surface 1a has a plurality of first regions 11 and a plurality of second regions 12 that are staggeredly distributed along the first direction X. The second region 12 includes a first sub-region 121 and a second sub-region 122 that are distributed along the first direction X. The first sub-region 121 and the second sub-region 122 have an overlapping area in the first direction X. The first sub-region 121 is specifically a predetermined area to be processed by the first laser, and the second sub-region 122 is specifically a predetermined area to be processed by the second laser.

[0075] like Figure 8 As shown, the first laser can sequentially modify the dielectric layer 4 in the plurality of first sub-regions 121 in the first direction X into a loose structure, and the modified dielectric layer 4 can react with the subsequent cleaning solution, thereby facilitating the removal of the dielectric layer 4, the first doped conductive layer 3 and the tunneling oxide layer 2 in the first sub-region 121. Figure 9 As shown, the second laser can modify the dielectric layer 4 in multiple second sub-regions 122 in the first direction X into a loose structure in sequence, and the modified dielectric layer 4 can react with the subsequent cleaning solution, thereby facilitating the removal of the dielectric layer 4, the first doped conductive layer 3 and the tunneling oxide layer 2 in the second sub-region 122.

[0076] The first sub-region 121 and the second sub-region 122 need to overlap to ensure that the dielectric layer 4 within the second region 12 can be modified through laser treatment, thereby preventing the first doped conductive layer 3 and the tunnel oxide layer 2 in the area covered by the unmodified dielectric layer 4 from reacting with the cleaning solution in subsequent steps due to the presence of the unmodified dielectric layer 4. Furthermore, in this embodiment, a first laser is first used to treat the plurality of first sub-regions 121 along the first direction X, and then a second laser is used to treat the plurality of second sub-regions 122 along the first direction X, so that there is an interval between the treatment times of the first sub-regions 121 and the second sub-regions 122 within the same second region 12. When the second sub-region 122 is processed by the second laser, the dielectric layer 4 in the first sub-region 121 in the same second region 12 as the second sub-region 122 has completed cooling, thereby preventing the dielectric layer 4 in the overlapping area of ​​the first sub-region 121 and the second sub-region 122 in the same second region 12 from undergoing secondary melting in a short period of time to form a denser oxide, thereby ensuring that the dielectric layer 4, the first doped conductive layer 3 and the tunneling oxide layer 2 in the second region 12 can all react with the cleaning solution in subsequent steps and be completely removed, thereby reducing defects on the first surface 1a and facilitating improved photoelectric conversion efficiency of the solar cell.

[0077] Step S4: removing the modified dielectric layer 4 , the first doped conductive layer 3 and the tunneling oxide layer 2 in the second region 12 .

[0078] In this step, the dielectric layer 4 in the second region 12 is modified into a loose structure by laser treatment, so that the dielectric layer 4 in the second region 12 can react with the cleaning solution and be removed. After the dielectric layer 4 in the second region 12 is removed, the first doped conductive layer 3 in the second region 12 can be exposed, and the first doped conductive layer 3 and the tunneling oxide layer 2 in the second region 12 can react with the cleaning solution and be removed.

[0079] Specifically, if Figure 10 and Figure 11 As shown, the specific method of step S4 includes:

[0080] Step S41 : performing a first alkaline washing to remove the modified dielectric layer 4 and a portion of the first doped conductive layer 3 in the second region 12 .

[0081] In this step, the first alkaline washing can be performed by tank alkaline washing. Specifically, the alkaline washing solution can be a NaOH solution with a concentration of 3% to 3.5%. The solar cell is placed in a cleaning tank filled with the alkaline washing solution for 100s to 300s, thereby removing the modified dielectric layer 4 and part of the first doped layer 3 (such as Figure 11As shown in the above figure). Wherein, the concentration of the NaOH solution can be specifically 3%, 3.05%, 3.1%, 3.15%, 3.2%, 3.25%, 3.3%, 3.35%, 3.4%, 3.45% or 3.5%, or other values ​​within the above range, which is not limited in this embodiment. The processing time can be specifically 100s, 120s, 140s, 160s, 180s, 200s, 220s, 250s, 280s or 300s, or other values ​​within the above range, which is not limited in this embodiment. When the solution concentration and processing time of the first alkali washing meet the above range, excessive etching in the alkali washing process can be avoided, and impurities can be prevented from diffusing into the interior of the substrate 1, thereby reducing the impact of the alkali washing process on the performance of the solar cell.

[0082] It should be noted that the dielectric layer 4 in the first region 11 does not react with the alkaline cleaning solution because it has not undergone laser modification. Therefore, the dielectric layer 4 in the first region 11 can protect the first doped conductive layer 3 and the tunneling oxide layer 2 in the first region 11 from reacting with the alkaline cleaning solution.

[0083] Step S42: washing with water.

[0084] In this step, water washing can remove the residual alkaline wash solution from the first washing on the surface of the solar cell to prevent it from affecting subsequent processing. Specifically, the water used for water washing can be deionized water. To ensure the effectiveness of the water washing process, the water washing time can be 100 seconds to 150 seconds, specifically 100 seconds, 110 seconds, 120 seconds, 130 seconds, 140 seconds, or 150 seconds, or other values ​​within the above range, which are not limited in this embodiment.

[0085] Step S43 : performing a second alkaline washing to remove the remaining first doped conductive layer 3 and tunnel oxide layer 2 in the second region 12 .

[0086] In this step, the second alkaline washing can be performed in a tank-type alkaline washing manner. Specifically, the alkaline washing solution can be a NaOH solution with a concentration of 2.9% to 3.1%. The solar cell is placed in a cleaning tank filled with the alkaline washing solution for 100s to 200s to remove the remaining first doped conductive layer 3 and the tunneling oxide layer 2 (such as Figure 11). The concentration of the NaOH solution can specifically be 2.9%, 2.95%, 3%, 3.05%, or 3.1%, or it can be other values ​​within the above range, and this embodiment does not limit this. The processing time can specifically be 100s, 120s, 140s, 160s, 180s or 200s, or it can be other values ​​within the above range, and this embodiment does not limit this. When the solution concentration and processing time of the second alkali washing meet the above ranges, excessive etching during the alkali washing process can be avoided, and impurities can be prevented from diffusing into the interior of the substrate 1, thereby reducing the impact of the alkali washing process on the performance of the solar cell.

[0087] Moreover, during the second alkali wash, a certain amount of etching additives can be added to the alkali wash solution to control the reaction rate of the alkali wash solution, thereby controlling the etching depth of the second alkali wash, avoiding over-etching, and helping to reduce damage to the silicon wafer surface during the etching process and maintain good surface quality. Specifically, the etching additive can be ammonium fluoride (NH4F) or potassium hydroxide (KOH), or other additives, which are not limited in this embodiment. The amount of the additive added can be adjusted according to the reaction rate of the alkali wash solution and the specific thickness of the first doped conductive layer 3 and the tunneling oxide layer 2, which is not limited in this embodiment.

[0088] In a specific embodiment, for step S2 and step S3, when the solar cell is a busbar-less cell, the specific scanning paths of the first laser and the second laser are as follows: Figure 12 As shown, the solid arrow indicates the scanning path of the first laser, and the dotted arrow indicates the scanning path of the second laser. Figure 12 The arrows and dashed arrows in FIG are only used to illustrate the scanning paths and forward directions of the first laser and the second laser, and are not used to limit the scanning starting point, scanning end point or scanning width of the first laser and the second laser. Figure 8 As shown, the first laser is used to sequentially scan the first sub-regions 121 of the plurality of second regions 12 along the first direction X, and when the first laser scans each first sub-region 121, it scans along the second direction Y to ensure that the first laser can completely scan each first sub-region 121. Furthermore, in order to improve the scanning efficiency of the first laser and reduce the moving distance of the laser, the scanning path of the first laser on the first surface 1a can be S-shaped, that is, the scanning end point of the first laser in one of the first sub-regions 121 and the scanning starting point of the first laser in another adjacent first sub-region 121 are located on the same side of the second direction Y. Similarly, as Figure 8 and Figure 12As shown, the second laser is used to sequentially scan the second sub-regions 122 within the plurality of second regions 12 along the first direction X. When scanning each second sub-region 122, the second laser scans along the second direction Y to ensure that the second laser can completely scan each second sub-region 122. Furthermore, to improve the scanning efficiency of the second laser and reduce the travel distance of the laser, the scanning path of the second laser on the first surface 1a can be S-shaped, i.e., the scanning endpoint of the second laser in one second sub-region 122 and the scanning starting point of the first laser in another adjacent second sub-region 122 are located on the same side of the second direction Y.

[0089] When the solar cell is a main grid cell, the specific scanning paths of the first laser and the second laser are as follows: Figure 13 As shown, the solid arrow indicates the scanning path of the first laser, and the dotted arrow indicates the scanning path of the second laser. Figure 13 The arrows and dashed arrows in FIG are only used to illustrate the scanning paths and forward directions of the first laser and the second laser, and are not used to limit the scanning starting point, scanning end point or scanning width of the first laser and the second laser. Figure 8 As shown, the first laser is used to perform multiple scans along the first direction X, and each first laser scans along the second direction Y, so that the first sub-regions 121 of the multiple second regions 12 can be scanned in sequence, and it is ensured that the first laser can completely scan each first sub-region 121. Furthermore, in order to improve the scanning efficiency of the first laser and reduce the moving distance of the laser, the scanning path of the first laser on the first surface 1a can be S-shaped. That is, the scanning end point of one of the first lasers and the scanning starting point of another first laser adjacent to the first direction X are located on the same side of the second direction Y. Similarly, as Figure 8 and Figure 13 As shown, the second laser is used to perform multiple scans along the first direction X, and each second laser scans along the second direction Y, thereby being able to sequentially scan the second sub-regions 122 of multiple second regions 12, and ensuring that the second laser can completely scan each second sub-region 122. Furthermore, in order to improve the scanning efficiency of the second laser and reduce the movement distance of the laser, the scanning path of the second laser on the first surface 1a can be S-shaped, that is, the scanning end point of one second laser and the scanning starting point of another second laser adjacent along the first direction X are located on the same side in the second direction Y.

[0090] It should be noted that when the solar cell is a main-grid cell, the first area 11 and the second area 12 are distributed in a grid pattern on the first surface 1a. Therefore, when each first laser and each second laser scan in the second direction Y, they are scanned at intervals. The specific scanning paths of the first laser and the second laser can be input into the laser machine, which controls the laser to perform laser operations in a specific pattern.

[0091] In this embodiment, the first laser and the second laser can use the same laser. First, the laser parameters are adjusted to the corresponding parameters of the first laser. Then, starting from the scanning starting point of the first laser, a plurality of first sub-regions 121 are scanned along an S-shaped path. Then, the laser parameters are adjusted to the corresponding parameters of the second laser and the laser is moved to the scanning starting point of the second laser. Then, starting from the scanning starting point of the second laser, a plurality of second sub-regions 122 are scanned along an S-shaped path. In order to ensure that the overlapping portion of the first sub-region 121 and the second sub-region 122 within the same second region 12 does not undergo secondary melting, the scanning starting point of the first laser and the scanning starting point of the second laser should be located on the same side of the first direction X. In order to further improve the scanning efficiency of the laser in the laser patterning step and reduce the total movement path of the laser, the scanning end point of the first laser and the scanning starting point of the second laser can be located on the same side of the second direction Y.

[0092] In a specific embodiment, the power of the first laser can be 50W to 55W, and the frequency of the first laser can be 500kHz to 600kHz, and / or the power of the second laser can be 50W to 55W, and the frequency of the second laser can be 500kHz to 600kHz. The power of the first laser and the power of the second laser can be the same or different, and the frequency of the first laser and the frequency of the second laser can be the same or different, and this embodiment does not impose any restrictions on this.

[0093] When the power and frequency of the first laser light fall within the aforementioned ranges, sufficient energy can be ensured for the first laser light, thereby ensuring the treatment depth and effectiveness of the first laser light treatment and preventing unmodified portions of the dielectric layer 4 within the first sub-region 121. The power of the first laser light can be 50 W, 51 W, 52 W, 53 W, 54 W, or 55 W, or other values ​​within the aforementioned ranges, which are not limited in this embodiment. The frequency of the first laser light can be 500 kHz, 510 kHz, 520 kHz, 530 kHz, 540 kHz, 550 kHz, 560 kHz, 570 kHz, 580 kHz, 590 kHz, or 600 kHz, or other values ​​within the aforementioned ranges, which are not limited in this embodiment.

[0094] Similarly, when the power and frequency of the second laser light fall within the aforementioned ranges, the second laser light can be ensured to have sufficient energy, thereby ensuring the treatment depth and effectiveness of the first laser light and preventing unmodified portions of the dielectric layer 4 within the second sub-region 122. The power of the second laser light can be 50 W, 51 W, 52 W, 53 W, 54 W, or 55 W, or other values ​​within the aforementioned ranges, which are not limited in this embodiment. The frequency of the second laser light can be 500 kHz, 510 kHz, 520 kHz, 530 kHz, 540 kHz, 550 kHz, 560 kHz, 570 kHz, 580 kHz, 590 kHz, or 600 kHz, or other values ​​within the aforementioned ranges, which are not limited in this embodiment.

[0095] In a specific embodiment, the scanning speed of the first laser is 55,000 mm / s to 60,000 mm / s, and / or the scanning speed of the second laser is 55,000 mm / s to 60,000 mm / s. The scanning speed of the first laser and the scanning speed of the second laser can be the same or different, and this embodiment does not impose any limitation on this.

[0096] When the scanning speed of the first laser falls within the above range, it is beneficial to improve the scanning efficiency of the first laser on the first sub-region 121, thereby improving the efficiency of the laser patterning process, and preventing the formation of dense oxides in part of the dielectric layer 4 due to excessive scanning speed. The scanning speed of the first laser can be specifically 55,000 mm / s, 56,000 mm / s, 57,000 mm / s, 58,000 mm / s, 59,000 mm / s, or 60,000 mm / s, or other values ​​within the above range, and this embodiment does not impose any limitation thereto.

[0097] Similarly, when the scanning speed of the second laser falls within the aforementioned range, it is beneficial to improve the scanning efficiency of the second laser on the second sub-region 122, thereby improving the efficiency of the laser patterning process, and preventing the formation of dense oxides in part of the dielectric layer 4 due to excessively fast scanning speeds. The scanning speed of the second laser can specifically be 55,000 mm / s, 56,000 mm / s, 57,000 mm / s, 58,000 mm / s, 59,000 mm / s, or 60,000 mm / s, or other values ​​within the aforementioned range, and this embodiment does not impose any limitation thereto.

[0098] In a specific embodiment, the size of the first laser spot in the first direction X should be 100 μm to 500 μm, and / or the size of the second laser spot in the first direction X should be 100 μm to 500 μm. The size of the first laser spot in the first direction X and the size of the second laser spot in the first direction X may be the same as or different from each other, and this embodiment does not impose any limitation on this.

[0099] When the size of the first laser spot in the first direction X is 100 μm to 500 μm, the size of the first sub-region 121 in the first direction X is correspondingly 100 μm to 500 μm, which can increase the processing width of the first laser without affecting the processing effect of the first laser. The size of the first laser spot in the first direction X can be 100 μm, 200 μm, 300 μm, 400 μm, or 500 μm, or other values ​​within the above range, and this embodiment is not limited to this.

[0100] Similarly, when the size of the second laser spot in the first direction X is 100 μm to 500 μm, the size of the second sub-region 122 in the first direction X is correspondingly 100 μm to 500 μm, which can increase the processing width of the second laser without affecting the processing effect of the second laser. The size of the second laser spot in the first direction X can specifically be 100 μm, 200 μm, 300 μm, 400 μm, or 500 μm, or other values ​​within the above range, and this embodiment is not limited to this.

[0101] Specifically, the size of the overlapping area between the first sub-area 121 and the second sub-area 122 in the first direction X is 100 μm to 200 μm, that is, the size of the area repeatedly processed by the first laser and the second laser in the first direction X should be 100 μm to 200 μm. This ensures that the first laser and the second laser can process the entire dielectric layer 4 in the second area 12 while reducing energy waste of the first laser and the second laser. The size of the overlapping area in the first direction X can specifically be 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, or 200 μm, or other values ​​within the above range, which is not limited in this embodiment.

[0102] In addition, this embodiment does not limit the wavelengths of the first laser and the second laser. The first laser and the second laser of different wavelengths can be selected according to the absorption rate of the dielectric layer 4 to the wavelength. That is, when the thickness or material of the dielectric layer 4 is different, the wavelengths of the first laser and the second laser can be changed accordingly.

[0103] In a specific embodiment, Figure 14 and Figure 15 As shown, before preparing the tunneling oxide layer 2, the first doped conductive layer 3 and the dielectric layer 4 in step S1, the preparation method further includes:

[0104] Step A1: performing texturing treatment on the second surface 1 b of the substrate 1 .

[0105] In this step, by processing the light-facing surface of the substrate 1 into a pyramid-shaped velvet structure, the absorption of photons by the substrate 1 can be increased, and the reflectivity of the second surface 1b can be reduced, thereby improving the short-circuit current and photoelectric conversion efficiency of the solar cell.

[0106] Step A2: preparing a second doped conductive layer 7 on the second surface 1b.

[0107] In this step, a deposition process can be used to deposit a second doped conductive layer 7 on the second surface 1b of the substrate 1. The second doped conductive layer 7 can specifically be a boron-doped polysilicon layer. Boron atoms can diffuse into the interior of the substrate 1 under high temperature, thereby forming a PN junction with the N-type substrate 1.

[0108] Step A3: performing alkali polishing on the first surface 1a.

[0109] In this step, the first surface 1a is corroded by an alkaline solution to remove the surface damage layer of the first surface 1a, improve the surface quality of the first surface 1a, and make the first surface 1a have a smooth surface structure, which can improve the reflectivity of the first surface 1a, thereby improving the light absorption effect of the substrate 1, which is beneficial to improving the photoelectric conversion efficiency of the solar cell.

[0110] In a specific embodiment, Figure 16 and Figure 17 As shown, after step S4, the preparation method further includes:

[0111] Step B1: removing the dielectric layer 4 in the plurality of first regions 11 by pickling.

[0112] In this step, a tank pickling method can be used to remove the unmodified dielectric layer 4 in the first region 11, thereby exposing the first doped conductive layer 3 in the first region 11. Specifically, the pickling can be performed using an HF solution or an HCl solution. HF and HCl solutions are highly corrosive and can efficiently remove the dielectric layer 4.

[0113] Step B2: preparing the first passivation layer 62 and the second passivation layer 82 respectively.

[0114] In this step, a first passivation layer 62 can be formed on one side of the first surface 1a by using a thermal oxidation method or an atomic deposition process, so that the first passivation layer 62 can cover the first surface 1a in the second region 12 and the surface of the first doped conductive layer 3 in the first region 11. Similarly, a second passivation layer 82 can be formed on one side of the second surface 1b by using a thermal oxidation method or an atomic deposition process, so that the second passivation layer 82 can cover the surface of the second doped conductive layer 7.

[0115] Step B3: preparing the first anti-reflection layer 61 and the second anti-reflection layer 81 respectively.

[0116] In this step, a first anti-reflection layer 61 can be formed on one side of the first surface 1a by plasma-enhanced chemical vapor deposition, so that the first anti-reflection layer 61 can cover the surface of the first passivation layer 62. Similarly, a second anti-reflection layer 81 can be formed on one side of the second surface 1b by plasma-enhanced chemical vapor deposition, so that the second anti-reflection layer 81 can cover the surface of the second passivation layer 82.

[0117] Step B4: Prepare the first electrode 5 and the second electrode 9 separately.

[0118] In this step, metal paste can be printed at a predetermined position within the first region 11 on the first surface 1a, and at a predetermined position on the second surface 1b, using methods such as screen printing, electroplating, or laser transfer. The silicon wafer is then laser sintered to complete the metallization process, thereby forming the first electrode 5 on the first surface 1a and the second electrode 9 on the second surface 1b.

[0119] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a solar cell, characterized in that: The solar cell comprises a substrate (1), the substrate (1) having a first surface (1a), the first surface (1a) having a plurality of first regions (11) and a plurality of second regions (12) staggered along a first direction, the second region (12) comprising a first subregion (121) and a second subregion (122) distributed along the first direction, the first subregion (121) and the second subregion (122) having an overlapping region in the first direction; Along the thickness direction of the substrate (1) and in a direction away from the substrate (1), the first region (11) is provided with a tunneling oxide layer (2) and a first doped conductive layer (3) in sequence; The preparation method comprises: Providing a substrate (1), and sequentially preparing the tunneling oxide layer (2), the first doped conductive layer (3), and the dielectric layer (4) on the first surface (1a); The second region (12) is patterned using a first laser, wherein the first laser sequentially modifies the dielectric layer (4) in the first sub-regions (121) of the plurality of second regions (12) into a loose structure along the first direction; The second region (12) is patterned using a second laser, wherein the second laser sequentially modifies the dielectric layer (4) in the second sub-regions (122) of a plurality of the second regions (12) into a loose structure along the first direction, wherein when the second sub-region (122) is processed by the second laser, the dielectric layer (4) in the first sub-region (121) of the same second region (12) as the second sub-region (122) has completed cooling; removing the modified dielectric layer (4), the first doped conductive layer (3) and the tunneling oxide layer (2) in the second region (12); The first direction is perpendicular to the thickness direction of the substrate (1).

2. The method for preparing a solar cell according to claim 1, wherein: When removing the modified dielectric layer (4), the first doped conductive layer (3) and the tunneling oxide layer (2) in the second region (12), the preparation method specifically comprises: A first alkali washing is performed to remove the modified dielectric layer (4) and a portion of the first doped conductive layer (3) in the second region (12); Wash with water; The second alkaline washing removes the first doped conductive layer (3) and the tunneling oxide layer (2) remaining in the second region (12).

3. The method for preparing a solar cell according to claim 2, wherein: The first alkali washing adopts a NaOH solution with a concentration of 3% to 3.5%, and the treatment time is 100s to 200s; And / or, the second alkaline washing uses a NaOH solution with a concentration of 2.9% to 3.1%, and the treatment time is 100s to 200s.

4. The method for preparing a solar cell according to claim 1, wherein: The power of the first laser is 50W~55W; And / or, the power of the second laser is 50W~55W.

5. The method for preparing a solar cell according to claim 1, wherein: The frequency of the first laser is 500kHz~600kHz; And / or, the frequency of the second laser is 500kHz~600kHz.

6. The method for preparing a solar cell according to claim 1, wherein: The scanning speed of the first laser is 55000mm / s~60000mm / s; And / or, the scanning speed of the second laser is 55000 mm / s~60000 mm / s.

7. The method for preparing a solar cell according to claim 1, wherein: The size of the first laser spot in the first direction is 100 μm to 500 μm; And / or, the size of the light spot of the second laser in the first direction is 100 μm to 500 μm.

8. The method for preparing a solar cell according to claim 1, wherein: The size of the overlapping area in the first direction is 100 μm to 200 μm.

9. The method for preparing a solar cell according to claim 1, wherein: When the second area (12) is patterned using a first laser, the scanning path of the first laser is S-shaped; And / or, when the second area (12) is patterned using a second laser, the scanning path of the second laser is S-shaped.

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