Double-sided solar cell and preparation method thereof

Abstract

A bifacial solar cell and a preparation method thereof, belonging to the field of solar cells. The preparation method comprises: obtaining a semi-finished product of a bifacial solar cell, the semi-finished product comprising a silicon wafer, and a P-type doped layer, a front passivation layer and a front anti-reflection layer sequentially formed on the front side of the silicon wafer, opening an opening corresponding to the front sub-grid on the front side of the semi-finished product, the opening sequentially penetrates the front anti-reflection layer and the front passivation layer and exposes the surface of the P-type doped layer, applying a non-burn-through slurry in contact with the P-type doped layer into the opening, sintering, and forming a front sub-grid. The above preparation method can improve the open circuit voltage and conversion efficiency of the prepared bifacial solar cell.

Description

Technical Field

[0001] The present application relates to the field of solar cells, and in particular, to a double-sided solar cell and a method for preparing the same. Background Art

[0002] At present, the front and back electrodes of bifacial solar cells, such as TOPCon (Tunnel Oxide Passivated Contact) bifacial solar cells, are made by screen printing, and the printing path is back silver main grid→back silver fine grid→front silver main grid→front silver aluminum fine grid. The TOPCon bifacial solar cells prepared by the above method have the problems of low Uoc (open circuit voltage) and low conversion efficiency. Summary of the invention

[0003] The present application provides a bifacial solar cell and a preparation method thereof, which can alleviate the problems of low open circuit voltage and low conversion efficiency of existing bifacial solar cells, especially TOPCon bifacial solar cells.

[0004] The embodiment of the present application is implemented as follows:

[0005] In a first aspect, the present application example provides a method for preparing a bifacial solar cell, which comprises the following steps:

[0006] A semi-finished product of a double-sided solar cell is obtained, wherein the semi-finished product comprises a silicon wafer, and a P-type doping layer, a front passivation layer and a front anti-reflection layer sequentially formed on the front side of the silicon wafer.

[0007] An opening corresponding to the front sub-grid is formed on the front side of the semi-finished product, and the opening sequentially penetrates the front anti-reflection layer and the front passivation layer and exposes the surface of the P-type doped layer.

[0008] A non-burn-through paste in contact with the P-type doping layer is coated into the opening and sintered to form a front sub-grid.

[0009] The preparation method of the bifacial solar cell provided in the present application, before printing the secondary grid on the front side of the cell, firstly opens the front passivation layer and the front anti-reflection layer, and then prints the non-burn-through type paste, so that the non-burn-through type paste can be in direct contact with the P-type doped layer, effectively reducing the contact resistance, and because the non-burn-through type paste contains a low content of glass powder, it will not damage the pn junction, so it can improve the open circuit voltage of the bifacial solar cell and improve the conversion efficiency of the bifacial solar cell.

[0010] In some optional embodiments, the non-fire-through paste contains glass powder in a mass percentage greater than 0 and not exceeding 1.5%.

[0011] Within the above range, due to the low glass powder content, excessive damage to the pn junction by the glass powder can be avoided.

[0012] Optionally, the non-fire-through type paste includes silver-aluminum paste.

[0013] In the above implementation process, the conversion efficiency of the silver-aluminum paste is high, and the preparation method provided in the present application can make the aluminum nails penetrate into the silicon wafer instead of forming an aluminum-silicon alloy, which can further reduce the contact barrier and improve the conversion efficiency of the bifacial solar cell.

[0014] Optionally, the bifacial solar cell is a TOPCon bifacial solar cell.

[0015] In some optional embodiments, the step of opening the opening corresponding to the front sub-grid on the front side of the semi-finished product includes: opening the opening on the front side of the semi-finished product by laser ablation.

[0016] In the above implementation process, the opening method of laser ablation is simple to operate and has high precision, and the opening can be obtained quickly, thereby improving the production efficiency.

[0017] Optionally, the size of the laser spot used for laser ablation is greater than 0 and does not exceed 60 μm.

[0018] In the above implementation process, since the width of the front sub-grid is relatively thin, the size of the above laser spot is reasonably selected to avoid excessive opening width caused by excessive laser spot size, exposing too much P-type doped layer, and resulting in low conversion efficiency of the bifacial solar cell.

[0019] In some optional embodiments, the step of opening an opening corresponding to the front sub-grid on the front side of the semi-finished product includes:

[0020] A patterned acid-resistant mask layer is formed on the surface of the front anti-reflection layer. The position of the acid-resistant mask layer corresponding to the front sub-grid has a hollow portion exposing the front anti-reflection layer. After the front anti-reflection layer and the front passivation layer corresponding to the hollow portion are acid-etched, the acid-resistant mask layer is removed.

[0021] In the above implementation process, the opening is prepared by using the acid-resistant etching mask layer, which is simple to operate and convenient for industrial production, and can effectively improve production efficiency.

[0022] In some optional embodiments, the step of opening an opening corresponding to the front sub-grid on the front side of the semi-finished product includes:

[0023] The etching slurry is printed on the surface of the front anti-reflection layer at a position corresponding to the front sub-grid.

[0024] In the above implementation process, the etching slurry is directly used for etching, and the operation method is simple and controllable.

[0025] In some optional embodiments, the silicon wafer is an N-type silicon wafer.

[0026] In the above implementation process, the arrangement of the silicon wafer as an N-type silicon wafer is beneficial to improving the efficiency of the double-sided solar cell.

[0027] In some optional embodiments, the front anti-reflection layer includes a silicon nitride layer or a silicon dioxide layer.

[0028] In some optional embodiments, the front passivation layer includes an aluminum oxide layer or a magnesium fluoride layer.

[0029] In a second aspect, the present application example provides a bifacial solar cell, comprising: a silicon wafer, and a P-type doped layer, a front passivation layer, a front anti-reflection layer and a front electrode formed in sequence on the front side of the silicon wafer, the bifacial solar cell having an opening that penetrates the front anti-reflection layer and the front passivation layer in sequence and exposes the surface of the P-type doped layer, the front electrode comprising a front sub-grid, the front sub-grid being formed in the opening and in ohmic contact with the P-type doped layer, and the front sub-grid being a non-burn-through type front sub-grid.

[0030] The double-sided solar cell has better open circuit voltage and better conversion efficiency.

[0031] In some optional embodiments, the front sub-grid is made of silver-aluminum paste with a mass content of glass powder greater than 0 and not exceeding 1.5%, and the aluminum in the front sub-grid is pinned into the silicon wafer.

[0032] In the above implementation process, since the aluminum nails penetrate into the silicon wafer instead of forming an aluminum-silicon alloy, the contact barrier can be further reduced and the conversion efficiency of the bifacial solar cell can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic diagram of the structure of the semi-finished product provided for this application;

[0035] Figure 2 This is a schematic diagram of the structure of the double-sided solar cell provided in this application.

[0036] Icon: 100-bifacial solar cell; 10-semi-finished product; 11-opening; 21-front electrode; 22-front anti-reflection layer; 23-front passivation layer; 24-P-type doped layer; 25-silicon wafer; 26-tunneling oxide layer; 27-intrinsic polysilicon layer; 28-doped polysilicon layer; 29-back anti-reflection layer; 30-back electrode. DETAILED DESCRIPTION

[0037] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0038] At present, the front side of the bifacial solar cell 100, such as the TOPCon bifacial solar cell, has a front passivation layer 23 and a front anti-reflection layer 22. Since the passivation film is thick and the anti-reflection film is dense and difficult to burn through, the front silver-containing paste used in the production process, such as silver-aluminum paste and silver paste, contains more than 3% glass powder. The high-content glass powder is used to burn through the front passivation layer 23 and the front anti-reflection layer 22, and then form a good ohmic contact with the P-type doping layer 24. In fact, since the thickness of the front film layer of the entire battery cell is not completely uniform, the high-content glass powder will inevitably destroy a part of the pn junction after burning through the front passivation layer 23 and the front anti-reflection layer 22, resulting in large surface metal composites of the solar cell, low open circuit voltage, and low conversion efficiency.

[0039] In order to solve the above problems, the inventors pre-opened an opening 11 corresponding to the front sub-grid on the surface of the front anti-reflection layer 22 before printing the sub-grid on the front side of the bifacial solar cell 100. The opening 11 sequentially penetrates the front anti-reflection layer 22 and the front passivation layer 23 and exposes the surface of the P-type doped layer 24. Then, a silver-containing paste is coated into the opening 11 so that the silver-containing paste is in direct contact with the P-type doped layer 24, thereby reducing the contact resistance. In addition, the above arrangement can effectively reduce the content of glass powder in the silver-containing paste, so that after sintering, not only a front sub-grid that forms a good ohmic contact with the P-type doped layer 24 can be formed, but also because the content of glass powder is significantly reduced, it is possible to avoid the damage of the pn junction caused by high-content glass powder, thereby effectively reducing metal recombination, improving the open circuit voltage of the bifacial solar cell 100, and improving the conversion efficiency of the bifacial solar cell 100.

[0040] The following is a detailed description of the bifacial solar cell 100 and its preparation method according to the embodiment of the present application:

[0041] like Figure 1 as well as Figure 2 As shown, a method for preparing a bifacial solar cell 100 comprises the following steps:

[0042] S1. Obtain a semi-finished product 10 of a bifacial solar cell 100, wherein the semi-finished product 10 comprises a silicon wafer 25, a P-type doping layer 24, a front passivation layer 23 and a front anti-reflection layer 22 sequentially formed on the front surface of the silicon wafer 25.

[0043] In addition to the above-mentioned front structure, the semi-finished product 10 also includes a back structure, which includes a tunneling oxide layer 26, an intrinsic polysilicon layer 27, a doped polysilicon layer 28 and a back anti-reflection layer 29 formed in sequence on the back of the silicon wafer 25.

[0044] The semi-finished product 10 of the above-mentioned double-sided solar cell 100 can be prepared by itself, and the preparation method of each layer can refer to the relevant technology and is not limited here.

[0045] Optionally, the bifacial solar cell 100 is a TOPCon bifacial solar cell.

[0046] The silicon wafer 25 may be a P-type silicon wafer 25 or an N-type silicon wafer 25 .

[0047] In some optional embodiments, in order to make the bifacial solar cell have higher efficiency, the silicon wafer 25 is an N-type silicon wafer 25 .

[0048] The front passivation layer 23 includes but is not limited to a silicon dioxide layer, and may also be an aluminum oxide layer or the like.

[0049] In some optional embodiments, the front passivation layer 23 is an aluminum oxide layer, wherein the aluminum oxide layer can be grown on the surface of the P-type doped layer 24 by different deposition methods such as AlD, PEALD, PECVD, etc., wherein the surface of the P-type doped layer 24 refers to the side thereof facing away from the silicon wafer 25.

[0050] Optionally, the thickness of the aluminum oxide layer is 2 nm-15 nm.

[0051] The front anti-reflection layer 22 includes but is not limited to a silicon nitride layer, and may also be a magnesium fluoride layer, etc.

[0052] In some optional embodiments, the front anti-reflection layer 22 is a silicon nitride layer.

[0053] Among them, the silicon nitride layer can be a single-layer structure or a multi-layer structure, specifically including but not limited to a SiNx single-layer structure, and can also be a SiNx / SiOxNy multi-layer structure, or a SiNx / SiOxNy / SiOx multi-layer structure. Technical personnel in this field can choose according to actual needs.

[0054] The thickness of the front anti-reflection layer 22 is 50 nm-120 nm. Within this thickness range, the anti-reflection requirement of the bifacial solar cell 100 can be met.

[0055] S2, opening 11 corresponding to the front sub-grid is formed on the front side of the semi-finished product 10, and the opening 11 sequentially penetrates the front anti-reflection layer 22 and the front passivation layer 23 and exposes the surface of the P-type doping layer 24.

[0056] The opening 11 is used to expose the surface of the P-type doping layer 24 so that the coated silver-containing paste can directly contact the surface of the P-type doping layer 24 in the subsequent step S3 to reduce the contact resistance.

[0057] There are many ways to open the opening 11 corresponding to the front sub-grid on the front side of the semi-finished product 10, and those skilled in the art can choose according to actual needs.

[0058] In some optional embodiments, the step of opening the opening 11 corresponding to the front sub-grid on the front side of the semi-finished product 10 includes: using laser ablation to open the opening 11 on the front side of the semi-finished product 10. The laser ablation method is simple to operate, can quickly prepare the opening 11, and improves the production efficiency.

[0059] It is understandable that ablation of the P-type doped layer 24 should be avoided during laser ablation. In actual use, the type, wavelength and power of the laser used can be selected according to actual needs, and the laser spot used can be a circular spot with dispersed spot energy or a square spot with uniform spot energy. The spacing between any two adjacent spots can also be selected according to actual needs, and is not limited here.

[0060] Since the width of the front sub-grid is relatively thin, in some optional embodiments, the size of the laser spot used for laser ablation is greater than 0 and does not exceed 60 μm. The size of the laser spot is reasonably selected to avoid the excessive width of the opening 11 caused by the excessive size of the laser spot, which may expose too much of the P-type doped layer 24 and result in low conversion efficiency of the bifacial solar cell 100.

[0061] In some optional embodiments, the step of opening an opening 11 corresponding to the front sub-grid on the front side of the semi-finished product 10 includes: forming a patterned acid-resistant corrosion mask layer on the surface of the front anti-reflection layer 22, the acid-resistant corrosion mask layer having a hollow portion exposing the front anti-reflection layer 22 at a position corresponding to the front sub-grid, and after acid-etching the front anti-reflection layer 22 and the front passivation layer 23 corresponding to the hollow portion, removing the acid-resistant corrosion mask layer.

[0062] The surface of the front anti-reflection layer 22 refers to a side of the front anti-reflection layer 22 facing away from the silicon wafer 25 .

[0063] The above method of preparing the opening 11 by using the acid-resistant etching mask layer is simple to operate and convenient for industrial production, thereby effectively improving production efficiency.

[0064] Optionally, the acid used for acid etching is hydrofluoric acid, and the material of the acid-resistant mask layer can be paraffin, which is easy to remove later and can effectively prevent it from remaining on the surface of the front anti-reflection layer 22 and causing pollution.

[0065] In some optional embodiments, the step of opening the opening 11 corresponding to the front sub-grid on the front of the semi-finished product 10 includes: printing etching slurry at the position corresponding to the front sub-grid on the surface of the front anti-reflection layer 22. The above operation method is simple and controllable, and effectively improves production efficiency.

[0066] Optionally, the etching slurry contains hydrofluoric acid.

[0067] S3 , coating a non-fire-through paste in contact with the P-type doping layer 24 into the opening 11 , and sintering to form a front sub-gate.

[0068] Since the opening 11 penetrates the front passivation layer 23 and the front anti-reflection layer 22 and exposes the surface of the P-type doped layer 24, the non-fire-through paste is printed to make it directly contact with the P-type doped layer 24 to reduce the contact resistance. Moreover, since the non-fire-through paste does not have excessive glass powder to damage the pn junction, it can effectively reduce metal recombination, increase the open circuit voltage of the bifacial solar cell 100, and improve the conversion efficiency of the bifacial solar cell 100.

[0069] The non-fire-through type paste refers to a paste containing a lower glass powder content than the traditional paste. During the sintering process, the burn-through ability is weak and there is no need to burn through the front passivation layer 23 and the front anti-reflection layer 22 .

[0070] Optionally, the non-fire-through paste contains glass powder with a mass percentage greater than 0 and not exceeding 1.5%; for example, the non-fire-through paste contains glass powder with a mass percentage of 0.1%, 0.3%, 0.5%, 0.7%, 1%, 1.3%, or 1.5%.

[0071] Non-fire-through pastes include but are not limited to silver paste or silver aluminum paste.

[0072] In some optional embodiments, the non-burn-through paste is silver-aluminum paste, which refers to a metal paste containing silver and aluminum for forming electrodes. The silver-aluminum paste has a high conversion efficiency, and the above method can make the aluminum nail penetrate into the silicon wafer 25 instead of forming an aluminum-silicon alloy, which can further reduce the contact barrier and improve the conversion efficiency of the bifacial solar cell 100.

[0073] It should be noted that the specific components of the silver-aluminum paste include silver powder, aluminum powder, glass powder and an organic carrier. The specific components of the silver-aluminum paste can be referred to in the relevant technology and are not limited here.

[0074] Before coating the silver-containing paste, the preparation method also includes: firstly screen-printing a back main grid and a back sub-grid on the surface of the back anti-reflection layer 29 (that is, the side of the back anti-reflection layer 29 facing away from the silicon wafer 25) and drying them to form a back electrode 30, and then using a flipping mechanism to flip the front side upward to form a front main grid on the surface of the front anti-reflection layer 22, wherein the front main grid and the front sub-grid together constitute the front electrode 21.

[0075] It should be noted that the front main grid can be prepared by the above-mentioned preparation method of the front sub-grid, or it can be prepared by screen printing on the surface of the front anti-reflection layer 22 and then drying. Those skilled in the art can make a choice according to actual needs.

[0076] See also Figure 2 The present application also provides a bifacial solar cell 100, which is manufactured by the above-mentioned manufacturing method.

[0077] Specifically, the bifacial solar cell 100 includes: a silicon wafer 25, and a P-type doped layer 24, a front passivation layer 23, a front anti-reflection layer 22, and a front electrode 21 formed sequentially on the front side of the silicon wafer 25. The bifacial solar cell 100 has an opening that sequentially penetrates the front anti-reflection layer 22 and the front passivation layer 23 and exposes the surface of the P-type doped layer 24. The front electrode 21 includes a front sub-grid, which is formed in the opening and is in ohmic contact with the P-type doped layer 24. The front sub-grid is a non-burn-through type front sub-grid. The non-burn-through type front sub-grid refers to a sub-grid obtained by sintering a non-burn-through type slurry.

[0078] The front electrode 21 includes a front main grid connected to the front sub-grid. In addition, the bifacial solar cell 100 has a tunneling oxide layer 26, an intrinsic polysilicon layer 27, a doped polysilicon layer 28, a back anti-reflection layer 29 and a back electrode 30 formed in sequence on the back of the silicon wafer 25. The back electrode 30 includes a back main grid and a back sub-grid. That is, the bifacial solar cell 100 is a TOPCon bifacial solar cell.

[0079] Optionally, the front sub-grid protrudes from the surface of the front anti-reflection layer 22 , that is, the thickness of the front sub-grid is greater than the total thickness of the front passivation layer 23 and the front anti-reflection layer 22 .

[0080] Optionally, the front sub-grid is made of silver-aluminum grid paste with a mass content of glass powder greater than 0 and not exceeding 1.5%, that is, the front sub-grid is a silver-aluminum grid, and the aluminum in the front sub-grid is pinned into the silicon wafer 25 .

[0081] The double-sided solar cell and its preparation method of the present application are further described in detail below in conjunction with the embodiments.

[0082] Example 1

[0083] like Figure 1 The method for preparing the TOPCon bifacial solar cell shown comprises the following steps:

[0084] (1) Obtain Figure 2The semi-finished product 10 shown in the figure comprises an N-type silicon wafer 25, a 1 μm thick P-type doped layer 24, a 5 nm thick front passivation layer 23 (Al2O3 layer), and a 72 nm thick front anti-reflection layer 22 (Si3N4 layer) formed sequentially on the front side of the N-type silicon wafer 25, and a 1 nm thick tunneling oxide layer 26 (SiO2), a 15 nm thick intrinsic polysilicon layer 27, a 120 nm thick doped polysilicon layer 28, and a 75 nm thick back anti-reflection layer 29 (Si3N4 layer) formed sequentially on the back side of the N-type silicon wafer 25.

[0085] A laser machine is used to perform laser ablation on the surface of the front anti-reflection layer 22 at a position corresponding to the front sub-grid to form an opening 11. The opening 11 sequentially penetrates the front anti-reflection layer 22 and the front passivation layer 23 and exposes the surface of the P-type doped layer 24. The laser spot is a circular spot with a single spot size of 55 μm. The laser uses a picosecond laser with a power set to 10 W and a real-virtual ratio of the laser grooving set to 3:1.

[0086] (2) The back silver main grid and the back silver sub-grid are screen-printed on the surface of the back anti-reflection layer 29 and dried, and the front side of the semi-finished product 10 is turned upward using a turning mechanism.

[0087] (3) The front silver main grid is screen-printed on the front of the semi-finished product 10 and dried, and the silver aluminum paste is accurately printed into the opening 11 to form a paste sub-grid. The silver aluminum paste here is a semi-burn-through paste with a glass powder mass content of 1.5%. After printing, the height of the paste sub-grid is 10 μm.

[0088] (4) Sintering in a sintering furnace at 760°C to form the slurry sub-grid into a back sub-grid.

[0089] Example 2

[0090] The difference between it and Example 1 is only that:

[0091] The laser parameters in step (1) are different: a laser machine is used to perform laser ablation on the surface of the front anti-reflection layer at a position corresponding to the front sub-grating to form an opening, the opening sequentially penetrates the front anti-reflection layer and the front passivation layer and exposes the surface of the P-type doped layer, the laser spot is a circular spot, the size of a single spot is 60μm, the laser uses a picosecond laser, the power is set to 8W, and the laser grooving is a continuous spot (no dotted line).

[0092] In step (3), the mass content of glass powder in the silver-aluminum paste is 0.8%.

[0093] Example 3

[0094] The difference between it and Example 2 is only that:

[0095] (1) A semi-finished product 10 is obtained, wherein the semi-finished product 10 includes an N-type silicon wafer 25, a 1 μm thick P-type doped layer 24, a 5 nm thick front passivation layer 23 (Al2O3 layer), and a 72 nm thick front anti-reflection layer 22 (Si3N4 layer) formed in sequence on the front surface of the N-type silicon wafer 25, and a 1 nm thick tunneling oxide layer 26 (SiO2), a 15 nm thick intrinsic polysilicon layer 27, a 120 nm thick doped polysilicon layer 28, and a 75 nm thick back anti-reflection layer 29 (Si3N4 layer) formed in sequence on the back surface of the N-type silicon wafer 25.

[0096] A front screen and a back screen are obtained. The front screen has a graphic area corresponding to the front sub-grid and impermeable to the slurry, and the rest of the area is permeable to the slurry. The back screen is permeable to the slurry.

[0097] A paraffin-containing acid-resistant slurry is printed on the surface of the front anti-reflection layer using a front screen, and a paraffin-containing acid-resistant slurry is printed on the surface of the back anti-reflection layer using a back screen, and then the layers are dried at 150°C, and the front screen and the back screen are removed to form a patterned acid-resistant and corrosion-resistant mask layer on the surface of the front anti-reflection layer, and a semi-finished product of a complete and patternless acid-resistant and corrosion-resistant mask layer is formed on the surface of the back anti-reflection layer, wherein a hollow portion exposing the front anti-reflection layer is provided at a position corresponding to the front sub-grid in the front patterned acid-resistant and corrosion-resistant mask layer.

[0098] In a tank cleaning machine, a cleaning acid solution is prepared according to a volume ratio of deionized water: HF = 10:3, and the semi-finished product with the acid-resistant mask layer is placed in the pickling tank and soaked for cleaning for 20 minutes, and the front anti-reflection layer and the front passivation layer corresponding to the hollow part are etched away with acid, and the residual acid on the semi-finished product is washed away with deionized water.

[0099] Then, a mixed aqueous solution (containing 1% sodium hydroxide and 3% hydrogen peroxide by mass percentage) is used to remove the acid-resistant mask layer on the front and back sides of the semi-finished product, followed by washing with water and drying.

[0100] Example 4

[0101] The difference between it and Example 2 is only that:

[0102] (1) Obtain a front screen having a graphic area corresponding to the front sub-grid and permeable to the slurry, and the remaining part is not permeable to the slurry, and use the front screen to print a fluorine-containing etching slurry on the surface of the front anti-reflection layer, so as to perform laser ablation at a position corresponding to the front sub-grid on the surface of the front anti-reflection layer to form an opening, the opening sequentially penetrates the front anti-reflection layer 22 and the front passivation layer and exposes the surface of the P-type doped layer.

[0103] Then, a mixed aqueous solution (containing 1% sodium hydroxide and 3% hydrogen peroxide by mass percentage) is used to remove the fluorine-containing etching slurry printed on the surface of the semi-finished product, and then the semi-finished product is washed with water and dried.

[0104] Comparative Example 1

[0105] The difference between it and Example 1 is only that:

[0106] In step (1), no opening is provided, and in step (3), the secondary grid is directly screen-printed on the front side of the semi-finished product.

[0107] Comparative Example 2

[0108] The difference between it and Example 2 is only that:

[0109] In step (3), the mass content of glass powder in the silver-aluminum paste is 2%.

[0110] Test Example 1

[0111] The TOPCon bifacial solar cells prepared in Examples 1-4 and Comparative Examples 1-2 were tested in the same manner, and the results are shown in Table 1.

[0112] In Table 1, BL indicates that the only difference from the corresponding groups is that no opening is set and the silver-aluminum paste with a glass powder mass content of 3% is used. Experiment indicates the TOPCon bifacial solar cells prepared by the corresponding groups. The difference value refers to the difference between the TOPCon bifacial solar cells prepared by each group and the corresponding BL.

[0113] Table 1 Test results

[0114]

[0115]

[0116] It can be seen from Table 1 that the preparation method adopted in the present application can effectively improve the conversion efficiency of TOPCon bifacial solar cells compared with Comparative Examples 1 and 2.

[0117] In summary, the present application utilizes the improvement of the preparation method of the bifacial solar cell to effectively improve the open circuit voltage of the prepared bifacial solar cell and improve the conversion efficiency of the bifacial solar cell.

[0118] The above are only specific embodiments of the present application and are 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 double-sided solar cell, characterized in that: The following steps are involved: Obtaining a semi-finished product of a bifacial solar cell, the semi-finished product comprising a silicon wafer, and a P-type doping layer, a front passivation layer, and a front anti-reflection layer sequentially formed on the front side of the silicon wafer; An opening corresponding to the front sub-grid is formed on the front side of the semi-finished product, wherein the opening sequentially penetrates the front anti-reflection layer and the front passivation layer and exposes the surface of the P-type doped layer; Coating a non-burn-through slurry in contact with the P-type doping layer into the opening, and sintering to form the front sub-gate, wherein the aluminum in the front sub-gate is pinned into the silicon wafer; The non-fire-through paste is a silver-aluminum paste, and the non-fire-through paste contains 0.8%-1.5% by mass of glass powder.

2. The preparation method according to claim 1, characterized in that: The double-sided solar cell is a TOPCon double-sided solar cell.

3. The preparation method according to any one of claims 1 to 2, characterized in that: The step of opening the opening corresponding to the front sub-grid on the front side of the semi-finished product comprises: opening the opening on the front side of the semi-finished product by laser ablation.

4. The preparation method according to claim 3, characterized in that: The size of the laser spot used in the laser ablation is greater than 0 and does not exceed 60 μm.

5. The preparation method according to any one of claims 1-2, characterized in that: The step of opening an opening corresponding to the front auxiliary grille on the front side of the semi-finished product comprises: A patterned acid-resistant mask layer is formed on the surface of the front anti-reflection layer, wherein the position of the acid-resistant mask layer corresponding to the front sub-grid has a hollow portion exposing the front anti-reflection layer, and after acid etching the front anti-reflection layer and the front passivation layer corresponding to the hollow portion, the acid-resistant mask layer is removed.

6. The preparation method according to any one of claims 1-2, characterized in that: The step of opening an opening corresponding to the front auxiliary grille on the front side of the semi-finished product comprises: The etching paste is printed on the surface of the front anti-reflection layer at a position corresponding to the front sub-grid.

7. The preparation method according to any one of claims 1-2, characterized in that: The silicon wafer is an N-type silicon wafer.

8. The preparation method according to any one of claims 1-2, characterized in that: The front anti-reflection layer includes a silicon nitride layer or a silicon dioxide layer.

9. The preparation method according to any one of claims 1-2, characterized in that: The front passivation layer includes an aluminum oxide layer or a magnesium fluoride layer.

10. A double-sided solar cell, characterized in that: It includes: A silicon wafer, and a P-type doped layer, a front passivation layer, a front anti-reflection layer and a front electrode sequentially formed on the front side of the silicon wafer, wherein the bifacial solar cell has an opening that sequentially penetrates the front anti-reflection layer and the front passivation layer and exposes the surface of the P-type doped layer, the front electrode comprises a front sub-grid, the front sub-grid is formed in the opening and is in ohmic contact with the P-type doped layer, and the front sub-grid is a non-burn-through type front sub-grid; The front sub-grid is made of silver-aluminum paste with a glass powder mass content of 0.8%-1.5%, and the aluminum in the front sub-grid is pinned into the silicon wafer.

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