WO2012162905A1

WO2012162905A1 - Method for manufacturing back contact crystalline silicon solar cell sheet

Info

Publication number: WO2012162905A1
Application number: PCT/CN2011/075420
Authority: WO
Inventors: 张凤; 王栩生; 章灵军
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: CN102800740B; CN102800740A

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) and performing texturing on surfaces (2,3) of the semiconductor wafer; forming a barrier layer (7) on one surface of the semiconductor wafer (1); printing a corrosive slurry surrounding the via (4) on the barrier layer (7) and cleaning the corrosive slurry to form a counter bore in the surrounding area of the via (4); diffusing on both surfaces (2,3) of the semiconductor wafer; removing the barrier layer (7) and processing the semiconductor wafer, thus obtaining the back contact crystalline silicon solar cell sheet. In the method, a local emitter junction (8) may be formed in the surrounding area of the via (4) by forming a window surrounding the via (4) on the backlight surface (3) before diffusion. So there is not a conductive layer which results in short circuit of the P-N junction. 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 This application claims priority to Chinese Patent Application No. 201110141248.6, entitled "Back Contact Crystal Silicon Solar Cell Manufacturing Method", filed on May 27, 2011, Chinese Patent Office, Application No. 201110141248.6 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 side 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 surface 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 damage of the cell itself is relatively large, and debris may occur during the laser isolation process, which increases the production of the cell. cost.

Summary of the invention

The invention provides a method for manufacturing a back contact crystalline silicon solar cell sheet, which is formed as a barrier layer on one surface of the semiconductor substrate before being diffused, and then etches a window around the surface through hole, so that when diffused, It is possible to diffuse only in the peripheral region of the through hole on the surface, so that the emitter junction on the backlight surface of the obtained solar cell sheet is a partial emission junction without a conductive layer short-circuiting the PN junction.

The method for manufacturing a back contact crystalline silicon solar cell sheet provided by the invention includes:

Opening and texturing the semiconductor substrate;

Forming a barrier layer on any surface of the semiconductor substrate after texturing;

Corrosive slurry is printed on a peripheral region of the through hole on a surface where the barrier layer is located, and the corrosive slurry is washed to form a counterbore in a peripheral region of the through hole;

Diffusion is performed on both surfaces of the semiconductor substrate forming the counterbore;

Removing the barrier layer on the semiconductor substrate after diffusion;

The semiconductor substrate after the removal of the barrier layer is processed to obtain a back contact crystalline silicon solar cell sheet. Preferably, the surrounding area of the through hole is: an area outside the through hole and having an edge of the through hole of 0.1 mm - 10 cm.

Preferably, the process of forming a barrier layer on either surface of the finished semiconductor substrate after the texturing is:

A barrier layer is formed by PECVD deposition, chemical oxidation, RTP, magnetron sputtering or evaporation. Preferably, the main component of the barrier layer is: silicon oxide, silicon nitride, titanium oxide and/or zinc oxide.

Preferably, the process of rinsing the corrosive slurry is: washing with lye or deionized water. Preferably, the lye is a potassium hydroxide or sodium hydroxide solution.

Preferably, the main component of the corrosive slurry is hydrogen fluoride ammonia or phosphoric acid.

Preferably, the process of processing the back contact crystalline silicon solar cell sheet is:

Etching the side surface of the semiconductor substrate after removing the barrier layer;

Coating a light-receiving surface of the semiconductor substrate after etching;

The electrode and the back electric field are printed on the semiconductor substrate after plating by screen printing; the semiconductor substrate is sintered after screen printing to obtain a back contact crystalline silicon solar cell sheet.

The method for manufacturing a back contact crystalline silicon solar cell sheet according to the present invention generates a barrier layer on any surface of the semiconductor before diffusing the semiconductor substrate after the texturing, and then surrounding the via hole on the surface of the barrier layer Printing the corrosive slurry and cleaning, so that a counterbore can be formed in the surrounding area of the through hole, and then the both sides of the semiconductor substrate are diffused, and then the subsequent removal of the barrier layer, etching, coating, preparation of the electrode and The back electric field finally results in a back contact crystalline silicon solar cell.

Before the diffusion, the method forms a barrier layer on any surface of the semiconductor substrate, and then etches the window around the surface via hole, so that when diffused, it can be performed only on the surrounding area of the through hole on the surface. Diffusion, so that the emitter junction on the backlight surface of the obtained solar cell sheet is a local emitter junction, and there is no conductive layer that short-circuits the PN junction.

Compared with the prior art, the method can reduce the laser isolation process, reduce the risk of battery leakage, and greatly reduce the fragmentation rate of the battery. 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 application or the technical solutions in the prior art, the drawings to be 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 of the embodiments described in the present application, and other drawings can be obtained from those skilled in the art without any creative work.

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 forming a barrier layer according to Embodiment 1; FIG. 5 is a schematic structural view of a silicon wafer after forming a counterbore according to Embodiment 1;

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

7 is a schematic structural view of a silicon wafer after removing a barrier layer according to Embodiment 1; FIG. 8 is a schematic structural view of a silicon wafer after etching according to Embodiment 1;

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

FIG. 10 is a schematic structural view of an electrode and a silicon wafer prepared by the back electric field according to the first 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 sheet, and chipping may occur, resulting in an increase in the defective rate of the battery sheet, which increases the production cost of the battery sheet.

To this end, the present invention proposes a solution, the basic idea is: before the diffusion, a barrier layer is formed on one surface of the semiconductor substrate, and then the window is etched around the surface via hole, so that when diffused, It is possible to diffuse only in the peripheral region of the through hole on the surface, so that the emitter junction on the backlight surface of the obtained solar cell sheet is a partial emission junction without a conductive layer short-circuiting the PN junction.

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 backlight 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 case of the carding, the carding may be performed on one side of the silicon wafer 1, or the carding may be performed on both sides of the silicon wafer 1. In the embodiment of the present application, as shown in FIG. Light-receiving surface 2 and backlight The surface 3 is textured, and the figure 6 is a suede. The purpose of the texturing is to form a convex and concave structure on the surface of the originally bright silicon wafer by a chemical reaction to prolong the propagation path of the light on the surface thereof, thereby improving the absorption of light by the silicon wafer. 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: forming a barrier layer on the entire surface of any surface on the silicon wafer;

A barrier layer is formed on the entire surface of any surface of the silicon wafer 1 after the texturing, in order to avoid diffusion of the surface on which the barrier layer is located during diffusion. There are various ways to form a barrier layer, including: PECVD deposition, chemical oxidation, RTP, magnetron sputtering or evaporation, and the material of the barrier layer may be silicon oxide, silicon nitride, titanium oxide or zinc oxide. Or any combination.

In the embodiment of the present application, it is preferable to deposit silicon oxide on the back surface of the silicon wafer by tubular PECVD, and the thickness of the silicon oxide is 70 nm, wherein at the time of deposition, the temperature is selected to be 500 ° C, the flow rate of N20 is 7 slm, and the flow rate of SiH4 is 200 sccm. , the pressure is lOmTorr, and the deposition time is 9 min. As shown in FIG. 4, a schematic structural view of the silicon wafer after the barrier layer is formed, and 7 is a barrier layer.

Step S104: printing a corrosive slurry on a region around the through hole of the surface on which the barrier layer is located on the silicon wafer, and rinsing the corrosive slurry to form a counterbore in a region around the through hole;

The area around the through hole can be selected from the edge of the through hole 4 to O.lmm-lOcm. After printing the chemical etching paste, the silicon wafer is dried at room temperature for 3 minutes, and then washed with an aqueous solution of 30 ° C. A counterbore is formed in a region around the through hole, that is, a region around the through hole forms a counterbore as compared with the barrier layer. As shown in Figure 5, the structure of the silicon wafer after forming the counterbore

Step S105: diffusing on the surface of the silicon wafer and the inner wall of the through hole to form a PN junction; diffusing the dopant atoms onto the pile surface 6 of the silicon wafer 1 and diffusing onto the inner wall of the through hole 4, as shown in FIG. Shown as a schematic diagram of the structure of the silicon wafer after diffusion, 8 is an emitter junction, and a counterbore is formed in the area around the through hole on the backlight surface before diffusion, so when diffused, a circle around the through hole on the backlight surface is formed. Shaped emission junction. The P-type silicon wafer 1 becomes N-type after diffusion, or the N-type silicon wafer 1 becomes P-type after diffusion, forming a PN junction, so that the silicon wafer 1 has a photovoltaic effect, and the concentration, depth, and uniformity of diffusion Directly affect the electrical properties of solar cells.

Step S106: removing the barrier layer on the silicon wafer;

Through this step, the barrier layer generated on the backlight surface of the silicon wafer 1 in step S104 can be removed, as shown in FIG. 7, which is a schematic structural view of the silicon wafer after removing the barrier layer, in the through hole 4 and on the backlight surface 3. An emitter junction is left in the surrounding area of the through hole 4. Step S107: etching a side surface of the silicon wafer;

The side of the silicon wafer 1 is etched for the purpose of removing the conductive layer formed on the side of the silicon wafer 1 and short-circuiting both ends of the PN junction. As shown in FIG. 8, it is a schematic structural view of the silicon wafer after etching.

Step S108: removing the doped glass layer on the silicon wafer;

Through this step, the doped glass layer formed by the silicon wafer 1 upon diffusion can be removed.

Step S109: performing coating on the light receiving surface of the silicon wafer;

The film is coated on the light-receiving surface of the silicon wafer 1, and the film serves to reduce the reflection of sunlight and maximize the use of solar energy. 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. 9, 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 employ other methods well known to those skilled in the art.

Step S110: preparing an electrode and a back electric field on the coated silicon wafer;

In an embodiment of the invention, preparing the electrode and the back electric field comprises: printing the electrode and the back electric field on the silicon wafer 1; sintering.

Among them, the back surface electrode, the light receiving surface electrode, and the backlight surface electric field can be printed on the silicon wafer 1 by screen printing. Fig. 10 is a schematic view showing the structure of the silicon wafer after preparation of the electrode and the back electric field. In the figure, 10 is the back electrode of the hole, 11 is the back electrode, 12 is the back electric field, 13 is the light receiving surface electrode, and 14 is the hole electrode. The light-receiving electrode, the hole electrode, and the back electrode of the hole may be separately formed, and the three electrodes may be of the same material or different materials. In other embodiments of the present invention, the electrode and the back electric field may be attached to the silicon wafer 1 by vacuum evaporation, sputtering or the like. An ohmic contact is formed between the electrode and the silicon wafer by sintering.

It can be seen from the above technical solutions that the back contact crystalline silicon solar cell manufacturing method provided by the embodiment of the present application generates a barrier layer on any surface of the semiconductor before diffusing the semiconductor substrate after the texturing, and then Corrosive slurry is printed on the peripheral region of the via hole on the surface of the barrier layer, and is cleaned, so that a counterbore can be formed in the peripheral region of the via hole, and then the both sides of the semiconductor substrate are diffused, and then subjected to subsequent diffusion. Etching, coating, electrode preparation and back electric field, and finally obtaining a back contact crystalline silicon solar cell.

Before the diffusion, the method forms a barrier layer on any surface of the semiconductor substrate, and then etches the window around the surface via hole, so that when diffusing, only the through hole can be formed on the surface. The surrounding area is diffused such that the resulting emitter junction on the backlight surface of the solar cell is a local emitter junction without a conductive layer that shorts the PN junction.

Compared with the prior art, the method can reduce the laser isolation process, reduce the risk of leakage of the battery, and greatly reduce the fragmentation rate of the battery. 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.

The above description is only a preferred embodiment of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments are obvious to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application is not limited to the embodiments shown herein, but the broadest scope consistent with the principles and novel features disclosed herein.

Claims

A method for manufacturing a back contact crystalline silicon solar cell, comprising: opening and texturing a semiconductor substrate;

Right

Removing the barrier layer on the semiconductor substrate after diffusion;

The semiconductor substrate after the removal of the barrier layer is treated to obtain a back contact crystalline silicon solar cell. 9

_ want

2. The method of claim 1 wherein the surrounding area of the through hole is:

An outer surface of the through hole and an edge of the through hole is an area of 0.1 mm - 10 cm.

The method according to claim 1, wherein the process of forming a barrier layer on any surface of the textured semiconductor substrate is:

A barrier layer is formed by PECVD deposition, chemical oxidation, RTP, magnetron sputtering or evaporation.

The method according to claim 3, characterized in that the main component of the barrier layer is: silicon oxide, silicon nitride, titanium oxide and/or zinc oxide.

5. The method of claim 1 wherein the rinsing of the corrosive slurry is: washing with lye or deionized water.

6. A method according to claim 5 wherein the lye is a potassium hydroxide or sodium hydroxide solution.

The method according to claim 1, wherein the main component of the corrosive slurry is hydrogen fluoride ammonia or phosphoric acid.

The method according to any one of claims 1 to 7, wherein the process of back-contacting the crystalline silicon solar cell for processing is:

Coating a light-receiving surface of the semiconductor substrate after etching;