CN112234109A

CN112234109A - Solar cell, front electrode thereof, preparation method and application

Info

Publication number: CN112234109A
Application number: CN202011231529.6A
Authority: CN
Inventors: 黄智�; 张�林; 夏伟; 冉东; 徐涛; 翟绪锦; 谢泰宏
Original assignee: Tongwei Solar Hefei Co Ltd
Current assignee: Tongwei Solar Anhui Co Ltd; Tongwei Solar Hefei Co Ltd
Priority date: 2020-11-06
Filing date: 2020-11-06
Publication date: 2021-01-15

Abstract

The invention discloses a solar cell, a front electrode thereof, a preparation method and application, and belongs to the technical field of solar cells. The number of welding points on a single main grid of the front electrode of the solar cell is 15-70, the width of a single welding point is 0.4-1.0mm, and the length of the single welding point is 0.1-0.6 mm; the preparation method of the front electrode adopts step-by-step printing of the main grid and the auxiliary grid, and specifically comprises the following steps: synchronously printing the main gate area by adopting front silver paste with the solid content of 80-95%, the tin applying area of more than 80%, the mean value of the pulling force of more than 1.0N and no silicon nitride burn-through; and then, synchronously printing the auxiliary gate region by adopting positive silver paste with the height-width ratio of more than 35% and capable of burning through silicon nitride. By adopting the technical scheme of the invention, the collecting effect of the front electrode on the current carriers can be effectively improved, so that the conversion efficiency of the solar cell can be improved.

Description

Solar cell, front electrode thereof, preparation method and application

Technical Field

The invention belongs to the technical field of solar cells, and particularly relates to a solar cell, a front electrode of the solar cell, a preparation method of the front electrode and application of the front electrode.

Background

PERC (Passivated Emitter and reader Cell, Emitter and back surface) solar cells were originally originated in the eighties of the last century and were developed by the Martin Green research group at the university of Newcastle, Australia. Compared with the conventional battery, the back surface of the battery adopts the technologies of dielectric film passivation and local metal contact, so that the back surface recombination rate is obviously reduced, the back reflection of the battery is increased, and the long wave effect of the battery is greatly improved. PERC cells have evolved into high efficiency solar cell products and technologies that have become mainstream in the market since 2017.

The SE (Selective Emitter) technique is to heavily dope the contact portion between a metal gate line (electrode) and a silicon wafer, and lightly dope the position between the electrodes. The structure reduces the surface recombination between the electrodes, can improve the short wave response of the silicon chip, and simultaneously reduces the contact resistance between the front metal electrode and the silicon, so that the short circuit current, the open circuit voltage and the filling factor are better improved, and the conversion efficiency is improved.

The design of the front electrode interweaves optimization, constraint and compromise of factors such as shading area, carrier collection, silver paste consumption, assembly welding and the like. With the increase of the silicon wafer size in recent years, the length of a fine grid is forced to be lengthened; the improvement of the screen printing technology, the thinner the grid line can be, the current 30 μm can be reached; and after the cost of the silicon wafer greatly slips down, the share of the positive silver paste in the production cost of the battery is gradually increased. These factors all place new demands on the design of the front electrode of the cell. MBB (Multi-Busbar) technology, i.e. inoculated with this trend and demand, reduces the secondary grid distance by increasing the number of primary grids; the shading area and the silver paste unit consumption are reduced by reducing the line width of the auxiliary grid and optimizing the design of the main grid; reliability such as welding precision, tension and the like of the MBB assembly is ensured through welding spot design, assembly process and equipment upgrading on the main grid, so that market share of the MBB technology is gradually improved, and further development is carried out on the technology without the main grid (busbar-free).

In the last two years, the PERC cell combines the technologies of SE (selective emitter), MBB, high-quality gallium-doped monocrystalline silicon wafers, alkali polishing, double-sided polishing and the like, namely the PERC + technology which is called by the industry, the photoelectric conversion efficiency of the PERC cell is improved from the initial 21.5 percent to about 23 percent, and the double-sided rate of the cell can reach over 75 percent. How to further improve the conversion efficiency of the PERC battery, reduce the conversion efficiency difference with high efficiency batteries such as hjt (heterojunction technology), TOPCon, etc., and maintain the advantage of comprehensive cost performance is a problem that the PERC + technology continuously faces in the future.

At present, in order to ensure the reliability, welding precision, tension and the like of the assembly, the MBB pattern (figure 1) design generally designs a welding point 3-1, a thin main grid 3-2 and an edge fishfork thin main grid 3-3 in a main grid area, meanwhile, in order to balance the relationship between the shading area and the silver paste consumption of the battery piece and the welding precision and the tensile force, the number of welding points and the size of the welding points of the anode of the conventional battery piece are greatly limited, for example, for 158 and 166 specifications of the battery piece, the number of welding points on the single main grid is generally designed to be 12-14, wherein the length of the welding points at the position of the fish fork is 0.7-1.0mm, the width is 1.2-2.0mm, the length of the other single welding points is generally 0.5-0.9mm, the width of the single welding points is generally 0.9-1.5mm, therefore, the collection effect of the battery piece on the current carriers is not ideal, and the improvement of the battery conversion efficiency is greatly limited.

Through retrieval, the application with the Chinese patent application number of 2018208979220 discloses a front electrode structure of a multi-main-grid battery and a solar battery, wherein the front electrode of the application comprises a main grid line, a bonding pad and an auxiliary grid line, the main grid line and the auxiliary grid line are vertically intersected, and a plurality of bonding pads are arranged on the main grid line; the secondary grid line comprises a straight line section and a deformation section, the deformation section is arranged at the joint of the secondary grid line and the main grid line, the width of the deformation section gradually becomes wider from the end part of the straight line section to the main grid line, the height of the deformation section is higher than that of the straight line section, and the total width of the deformation section is larger than or equal to that of the bonding pad. By adopting the technical scheme of the application, the problem of welding breakage of the auxiliary grid line in the multi-main-grid battery welding process can be well solved, but when the front electrode structure is adopted, the conversion efficiency of the solar battery still needs to be further improved.

Disclosure of Invention

1. Problems to be solved

The invention aims to overcome the defect that the conversion efficiency of a solar cell still needs to be further improved due to the relatively poor current carrier collecting effect of a front electrode for the conventional cell, and provides the solar cell, the front electrode, a preparation method and application thereof. By adopting the technical scheme of the invention, the collecting effect of the front electrode on the current carriers can be effectively improved, so that the conversion efficiency of the solar cell is further improved.

2. Technical scheme

The front electrode of the solar cell comprises main grids and auxiliary grids, wherein the number of the main grids is more than or equal to 9, the number of welding points on a single main grid is 15-70, the width of a single welding point is 0.4-1.0mm, and the length of the single welding point is 0.1-0.6 mm.

Furthermore, the distance between adjacent welding points on the single main grid is 3-11.5mm, the number of the welding points on the single main grid is 15-56 for 158 and 166 specification silicon wafers, the number of the welding points on the single main grid is 17-60 for 182 specification silicon wafers, and the number of the welding points on the single main grid is more than 19 for 210 specification and larger specification silicon wafers.

Furthermore, the main grid and the auxiliary grid are formed by step-by-step printing, wherein the main grid region is formed by synchronously printing the positive silver paste which has the solid content of 80-95%, the tin applying area of more than 80%, the mean value of the pulling force of more than 1.0N and does not burn through silicon nitride, and the auxiliary grid region is formed by synchronously printing the positive silver paste which has the aspect ratio of more than 35% and can burn through silicon nitride.

Furthermore, the main grid consists of a thin main grid, two edge fishfork thin main grids at two ends of the thin main grid and welding points which are arranged on the thin main grid at intervals; the auxiliary grid is perpendicular to the main grid.

Furthermore, the main grid region consists of a thin main grid and a welding spot, and the auxiliary grid region consists of a thin main grid with a fish fork at the edge and an auxiliary grid; or the main grid region consists of all welding points, and the auxiliary grid region consists of a thin main grid, an edge fishfork thin main grid and an auxiliary grid.

Furthermore, the width of the welding point at the position of the fish fork is 0.8-1.9mm, the length is 0.4-0.9mm, and the width of the other single welding point is 0.4-1.0mm, and the length is 0.1-0.6 mm.

Furthermore, a first lapping antenna is arranged on the auxiliary grid connected with the thin main grid, and lapping of the auxiliary grid and the thin main grid is realized through the first lapping antenna; and second lapping feelers are arranged at two ends of the welding spot, and the welding spot is connected with the auxiliary grid in a lapping way through the second lapping feelers.

Furthermore, the first lapping antenna and the second lapping antenna are both designed in a gradual change trapezoid shape with the thickness of 0.03-0.12mm, the thin main grid is designed in a bamboo joint gradual change structure, and the gradual change specification is 0.03-0.1 mm.

Secondly, the preparation method of the front electrode of the invention adopts step-by-step printing of the main grid and the auxiliary grid, and specifically comprises the following steps:

step one, printing a main grid region

Synchronously printing the main gate area by adopting front silver paste with the solid content of 80-95%, the tin applying area of more than 80%, the mean value of the pulling force of more than 1.0N and no silicon nitride burn-through;

step two, printing the auxiliary grid region

And synchronously printing the auxiliary gate region by adopting the positive silver paste with the height-width ratio of more than 35% and capable of burning through silicon nitride.

And thirdly, the front electrode is applied to the solar cell.

Fourthly, the solar cell adopts the front electrode.

Furthermore, the battery comprises a back auxiliary grid electrode, a back passivation layer, a silicon chip substrate, a front emitting electrode and a front passivation and antireflection layer which are arranged from bottom to top, wherein the front electrode is positioned above the front surface of the front passivation and antireflection layer.

Furthermore, the front electrode penetrates through the front passivation and antireflection layer and forms ohmic contact with the front emitter.

Furthermore, the front emitter is composed of a heavily doped region and a lightly doped region, wherein the heavily doped region corresponds to the position of the auxiliary gate of the front electrode or corresponds to the position of the auxiliary gate and the fine main gate of the front electrode.

Furthermore, the square resistance of the heavily doped region is 30-90 omega/□.

Fifthly, the preparation method of the solar cell adopts a step-by-step printing process to print the main grid of the front electrode on the front surface of the cell, and specifically comprises the following steps:

step one, printing a main grid region

step two, printing the auxiliary grid region

Further, the preparation method comprises the following steps:

texturing on the front surface of a silicon wafer substrate to form a textured structure;

diffusing the front surface of the silicon wafer after texturing to form a front emitter 8; and

and carrying out laser SE on the front surface of the diffused silicon wafer and the metalized area corresponding to the grid line of the front electrode to form a selective emitter structure.

Furthermore, in the laser SE operation, laser doping is performed only in the metalized region corresponding to the front electrode sub-grid line to form a heavily doped region.

Furthermore, in the laser SE operation, laser doping is performed on the metalized regions corresponding to the front electrode secondary grid lines and the thin main grid lines to form heavily doped regions.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) the front electrode of the PERC solar cell comprises the main grid and the auxiliary grid, and through design of a front electrode graph, especially through optimization of the number of welding points and the size of the welding points on a single main grid, the current carrier collecting effect of the front electrode can be greatly improved under the condition that the front shading area and the silver paste consumption are not negatively affected, and therefore the conversion efficiency of a cell is improved.

(2) According to the front electrode of the PERC solar cell, the main grid and the auxiliary grid adopt the step-by-step printing process, different printing pastes are selected, and particularly, the high-tension, high-weldability and non-burn-through type front silver paste is adopted as the main grid printing paste, so that the tension of a cell basically meets the requirements of component welding quality, precision and reliability under the condition that the area of a single welding spot is relatively reduced, the realization of greatly improving the current carrier collecting effect of the front electrode is ensured, and meanwhile, the metallization composite of the main grid region is reduced.

(3) According to the front electrode of the PERC solar cell, the auxiliary grid connected with the thin main grid is provided with the first lapping antenna, the two ends of the welding spot on the main grid are provided with the second lapping antennas, and effective lapping of the main grid region and the auxiliary grid region can be ensured through antenna design and optimization.

(4) According to the preparation method of the front electrode of the PERC solar cell, a step-by-step printing mode is adopted, particularly, the specific printing process and the matching optimization of slurry are adopted, so that on one hand, the problems of tension reduction and the like caused by the reduction of the size of a single welding spot are improved, the performances of assembly tension, reliability and the like are ensured, the increase of the number of the welding spots on a single main grid can be realized, and the conversion efficiency of the cell is effectively improved; on the other hand, the limitation of the auxiliary grid slurry on the requirement of the main grid region on too high tension is broken, and the metallization performance of the auxiliary grid region is improved. The front electrode prepared by the method can improve the photoelectric conversion efficiency of the PERC cell by over 0.1 percent.

(5) According to the PERC solar cell, the pattern of the front electrode is optimally designed, so that the current carrier collection effect of the front electrode is greatly improved under the condition that the front shading area and the silver paste consumption are not negatively influenced, and the conversion efficiency of a cell is improved. Meanwhile, the position distribution of the heavily doped region on the front emitter is optimized, so that the conversion efficiency of the battery is further improved.

(6) According to the preparation method of the PERC solar cell, the number of welding points on a single main grid can be increased by optimally designing the positive electrode printing process and the printing slurry, and the tension of the cell can be ensured to meet the requirements of welding quality, precision and reliability under the condition that the area of a single welding point is relatively reduced, so that the conversion efficiency of the cell can be effectively improved. Through laser SE pattern design, surface recombination of a front electrode main gate region caused by heavy doping and a laser process is reduced, and therefore conversion efficiency of the cell is further improved.

Drawings

FIG. 1 is a schematic structural diagram of a conventional MBB front electrode (12 welding spot);

FIG. 2 is a laser SE pattern;

FIG. 3 is an enlarged view of a portion of the laser doped region of FIG. 2;

FIG. 4 is a schematic diagram of a screen structure of the front electrode (20 pads) according to the present invention;

FIG. 5 is a step-by-step printing of a master grid pattern;

FIG. 6 is a step-by-step printing of a subgrid pattern;

FIG. 7 is a schematic diagram of a portion of the main gate of FIG. 5;

FIG. 8 is a schematic enlarged view of a portion of the secondary gate of FIG. 6;

FIG. 9 is a step-by-step printing of a master grid pattern;

FIG. 10 is a step-by-step printing of a subgrid pattern;

FIG. 11 is a cross-sectional view of a battery structure according to the present invention.

In the figure: 1. a front electrode; 2. a front electrode sub-grid; 2-1, a first overlapping antenna; 2-2, a welding spot area; 3. a front electrode main grid; 3-1, welding spots; 3-2, thin main grid; 3-3, a thin main grid with a fish fork at the edge; 3-4, a second lapping antenna; 4. a sub-gate laser doped region; 5. laser facula; 6. a main gate region; 7. a silicon wafer substrate; 8. a front emitter; 8-1, a heavily doped region; 8-2, a shallow doped region; 9. a front surface oxidation layer; 10. a front passivation and anti-reflection layer; 11. a back passivation layer; 12. a back side sub-gate electrode; 13. and laser grooving on the back.

Detailed Description

As shown in FIG. 4, the front electrode 1 of the invention comprises main grids 3 and auxiliary grids 2, wherein the number of the main grids 3 is more than or equal to 9, the number of welding points 3-1 on a single main grid 3 is 15-70, the width of the single welding point 3-1 is 0.4-1.0mm, the length is 0.1-0.6mm, and the distance between adjacent welding points is 3-11.5 mm. Specifically, the number of welding points on a single main grid is 15-56 for 158 and 166 specification silicon wafers, the number of welding points on a single main grid is 17-60 for 182 specification silicon wafers, the number of welding points on a single main grid is more than 19 for 210 specification and larger specification silicon wafers, and the number of welding points on the single main grid corresponding to the 210 specification silicon wafer is 19-70. According to the invention, through designing the front electrode pattern, especially through optimizing the number of welding spots on the single main grid and the size of the welding spots, the current carrier collecting effect of the front electrode can be greatly improved under the condition of not having negative effects on the front shading area and the silver paste consumption, so that the conversion efficiency of the cell is improved.

It should be noted that, the design of the solder joints on the single main grid of the front electrode needs to balance the following requirements: the main grid welding points need to meet the requirements of assembly welding tension, and the area (mainly the length of the welding points) of a single welding point cannot be too small; in the MBB assembly welding technology, in view of the limitation of the precision of the current equipment, the width of a welding spot cannot be too small, and due to too small design, the welding deviation is easy to cause cold joint; if too many welding spots can cause the negative effects of too high silver paste consumption and too large shading area at the battery end; when the assembly end is welded, too many welding spots easily influence the welding process. Therefore, under the influence of factors such as assembly welding tension requirements, welding quality, silver paste consumption, shading area and the like, the distribution of the front electrode pattern, particularly the number of welding points and the size of the welding points on the main grid are greatly limited, for example, in the conventional 158 and 166-sized battery piece, the number of the welding points on a single main grid is generally designed to be 12-14, the width of the welding point at the position of the fish fork is 0.8-1.9mm, the length of the welding point is 0.4-0.9mm, the length of the rest single welding points is generally 0.5-0.9mm, the width of the single welding point is generally 0.9-1.5mm, and the distance between the welding points is generally 11-12 mm; for the conventional 182 or 210 large-size silicon wafer, the number of the welding spots is respectively between 14-16 and 16-18, so that the current collecting effect of the front electrode of the conventional solar cell on the current carriers is not ideal, and the conversion efficiency of the solar cell is limited.

Therefore, how to improve the welding tension of the main grid and ensure the welding precision and reliability is crucial to realizing the improvement of the number of welding points on the main grid on the basis of not influencing the shading area of the front electrode and the consumption of silver paste, namely realizing the improvement of the conversion efficiency of the solar cell, which is also a main difficulty influencing the conversion efficiency of the solar cell at present. Based on this, the inventor of this application is through a large amount of experimental research, through the design optimization of main grid specification, through substep printing technology mode, and optimize the collocation to main grid, vice grid for the printing thick liquids, thereby can effectively solve the pulling force reduction and the welding problem that single solder joint size reduction arouses, consequently can realize the promotion of the quantity of solder joint on the main grid on the basis of not increasing positive shading area and silver thick liquid consumption, guarantee welding precision and reliability, and then realized the improvement of solar cell conversion efficiency.

Specifically, the printing process of the front electrode comprises main gate area printing and auxiliary gate area printing, wherein the main gate area printing adopts front silver paste with high solid content, high weldability and no burn-through of silicon nitride, and preferably the front silver paste with the solid content of 80-95%, the tin feeding area of more than 80%, the single-point tension of more than 1N and the mean tension of more than 1.0N is selected from the group consisting of IEC 61215: DH1000 is less than 2.5% under 2016 standard test conditions; PID192h is less than 3%; TC200 less than 3%, such as polymerized CSP-M3M-FB07-6 or Heraeus (Hercules) -SOL6600B-NC00-1993 positive silver paste; the printing of the auxiliary gate area adopts the positive silver paste with excellent aspect ratio and burn-through silicon nitride, and preferably the positive silver paste with the aspect ratio of more than 35 percent, such as polymerized CSP-M3D-AL1086, polymerized CSP-M3D-S6009V229, Dike DK92B or Shuozhe 590B, thereby reducing the metallization recombination of the main gate area and ensuring the metallization of the auxiliary gate area and the collection of carriers. In addition, at present, because the front electrode is prepared by generally adopting a single-time printing mode for the alignment precision problem, the printing height-width ratio of the auxiliary grid and the tension of the main grid need to be considered in the selection of the front silver paste, and the improvement and cost reduction in the metallization aspect are not facilitated. The invention optimizes the matching of the main grid and the auxiliary grid slurry through the step-by-step printing process, thereby reducing the metallization composition of the main grid region.

Further preferably, the main grid of the front electrode in the invention is composed of a thin main grid 3-2, a fishfork thin main grid 3-3 at the edge of two ends of the thin main grid 3-2 and welding points 3-1 which are distributed at intervals on the thin main grid 3-2, the auxiliary grid 2 is perpendicular to the main grid 3, wherein the width of the welding point 3-1 at the position of the fishfork is 0.8-1.9mm, the length is 0.4-0.9mm, the width of the other single welding point 3-1 is 0.4-1.0mm, and the length is 0.1-0.6 mm.

More preferably, the main grid area consists of a thin main grid 3-2 and a welding point 3-1, and the auxiliary grid area consists of an edge harpoon thin main grid 3-3 and an auxiliary grid 2; or the main grid region consists of all welding points 3-1, and the auxiliary grid region consists of a thin main grid 3-2, a thin main grid 3-3 with a fish spear at the edge and an auxiliary grid 2. That is, when the front electrode is prepared by the step-by-step printing process, the welding points on the main grid and the fine main grid are printed synchronously (as shown in fig. 5) or only the welding points on the main grid are printed (as shown in fig. 9); and then synchronously printing the thin main grid and the auxiliary grid of the harpoon on the main grid area 6 (as shown in figure 6) or synchronously printing the thin main grid, the thin main grid of the harpoon and the auxiliary grid (as shown in figure 10).

More preferably, with reference to fig. 7 and 8, both ends of the welding point 3-1 on the main grid 3 are provided with second overlapping antennae 3-4, and the welding point 3-1 is connected with the auxiliary grid 2 in an overlapping manner through the second overlapping antennae 3-4. A welding spot area 2-2 is arranged on the auxiliary grid 2 connected with the welding spot 3-1, and the auxiliary grid 2 is divided into two sections by the welding spot area 2-2; the auxiliary grid 2 connected with the thin main grid 3-2 is provided with a first lapping antenna 2-1, and the lapping of the auxiliary grid 2 and the thin main grid 3-2 is realized through the first lapping antenna 2-1. The first lapping antenna 2-1 and the second lapping antenna 3-4 are both designed to be gradually changed into trapezoids with the width of 0.03-0.12mm (the width of the upper bottom is 0.03mm at the narrow end of the trapezoid, and the width of the lower bottom is 0.12mm at the wide end of the trapezoid), wherein the narrow end of the trapezoid is arranged at the end close to the auxiliary grid, and the wide end of the trapezoid is arranged at the end close to the main grid, so that the firmness of connection between the main grid and the auxiliary grid is guaranteed. The thin main grid 3-2 adopts a bamboo joint gradual change structure design (a step type subsection structure), and the gradual change specification is 0.03-0.1mm (the diameter is gradually increased from 0.03mm to 0.1 mm).

When the front electrode prepared by the method is applied to a solar cell, the photoelectric conversion efficiency can be improved by more than 0.1% compared with the conventional cell. Wherein the front electrode 1 passes through the front passivation and anti-reflection layer 10 and forms ohmic contact with the front emitter 8.

Further preferably, the front emitter 8 is composed of a heavily doped region 8-1 and a lightly doped region 8-2, wherein the heavily doped region 8-1 corresponds to the position of the sub-gate 2 of the front electrode or corresponds to the positions of the sub-gate 2 and the thin main gate 3-2 of the front electrode. Although the width of a grid line of a positive electrode of the current screen printing reaches a narrow line width of 30 μm, in order to ensure the overprinting precision of the positive electrode and a laser heavily doped region and the stability of yield rate during scale production, a laser spot of laser SE generally adopts a square or rectangular mode, the width is 90-110 μm, and the distance between laser spots 5 is 0-10 μm (shown in FIG. 3). Too wide a spot size increases the damage caused by the laser SE itself, affecting the short wave effect. The laser SE is only doped at the position of the secondary grid of the positive electrode pattern, namely only the secondary grid laser doping region 4 exists, or only the secondary grid 2 of the positive electrode pattern and the thin main grid 3-2 are doped, compared with the conventional laser pattern, the laser doping of the main grid region is cancelled or reduced (as shown in figure 2).

In order to further understand the technical solution of the present invention, the present invention will be described with reference to specific examples.

Example 1

The preparation method of the solar cell of the embodiment comprises the following steps:

1. texturing: a monocrystal P-type silicon wafer (158 specification size) is adopted, and front and back texturing is carried out by alkali to form a textured structure.

2. Diffusion: and reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to ensure that the front surface is diffused to form a PN emitter junction, wherein the square resistance of the front surface thin layer after diffusion is 160 omega/□.

3. Laser SE: and performing laser doping on the front surface of the diffused silicon wafer and the metalized area corresponding to the positive electrode grid line by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area, wherein the square resistance of the heavily doped area is between 70 omega/□. The laser SE pattern uses a pattern without a master gate (fig. 2).

4. Thermal oxidation: and introducing oxygen into the silicon wafer after the laser SE for oxidation.

5. Removing PSG: and (4) removing the PSG on the back surface and the periphery of the silicon wafer after thermal oxidation by using HF.

6. Alkali polishing: and polishing the back and the edge of the silicon wafer after the PSG is removed, and removing the PSG on the front side.

7. Oxidizing and annealing: and (3) carrying out oxidation and annealing treatment on the silicon wafer subjected to the alkali polishing to form a front surface oxidation layer 9.

8. Depositing a passivation film on the back: and preparing a passivation film, namely a back passivation layer 11, on the back of the annealed silicon wafer.

9. Front side deposition of an antireflection film: and preparing a passivation and antireflection layer 10 on the front surface of the silicon wafer.

10. Back laser: and (3) carrying out laser drilling on the silicon wafer with the passivation film prepared on the back surface to form a back surface laser groove 13.

11. Back electrode printing: and carrying out screen printing on the silicon wafer after laser hole opening on the front side and the back side to prepare a back electrode.

12. Back side sub-grid printing: the back side sub-gate electrode 12 is screen printed on the printed back electrode silicon wafer.

13. Printing a positive electrode main gate region: adopting a front silver paste (adopting polymerization M3M-FB07-6 in the embodiment) with high solid content, high weldability and no burn-through of silicon nitride, preparing a positive electrode main grid on a silicon wafer printed with a back aluminum grid line by screen printing, wherein a main grid pattern adopts a printing mode of a main grid welding spot and a thin main grid (shown in figure 5); each main grid welding point is provided with an antenna with the gradual change of 0.03-0.12mm, the effective lapping with the auxiliary grid line is realized, and the fine main grid adopts the gradual change of 0.03-0.1mm bamboo joints. The number of the main grids is 9; the number of welding points on the single main grid is 20, the width of the welding points at the position of the fish spear is 1.9mm, the length of the welding points is 0.8mm, and the width of the other welding points is 0.9mm and the length of the other welding points is 0.45 mm.

14. Printing a positive electrode secondary grid region: adopting positive silver paste with high aspect ratio and burning-through silicon nitride (CSP-M3D-AL 1086 is adopted in the embodiment), and preparing a positive electrode auxiliary grid on a silicon wafer printed with a positive electrode main grid by screen printing, wherein the pattern of the step adopts the patterns of the auxiliary grid corresponding to the main grid pattern and the fine fish fork main grid (figure 6); and an antenna with the gradual change of 0.03-0.12mm is designed on the auxiliary grid of the thin main grid region, so that the effective lap joint with the main grid is realized.

15. And (3) sintering: and (3) co-sintering the silicon chip with the front electrode printed, wherein the sintering peak temperature is 720 ℃.

16. Electric injection: and performing electro-injection treatment on the sintered battery piece.

17. And (3) finished product: and testing, sorting, packaging and warehousing the product battery pieces.

The section structure of the obtained battery piece is shown in fig. 11, and comprises a back auxiliary grid electrode 12, a back passivation layer 11, a silicon chip substrate 7, a front emitter 8, a front oxide layer 9, a front passivation and antireflection layer 10 and a front electrode 1 which are arranged from bottom to top in sequence.

Example 2

The preparation method of the PERC solar cell of the present embodiment includes the following steps:

1. texturing: a single crystal P-type silicon wafer (166 specification size) is adopted, and front and back surface texturing is carried out by alkali to form a textured structure.

2. Diffusion: and (3) reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to diffuse the front side to form a PN emitter junction. The sheet resistance of the front surface sheet after diffusion was 150 Ω/□.

3. Laser SE: and performing laser doping on the front surface of the diffused silicon wafer and the metalized area corresponding to the positive electrode grid line by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area. The square resistance of the heavily doped region is between 60 omega/□. The laser SE pattern uses a pattern without a master gate (fig. 2).

7. Oxidizing and annealing: and carrying out oxidation and annealing treatment on the silicon wafer subjected to alkali polishing.

8. Depositing a passivation film on the back: and preparing a passivation film on the back of the annealed silicon wafer.

9. Front side deposition of an antireflection film: and preparing a passivation and antireflection layer on the front side of the silicon wafer.

10. Back laser: and carrying out laser drilling on the silicon wafer with the passivation film prepared on the back surface.

12. Back side sub-grid printing: and screen printing a back auxiliary grid electrode on the printed back electrode silicon wafer.

13. Printing a positive electrode main gate region: adopting positive silver slurry (Heisha 1993 is adopted in the embodiment) with high solid content, high weldability and no burn-through of silicon nitride, and carrying out screen printing on a silicon wafer printed with a back aluminum grid line to prepare a positive electrode main grid, wherein a main grid pattern adopts a main grid welding spot (figure 9); each main grid welding point is provided with a gradual change antenna with the thickness of 0.03-0.12mm, effective lap joint with the auxiliary grid line is realized, and the fine main grid adopts the gradual change of bamboo joints with the thickness of 0.03-0.1 mm. The main grid adopts a multi-main-grid structure with 9 bars, the number of welding points on a single main grid is 20, the width of the welding point at the position of the fish spear is 1.8mm, the length of the welding point is 0.8mm, and the width of the other single welding points is 1.00mm and the length of the other single welding points is 0.4 mm.

14. Printing a positive electrode secondary grid region: adopting a positive silver paste (adopting Dike DK928B in the embodiment) with high aspect ratio and burn-through silicon nitride to prepare a positive electrode auxiliary grid on a silicon wafer printed with a positive electrode main grid by screen printing, wherein the pattern of the step adopts the patterns of the auxiliary grid, the thin main grid and the harpoon thin main grid (figure 10) corresponding to the main grid pattern; and an antenna with the gradual change of 0.03-0.12mm is designed on the auxiliary grid of the thin main grid region, so that the effective lap joint with the main grid is realized.

15. And (3) sintering: and (3) co-sintering the silicon chip with the front electrode printed, wherein the sintering peak temperature is 800 ℃.

Example 3

2. Diffusion: and (3) reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to diffuse the front side to form a PN emitter junction. The sheet resistance of the front surface sheet after diffusion was 120 Ω/□.

13. Printing a positive electrode main gate region: adopting positive silver slurry (Heisha 1993 is adopted in the embodiment) with high solid content, high weldability and no burn-through of silicon nitride, and carrying out screen printing on a silicon wafer printed with a back aluminum grid line to prepare a positive electrode main grid, wherein a main grid pattern adopts a main grid welding spot (figure 9); each main grid welding point is provided with a gradual change antenna with the thickness of 0.03-0.12mm, effective lap joint with the auxiliary grid line is realized, and the fine main grid adopts the gradual change of bamboo joints with the thickness of 0.03-0.1 mm. The main grid adopts a multi-main-grid structure with 9 bars, the number of welding spots on a single main grid is 26, the width of the welding spot at the position of the fish spear is 1.8mm, the length of the welding spot is 0.8mm, the rest welding spots are divided into two specifications, one specification is 1.00mm, the length of the welding spot is 0.6mm, the other specification is 0.8mm, the length of the welding spot is 0.35mm, and the two specifications are alternately and uniformly distributed and arranged.

15. And (3) sintering: and (3) co-sintering the silicon wafer with the front electrode printed, wherein the sintering peak temperature is 780 ℃.

Example 4

2. Diffusion: and (3) reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to diffuse the front side to form a PN emitter junction. The sheet resistance of the front surface sheet after diffusion was 110 Ω/□.

3. Laser SE: and performing laser doping on the front surface of the diffused silicon wafer and the metalized areas corresponding to the secondary grid lines and the thin main grid by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area. The square resistance of the heavily doped region is between 60 omega/□.

13. Printing a positive electrode main gate region: the method comprises the steps of adopting front silver paste with solid content of 85%, tin applying area of more than 80%, single-point tension of more than 1N and tension mean value of more than 1.0N, carrying out screen printing on all welding points on a silicon wafer printed with a back aluminum grid line to form a main grid region, wherein each main grid welding point is provided with a gradual change antenna of 0.03-0.12mm, effective lap joint with an auxiliary grid line is realized, and the fine main grid adopts a bamboo joint gradual change of 0.03-0.1 mm. The main grid adopts a 12-strip multi-main-grid structure, the number of welding points on a single main grid is 50, the width of the single welding point is 0.6mm, the length of the single welding point is 0.4mm, and the edge-free harpoon thin main grid is of a 3-3 structure.

14. Printing a positive electrode secondary grid region: the positive silver paste with the height-width ratio of more than 35% and burning through silicon nitride is adopted to prepare a positive electrode auxiliary grid and a thin main grid on a silicon chip printed with a positive electrode main grid region through screen printing, and an antenna gradually changed by 0.03-0.12mm is designed on the auxiliary grid of the thin main grid region to realize effective lap joint with the main grid.

15. And (3) sintering: and (3) co-sintering the silicon wafer printed with the front electrode, wherein the sintering peak temperature is 790 ℃.

Example 5

2. Diffusion: and (3) reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to diffuse the front side to form a PN emitter junction. The sheet resistance of the front surface sheet after diffusion was 180 Ω/□.

3. Laser SE: and performing laser doping on the front surface of the diffused silicon wafer and the metalized area corresponding to the positive electrode grid line by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area. The square resistance of the heavily doped region is between 70 omega/□. The laser SE pattern uses a pattern without a master gate (fig. 2).

13. Printing a positive electrode main gate region: adopting a front silver paste (the embodiment adopts Heliothis 1993) with high solid content, high weldability and no burn-through of silicon nitride, and carrying out screen printing on a silicon wafer printed with a back aluminum grid line to prepare a positive electrode main grid, wherein a main grid pattern adopts a main grid welding spot (figure 5); each main grid welding point is provided with a gradual change antenna with the thickness of 0.03-0.12mm, effective lap joint with the auxiliary grid line is realized, and the fine main grid adopts the gradual change of bamboo joints with the thickness of 0.03-0.1 mm. The main grid adopts a multi-main-grid structure with 9 bars, the number of welding points on a single main grid is 30, the width of the welding point at the position of the fish spear is 1.5mm, the length of the welding point is 0.7mm, and the widths of the rest welding points are 0.8mm and the length of the other welding points is 0.45 mm.

14. Printing a positive electrode secondary grid region: adopting a positive silver paste (adopting Dike DK928B in the embodiment) with high aspect ratio and burn-through silicon nitride to prepare a positive electrode auxiliary grid on a silicon wafer printed with a positive electrode main grid by screen printing, wherein the pattern of the step adopts the patterns of the auxiliary grid, the thin main grid and the harpoon thin main grid (figure 6) corresponding to the main grid pattern; and an antenna with the gradual change of 0.03-0.12mm is designed on the auxiliary grid of the thin main grid region, so that the effective lap joint with the main grid is realized.

Example 6

1. texturing: a monocrystal P-type silicon wafer (182 specification size) is adopted, and front and back texturing is carried out by alkali to form a textured structure.

2. Diffusion: and (3) reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to diffuse the front side to form a PN emitter junction. The sheet resistance of the front surface sheet after diffusion was 170 Ω/□.

3. Laser SE: and performing laser doping on the front surface of the diffused silicon wafer and the metalized area corresponding to the positive electrode grid line by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area. The square resistance of the heavily doped region is between 75 omega/□. The laser SE pattern uses a pattern without a master gate (fig. 2).

13. Printing a positive electrode main gate region: adopting positive silver slurry (Heisha 1993 is adopted in the embodiment) with high solid content, high weldability and no burn-through of silicon nitride, and carrying out screen printing on a silicon wafer printed with a back aluminum grid line to prepare a positive electrode main grid, wherein a main grid pattern adopts a main grid welding spot (figure 9); each main grid welding point is provided with a gradual change antenna with the thickness of 0.03-0.12mm, effective lap joint with the auxiliary grid line is realized, and the fine main grid adopts the gradual change of bamboo joints with the thickness of 0.03-0.1 mm. The main grid adopts a multi-main-grid structure with 10 bars, the number of welding points on a single main grid is 32, the width of the welding point at the position of the fish spear is 1.5mm, the length of the welding point is 0.7mm, and the widths of the rest welding points are 0.8mm and the length of the other welding points is 0.45 mm.

14. Printing a positive electrode secondary grid region: adopting positive silver paste with excellent aspect ratio and burning-through silicon nitride (the embodiment adopts polymerized CSP-M3D-S6009V229), preparing a positive electrode auxiliary gate on a silicon wafer printed with a positive electrode main gate by screen printing, wherein the pattern of the step adopts the patterns of the auxiliary gate, the thin main gate and the harpoon thin main gate (figure 10) corresponding to the main gate pattern; and an antenna with the gradual change of 0.03-0.12mm is designed on the auxiliary grid of the thin main grid region, so that the effective lap joint with the main grid is realized.

15. And (3) sintering: and (3) co-sintering the silicon chip with the front electrode printed, wherein the sintering peak temperature is 750 ℃.

Example 7

2. Diffusion: and (3) reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to diffuse the front side to form a PN emitter junction. The sheet resistance of the front surface sheet after diffusion was 160 Ω/□.

3. Laser SE: and performing laser doping on the front surface of the diffused silicon wafer and the metalized area corresponding to the positive electrode grid line by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area. The square resistance of the heavily doped region is between 70 omega/□. The laser SE pattern adopts a pattern without a master grid.

13. Printing a positive electrode main gate region: adopting a front silver paste (the embodiment adopts Heliothis 1993) with high solid content, high weldability and no burn-through of silicon nitride, and carrying out screen printing on a silicon wafer printed with a back aluminum grid line to prepare a positive electrode main grid, wherein a main grid pattern adopts a main grid welding spot (figure 5); each main grid welding point is provided with a gradual change antenna with the thickness of 0.03-0.12mm, effective lap joint with the auxiliary grid line is realized, and the fine main grid adopts the gradual change of bamboo joints with the thickness of 0.03-0.1 mm. The main grid adopts a multi-main-grid structure with 11 bars, the number of welding spots on a single main grid is 28, the width of the welding spot at the position of the fish spear is 1.8mm, the length of the welding spot is 0.8mm, the other welding spots are divided into two specifications, the width of one specification is 1.00mm, the length of the other specification is 0.6mm, the width of the other specification is 0.8mm, the length of the other specification is 0.4mm, and the two specifications are alternately and uniformly distributed and arranged.

14. Printing a positive electrode secondary grid region: adopting a positive silver paste (in the embodiment, Shuozao 590B) with high aspect ratio and burning-through silicon nitride to prepare a positive electrode auxiliary grid on a silicon wafer printed with the positive electrode main grid by screen printing, wherein the graphs in the step adopt graphs of the auxiliary grid, the thin main grid and the harpoon thin main grid (figure 6) corresponding to the graphs of the main grid; and an antenna with the gradual change of 0.03-0.12mm is designed on the auxiliary grid of the thin main grid region, so that the effective lap joint with the main grid is realized.

15. And (3) sintering: and (3) co-sintering the silicon chip with the front electrode printed, wherein the sintering peak temperature is 730 ℃.

Example 8

2. Diffusion: and (3) reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to diffuse the front side to form a PN emitter junction. The sheet resistance of the front surface sheet after diffusion was 185 Ω/□.

3. Laser SE: and performing laser doping on the front surface of the diffused silicon wafer and the metalized area corresponding to the positive electrode grid line by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area. The square resistance of the heavily doped region is between 55 omega/□. The laser SE pattern adopts a pattern without a master grid.

13. Printing a positive electrode main gate region: adopting a front silver paste with solid content of 80-95%, tin applying area of more than 80%, single-point tension of more than 1N, mean tension of more than 1.0N and no burn-through of silicon nitride, and preparing a positive electrode main grid on a silicon wafer printed with a back aluminum grid line by screen printing, wherein the main grid pattern adopts a main grid welding spot (figure 9) mode; each main grid welding point is provided with a gradual change antenna with the thickness of 0.03-0.12mm, effective lap joint with the auxiliary grid line is realized, and the fine main grid adopts the gradual change of bamboo joints with the thickness of 0.03-0.1 mm. The main grid adopts a multi-main-grid structure with 10 bars, the number of welding points on a single main grid is 45, the width of the welding point at the position of the fish spear is 1.8mm, the length of the welding point is 0.8mm, and the width and the length of the other single welding points are 0.5mm and 0.3 mm.

14. Printing a positive electrode secondary grid region: adopting positive silver slurry with the height-to-width ratio of more than 35% and capable of burning through silicon nitride, and preparing a positive electrode auxiliary grid on a silicon wafer printed with a positive electrode main grid by screen printing, wherein the graphs of the auxiliary grid, the thin main grid and the harpoon thin main grid (figure 10) corresponding to the main grid graph are adopted in the step; and an antenna with the gradual change of 0.03-0.12mm is designed on the auxiliary grid of the thin main grid region, so that the effective lap joint with the main grid is realized.

Example 9

1. texturing: a single crystal P-type silicon wafer (210 specification size) is adopted, and front and back texturing is carried out by alkali to form a textured structure.

3. Laser SE: and performing laser doping on the front surface of the diffused silicon wafer and the metalized area corresponding to the positive electrode grid line by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area. The square resistance of the heavily doped region is between 80 omega/□. The laser SE pattern adopts a pattern without a master grid.

13. Printing a positive electrode main gate region: adopting positive silver slurry (Heisha 1993 is adopted in the embodiment) with high solid content, high weldability and no burn-through of silicon nitride, and carrying out screen printing on a silicon wafer printed with a back aluminum grid line to prepare a positive electrode main grid, wherein a main grid pattern adopts a main grid welding spot (figure 9); each main grid welding point is provided with a gradual change antenna with the thickness of 0.03-0.12mm, effective lap joint with the auxiliary grid line is realized, and the fine main grid adopts the gradual change of bamboo joints with the thickness of 0.03-0.1 mm. The main grid adopts a 12-bar multi-main-grid structure, the number of welding points on a single main grid is 24, the width of the welding point at the position of the fish fork is 1.8mm, the length of the welding point is 0.8mm, and the width of the other single welding points is 0.9mm and the length of the other single welding points is 0.55 mm.

15. And (3) sintering: and (3) co-sintering the silicon chip with the front electrode printed, wherein the sintering peak temperature is 755 ℃.

Example 10

2. Diffusion: and (3) reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to diffuse the front side to form a PN emitter junction. The sheet resistance of the front surface sheet after diffusion was 155 Ω/□.

3. Laser SE: and performing laser doping on the front surface of the diffused silicon wafer and the metalized area corresponding to the positive electrode grid line by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area. The square resistance of the heavily doped region is between 65 omega/□. The laser SE pattern adopts a pattern without a master grid.

13. Printing a positive electrode main gate region: adopting a front silver paste with solid content of 80-95%, tin applying area of more than 80%, single-point tension of more than 1N, mean tension of more than 1.0N and no burn-through of silicon nitride, and preparing a positive electrode main grid on a silicon wafer printed with a back aluminum grid line by screen printing, wherein a main grid graph adopts a main grid welding spot (shown in figure 5); each main grid welding point is provided with a gradual change antenna with the thickness of 0.03-0.12mm, effective lap joint with the auxiliary grid line is realized, and the fine main grid adopts the gradual change of bamboo joints with the thickness of 0.03-0.1 mm. The main grid adopts a 12-bar multi-main-grid structure, the number of welding spots on a single main grid is 36, the width of the welding spot at the position of the fish spear is 1.8mm, the length of the welding spot is 0.8mm, the rest welding spots are divided into two specifications, one specification is 1.00mm, the length of the welding spot is 0.6mm, the other specification is 0.8mm, the length of the welding spot is 0.35mm, and the two specifications are alternately and uniformly distributed and arranged.

15. And (3) sintering: and (3) co-sintering the silicon chip with the front electrode printed, wherein the sintering peak temperature is 760 ℃.

Claims

1. A front electrode of a solar cell comprising a primary grid (3) and a secondary grid (2), characterized in that: the number of the main grids (3) is more than or equal to 9, the number of welding points (3-1) on a single main grid (3) is 15-70, the width of the single welding point (3-1) is 0.4-1.0mm, and the length of the single welding point (3-1) is 0.1-0.6 mm.

2. The front electrode for a solar cell according to claim 1, wherein: the distance between adjacent welding points (3-1) on a single main grid is 3-11.5mm, the number of the welding points (3-1) on the single main grid (3) is 15-56 aiming at 158 and 166 specification silicon wafers, the number of the welding points (3-1) on the single main grid (3) is 17-60 aiming at 182 specification silicon wafers, and the number of the welding points (3-1) on the single main grid (3) is more than 19 aiming at 210 specification and larger specification silicon wafers.

3. The front electrode for a solar cell according to claim 2, wherein: the main grid (3) and the auxiliary grid (2) are formed by step-by-step printing, wherein the main grid region is formed by synchronously printing positive silver paste which has the solid content of 80-95%, the tin applying area of more than 80%, the average tension value of more than 1.0N and does not burn through silicon nitride, and the auxiliary grid region is formed by synchronously printing positive silver paste which has the aspect ratio of more than 35% and can burn through silicon nitride.

4. The front electrode of a solar cell according to any one of claims 1 to 3, characterized in that: the main grid (3) consists of a thin main grid (3-2), edge fish fork thin main grids (3-3) at two ends of the thin main grid (3-2) and welding points (3-1) which are positioned on the thin main grid (3-2) and distributed at intervals; the auxiliary grid (2) is perpendicular to the main grid (3).

5. The front electrode for a solar cell according to claim 4, wherein: the main grid region consists of a thin main grid (3-2) and a welding spot (3-1), and the auxiliary grid region consists of an edge fish fork thin main grid (3-3) and an auxiliary grid (2); or the main grid region consists of all welding points (3-1), and the auxiliary grid region consists of a thin main grid (3-2), a thin main grid (3-3) with a fish spear at the edge and an auxiliary grid (2).

6. The front electrode for a solar cell according to claim 4, wherein: the width of the welding point (3-1) at the position of the fish fork is 0.8-1.9mm, the length is 0.4-0.9mm, and the width of the other single welding point (3-1) is 0.4-1.0mm, and the length is 0.1-0.6 mm.

7. The front electrode for a solar cell according to claim 4, wherein: a first overlapping antenna (2-1) is arranged on the auxiliary grid (2) connected with the thin main grid (3-2), and the overlapping of the auxiliary grid (2) and the thin main grid (3-2) is realized through the first overlapping antenna (2-1); and second lapping antennae (3-4) are arranged at two ends of the welding spot (3-1), and the welding spot (3-1) is connected with the auxiliary grid (2) in a lapping way through the second lapping antennae (3-4).

8. The front electrode for a solar cell according to claim 7, wherein: the first lapping antenna (2-1) and the second lapping antenna (3-4) are both designed to be gradually changed into trapezoids with the thickness of 0.03-0.12mm, the thin main grid (3-2) is designed to be in a bamboo joint gradually changing structure, and the gradually changing specification is 0.03-0.1 mm.

9. A method for producing a front-side electrode according to any of claims 1 to 8, characterized in that the primary grid (3) and the secondary grid (2) are printed in steps, in particular:

step one, printing a main grid region

step two, printing the auxiliary grid region

10. Use of a front electrode as claimed in any of claims 1 to 8 in a solar cell.

11. A solar cell, characterized by: the battery employs a front electrode (1) according to any one of claims 1 to 8.

12. A solar cell according to claim 11, characterized in that: the cell comprises a back auxiliary grid electrode (12), a back passivation layer (11), a silicon chip substrate (7), a front emitter (8) and a front passivation and antireflection layer (10) which are arranged from bottom to top, wherein the front electrode (1) is positioned above the front surface of the front passivation and antireflection layer (10).

13. A solar cell according to claim 11 or 12, characterized in that: the front electrode (1) penetrates through the front passivation and antireflection layer (10) and forms ohmic contact with the front emitter (8).

14. A solar cell according to claim 13, characterized in that: the front emitter (8) is composed of a heavily doped region (8-1) and a lightly doped region (8-2), wherein the heavily doped region (8-1) corresponds to the position of the auxiliary grid (2) of the front electrode or corresponds to the positions of the auxiliary grid (2) and the thin main grid (3-2) of the front electrode.

15. A solar cell according to claim 14, wherein: the square resistance of the heavily doped region (8-1) is 30-90 omega/□.

16. A method for manufacturing a solar cell according to any of claims 11-15, characterized in that the main grid (3) of the front electrode (1) is printed on the front side of the cell by a step-wise printing process, in particular:

step one, printing a main grid region

step two, printing the auxiliary grid region

17. The method for manufacturing a solar cell according to claim 16, comprising:

texturing on the front side of the silicon wafer substrate (7) to form a textured structure;

18. The method for manufacturing a solar cell according to claim 17, characterized in that: in the laser SE operation, laser doping is carried out on the metalized region corresponding to the front electrode secondary grid line only to form a heavily doped region (8-1).

19. The method for manufacturing a solar cell according to claim 17, characterized in that: in the laser SE operation, laser doping is carried out on the metalized areas corresponding to the front electrode secondary grid lines and the thin main grid lines to form a heavily doped area (8-1).