WO2012162901A1

WO2012162901A1 - Method for manufacturing back contact crystalline silicon solar cell sheet

Info

Publication number: WO2012162901A1
Application number: PCT/CN2011/075415
Authority: WO
Inventors: 章灵军; 张凤; 吴坚; 王栩生
Original assignee: 苏州阿特斯阳光电力科技有限公司
Priority date: 2011-05-27
Filing date: 2011-06-07
Publication date: 2012-12-06
Also published as: JP5817046B2; CN102800741A; CN102800741B; JP2013544037A

Abstract

A method for manufacturing a back contact crystalline silicon solar cell sheet is provided. The method comprises: forming a via (4) on a semiconductor wafer (1); performing texturing and diffusion processes on surfaces (2, 3) of the semiconductor wafer; etching the diffused semiconductor wafer and performing the subsequent processes, thus obtaining the back contact crystalline silicon solar cell sheet, wherein the etching includes etching the backlight surface (3) and the edge of the light receiving surface (2) of the semiconductor wafer. In the method, the edge of the light receiving surface of the wafer and the emitter junction formed by diffusing on the backlight surface of the wafer are removed by etching at the same time. So there is not a short circuit conductive layer between the backlight surface and the conductive via of the solar cell sheet. Compared with the prior art, the method avoids the laser isolating process and then reduces the risk of leakage and the breakage rate of the cell sheet.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present application claims priority to Chinese Patent Application No. 201110141250.3, entitled "Back Contact Crystalline Solar Cell Sheet Manufacturing Method", filed on May 27, 2011, with the Chinese Patent Office. The entire contents of which are incorporated herein by reference. Technical field

The present invention relates to the field of solar cell technology, and in particular to a method for manufacturing a back contact crystalline silicon solar cell.

Background technique

A solar cell, also called a photovoltaic cell, is a semiconductor device that converts the solar light energy directly into electrical energy. Because it is a green product, it does not cause environmental pollution, and it is a renewable resource. Therefore, in today's energy shortage, solar cells are a new type of energy with broad development prospects. At present, more than 80% of solar cells are made of crystalline silicon materials. Therefore, the preparation of high-efficiency crystalline silicon solar cells is of great significance for large-scale utilization of solar power, because the light-receiving surface of back-contact crystalline silicon solar cells does not have The main grid line, the positive pole and the negative pole are all located on the backlight surface of the cell sheet, which greatly reduces the shading rate of the light-receiving surface grid line and improves the conversion efficiency of the cell sheet. Therefore, the back-contact crystalline silicon solar cell has become a hot spot for solar cell research and development. .

At present, the manufacturing process of back-contact crystalline silicon solar cells has been standardized, and the main steps are as follows:

1. Opening: Use a laser to open at least one conductive hole in the silicon.

2. Texturing: The surface of the original bright silicon wafer (including the front and back) is formed into a convex and concave structure by chemical reaction to prolong the propagation path of light on the surface, thereby improving the absorption of light by the solar cell.

3. Diffusion bonding: The P-type silicon wafer becomes an N-type electrode on the surface after diffusion and the inner wall of the conductive hole, or the N-type silicon wafer becomes a P-type electrode on the surface after diffusion and the inner wall of the conductive hole, forming a PN junction, so that the silicon wafer Has a photovoltaic effect.

4. Peripheral etching: Etching the edge of the silicon wafer.

5. Removal of the doped glass layer: The doped glass layer formed when the surface of the silicon wafer is diffused is removed. 6. Coating: The anti-reflection film is coated on the surface of the silicon wafer. At present, there are mainly two types of anti-reflection films, silicon nitride film and titanium oxide film, which mainly play the role of anti-reflection and passivation.

7. Print electrode and electric field: Print the back electrode, front electrode and back surface electric field onto the silicon wafer.

8. Sintering: Forming an alloy between the printed electrode, the back electric field and the silicon wafer.

9. Laser Isolation: The purpose of this step is to remove the conductive layer formed between the back side of the silicon wafer and the conductive via that is short-circuited between the P-N junction during diffusion bonding.

In the existing manufacturing process, in the diffusion-knotting step, a conductive layer that short-circuits the PN junction is formed between the backlight surface of the solar cell and the conductive hole, which greatly reduces the parallel resistance of the cell, and is prone to leakage. The conductive layer between the PN junctions needs to be removed by a laser isolation step. However, the use of laser isolation may cause a new leakage path for the solar cell, resulting in a decrease in the performance of the cell. In addition, the laser damage to the cell itself is relatively large, and debris may occur during the laser isolation process, which increases the production cost of the cell. Summary of the invention

In view of this, an embodiment of the present invention provides a method for manufacturing a back contact crystalline silicon solar cell sheet, which removes an emitter junction formed on a back surface of the silicon wafer by diffusion, that is, a PN between the backlight surface and the conductive hole. The junction conductive layer is removed, so that the obtained solar cell achieves PN junction insulation.

The technical solution provided by the embodiment of the present invention is as follows:

A method for manufacturing a back contact crystalline silicon solar cell comprises etching an open-cell, a texturing, and a diffused semiconductor substrate, and processing the semiconductor substrate after etching to obtain a back-contact crystalline silicon solar cell , wherein: the etching comprises:

The light-receiving surface edge and the backlight surface of the semiconductor substrate are etched.

Preferably, the etching further comprises:

The via holes of the semiconductor substrate are etched.

Preferably, etching the edge of the light-receiving surface of the semiconductor substrate further comprises: etching the side surface of the semiconductor substrate and the edge of the via hole.

Preferably, the process of etching the through holes of the semiconductor substrate is:

Etching the entire through hole; Or etching a through hole in the axial direction.

Preferably, the etching is: etching with a chemical agent.

Preferably, the chemical agent is: a chemical liquid, a chemical etching slurry or a plasma gas.

Preferably, the etching process using a chemical liquid is:

The backlight surface of the semiconductor substrate is in full contact with the chemical liquid, and the side surface and the edge portion of the through hole are in contact with the chemical liquid.

Preferably, the etching using the chemical etching slurry is:

A chemical etching paste is printed on the edge of the light receiving surface of the semiconductor substrate and on the backlight surface.

Preferably, the etching process using a plasma gas is:

The through holes, side faces, and backlight faces of the semiconductor substrate are in direct contact with the plasma gas.

Preferably, the silicon wafer is processed after etching to:

Removing the doped glass layer on the semiconductor substrate after etching;

Coating a light-receiving surface of the semiconductor substrate after removing the doped glass layer;

An electrode and a back electric field are prepared on the semiconductor substrate after coating to obtain a back contact crystalline silicon solar cell sheet.

It can be seen from the above technical solution that the method for manufacturing the back contact crystalline silicon solar cell sheet provided by the embodiment of the invention etches the emitter junction formed on the back surface of the silicon wafer while etching the edge of the light receiving surface of the silicon wafer. After being removed, there is no short-circuited conductive layer between the backlight surface of the obtained solar cell sheet and the conductive hole, that is, the PN junction between the backlight surface and the conductive hole is disconnected, thereby improving the parallel resistance and conversion efficiency of the battery.

Compared with the prior art, the method reduces the laser isolation process, thereby reducing the risk of leakage of the battery and the fragmentation rate of the battery due to laser isolation. In addition, the laser isolation process is reduced, the process is more compact, and the equipment cost is reduced, which is advantageous for large-scale industrial production.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description It is only some embodiments described in the present invention, and those skilled in the art can obtain the same according to these drawings without any creative work. His drawings.

1 is a flow chart of a method for manufacturing a back contact crystalline silicon solar cell sheet according to Embodiment 1;

2 is a schematic structural view of a silicon wafer after opening according to the first embodiment;

3 is a schematic structural view of a silicon wafer after being subjected to the invention according to the first embodiment;

4 is a schematic structural view of a silicon wafer after diffusion according to Embodiment 1;

FIG. 5 is a schematic structural diagram of an etched silicon wafer according to Embodiment 1; FIG.

6 is a schematic structural view of a silicon wafer after plating according to the first embodiment;

7 is a schematic structural view of a silicon wafer after screen printing according to Embodiment 1; FIG. 8 is a flow chart of a method for manufacturing a back contact crystalline silicon solar cell according to Embodiment 2;

9 is a schematic structural view of an etched silicon wafer provided in the second embodiment;

10 is a schematic structural view of a silicon wafer after screen printing according to the second embodiment; FIG. 11 is a flow chart of a method for manufacturing a back contact crystalline silicon solar cell according to the third embodiment;

12 is a schematic structural view of a silicon wafer after etching according to Embodiment 3;

FIG. 13 is a schematic structural view of a silicon wafer after screen printing according to the third embodiment.

detailed description

The above described objects, features, and advantages of the present invention will become more apparent from the aspects of the appended claims.

In the following description, numerous specific details are set forth in order to provide a full understanding of the present invention, but the invention may be practiced in other ways than those described herein, and those skilled in the art can do without departing from the scope of the invention. The invention is not limited by the specific embodiments disclosed below.

2 is a detailed description of the present invention in conjunction with the accompanying drawings. In the detailed description of the embodiments of the present invention, the cross-sectional views showing the structure of the device may not be partially enlarged according to the general proportion, and the schematic diagram is only an example, which should not be limited herein. The scope of protection of the present invention. In addition, the actual three-dimensional dimensions of length, width and depth should be included in the actual production. In the manufacturing process of the existing back contact crystalline silicon solar cell sheet, in the diffusion and binding step after opening and texturing, a conductive layer for short-circuiting the PN junction is formed between the backlight surface of the solar cell and the conductive hole. This greatly reduces the parallel resistance of the battery and is prone to leakage. Therefore, in order to disconnect the PN junction, the existing process needs to provide an isolation trench around the conductive hole after the sintering step by laser isolation step. The conductive layer between the PN junctions is removed.

Through the prior art research, the applicant found that: in the sintering step, the battery sheet may be thermally deformed, and the surface is not flat, which makes the alignment precision of the borrowed light higher during laser isolation, otherwise the deviation occurs. This will lead to new leakage paths, which will degrade the performance of the battery. In addition, the use of a laser may cause damage to the battery chip, and chipping may occur, resulting in an increase in the defective rate of the battery chip, which increases the production cost of the battery chip. To this end, the present invention proposes a solution. The basic idea is: after the semiconductor substrate is diffused, the emitter junction formed on the backlight surface is removed by etching, that is, the PN junction between the backlight surface and the conductive hole. The conductive layer is removed to achieve PN junction insulation. The following is a description of the technical solution of the present invention by using a silicon wafer as a semiconductor substrate:

Embodiment 1:

Please refer to FIG. 1. FIG. 1 is a flowchart of a method for manufacturing a back contact crystalline silicon solar cell according to Embodiment 1. As shown in FIG. 1, the method includes the following steps:

Step S101: opening a hole in the silicon wafer;

The laser is used to open at least one through hole on the silicon wafer, and the electrode can be disposed in the through hole to guide the current of the light receiving surface of the battery to the backlight surface of the battery sheet, so that the positive and negative electrodes of the battery are located in the battery. The back side of the sheet reduces the shading rate of the front grid lines. In the embodiment of the present invention, the wavelength of the laser used for the opening may be 1064 nm, 1030 nm, 532 nm or 355 nm. The structure diagram of the silicon wafer after opening is shown in Fig. 2. In the figure, 1 is a silicon wafer, 2 is a light receiving surface, 3 is a back surface, 4 is a through hole, and 5 is a through hole inner wall.

Step S102: performing texturing on the surface of the silicon wafer to form a surface structure;

In the embodiment of the present invention, the selection of the texturing is performed on both sides of the silicon wafer 1. The purpose of the texturing is to form a convex and concave structure on the surface of the original bright silicon wafer by chemical reaction to extend the light on the surface thereof. The propagation path, thereby increasing the absorption of light by the silicon wafer. The structure of the silicon wafer after the pile is shown in Fig. 3, and the figure 6 is the pile surface. Further, it is necessary to remove the oil stain and metal impurities on the surface of the silicon wafer 1 before the fleece, and to remove the cut damage layer on the surface of the silicon wafer 1.

Step S103: diffusing a surface of the silicon wafer to form a P-N junction;

Dispersing the dopant atoms to the two fluffs 6 of the silicon wafer 1, the inner wall 5 of the via hole, and the side surface, as shown in FIG. 4, which is a schematic structural view of the silicon wafer after diffusion, and 7 is an N-type or P-type emission. Knot. After the N-type silicon wafer 1 diffuses, its surface becomes an N-type emitter junction, or the surface of the N-type silicon wafer 1 becomes a P-type emitter junction after diffusion, forming a PN junction, so that the silicon wafer 1 has a photovoltaic effect, and the concentration of diffusion, Depth and uniformity directly affect the electrical properties of solar cells.

Step S104: etching the edge of the light receiving surface of the silicon wafer and the backlight surface;

The edge of the light-receiving surface of the silicon wafer 1 and the backlight surface are etched. As shown in FIG. 5, 8 is an etched trench formed at the edge of the light-receiving surface after etching, and the purpose is to form the edge of the silicon wafer 1 when the diffusion is formed. A conductive layer that shorts both ends of the PN junction. The backlight surface of the silicon wafer 1 is etched for the purpose of removing the emitter junction formed on the backlight surface of the silicon wafer 1 during diffusion bonding.

In the embodiment of the present invention, when etching, a chemical etching paste can be printed on the edge of the light receiving surface of the silicon wafer 1 and the backlight surface, and when the chemical etching paste is printed on the edge of the light receiving surface of the silicon wafer 1, the silicon is selected. When the chemical etching slurry is printed on the entire backlight surface of the film i, and the chemical etching of the slurry is performed, the silicon wafer 1 is dried at room temperature for 3 minutes, and finally, the etching is performed by using an aqueous solution of 30 ° C to complete the etching.

Step S105: removing the doped glass layer on the silicon wafer;

By this step, the doped glass layer formed on the surface of the silicon wafer 1 during diffusion can be removed.

Step S106: performing coating on the light receiving surface of the silicon wafer;

The coating is performed on the light-receiving surface 2 of the silicon wafer 1, and the film functions to reduce the reflection of sunlight and to utilize solar energy to the utmost extent. In the embodiment of the present invention, an antireflection film is formed on the silicon wafer 1 by PECVD (Plasma Enhanced Chemical Vapor Deposition). As shown in Fig. 6, 9 is an anti-reflection film. Further, the use of PECVD is only one embodiment of the present invention and should not be construed as limiting the invention. In other embodiments of the present invention, the coating method may also employ other methods well known to those skilled in the art.

Step S107: printing an electrode and a back electric field on the coated silicon wafer; In the embodiment of the present invention, the backlight surface electrode, the light-receiving surface electrode, and the backlight surface may be electrically printed on the silicon wafer 1 by screen printing. Fig. 7 is a schematic view showing the structure of a silicon wafer after screen printing. In the figure, 10 is a back surface electrode, 11 is a back surface electrode, 12 is a backlight surface electric field, 13 is a light receiving surface electrode, and 14 is a hole electrode.

The light-receiving surface electrode 13, the hole electrode 14, and the hole back electrode 10 may be separately formed. The three electrodes may be of the same material or different materials. In other embodiments of the present invention, the electrode and the electric field may be attached to the silicon wafer 1 by vacuum evaporation, sputtering or the like.

Step 108: Sintering.

By sintering, an alloy can be formed between the printed light-receiving surface electrode 13, the hole electrode 14, the hole back electrode 10, the backlight surface electrode 11, the backlight surface electric field 12, and the silicon wafer 1, so that an ohmic contact is formed between the electrode and the silicon wafer. The preparation of electrodes and electric fields can be achieved by screen printing and sintering.

It can be seen from the above steps that the method for manufacturing the back contact crystalline silicon solar cell provided by the embodiment of the present invention etches the emitter junction formed on the back surface of the silicon wafer while etching the edge of the light receiving surface of the silicon wafer. Removed, so that there is no short-circuited conductive layer between the backlight surface of the obtained solar cell and the conductive hole, that is, the PN junction between the backlight surface and the conductive hole is broken, and the emitter junction in the conductive hole is well insulated. , improve the parallel resistance and conversion efficiency of the battery.

Compared with the prior art, the method reduces the laser isolation process, thereby reducing the risk of leakage of the battery and the fragmentation rate of the battery due to laser isolation. In addition, the laser isolation process is reduced, the process is more compact, and the equipment cost is reduced, which is advantageous for large-scale industrial production. Embodiment 2:

Please refer to FIG. 8, FIG. 8 is a flowchart of a method for manufacturing a back contact crystalline silicon solar cell according to Embodiment 2. As shown in FIG. 8, the method includes the following steps:

In the embodiment of the present invention, the steps 201 to 203 are the same as the steps 101 to 103 in the first embodiment, and details are not described herein again.

Step S204: etching the side surface of the silicon wafer, the backlight surface, and all the through holes;

FIG. 9 is a schematic view showing the structure of the etched silicon wafer. As shown in FIG. 9, after the etching, there is no emitter junction on the inner wall 5 and the side surface of the through hole. In the embodiment of the present invention, the entire surface of the entire surface of the silicon wafer 1, the entire backlight surface, and all the through holes can be completely in contact with the chemical liquid during the etching. The method can completely immerse all sides of the silicon wafer, the entire backlight surface and all the through holes by using HF (hydrogen fluoride) solution, or flush all sides of the silicon wafer, the entire backlight surface and all the through holes by using the HF (hydrogen fluoride) solution. The pores, or by means of spraying, are preferably etched in this embodiment by means of wetting.

In addition, during etching, plasma gas can also be used to etch all sides of the silicon wafer 1, the entire backlight surface and all the via holes for 15 min, wherein the flow rate of SF6 in the plasma gas is 200 sccm, the flow rate of 02 is 30 sccm, and the flow rate of N2. For 300 sccm, the pressure is chosen to be 50 Pa and the glow power is chosen to be 700 W.

The steps S205 to S208 after the etching are the same as the steps 105 to 108 in the first embodiment, and are not described herein again. FIG. 10 is a schematic structural diagram of the silicon wafer after screen printing according to the embodiment of the present invention. There is no emitter junction on the inner wall of the through hole. Embodiment 3:

Referring to FIG. 11, FIG. 11 is a flowchart of a method for manufacturing a back contact crystalline silicon solar battery chip according to the second embodiment. As shown in FIG. 11, the method includes the following steps:

In the embodiment of the present invention, the steps 301 to 303 are the same as the steps 201 to 203 in the second embodiment, and details are not described herein again.

Step S304: etching the side surface of the silicon wafer, the entire backlight surface, and a part of the through holes. FIG. 12 is a schematic structural view of the etched silicon wafer. As shown in FIG. 12, when etching the through hole, selective etching is performed. A section of the through hole in the direction of the axis of the through hole, so that after etching, there is a local emission junction on the inner wall 5 of the through hole. In addition, when etching the side surface of the silicon wafer, the entire surface of all the sides of the silicon wafer may be etched, or part of the surface of all the side surfaces may be etched.

In the embodiment of the present invention, when etching, the backlight surface can be immersed in the chemical liquid to a certain depth, so that part of the side surface and part of the through hole can be etched.

The steps S305 to S308 after the etching are the same as the steps 205 to 208 in the second embodiment, and are not described herein again. FIG. 13 is a schematic structural diagram of the silicon wafer after screen printing according to an embodiment of the present invention. There is no emitter junction on the inner wall of the through hole.

The above is only a preferred embodiment of the present invention, and those skilled in the art can understand or implement the present invention. Many modifications to these embodiments will be apparent to those skilled in the art. It is obvious that the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but the scope of the inventions

Claims

Rights request

A method for manufacturing a back contact crystalline silicon solar cell, comprising etching an open-cell, a velvet, and a diffused semiconductor substrate, and processing the semiconductor substrate after etching to obtain a back-contact crystalline silicon solar energy The battery sheet is characterized in that the etching comprises: etching a light receiving surface edge and a backlight surface of the semiconductor substrate.

2. The method according to claim 1, wherein the etching further comprises: etching a via hole of the semiconductor substrate.

3. The method according to claim 1, wherein etching the edge of the light-receiving surface of the semiconductor substrate further comprises etching the side surface of the semiconductor substrate and the edge of the via hole.

The method according to claim 2, wherein the etching the through holes of the semiconductor substrate is: etching the entire through holes;

Or etching a through hole in the axial direction.

The method according to claim 3 or 4, wherein the etching is: etching with a chemical agent.

6. A method according to claim 5 wherein the chemical agent is: a chemical liquid, a chemically aggressive slurry or a plasma gas.

7. The method according to claim 6, wherein the etching using the chemical liquid is: completely contacting the backlight surface of the semiconductor substrate with a chemical liquid, the side surface and the edge portion of the through hole Contact with chemical liquid.

The method according to claim 6, wherein the etching using the chemical etching paste is: printing a chemical etching paste on the edge of the light receiving surface of the semiconductor substrate and the backlight surface.

9. The method of claim 6 wherein the etching using plasma gas is: The through holes, side faces, and backlight faces of the semiconductor substrate are in direct contact with the plasma gas.

The method according to any one of claims 1 to 4, wherein the silicon wafer after etching is processed as:

After the etching, the semiconductor substrate is doped with a glass layer; after the doped glass layer is removed, the semiconductor substrate is coated on the light receiving surface;