Preparation method of solar cell and solar cell

Abstract

The invention relates to a preparation method of a solar cell and the solar cell, the solar cell comprises a substrate, a first surface of the substrate is provided with a plurality of first areas and a plurality of second areas which are distributed in a staggered manner, and each second area comprises a first sub-area and a second sub-area which are distributed along a first direction; the first region is provided with a tunneling oxide layer and a first doped conductive layer. The preparation method comprises the following steps: providing a substrate, and sequentially preparing a tunneling oxide layer, a first doped conductive layer and a dielectric layer on a first surface; performing graphical processing on the second region by adopting first laser, and sequentially modifying the dielectric layers in the plurality of first sub-regions into loose structures along the first direction; performing graphical processing on the second region by adopting second laser, and modifying the dielectric layers in the plurality of second sub-regions into loose structures in sequence along the first direction; and removing the modified dielectric layer, the first doped conductive layer and the tunneling oxide layer in the second region. The preparation method can reduce the surface defects of the battery and can improve the conversion efficiency of the battery.

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 overly thick first doped conductive layer will cause parasitic absorption of infrared light on the back of the silicon wafer, low electron mobility, and heavy carrier recombination losses, leading to a series of problems such as poor long-wave response and low bifaciality of silicon solar cells, which restrict further improvement of solar cell conversion efficiency.

[0003] In the prior art, laser patterning technology is usually used to modify the oxide layer on the surface of the non-metallic area on the back of the TOPCon cell, and then the modified oxide layer and the passivation contact structure in the non-metallic area are cleaned and removed to reduce the parasitic absorption of the non-metallic area. However, due to the limitation of laser technology, the existing laser width is too small, and the oxide layer in the same non-metallic area needs two lasers to be processed. However, the oxide layer in the area repeatedly processed by the two lasers will form a denser oxide due to secondary melting in a short period of time, resulting in the passivation contact structure in this area cannot be cleaned in the subsequent cleaning steps, thereby affecting the photoelectric 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 of low photoelectric conversion efficiency of solar cells caused by defects in the laser patterning process in the prior art.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a solar cell, wherein the solar cell comprises a substrate, wherein the substrate comprises a first surface, wherein the first surface comprises a plurality of first regions and a plurality of second regions staggeredly distributed along a first direction, wherein the second region comprises a first sub-region and a second sub-region distributed along the first direction, wherein the first sub-region and the second sub-region have an overlapping region in the first direction; wherein a tunneling oxide layer, a first doped conductive layer and a dielectric layer are sequentially arranged in the first region in a direction away from the substrate along the thickness direction of the substrate; wherein the preparation method comprises: providing a substrate, sequentially preparing the tunneling oxide layer, the first doped conductive layer and the dielectric layer on the first surface; performing patterning on the second region using a first laser, wherein the first laser sequentially modifies the dielectric layer in the first sub-region of the plurality of second regions into a loose structure along the first direction; performing patterning on the second region using a second laser, wherein the second laser sequentially modifies 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; wherein the first direction is perpendicular to the thickness direction of the substrate.

[0006] In a 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% for 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% for a treatment time of 100s to 200s.

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

[0009] In a possible implementation manner, 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 55000 mm / s to 60000 mm / s; and / or the scanning speed of the second laser is 55000 mm / s to 60000 mm / s.

[0011] In a possible implementation manner, a size of the light spot of the first laser in the first direction is 100 μm to 500 μm; and / or a size of the light spot of the second laser 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 the second aspect, an embodiment of the present application provides a solar cell, which is made by the above-mentioned method for preparing a solar cell, and the solar cell at least includes: 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; a first doped conductive layer, arranged on a side surface of the tunneling oxide layer away from the substrate.

[0015] In the present application, the first laser can sequentially modify the dielectric layers in the multiple first sub-regions in the first direction into loose structures, and the modified dielectric layers can react with the subsequent cleaning solution, so as to facilitate the removal of the dielectric layers, the first doped conductive layers and the tunneling oxide layers in the first sub-region. The second laser can sequentially modify the dielectric layers in the multiple second sub-regions in the first direction into loose structures, and the modified dielectric layers can react with the cleaning solution, so as to facilitate the removal of the dielectric layers, the first doped conductive layers and the tunneling oxide layers in the second sub-region. Among them, there needs to be an overlapping area between the first sub-region and the second sub-region to ensure that the dielectric layers in the second region can be modified by laser treatment, so as to avoid the situation that the first doped conductive layer and the tunneling oxide layer in the area covered by the unmodified dielectric layer cannot react with the cleaning solution due to the presence of the unmodified dielectric layer in the subsequent steps. Moreover, in the present embodiment, the first laser is first used to process the multiple first sub-regions respectively along the first direction, and then the second laser is used to process the multiple second sub-regions respectively along the first direction, so that there is an interval between the processing time of the first sub-region and the second sub-region in 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 tunneling oxide layer in the second region can all react with the cleaning solution in subsequent steps and be removed cleanly, thereby reducing defects on the first surface and facilitating improving the photoelectric conversion efficiency of the solar cell.

[0016] It should be understood that the foregoing general description and the following detailed description are exemplary only 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 drawings required for use in the embodiments will be briefly introduced below. 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 paying creative labor.

[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 diagram of the backlight structure 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 diagram of the backlight structure 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 a method for preparing a solar cell provided in this application;

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

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

[0026] Fig. 9 This is a schematic diagram of the structure during the second laser treatment in the method for preparing a solar cell provided in the present application;

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

[0028] Fig.11 for Fig.10 A schematic diagram of the process flow corresponding to the preparation method;

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

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

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

[0032] Fig.15 for Fig.14 A schematic diagram of the process flow corresponding to the preparation method;

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

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

[0035] Reference numerals:

[0036] 1- substrate;

[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 through the oxide layer;

[0044] 3-a 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- a first passivation layer;

[0051] 7- a 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 described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0057] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" 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 other meanings.

[0058] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0059] The present application embodiment provides a solar cell, such as Figure 1 As shown, the solar cell is a TOPCon cell, including 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 by taking 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 surface of the substrate 1, that is, the surface that is not directly illuminated by sunlight, and the second surface 1b is specifically the light-facing surface of the substrate 1, that is, the surface that can be directly illuminated by 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 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 thick bottom 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. Among them, the tunneling oxide layer 2 and the first doped conductive layer 3 form a passivation contact structure, and the tunneling oxide layer 2 may include at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, amorphous silicon and polycrystalline silicon, which can chemically passivate the first surface 1a, and can reduce the recombination center of the contact surface between the tunneling oxide layer 2 and the substrate 1, so as to reduce 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, which 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 tunnel 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, and 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 an integral 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 an integral structure. Among them, the first anti-reflection layer 61 uses thin film interference to reduce the reflection of light and increase the incidence rate of light incident on the first surface 1a, and can specifically 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 is specifically the negative electrode of the solar cell, and at least a part 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 composed of the first electrode 5, the tunneling oxide layer 2 and the doped wire layer 2 is only provided in the first region 11, which can reduce the metal contact recombination between the passivation contact structure and the first electrode 5, thereby improving the carrier collection capability of the first electrode 5.

[0063] like Figure 1 As shown, along the thickness direction Z of the substrate 1 in the 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 realize the selective transmission of majority carriers, thereby reducing the carrier recombination rate. The second anti-reflection layer 81 uses thin film interference to reduce the reflection of light and increase the incidence rate of light incident on the second surface 1b, and can specifically 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, which can play a good passivation role, enhance the carrier concentration of the second surface 1b, and improve 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 part of the structure 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 may 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 main grid cell, the first fine grid 52 extends along the first direction X, and the first main grid 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 main grid 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-free 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 numbers of the first main grid 51 and the second fine grid 52 are only for illustration and do not represent the actual numbers in the solar cell structure. The present embodiment does not limit the specific numbers 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 deposit a tunnel oxide layer 2 on the first surface 1a of the substrate 1, or a deposition process can be used to deposit a first doped conductive layer 3 on the back of the tunnel oxide layer 2, or a deposition process can be used to deposit a dielectric layer 4 on the back of the first doped conductive layer 3, and 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, and this embodiment is introduced with the dielectric layer 4 being 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: using a first laser to perform patterning on the second region 12 , wherein 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: using a second laser to perform patterning on the second region 12 , and the second laser sequentially modifies the dielectric layer 4 in the second sub-regions 122 of the plurality of second regions 12 along the first direction X into a loose structure.

[0074] In the above steps S2 and S3, 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, and 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 preset region to be processed by the first laser, and the second sub-region 122 is specifically a preset region 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. Fig. 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] Among them, the first sub-region 121 and the second sub-region 122 need to have an overlapping area to ensure that the dielectric layer 4 in the second region 12 can be modified by laser processing, so as to avoid the situation in which the first doped conductive layer 3 and the tunneling oxide layer 2 in the area covered by the unmodified dielectric layer 4 cannot react with the cleaning solution due to the presence of the unmodified dielectric layer 4 in the subsequent steps. Moreover, in this embodiment, the first laser is first used to process the multiple first sub-regions 121 along the first direction X, and then the second laser is used to process the multiple second sub-regions 122 along the first direction X, so that there is an interval between the processing time of the first sub-region 121 and the second sub-region 122 in 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 removed cleanly, thereby reducing defects on the first surface 1a and facilitating improving the 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, since the dielectric layer 4 in the second region 12 is modified into a loose structure by laser treatment, 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, Fig.10 and Fig.11 As shown, the specific method of step S4 includes:

[0080] Step S41 : performing a first alkali 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 alkali washing can be performed by tank alkali washing. Specifically, the alkali 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 alkali washing solution for 100s to 300s, thereby removing the modified dielectric layer 4 and part of the first doped layer 3 (such as Fig.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 been laser modified. 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 solution of the first alkaline washing remaining on the surface of the solar cell to avoid affecting subsequent treatment. Specifically, the water used for water washing can be deionized water. In order to ensure the effect of the water washing process, the water washing time can be 100s to 150s, specifically 100s, 110s, 120s, 130s, 140s or 150s, or other values ​​within the above range, which is 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 alkali washing can be performed by tank alkali washing. Specifically, the alkali 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 alkali washing solution for 100s to 200s, thereby removing the remaining first doped conductive layer 3 and the tunneling oxide layer 2 (such as Fig.11). The concentration of the NaOH solution may be 2.9%, 2.95%, 3%, 3.05%, or 3.1%, or other values ​​within the above range, which is not limited in this embodiment. The treatment time may be 100s, 120s, 140s, 160s, 180s or 200s, or other values ​​within the above range, which is not limited in this embodiment. When the solution concentration and treatment time of the second alkali washing meet the above range, 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 washing, a certain amount of etching additives can be added to the alkali washing solution to control the reaction rate of the alkali washing solution, thereby controlling the etching depth of the second alkali washing, avoiding over-etching, and helping to reduce the 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 additive added can be adjusted according to the reaction rate of the alkali washing 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-free cell, the specific scanning paths of the first laser and the second laser are as follows: Fig.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. Fig.12 The arrows and dashed arrows in FIG. 1 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 start 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, Figure 8 and Fig.12As shown, the second laser is used to sequentially scan the second sub-regions 122 in the plurality of second regions 12 along the first direction X, and the second laser scans along the second direction Y when scanning each second sub-region 122, so as to ensure that the second laser can completely scan each second sub-region 122. Further, in order to improve the scanning efficiency of the second laser and reduce the moving 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 the second laser in one of the second sub-regions 122 and the scanning start 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: Fig.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. Fig.13 The arrows and dashed arrows in FIG. 1 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 start 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-areas 121 of multiple second areas 12 can be scanned in sequence, and it is ensured that the first laser can completely scan each first sub-area 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, Figure 8 and Fig.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, so that the second sub-regions 122 of the plurality of second regions 12 can be scanned in sequence, and it is ensured that the second laser can completely scan each second sub-region 122. Further, in order to improve the scanning efficiency of the second laser and reduce the moving 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 start point of another second laser adjacent to the first direction X are located on the same side of 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 shape 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, and the laser machine 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 adjust the parameters of the laser to the corresponding parameters of the first laser, and then scan the multiple first sub-regions 121 along the S-shaped path from the scanning starting point of the first laser; then adjust the parameters of the laser to the corresponding parameters of the second laser and move the laser to the scanning starting point of the second laser, and then scan the multiple second sub-regions 122 along the S-shaped path from the scanning starting point of the second laser. In order to ensure that the overlapping part of the first sub-region 121 and the second sub-region 122 in the same second region 12 will 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 moving 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 implementation, the power of the first laser may be 50W to 55W, the frequency of the first laser may be 500kHz to 600kHz, and / or the power of the second laser may be 50W to 55W, the frequency of the second laser may be 500kHz to 600kHz. The power of the first laser may be the same as or different from the power of the second laser, and the frequency of the first laser may be the same as or different from the frequency of the second laser, which is not limited in this embodiment.

[0093] When the power and frequency of the first laser meet the above ranges, it can ensure that the first laser has sufficient energy, thereby ensuring the processing depth and processing effect of the first laser, and avoiding the presence of unmodified parts of the dielectric layer 4 in the first sub-region 121. The power of the first laser can be 50W, 51W, 52W, 53W, 54W or 55W, or other values ​​within the above ranges, which are not limited in this embodiment. The frequency of the first laser can be 500kHz, 510kHz, 520kHz, 530kHz, 540kHz, 550kHz, 560kHz, 570kHz, 580kHz, 590kHz or 600kHz, or other values ​​within the above ranges, which are not limited in this embodiment.

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

[0095] In a specific implementation, the scanning speed of the first laser is 55000 mm / s to 60000 mm / s, and / or the scanning speed of the second laser is 55000 mm / s to 60000 mm / s. The scanning speed of the first laser may be the same as or different from the scanning speed of the second laser, which is not limited in this embodiment.

[0096] When the scanning speed of the first laser meets 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 step, and will not cause 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 55000mm / s, 56000mm / s, 57000mm / s, 58000mm / s, 59000mm / s or 60000mm / s, or other values ​​within the above range, which is not limited in this embodiment.

[0097] Similarly, when the scanning speed of the second laser meets the above 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 step, and will not cause the formation of dense oxides in part of the dielectric layer 4 due to excessive scanning speed. The scanning speed of the second laser can be 55000mm / s, 56000mm / s, 57000mm / s, 58000mm / s, 59000mm / s or 60000mm / s, or other values ​​within the above range, which is not limited in this embodiment.

[0098] In a specific implementation, the size of the light spot of the first laser in the first direction X should be 100 μm to 500 μm, and / or the size of the light spot of the second laser in the first direction X should be 100 μm to 500 μm. The size of the light spot of the first laser in the first direction X and the size of the light spot of the second laser in the first direction X may be the same or different, and this embodiment does not limit this.

[0099] When the size of the spot of the first laser in the first direction X is 100 μm to 500 μm, correspondingly, the size of the first sub-region 121 in the first direction X is 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 spot of the first laser 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, which is not limited in this embodiment.

[0100] Similarly, when the size of the spot of the second laser in the first direction X is 100 μm to 500 μm, correspondingly, the size of the second sub-region 122 in the first direction X is 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 spot of the second laser 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, which is not limited in this embodiment.

[0101] Specifically, the size of the overlapping area of ​​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, so that the first laser and the second laser can process all the dielectric layers 4 in the second area 12, while reducing the energy waste of the first laser and the second laser. The size of the overlapping area in the first direction X can 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 with 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, Fig.14 and Fig.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 1b 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 present 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, Fig.16 and Fig.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, the unmodified dielectric layer 4 in the first region 11 can be removed by tank pickling, so that the first doped conductive layer 3 in the first region 11 is exposed. Specifically, the pickling can be carried out by HF solution or HCl solution, which has strong corrosiveness and can remove the dielectric layer 4 efficiently.

[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 may be prepared on one side of the first surface 1a by 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 may be prepared on one side of the second surface 1b by 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: prepare the first anti-reflection layer 61 and the second anti-reflection layer 81 respectively.

[0116] In this step, the first anti-reflection layer 61 can be prepared 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, the second anti-reflection layer 81 can be prepared 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 respectively.

[0118] In this step, metal paste can be printed at a preset position in the first area 11 on one side of the first surface 1a, and metal paste can be printed at a preset position on one side of the second surface 1b by screen printing, electroplating, or laser transfer. Then, the silicon wafer is laser sintered to complete the metallization process, thereby forming a first electrode 5 on one side of the first surface 1a, and forming a second electrode 9 on one side of the second surface 1b.

[0119] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope 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) distributed alternately along a first direction, the second region (12) comprising a first sub-region (121) and a second sub-region (122) distributed along the first direction, the first sub-region (121) and the second sub-region (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 a plurality of the 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; 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, characterized in that: 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 removes the modified dielectric layer (4) and a portion of the first doped conductive layer (3) in the second region (12); Washing; 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, characterized in that: The first alkali washing uses 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, characterized in that: The power of the first laser is 50W to 55W; And / or, the power of the second laser is 50W-55W.

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

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

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

10. A solar cell, characterized in that: The solar cell is manufactured by the method for manufacturing a solar cell according to any one of claims 1 to 9, and the solar cell at least comprises: A substrate (1) having a first surface (1a), wherein the first surface (1a) has a plurality of first regions (11) and a plurality of second regions (12) distributed alternately along a first direction; A tunneling oxide layer (2) is arranged in the first region (11); A first doped conductive layer (3) is arranged on a surface of the tunnel oxide layer (2) that is away from the substrate (1).

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