Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to the technical field of solar cells, in particular to a solar cell, a preparation method thereof and a photovoltaic module. The solar cell comprises a silicon wafer, a first doped silicon layer, a first functional film and a light receiving surface electrode. The silicon wafer has a light-receiving surface. The first doped silicon layer is arranged on the light receiving surface. And the first functional film is arranged on one surface, deviating from the silicon wafer, of the first doped silicon layer. The light receiving surface electrode comprises an auxiliary grid line, and the auxiliary grid line penetrates through the first functional film and is in ohmic contact with the first doped silicon layer. And the density of the auxiliary grid lines is 0.483 pieces / cm < 2 > to 0.604 pieces / cm < 2 >. The line width of the auxiliary grid line is 8-12 [mu] m. The distance between the adjacent auxiliary grid lines is 0.91 mm-1. 25 mm. The contact interface of the auxiliary grid lines and the first doped silicon layer forms a silver-silicon mixed contact structure with the density of (5-7) * 10 < 6 > / cm < 2 >. The solar cell has low contact resistance, low metal region recombination and high fill factor at the same time.

Description

Technical Field

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

[0002] The secondary grid of the solar cell is formed by printing the paste on the coated silicon substrate and then sintering the paste. Taking the formation process of the secondary grid on the light-receiving surface of the N-type passivated contact cell as an example, during the sintering process, the glass in the paste softens first, corroding the film layer on the light-receiving surface, and then the silver and aluminum in the silver-aluminum paste react with the exposed silicon substrate to form silver-aluminum spikes. Among them, aluminum has greater activity, lower softening point, and good fluidity, which is conducive to forming good contact and reducing contact resistance. However, the presence of aluminum will also cause the metal area to recombine and lose open circuit voltage. Although the total area of ​​the secondary grid can be reduced by reducing the number of secondary grid strips on the light-receiving surface, thereby reducing the metal area recombination. However, on a certain area, when the line width of the secondary grid remains unchanged, the fewer the number of secondary grid strips, the larger the spacing between the secondary grids, the longer the current transmission distance, and the smaller the fill factor.

[0003] In general, the use of silver-aluminum spikes as contact structures makes it difficult for solar cells to simultaneously have low contact resistance, low metal area recombination, and high fill factor. Summary of the invention

[0004] In order to solve the above technical problems, the present application discloses a solar cell and a preparation method thereof, and a photovoltaic module. The solar cell adopts a silver-silicon hybrid contact structure to form good contact while avoiding serious recombination problems caused by silver-aluminum spikes, and then adopts high-density secondary grid lines to reduce the spacing between the secondary grid lines, reduce the lateral transmission distance of carriers, and improve the fill factor; by narrowing the line width of the secondary grid lines, it is avoided that the secondary grid line shading area is too large due to the high-density secondary grid lines, which affects the conversion efficiency; finally, by forming a high-density silver-silicon hybrid contact structure, the problem of a decrease in the fill factor due to the narrowing of the line width of the secondary grid lines is avoided, so that the solar cell has lower contact resistance, lower metal area recombination and higher fill factor at the same time.

[0005] In a first aspect, an embodiment of the present application provides a solar cell, comprising:

[0006] A silicon wafer, wherein the silicon wafer has a light-receiving surface;

[0007] a first doped silicon layer, wherein the first doped silicon layer is disposed on the light receiving surface;

[0008] a first functional film, the first functional film being disposed on a surface of the first doped silicon layer facing away from the silicon wafer; and

[0009] The light-receiving surface electrode comprises a secondary grid line, the secondary grid line penetrates the first functional film and makes ohmic contact with the first doped silicon layer; the density of the secondary grid line is 0.483 pieces / cm 2 ~0.604 / cm 2 The line width of the secondary gate line is 8 μm to 12 μm, the spacing between adjacent secondary gate lines is 0.91 mm to 1.25 mm, and the contact interface formation density between the secondary gate line and the first doped silicon layer is (5 to 7)×10 6 Pieces / cm 2 Silver-silicon hybrid contact structure.

[0010] Optionally, the solar cell further comprises a dielectric layer, a second doped silicon layer, a second functional film and a backlight surface electrode;

[0011] The silicon wafer also has a backlight surface, the dielectric layer, the second doped silicon layer and the second functional film are stacked in sequence on the backlight surface away from the silicon wafer, the silicon wafer and the second doped silicon layer are of a first conductivity type, and the first doped silicon layer has a second conductivity type opposite to the first conductivity type;

[0012] The backlight surface electrode penetrates the second functional film and is in ohmic contact with the second doped silicon layer.

[0013] Optionally, the silicon wafer is an N-type silicon wafer;

[0014] And / or, the first doped silicon layer is a P-type doped silicon layer;

[0015] And / or, the first functional film includes an aluminum oxide passivation layer and a silicon nitride anti-reflection layer;

[0016] And / or, the dielectric layer is a silicon oxide layer;

[0017] And / or, the thickness of the dielectric layer is 0.1 nm to 5 nm;

[0018] And / or, the second doped silicon layer is an N-type doped polysilicon layer;

[0019] And / or, the second functional film includes a silicon nitride anti-reflection layer.

[0020] Optionally, the area of ​​the silicon wafer is 331.24 cm 2 , the number of the secondary grid lines is 160 to 200;

[0021] Or, the area of ​​the silicon wafer is 382.2 cm 2 , the number of the secondary grid lines is 185 to 230;

[0022] Or, the area of ​​the silicon wafer is 347.62cm2 , the number of the secondary grid lines is 168 to 209;

[0023] Or, the area of ​​the silicon wafer is 441cm 2 The number of the secondary grid lines is 214 to 266.

[0024] Optionally, the silver-silicon hybrid contact structure is a bifurcated structure;

[0025] And / or, the silver-silicon hybrid contact structure is a submicron structure.

[0026] In a second aspect, an embodiment of the present application provides a method for preparing a solar cell as described in the first aspect, comprising the following steps:

[0027] Preparing a first doped silicon layer on the light-receiving surface of the silicon wafer;

[0028] forming the first functional film on a surface of the first doped silicon layer facing away from the silicon wafer;

[0029] Silver paste is printed on the side of the first functional film away from the first doped silicon layer according to the pattern of the secondary grid lines; wherein the density of the secondary grid lines is 0.483 pieces / cm 2 ~0.604 / cm 2 , the line width of the secondary grid lines is 8 μm to 12 μm, and the spacing between adjacent secondary grid lines is 0.91 mm to 1.25 mm; the mass proportion of aluminum in the silver paste is less than 1%, and the mass proportion of silver in the silver paste is greater than 90%;

[0030] Co-sintering the silicon wafer printed with the silver paste to obtain the auxiliary gate line; wherein the auxiliary gate line penetrates the first functional film and makes ohmic contact with the first doped silicon layer;

[0031] The auxiliary gate line is laser processed by using laser induced sintering technology; wherein after the laser processing, the contact interface between the auxiliary gate line and the first doped silicon layer forms a density of (5-7)×10 6 Pieces / cm 2 Silver-silicon hybrid contact structure.

[0032] Optionally, in the step of laser processing the auxiliary grid lines using the laser induced sintering technology, the laser frequency is 30 Hz to 50 Hz, and the laser action time on the auxiliary grid lines is 10 ns to 10 ms;

[0033] The laser generates a current at the contact interface between the auxiliary gate line and the first doped silicon layer, with a current intensity of 20A to 40A and a current density of 1000A / cm 2 ~12000A / cm 2 .

[0034] Optionally, the step of preparing a first doped silicon layer on the light-receiving surface of the silicon wafer includes:

[0035] Diffusion is performed on the silicon wafer, so that the light-receiving surface is diffused to form the first doped silicon layer and the doped glass layer; wherein the sheet resistance of the first doped silicon layer after diffusion is 90Ω / □ to 110Ω / □;

[0036] After the step of preparing the first doped silicon layer on the light-receiving surface of the silicon wafer and before the step of preparing the first functional film on the surface of the first doped silicon layer facing away from the silicon wafer, the method for preparing a solar cell further comprises:

[0037] Using the doped glass layer, laser doping is performed on the light-receiving surface of the silicon wafer according to the pattern of the secondary gate line to form a heavily doped region on the first doped silicon layer; wherein the square resistance of the heavily doped region is 70Ω / □ to 100Ω / □;

[0038] The silicon wafer is heated and oxidized to form an oxide layer.

[0039] Optionally, after the step of heating and oxidizing the silicon wafer to form an oxide layer and before the step of preparing the first functional film on the side of the first doped silicon layer facing away from the silicon wafer, the method for preparing a solar cell further comprises the following steps:

[0040] Using hydrofluoric acid to remove the edge of the silicon wafer and the doped glass layer and the oxide layer on the backlight surface of the silicon wafer, and retaining the doped glass layer and the oxide layer on the light-receiving surface;

[0041] The backlight surface and the edge of the silicon wafer are subjected to alkali polishing.

[0042] Optionally, after the step of alkali polishing the backlight surface and the edge of the silicon wafer and before the step of preparing the first functional film on the side of the first doped silicon layer facing away from the silicon wafer, the method for preparing the solar cell further includes:

[0043] On the backlight surface, a dielectric layer and a second doped silicon layer are prepared, which are stacked in sequence and are away from the silicon wafer; wherein the silicon wafer and the second doped silicon layer both have a first conductivity type, and the first doped silicon layer has a second conductivity type opposite to the first conductivity type;

[0044] Annealing the silicon wafer to crystallize the second doped silicon layer;

[0045] Removing the coating around the second doped silicon layer on the light-receiving surface and the edge of the silicon wafer;

[0046] Removing the coating of the dielectric layer on the light-receiving surface and the edge of the silicon wafer;

[0047] The doped glass layer and the oxide layer remaining on the light receiving surface are removed.

[0048] Optionally, the step of preparing the first functional film on a side of the first doped silicon layer facing away from the silicon wafer includes:

[0049] Depositing an aluminum oxide passivation layer on a surface of the first doped silicon layer facing away from the silicon wafer;

[0050] Depositing a silicon nitride anti-reflection layer on a side of the aluminum oxide passivation layer facing away from the silicon wafer;

[0051] After the step of preparing the first functional film on the side of the first doped silicon layer away from the silicon wafer, and before the step of printing silver paste according to the pattern of the secondary grid lines on the side of the first functional film away from the first doped silicon layer, the method for preparing a solar cell further includes:

[0052] preparing a second functional film on a side of the second doped silicon layer away from the dielectric layer;

[0053] Printing a backlight surface electrode on the second functional film away from the second doped silicon layer;

[0054] A main grid is printed on a side of the first functional film away from the first doped silicon layer; the main grid and the auxiliary grid line form a light-receiving surface electrode.

[0055] Optionally, in the step of co-sintering the silicon wafer printed with the silver paste to obtain the secondary gate line, the sintering peak temperature is 790° C. to 870° C.

[0056] Optionally, before the step of preparing the first doped silicon layer on the first surface of the silicon wafer, the method for preparing the solar cell further comprises the following steps:

[0057] The light-receiving surface and the backlight surface are textured to form a textured pyramid light-trapping structure;

[0058] And / or, after the step of co-sintering the silicon wafer printed with the silver paste to obtain the auxiliary grid line, and before the step of laser processing the auxiliary grid line using the laser induced sintering technology, the method for preparing the solar cell further comprises the following steps:

[0059] The sintered solar cell is subjected to light injection treatment.

[0060] In a third aspect, an embodiment of the present application provides a photovoltaic module, comprising a solar cell as described in any one of the first aspects or a solar cell prepared by the method for preparing a solar cell as described in the second aspect.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] The solar cell adopts a silver-silicon hybrid contact structure to form good contact while avoiding serious recombination problems caused by silver-aluminum spikes, and then adopts high-density secondary grid lines to reduce the spacing between the secondary grid lines, reduce the lateral transmission distance of carriers, and improve the fill factor; by narrowing the line width of the secondary grid lines, it is avoided that the secondary grid line shading area is too large due to the high-density secondary grid lines, which affects the conversion efficiency. Finally, by forming a high-density silver-silicon hybrid contact structure, the problem of a decrease in the fill factor due to the narrowing of the line width of the secondary grid lines is avoided, so that the solar cell has lower contact resistance, lower metal area recombination and higher fill factor at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, 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 invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0064] Figure 1 It is a schematic diagram of the structure of a solar cell disclosed in an embodiment of the present application;

[0065] Figure 2 is a SEM image of a solar cell disclosed in an embodiment of the present application;

[0066] Figure 3 This is a flow chart of a method for preparing a solar cell in Example 1 of the present application.

[0067] Description of Figure Numbers:

[0068] 100, solar cell; 110, silicon wafer; 120, first doped silicon layer; 130, first functional film; 131, aluminum oxide passivation layer; 132, silicon nitride anti-reflection layer; 150, secondary grid line; 151, silver-silicon hybrid contact structure; 160, dielectric layer; 170, second doped silicon layer; 180, second functional film; 190, backlight electrode. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] As mentioned above, the solar cells in the related art form silver-aluminum spikes to form good contact and reduce contact resistance. However, the presence of aluminum will also cause the metal area to recombine more and lose open-circuit voltage. It is difficult for the above-mentioned solar cells to improve efficiency through a dense grid structure. The dense grid structure improves efficiency because the more the number of sub-grids, the smaller the current transmission distance, and the better the carriers can be collected. However, due to the high activity of aluminum in the silver-aluminum paste, the increase in the metal area will seriously aggravate the metal area recombination, causing the open-circuit voltage to drop significantly, limiting the efficiency improvement space of the dense grid structure, resulting in the current passivation contact battery grid line density is low and the line width is wide. Taking a 182mm×182mm battery as an example, the number of sub-grids on the light-receiving surface is 130 to 148, and the sub-grid line width is ≥13μm.

[0071] In related technologies, the most commonly used solution to the problem of front-side dense grid design causing aggravated recombination in the metal area is to use a high diffusion square resistance to reduce minority carrier recombination in the non-metal area. However, increasing the diffusion square resistance will increase the sheet resistance, increase the lateral carrier transmission resistance, and lose the fill factor, making it difficult to improve the conversion efficiency.

[0072] Another technical solution in the related art is to use a dense grid structure with a narrowed secondary grid line width to maintain the total area of ​​the metal area unchanged, but the narrowing of the grid line width will reduce the cross-sectional area of ​​the silver-aluminum electrode in contact with the silicon substrate, increase the contact resistance, and cause the fill factor to decrease, resulting in the dense grid design being unable to reflect the effect of improving the conversion efficiency. Although the improvement of the glass body in the slurry can optimize the contact to a certain extent, it will inevitably cause the metal area to recombine more severely.

[0073] In general, it is difficult for solar cells using silver-aluminum spikes as contact structures to simultaneously have low contact resistance, low metal area recombination, and high fill factor.

[0074] Based on the above analysis, the present application provides a solar cell and a preparation method thereof, and a photovoltaic module. The solar cell adopts a silver-silicon hybrid contact structure to form good contact while avoiding serious recombination problems caused by silver-aluminum spikes, and then adopts high-density secondary grid lines to reduce the spacing between the secondary grid lines, reduce the lateral transmission distance of carriers, and improve the fill factor; by narrowing the line width of the secondary grid lines, avoid the secondary grid lines The grid line shading area is too large due to the dense secondary grid lines, which affects the conversion efficiency. Finally, by forming a high-density silver-silicon hybrid contact structure, the problem of a decrease in the fill factor due to the narrowing of the line width of the secondary grid lines is avoided, so that the solar cell has lower contact resistance, lower metal area recombination and higher fill factor at the same time.

[0075] The technical solution of the present invention will be described below in conjunction with embodiments and drawings.

[0076] The first aspect, such as Figure 1 As shown, the embodiment of the present application provides a solar cell 100, including a silicon wafer 110, a first doped silicon layer 120, a first functional film 130 and a light-receiving surface electrode. The silicon wafer 110 has a light-receiving surface. The first doped silicon layer 120 is arranged on the light-receiving surface. The first doped silicon layer 120 can be a doped layer formed by element diffusion, or a polysilicon layer doped in situ, or an intrinsic silicon layer doped in substitution.

[0077] The first functional film 130 is disposed on the side of the first doped silicon layer 120 away from the silicon wafer 110. The light-receiving surface electrode includes a secondary gate line 150, which penetrates the first functional film 130 and makes ohmic contact with the first doped silicon layer 120.

[0078] The density of the secondary grid lines 150 is 0.483 / cm 2 ~0.604 / cm 2 The grid density of solar cells in related technologies is 0.392 grids / cm 2 ~0.447 / cm 2 , the density of the secondary grid lines 150 of the present application is higher, that is, a dense grid structure is adopted. The spacing between adjacent secondary grid lines 150 of the present application is 0.91mm to 1.25mm. On a solar cell 100 of a certain area, the higher the density of the secondary grid lines 150, the smaller the spacing D between adjacent secondary grid lines 150, the shorter the transmission path of the lateral current, the smaller the series resistance, and the higher the filling factor and output power. However, the higher the density of the secondary grid lines 150, the more the number of secondary grid lines 150 per unit area, which also means that the secondary grid lines 150 occupy more light-receiving area.

[0079] The line width W of the secondary grid line 150 is 8 μm to 12 μm. Compared with the secondary grid line width of solar cells in the related art, which is ≥ 13 μm, the line width of the secondary grid line 150 of the present application is narrower. The line width of the secondary grid line 150 determines the cross-sectional area of ​​the secondary grid line 150. The smaller the line width of the secondary grid line 150, the smaller the light receiving area occupied by the secondary grid line 150, which alleviates the problem of large light shielding area caused by the high density of the secondary grid line 150. However, the line width of the secondary grid line 150 cannot be too small. On the one hand, the printing accuracy is difficult to meet. On the other hand, the smaller the line width of the secondary grid line 150, the smaller the cross-sectional area of ​​the secondary grid line 150, and the greater its resistance.

[0080] The contact interface density between the secondary gate line 150 and the first doped silicon layer 120 is (5-7)×10 6 Pieces / cm 2 The silver-silicon hybrid contact structure 151 of the present application has a higher density than the density of the silver-aluminum spikes. The high-density silver-silicon hybrid contact structure 151 can alleviate the problem of the cross-sectional area of ​​the secondary gate line 150 being reduced and the resistance being increased due to the reduced line width of the secondary gate line 150.

[0081] The silver-silicon hybrid contact structure 151 of the solar cell 100 can be made by laser induced sintering (LIF) technology, which excites charge carriers by irradiating the cell with high-intensity laser, and applies a deflection voltage to generate local current, which triggers sintering, significantly reducing the contact resistance between silver and silicon, thereby improving the fill factor. The silver-silicon hybrid contact structure 151 avoids using aluminum as the material of the contact structure, thereby avoiding the problem of metal area compound enlargement caused by the presence of aluminum.

[0082] When metal region recombination is reduced, increasing the metal region area, that is, the area of ​​the light-receiving surface electrode, will not aggravate metal region recombination. Thus, high-density secondary grid lines 150 are used to reduce the spacing between secondary grid lines 150, reduce the lateral transmission distance of carriers, and improve the fill factor.

[0083] Furthermore, by narrowing the line width of the secondary grid line 150, it is avoided that the secondary grid line 150 shading area is too large due to the high density of the secondary grid line 150, which affects the conversion efficiency. Finally, by forming a high-density silver-silicon hybrid contact structure 151, it is avoided that the resistance increases due to the narrowing of the line width of the secondary grid line 150, so that the solar cell 100 has lower contact resistance, lower metal area recombination and higher fill factor.

[0084] Furthermore, the solar cell 100 further includes a dielectric layer 160 , a second doped silicon layer 170 , a second functional film 180 and a backlight electrode 190 .

[0085] The silicon wafer 110 also has a backlight surface, and the dielectric layer 160, the second doped silicon layer 170 and the second functional film 180 are stacked in sequence on the backlight surface away from the silicon wafer 110. The silicon wafer 110 and the second doped silicon layer 170 are of the first conductivity type, and the first doped silicon layer 120 has a second conductivity type opposite to the first conductivity type. The backlight surface electrode 190 penetrates the second functional film 180 and is in ohmic contact with the second doped silicon layer 170.

[0086] The dielectric layer 160 and the second doped silicon layer 170 form a passivation contact structure, which can achieve excellent surface passivation and selective collection of carriers.

[0087] The material of the dielectric layer 160 may include a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Specifically, the dielectric layer 160 may be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent passivation properties, can minimize the recombination loss of minority carriers on the surface of the semiconductor substrate, and is a film with excellent durability to subsequent high-temperature processes.

[0088] The dielectric layer 160 acts as a barrier to electrons and holes and can be combined with the polysilicon layer to prevent minority carriers from passing through. The dielectric layer 160 can also have a pinhole channel effect, allowing the carriers in the solar cell 100 to move freely, and the selective passage of the majority carriers through the heavily doped polysilicon is beneficial to reduce the recombination loss of the minority carriers. In addition, the dielectric layer 160 can be used as a diffusion barrier to prevent the dopant of the doped polysilicon layer from diffusing into the semiconductor substrate.

[0089] Optionally, the silicon wafer 110 is an N-type silicon wafer;

[0090] and / or, the first doped silicon layer 120 is a P-type doped silicon layer;

[0091] And / or, the first functional film 130 includes an aluminum oxide passivation layer 131 and a silicon nitride anti-reflection layer 132;

[0092] And / or, the dielectric layer 160 is a silicon oxide layer;

[0093] And / or, in order to better provide interface passivation for the substrate, the thickness of the dielectric layer 160 is 0.1 nm to 5 nm, including any value within the thickness range, such as 0.1 nm, 1 nm, 3 nm or 5 nm;

[0094] and / or, the second doped silicon layer 170 is an N-type doped polysilicon layer;

[0095] And / or, the second functional film 180 includes a silicon nitride anti-reflection layer.

[0096] Optionally, the area of ​​silicon wafer 110 is 331.24 cm 2 For example, for a silicon wafer with a size of 182 mm×182 mm, the number of the secondary gate lines 150 is 160 to 200, including any value within the range, such as 160, 180 or 200;

[0097] Or, the area of ​​the silicon wafer is 382.2 cm 2 For example, for a silicon wafer with a size of 182 mm×210 mm, the number of secondary gate lines is 185 to 230, including any point value within the range, such as 185, 200 or 230;

[0098] Or, the area of ​​the silicon wafer is 347.62cm 2 For example, for a silicon wafer with a size of 182 mm×191 mm, the number of secondary gate lines is 168 to 209, including any point value within the range, such as 168, 200 or 209;

[0099] Or, the area of ​​the silicon wafer is 441cm 2 For example, for a silicon wafer with a size of 210 mm×210 mm, the number of secondary gate lines is 214 to 266, including any point value within the range, such as 214, 230 or 266.

[0100] Optionally, the silver-silicon hybrid contact structure 151 is a forked structure; the silver-silicon hybrid contact structure 151 is composed of a plurality of fibrous branches, and the term "forked" means being divided into a plurality of branches at a specific point, and the forked structure is conducive to forming good contact.

[0101] And / or, the silver-silicon hybrid contact structure 151 is a submicron structure. The term "submicron" refers to 100nm-1.0μm. The silver-silicon hybrid contact structure 151 is extremely small in size, so that it can be distributed with high density in a small area.

[0102] In a second aspect, an embodiment of the present application provides a method for preparing a solar cell according to the first aspect, comprising the following steps:

[0103] Preparing a first doped silicon layer on the light-receiving surface of the silicon wafer;

[0104] Forming a first functional film on a surface of the first doped silicon layer facing away from the silicon wafer;

[0105] Silver paste is printed on the side of the first functional film away from the first doped silicon layer according to the pattern of the secondary grid lines; wherein the density of the secondary grid lines is 0.483 pieces / cm 2 ~0.604 / cm 2, the line width of the secondary grid line is 8μm to 12μm, and the spacing between adjacent secondary grid lines is 0.91mm to 1.25mm; the mass proportion of aluminum in the silver paste is less than 1%, and the mass proportion of silver in the silver paste is greater than 90%;

[0106] Co-sintering the silicon wafer printed with silver paste to obtain a secondary gate line; wherein the secondary gate line penetrates the first functional film and makes ohmic contact with the first doped silicon layer;

[0107] The auxiliary gate line is laser processed by using laser induced sintering technology; wherein the contact interface density between the auxiliary gate line and the first doped silicon layer after laser processing is (5-7)×10 6 Pieces / cm 2 Silver-silicon hybrid contact structure.

[0108] The preparation method of the solar cell adopts silver paste with low aluminum content to print the secondary grid line, so as to avoid the problem of increased metal area recombination caused by the presence of a large amount of aluminum at the contact interface. The secondary grid line is laser processed by laser induced sintering technology. The laser induced sintering technology is to irradiate the cell with high-intensity laser to excite the charge carriers, and at the same time apply the deflection voltage to generate local current, induce sintering, and significantly reduce the contact resistance between silver and silicon, thereby improving the filling factor. The obtained silver-silicon mixed contact structure has the characteristics of high density, low contact resistance and less recombination, so as to reduce the metal area recombination and improve the contact.

[0109] In the case of reduced metal area recombination, increasing the metal area area will not aggravate the metal area recombination, and the graphics of the secondary grid lines can adopt high-density secondary grid line graphics. The higher the secondary grid line density, the smaller the spacing between adjacent secondary grid lines, the shorter the lateral current transmission path, the smaller the series resistance, and the higher the fill factor and output power. However, the higher the density of the secondary grid lines, the more secondary grid lines there are per unit area, which also means that the secondary grid lines occupy more light-receiving area. In order to reduce the impact on the light-receiving area, the graphics of the secondary grid lines of the present application adopt a narrowed secondary grid line width, and the line width of the secondary grid line is 8μm to 12μm. The narrowing of the line width of the secondary grid line leads to the problem of smaller cross-sectional area of ​​the secondary grid line and increased resistance. Furthermore, the preparation method forms a contact interface between the secondary grid line and the first doped silicon layer with a density of (5 to 7)×10 6 Pieces / cm 2 Silver-silicon hybrid contact structure, please refer to Figure 2 , Figure 2 This is a SEM image of a solar cell disclosed in an embodiment of the present application. The SEM image shows the silver-silicon hybrid contact structure at the contact interface. The magnification is 50,000 times. The gray-white bright spots with high-density multi-point distribution in the image are the silver-silicon hybrid contact structure of the present application. The high-density silver-silicon hybrid contact structure allows good contact to be maintained even if the line width of the secondary grid line is narrow, and the contact resistance is small.

[0110] Further, in the step of laser processing the auxiliary grid lines using the laser induced sintering technology, the laser frequency is 30 Hz to 50 Hz, including any value within the frequency range, such as 30 Hz, 40 Hz or 50 Hz, and the laser action time on the auxiliary grid lines is 10 ns to 10 ms, including any value within the time range, such as 10 ns, 1 ms or 10 ms;

[0111] The laser generates a current at the contact interface between the secondary gate line and the first doped silicon layer. The current intensity is 20A-40A, including any point value within the current intensity range, such as 20A, 30A or 40A, and the current density is 1000A / cm 2 ~12000A / cm 2 Includes any point value within the current density range, for example, 1000A / cm 2 、5000A / cm 2 or 12000A / cm 2 .

[0112] By selecting the above laser frequency, action time, current intensity and current density, a high-density silver-silicon hybrid contact structure can be formed after laser processing.

[0113] Furthermore, the step of preparing a first doped silicon layer on the light-receiving surface of the silicon wafer includes:

[0114] Diffusion is performed on the silicon wafer so that the light-receiving surface is diffused to form a first doped silicon layer and a doped glass layer; wherein the sheet resistance of the first doped silicon layer after diffusion is 90Ω / □ to 110Ω / □;

[0115] After the step of preparing a first doped silicon layer on the light-receiving surface of the silicon wafer and before the step of preparing a first functional film on the side of the first doped silicon layer facing away from the silicon wafer, the method for preparing a solar cell further comprises:

[0116] Using the doped glass layer, laser doping is performed on the light-receiving surface of the silicon wafer according to the pattern of the secondary grid lines to form a heavily doped area on the first doped silicon layer; wherein the square resistance of the heavily doped area is 70Ω / □ to 100Ω / □;

[0117] The silicon wafer is heated and oxidized to form an oxide layer.

[0118] By forming a heavily doped area, a selective emitter structure is formed on the light-receiving surface, thereby reducing the contact resistance between the light-receiving surface electrode and the silicon wafer. Low-concentration doping is performed on the silicon wafer area other than the light-receiving surface electrode to reduce recombination.

[0119] Optionally, after the step of heating and oxidizing the silicon wafer to form an oxide layer and before the step of preparing a first functional film on a side of the first doped silicon layer facing away from the silicon wafer, the method for preparing a solar cell further comprises the following steps:

[0120] Use hydrofluoric acid to remove the doped glass layer and oxide layer on the edge of the silicon wafer and the backlight side of the silicon wafer, and retain the doped glass layer and oxide layer on the light-receiving side;

[0121] The backlight surface and the edge of the silicon wafer are alkaline polished.

[0122] Optionally, after the step of alkali polishing the backlight surface and the edge of the silicon wafer, and before the step of preparing the first functional film on the side of the first doped silicon layer facing away from the silicon wafer, the method for preparing the solar cell further comprises:

[0123] On the backlight surface, a dielectric layer and a second doped silicon layer are stacked in sequence away from the silicon wafer, wherein both the silicon wafer and the second doped silicon layer have a first conductivity type, and the first doped silicon layer has a second conductivity type opposite to the first conductivity type;

[0124] Annealing the silicon wafer to crystallize the second doped silicon layer;

[0125] Removing the coating around the second doped silicon layer on the light-receiving surface and the edge of the silicon wafer;

[0126] Removing the coating of the dielectric layer on the light-receiving surface and the edge of the silicon wafer;

[0127] Remove the remaining doped glass layer and oxide layer on the light-receiving surface.

[0128] Optionally, the step of preparing a first functional film on a side of the first doped silicon layer facing away from the silicon wafer includes:

[0129] Depositing an aluminum oxide passivation layer on a side of the first doped silicon layer facing away from the silicon wafer;

[0130] Depositing a silicon nitride anti-reflection layer on the side of the aluminum oxide passivation layer facing away from the silicon wafer;

[0131] After the step of preparing a first functional film on the side of the first doped silicon layer facing away from the silicon wafer, and before the step of printing silver paste according to the pattern of the secondary grid lines on the side of the first functional film facing away from the first doped silicon layer, the method for preparing a solar cell further includes:

[0132] preparing a second functional film on a side of the second doped silicon layer facing away from the dielectric layer;

[0133] Printing a backlight surface electrode on the second functional film away from the second doped silicon layer;

[0134] The main grid is printed on the side of the first functional film away from the first doped silicon layer; the main grid and the auxiliary grid line form a light-receiving surface electrode.

[0135] Optionally, in the step of co-sintering the silicon wafer printed with silver paste to obtain the secondary gate line, the sintering peak temperature is 790° C. to 870° C.

[0136] Optionally, before the step of preparing the first doped silicon layer on the first surface of the silicon wafer, the method for preparing the solar cell further comprises the following steps:

[0137] The light-receiving surface and the backlight surface are textured to form a velvet pyramid light-trapping structure.

[0138] After the light-receiving surface is textured, the surface light reflection is reduced, which means that more light enters the solar cell, thus generating more photogenerated carriers.

[0139] Optionally, after the step of co-sintering the silicon wafer printed with silver paste to obtain the auxiliary grid lines and before the step of laser processing the auxiliary grid lines using the laser induced sintering technology, the method for preparing the solar cell further comprises the following steps:

[0140] The sintered solar cells are subjected to light injection treatment.

[0141] After the solar cells are printed and sintered, they are then injected with light, and their efficiency is significantly improved, mainly in terms of open circuit voltage and fill factor.

[0142] In a third aspect, an embodiment of the present application provides a photovoltaic module, comprising a solar cell as described in any one of the first aspects or a solar cell prepared by the method for preparing a solar cell as described in the second aspect.

[0143] The technical solution of the present invention will be described below in conjunction with embodiments and drawings.

[0144] Example 1

[0145] like Figure 3 As shown, the preparation method of the solar cell provided in this embodiment comprises the following steps:

[0146] S1. Texturing the light-receiving surface and the back-light surface to form a velvet pyramid light-trapping structure: using a single crystal N-type silicon wafer with a size of 182mm×182mm, using alkali to texturing the light-receiving surface and the back-light surface to form a velvet pyramid light-trapping structure.

[0147] S2. Diffusion of silicon wafers to form the first doped silicon layer and doped glass layer on the light-receiving surface: boron trichloride and silicon wafers are reacted at high temperature to diffuse the light-receiving surface to form a PN emitter junction, i.e. the first doped silicon layer, and a BSG (Boron-Silicate Glass) layer, i.e. the doped glass layer. The sheet resistance of the first doped silicon layer after diffusion is 90Ω / □.

[0148] S3. Using the doped glass layer, laser doping is performed on the light-receiving surface of the silicon wafer according to the pattern of the secondary gate lines to form a heavily doped area on the first doped silicon layer: using the BSG layer formed in the diffusion process, laser doping is performed on the light-receiving surface of the silicon wafer after diffusion and on the metallized area corresponding to the light-receiving surface electrode. The pattern of the metallized area includes the pattern of the secondary gate lines. Laser doping forms a heavily doped area, thereby realizing a selective emitter structure on the light-receiving surface of the silicon wafer. The block resistance of the heavily doped area is 70Ω / □, and the number of secondary gate lines is 160.

[0149] S4. Heat and oxidize the silicon wafer to form an oxide layer: The diffused silicon wafer is passed through oxygen at high temperature to form an oxide layer on the light-receiving surface to protect the PN junction of the light-receiving surface from being damaged.

[0150] S5. Use hydrofluoric acid to remove the doped glass layer and oxide layer on the edge of the silicon wafer and the backlight surface of the silicon wafer, and retain the doped glass layer and oxide layer on the light-receiving surface: Use hydrofluoric acid to remove the BSG layer and oxide layer on the edge of the silicon wafer and the backlight surface after thermal oxidation.

[0151] S6. Alkali polishing of the backlight surface and the edge of the silicon wafer: polishing of the backlight surface and the edge of the silicon wafer.

[0152] S7. Prepare a dielectric layer and a second doped silicon layer stacked in sequence away from the silicon wafer on the backlight surface: deposit a thin layer of silicon oxide and a phosphorus-doped polysilicon layer in sequence on the backlight surface after alkali polishing, the thin layer of silicon oxide is the dielectric layer, and the phosphorus-doped polysilicon layer is the second doped silicon layer.

[0153] S8. Annealing the silicon wafer to crystallize the second doped silicon layer: performing heat treatment at 910° C. to crystallize the phosphorus-doped polysilicon layer on the backlight side.

[0154] S9, removing the coating of the second doped silicon layer on the light-receiving surface and the edge of the silicon wafer, removing the coating of the dielectric layer on the light-receiving surface and the edge of the silicon wafer, and removing the remaining doped glass layer and oxide layer on the light-receiving surface.

[0155] S10, depositing an aluminum oxide passivation layer on a side of the first doped silicon layer facing away from the silicon wafer: depositing an aluminum oxide passivation layer on a side of the first doped silicon layer facing away from the silicon wafer by atomic layer deposition.

[0156] S11. Depositing a silicon nitride anti-reflection layer on the side of the aluminum oxide passivation layer facing away from the silicon wafer: using PECVD to deposit a silicon nitride anti-reflection film on the side of the aluminum oxide film layer facing away from the silicon wafer.

[0157] S12, preparing a second functional film on a side of the second doped silicon layer away from the dielectric layer: using PECVD to deposit a silicon nitride film, ie, the second functional film, on a side of the phosphorus-doped polysilicon layer away from the dielectric layer.

[0158] S13, printing a backlight side electrode on the second functional film away from the second doped silicon layer: using a backlight side electrode design pattern, printing a backlight side electrode on the second functional film away from the second doped silicon layer by screen printing.

[0159] S14. Print the main grid on the side of the first functional film away from the first doped silicon layer, and print silver paste according to the pattern of the secondary grid lines on the side of the first functional film away from the first doped silicon layer: first print the main grid on the side of the first functional film away from the first doped silicon layer; then use silver paste to prepare the secondary grid lines by screen printing according to the pattern of 160 secondary grid lines, the line width of the secondary grid lines is 12μm, the main grid and the secondary grid lines constitute the light-receiving surface electrode, the mass content of aluminum in the silver paste is less than 1%, and the mass content of silver is 91%.

[0160] S15. Co-sinter the silicon wafer printed with silver paste to obtain the auxiliary grid line: co-sinter the silicon wafer printed with the light-receiving surface electrode and the backlight surface electrode, with the sintering peak temperature of 850°C, to obtain the light-receiving surface electrode and the backlight surface electrode, wherein the light-receiving surface electrode includes the above-mentioned auxiliary grid line, that is, the above-mentioned auxiliary grid line is obtained.

[0161] S16, performing light injection treatment on the sintered solar cells: performing light injection treatment on the sintered cells.

[0162] S17. Use laser induced sintering technology to laser process the auxiliary grid lines: laser process the light-receiving surface of the cell after light injection to improve the contact performance of the auxiliary grid lines on the light-receiving surface; the laser frequency is 40KHz, and the laser action time on the auxiliary grid lines is 1ms; the laser of this frequency forms a current at the contact interface between the auxiliary grid lines and the first doped silicon layer, with a current intensity of 30A and a current density of 6000A / cm 2 After laser treatment, the contact interface density between the auxiliary gate line and the first doped silicon layer is 6×10 6 Pieces / cm 2 Silver-silicon hybrid contact structure.

[0163] Example 2

[0164] The difference between this embodiment and embodiment 1 is that:

[0165] In step S2, the sheet resistance of the first doped silicon layer after diffusion is 110Ω / □.

[0166] In step S3, the sheet resistance of the heavily doped region is 100Ω / □.

[0167] Example 3

[0168] The difference between this embodiment and embodiment 2 is that:

[0169] In step S3, the number of secondary gate lines is 180.

[0170] In step S14, secondary grid lines are prepared by screen printing according to a pattern of 180 secondary grid lines, and the line width of the secondary grid lines is 10 μm.

[0171] Example 4

[0172] The difference between this embodiment and embodiment 2 is that:

[0173] In step S3, the number of secondary gate lines is 200.

[0174] In step S14, secondary grid lines are prepared by screen printing according to a pattern of 200 secondary grid lines, and the line width of the secondary grid lines is 8 μm.

[0175] Example 5

[0176] The difference between this embodiment and Embodiment 1 is that step S3 is not performed, that is, laser doping is not performed.

[0177] Example 6

[0178] The difference between this embodiment and embodiment 1 is that the peak sintering temperature is 890°C.

[0179] Example 7

[0180] The difference between this embodiment and embodiment 1 is that the laser frequency is 60 KHz, and the contact interface density between the auxiliary gate line and the first doped silicon layer after laser treatment is 6.5×10 6 Pieces / cm 2 Silver-silicon hybrid contact structure.

[0181] Example 8

[0182] The difference between this embodiment and embodiment 1 is that the laser frequency is 20 KHz, and the contact interface density between the auxiliary gate line and the first doped silicon layer after laser treatment is 3×10 6 Pieces / cm 2 Silver-silicon hybrid contact structure.

[0183] Comparative Example 1

[0184] The difference between Comparative Example 1 and Example 1 is only that:

[0185] In step S3, the number of secondary grid lines is 148.

[0186] In step S14, the secondary grid lines are prepared using silver-aluminum paste, wherein the mass proportion of silver in the silver-aluminum paste is 91%, and the mass proportion of aluminum in the silver-aluminum paste is 2%; the secondary grid lines are prepared by screen printing according to a pattern of 148 secondary grid lines, and the line width of the secondary grid lines is 14μm.

[0187] And step S17 is not performed.

[0188] Comparative Example 2

[0189] The difference between Comparative Example 2 and Example 1 is that: in step S14, silver-aluminum paste is used to prepare the secondary gate line, wherein the mass proportion of silver in the silver-aluminum paste is 91%, and the mass proportion of aluminum in the silver-aluminum paste is 2%;

[0190] Step S17 is not performed, that is, laser processing of the auxiliary gate lines using the laser induced sintering technology is not performed.

[0191] Comparative Example 3

[0192] The difference between Comparative Example 3 and Example 2 is that: in step S14, silver-aluminum paste is used to prepare the secondary gate line, wherein the mass proportion of silver in the silver-aluminum paste is 91%, and the mass proportion of aluminum in the silver-aluminum paste is 2%;

[0193] Step S17 is not performed, that is, laser processing of the auxiliary gate lines using the laser induced sintering technology is not performed.

[0194] Comparative Example 4

[0195] The only difference between the preparation method of the solar cell of this comparative example and that of Example 1 is that in step S3, the number of secondary grid lines is 148.

[0196] In step S14, secondary grid lines are prepared by screen printing according to a pattern of 148 secondary grid lines, and the line width of the secondary grid lines is 14 μm.

[0197] The electrical properties of the solar cells prepared in various embodiments and comparative examples were tested, and the test results are shown in Table 1. In Table 1, R1 represents the square resistance of the first doped silicon layer after diffusion, R2 represents the square resistance of the re-expanded area, LIF represents the laser induced sintering technology, D represents the spacing between the auxiliary grid lines, and W represents the line width of the auxiliary grid lines.

[0198] Table 1: Electrical performance test results of solar cells prepared in various embodiments and comparative examples

[0199]

[0200]

[0201] As shown in Table 1, compared with Example 1, since Comparative Example 1 uses silver aluminum paste to make the secondary grid lines to improve the contact, the presence of aluminum will also cause the metal area to increase and lose the open circuit voltage; the solar cell of Comparative Example 1 is difficult to improve the efficiency through the dense grid structure, so that the density of the secondary grid lines of Comparative Example 1 is only 0.447 / cm 2In order to avoid the increase of resistance due to the narrow width of the secondary grid line, the width of the secondary grid line of comparative example 1 is wider, reaching 14μm. The silver-aluminum spikes after sintering lead to more serious metal area recombination, and the lower density of the secondary grid line increases the current transmission distance.

[0202] In Example 1, laser induced sintering (LIF) technology is used to make a silver-silicon hybrid contact structure. The silver-silicon hybrid contact structure avoids the use of aluminum as the material of the contact structure, thereby avoiding the problem of increased metal area recombination due to the presence of aluminum. When the metal area recombination is reduced, increasing the metal area area, that is, the area of ​​the light-receiving surface electrode, will not aggravate the metal area recombination, and then using high-density secondary grid lines to reduce the spacing between the secondary grid lines, reduce the lateral transmission distance of carriers, and improve the fill factor. By narrowing the line width of the secondary grid lines, the conversion efficiency is not affected by the excessive shading area of ​​the secondary grid lines caused by the high-density secondary grid lines. Finally, by forming a high-density silver-silicon hybrid contact structure, the problem of increased resistance due to the narrowing of the line width of the secondary grid lines is avoided, so that the solar cell has lower contact resistance, lower metal area recombination and higher fill factor at the same time. The contact resistance of Example 1 is reduced by 0.4 mΩ / cm compared with Comparative Example 1. 2 , the open circuit voltage increased by 2mV and the fill factor increased by 0.3%.

[0203] Comparative Example 2 did not perform step S17, that is, it did not use laser induced sintering technology (LIF) to make a silver-silicon hybrid contact structure, resulting in the contact interface between the secondary grid line and the first doped silicon layer of the solar cell in Comparative Example 2 not forming a high-density contact structure. In order to form a better contact, Comparative Example 2 used silver aluminum paste to make the secondary grid line, but the presence of aluminum also caused the metal area to increase and lose the open circuit voltage. While Example 1 used laser induced sintering technology (LIF) to make a high-density silver-silicon hybrid contact structure layer to improve the contact performance, the contact resistance was reduced by 0.65mΩ / cm compared with Comparative Example 2. 2 , and the open circuit voltage is increased by 1 mV, and the fill factor is increased by 0.1%, indicating that even though Comparative Example 2 uses the same secondary gate line density, line width and spacing as Example 1, due to the lack of LIF, Comparative Example 2 does not have lower contact resistance, lower metal area recombination and higher fill factor at the same time.

[0204] Similarly, Example 2 adds laser induced sintering technology (LIF) to produce a high-density silver-silicon hybrid contact structure layer compared to Comparative Example 3, which improves the contact performance and reduces the contact resistance by 1.06 mΩ / cm compared to Comparative Example 3. 2, and the open circuit voltage is increased by 5mV, and the fill factor is increased by 0.2%. Compared with Example 1, Example 2 increases the square resistance of the first doped silicon layer after diffusion and the square resistance of the re-expansion area. Although the contact resistance of Example 2 is increased by 0.06mΩ / cm compared with Example 1, 2 , but reduces the minority carrier recombination in the non-metallic area. The term "non-metallic area" refers to the light-receiving surface area outside the coverage of the light-receiving surface electrode, so that the open circuit voltage of Example 2 is improved relative to Example 1.

[0205] Comparative Example 4 uses a lower secondary gate line density and a wider line width compared to Example 1. Although it has undergone LIF treatment, its fill factor is lower than that of Example 1. Example 1 uses a higher secondary gate line density, the line width of the secondary gate line is narrower, the lateral transmission distance of the carriers is reduced, the fill factor is improved, and the conversion efficiency is correspondingly improved.

[0206] Compared with Example 2, Example 3 increases the density of the secondary grid lines and reduces the width of the secondary grid lines, so that the lateral transmission distance of the solar cell carriers in Example 3 is reduced, and Example 3 improves the fill factor compared with Example 2. However, due to the smaller width of the secondary grid lines, the cross-sectional area is reduced, so the contact resistance of Example 3 is increased by 0.04 mΩ / cm compared with Example 2. 2 .

[0207] Compared with Example 2, Example 4 further improves the density of the secondary grid lines and reduces the width of the secondary grid lines, so that the lateral transmission distance of the solar cell carriers in Example 4 is reduced, and Example 4 improves the fill factor compared with Example 2. However, due to the smaller width of the secondary grid lines, the cross-sectional area is reduced, so the contact resistance of Example 4 is increased by 0.37 mΩ / cm compared with Example 2. 2 , indicating that further increasing the density of the secondary gate lines and further reducing the width of the secondary gate lines will aggravate the impact on the contact resistance.

[0208] Compared with Example 1, Example 5 did not perform laser doping, and the square resistance of the first doped silicon layer was consistent at all locations, all of which were 90Ω / □, that is, no heavily doped region was formed, and there was a lack of a selective emitter structure for improving contact. However, Example 1 performed laser doping and heated oxidation to obtain a heavily doped region, that is, a selective emitter structure was made, so that Example 1 had lower contact resistance, higher conversion efficiency, fill factor, and open circuit voltage.

[0209] Compared with Example 1, the sintering peak temperature of Example 6 is too high. The excessively high sintering peak temperature causes puncture of the silver paste, resulting in higher contact resistance of Example 6. The excessively high sintering peak temperature also causes more serious damage to the silicon wafer and more serious recombination of carriers at the interface, resulting in a decrease in the conversion efficiency, open circuit voltage and fill factor of Example 6.

[0210] Compared with Example 1, the laser frequency used in Example 7 is too high. The too high laser frequency will cause a certain degree of damage to the contact interface between the auxiliary gate line and the first doped silicon layer, resulting in the occurrence of puncture phenomenon. The puncture phenomenon leads to increased recombination, which is reflected in the lower open circuit voltage and conversion efficiency of Example 7.

[0211] Compared with Example 1, the laser frequency used in Example 8 is too low, resulting in a low density of the silver-silicon hybrid contact structure. At the same time, the secondary gate line adopts a narrower line width, which results in a smaller cross-sectional area of ​​the secondary gate line and an increased resistance, which leads to a higher contact resistance in Example 8. Since the density of the silver-silicon hybrid contact structure is low, it is difficult to avoid the problem of a decrease in fill factor due to the narrowing of the line width of the secondary gate line, resulting in a low fill factor and conversion efficiency in Example 8.

[0212] A solar cell and a preparation method thereof, and a photovoltaic module disclosed in an embodiment of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand a solar cell and a preparation method thereof, a photovoltaic module and its core concept of the present invention. At the same time, for a person skilled in the art, according to the concept of the present invention, there will be changes in the specific implementation mode and the scope of application. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A solar cell, characterized in that: include: A silicon wafer, wherein the silicon wafer has a light-receiving surface; a first doped silicon layer, wherein the first doped silicon layer is disposed on the light receiving surface; a first functional film, wherein the first functional film is disposed on a surface of the first doped silicon layer facing away from the silicon wafer; as well as The light-receiving surface electrode comprises a secondary grid line, the secondary grid line penetrates the first functional film and makes ohmic contact with the first doped silicon layer; the density of the secondary grid line is 0.483 pieces / cm 2 ~0.604 / cm 2 The line width of the secondary gate line is 8 μm to 12 μm, the spacing between adjacent secondary gate lines is 0.91 mm to 1.25 mm, and the contact interface formation density between the secondary gate line and the first doped silicon layer is (5 to 7)×10 6 Pieces / cm 2 Silver-silicon hybrid contact structure.

2. The solar cell according to claim 1, characterized in that: The solar cell also includes a dielectric layer, a second doped silicon layer, a second functional film and a backlight electrode; The silicon wafer also has a backlight surface, the dielectric layer, the second doped silicon layer and the second functional film are stacked in sequence on the backlight surface away from the silicon wafer, the silicon wafer and the second doped silicon layer are of a first conductivity type, and the first doped silicon layer has a second conductivity type opposite to the first conductivity type; The backlight surface electrode penetrates the second functional film and is in ohmic contact with the second doped silicon layer.

3. The solar cell according to claim 2, characterized in that: The silicon wafer is an N-type silicon wafer; And / or, the first doped silicon layer is a P-type doped silicon layer; And / or, the first functional film includes an aluminum oxide passivation layer and a silicon nitride anti-reflection layer; And / or, the dielectric layer is a silicon oxide layer; And / or, the thickness of the dielectric layer is 0.1 nm to 5 nm; And / or, the second doped silicon layer is an N-type doped polysilicon layer; And / or, the second functional film includes a silicon nitride anti-reflection layer.

4. The solar cell according to any one of claims 1 to 3, characterized in that The area of ​​the silicon wafer is 331.24 cm 2 , the number of the secondary grid lines is 160 to 200; Or, the area of ​​the silicon wafer is 382.2 cm 2 , the number of the secondary grid lines is 185 to 230; Or, the area of ​​the silicon wafer is 347.62cm 2 , the number of the secondary grid lines is 168 to 209; Or, the area of ​​the silicon wafer is 441cm 2 The number of the secondary grid lines is 214 to 266.

5. The solar cell according to any one of claims 1 to 3, characterized in that The silver-silicon hybrid contact structure is a bifurcated structure; And / or, the silver-silicon hybrid contact structure is a submicron structure.

6. A method for preparing a solar cell according to any one of claims 1 to 5, characterized in that: The following steps are involved: Preparing a first doped silicon layer on the light-receiving surface of the silicon wafer; forming the first functional film on a surface of the first doped silicon layer facing away from the silicon wafer; Silver paste is printed on the side of the first functional film away from the first doped silicon layer according to the pattern of the secondary grid lines; wherein the density of the secondary grid lines is 0.483 pieces / cm 2 ~0.604 / cm 2 , the line width of the secondary grid lines is 8 μm to 12 μm, and the spacing between adjacent secondary grid lines is 0.91 mm to 1.25 mm; the mass proportion of aluminum in the silver paste is less than 1%, and the mass proportion of silver in the silver paste is greater than 90%; Co-sintering the silicon wafer printed with the silver paste to obtain the auxiliary gate line; wherein the auxiliary gate line penetrates the first functional film and makes ohmic contact with the first doped silicon layer; The auxiliary gate line is laser processed by using laser induced sintering technology; wherein after the laser processing, the contact interface between the auxiliary gate line and the first doped silicon layer forms a density of (5-7)×10 6 Pieces / cm 2 Silver-silicon hybrid contact structure.

7. The method for preparing a solar cell according to claim 6, characterized in that: In the step of laser processing the auxiliary grid lines using the laser induced sintering technology, the laser frequency is 30KHz to 50KHz, and the laser action time on the auxiliary grid lines is 10ns to 10ms; The laser generates a current at the contact interface between the auxiliary gate line and the first doped silicon layer, with a current intensity of 20A to 40A and a current density of 1000A / cm 2 ~12000A / cm 2 .

8. The method for preparing a solar cell according to claim 6, characterized in that: The step of preparing a first doped silicon layer on the light-receiving surface of the silicon wafer comprises: Diffusion is performed on the silicon wafer, so that the light-receiving surface is diffused to form the first doped silicon layer and the doped glass layer; wherein the sheet resistance of the first doped silicon layer after diffusion is 90Ω / □ to 110Ω / □; After the step of preparing the first doped silicon layer on the light-receiving surface of the silicon wafer and before the step of preparing the first functional film on the surface of the first doped silicon layer facing away from the silicon wafer, the method for preparing a solar cell further comprises: Using the doped glass layer, laser doping is performed on the light-receiving surface of the silicon wafer according to the pattern of the secondary gate line to form a heavily doped region on the first doped silicon layer; wherein the square resistance of the heavily doped region is 70Ω / □ to 100Ω / □; The silicon wafer is heated and oxidized to form an oxide layer.

9. The method for preparing a solar cell according to claim 8, characterized in that: After the step of heating and oxidizing the silicon wafer to form an oxide layer and before the step of preparing the first functional film on the side of the first doped silicon layer facing away from the silicon wafer, the method for preparing a solar cell further comprises the following steps: Using hydrofluoric acid to remove the edge of the silicon wafer and the doped glass layer and the oxide layer on the backlight surface of the silicon wafer, and retaining the doped glass layer and the oxide layer on the light-receiving surface; The backlight surface and the edge of the silicon wafer are subjected to alkali polishing.

10. The method for preparing a solar cell according to claim 9, characterized in that: After the step of alkali polishing the backlight surface and the edge of the silicon wafer, and before the step of preparing the first functional film on the side of the first doped silicon layer facing away from the silicon wafer, the method for preparing a solar cell further includes: On the backlight surface, a dielectric layer and a second doped silicon layer are prepared, which are stacked in sequence and are away from the silicon wafer; wherein the silicon wafer and the second doped silicon layer both have a first conductivity type, and the first doped silicon layer has a second conductivity type opposite to the first conductivity type; Annealing the silicon wafer to crystallize the second doped silicon layer; Removing the coating around the second doped silicon layer on the light-receiving surface and the edge of the silicon wafer; Removing the coating of the dielectric layer on the light-receiving surface and the edge of the silicon wafer; The doped glass layer and the oxide layer remaining on the light receiving surface are removed.

11. The method for preparing a solar cell according to claim 10, characterized in that: The step of preparing the first functional film on the side of the first doped silicon layer facing away from the silicon wafer comprises: Depositing an aluminum oxide passivation layer on a surface of the first doped silicon layer facing away from the silicon wafer; Depositing a silicon nitride anti-reflection layer on a side of the aluminum oxide passivation layer facing away from the silicon wafer; After the step of preparing the first functional film on the side of the first doped silicon layer away from the silicon wafer, and before the step of printing silver paste according to the pattern of the secondary grid lines on the side of the first functional film away from the first doped silicon layer, the method for preparing a solar cell further includes: preparing a second functional film on a side of the second doped silicon layer away from the dielectric layer; Printing a backlight surface electrode on the second functional film away from the second doped silicon layer; A main grid is printed on a side of the first functional film away from the first doped silicon layer; the main grid and the auxiliary grid line form a light-receiving surface electrode.

12. The method for preparing a solar cell according to any one of claims 6 to 11, characterized in that: In the step of co-sintering the silicon wafer printed with the silver paste to obtain the secondary gate line, the sintering peak temperature is 790° C. to 870° C.

13. The method for preparing a solar cell according to any one of claims 9 to 11, characterized in that: Before the step of preparing the first doped silicon layer on the first surface of the silicon wafer, the method for preparing the solar cell further comprises the following steps: The light-receiving surface and the backlight surface are textured to form a textured pyramid light-trapping structure; And / or, after the step of co-sintering the silicon wafer printed with the silver paste to obtain the auxiliary grid line, and before the step of laser processing the auxiliary grid line using the laser induced sintering technology, the method for preparing the solar cell further comprises the following steps: The sintered solar cell is subjected to light injection treatment.

14. A photovoltaic module, characterized in that: A solar cell comprising the solar cell according to any one of claims 1 to 5 or a solar cell prepared by the method for preparing a solar cell according to any one of claims 6 to 13.

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