WO2012162903A1

WO2012162903A1 - Method for manufacturing back contact crystalline silicon solar battery piece

Info

Publication number: WO2012162903A1
Application number: PCT/CN2011/075418
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: CN102800742A; CN102800742B

Abstract

A method for manufacturing a back contact crystalline silicon solar battery piece includes: opening a through hole (4), performing diffusion into a textured (6) semiconductor substrate (1); processing the diffused semiconductor substrate (1) to achieve back contact crystalline silicon solar battery pieces; also includes: forming a barrier layer (7) on any surface of the textured (6) semiconductor substrate (1) before diffusion, to avoid diffusing into the barrier layer (7) when diffusing; after diffusing, removing the barrier layer (7) on the diffused semiconductor substrate (1). The method can avoid diffusing on a backlight surface (3) to form P-N junction by forming the barrier layer (7) on the backlight surface (3) of the semiconductor substrate (1), before diffusing into the semiconductor substrate (1). The method reduces laser isolating process, reduces leakage risk of the battery piece, and largely reduces fragment rate of the battery piece.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present application claims priority to Chinese Patent Application No. 201110141259.4, entitled "Back Contact Crystal Silicon Solar Cell 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 application relates to the field of solar cell technology, and in particular, to a method of fabricating 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

In view of this, the embodiments of the present application provide a method for manufacturing a back contact crystalline silicon solar cell sheet, which generates a barrier layer on one surface of the semiconductor substrate before diffusion, thereby preventing diffusion on the surface of the semiconductor substrate during diffusion. A conductive layer that short-circuits the PN junction is not formed between the backlight surface of the obtained solar cell sheet and the conductive hole. In order to achieve the above objectives, the technical solutions provided by the embodiments of the present application are as follows:

A method for manufacturing a back contact crystalline silicon solar cell, comprising: diffusing a holed, textured semiconductor substrate, and processing the semiconductor substrate after diffusion to obtain a back contact crystalline silicon solar cell, further comprising :

Before the diffusion, a barrier layer is formed on any surface of the semiconductor substrate after the texturing to avoid diffusion on the surface where the barrier layer is formed during diffusion; after diffusion, the barrier on the semiconductor substrate after diffusion is removed Floor.

Preferably, before diffusion, a barrier layer is formed on the inner wall of the through hole of the semiconductor substrate after texturing to prevent diffusion on the inner wall of the through hole when diffused. Preferably, the process of forming a barrier layer on either surface of the semiconductor substrate after texturing comprises:

Forming a barrier layer on the entire surface of any surface of the semiconductor substrate,

Alternatively, a barrier layer is formed on a region around the via hole on either surface of the semiconductor substrate. Preferably, the process of forming a barrier layer on either surface of the semiconductor substrate after texturing is:

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

Preferably, the main component of the barrier layer is: one or any combination of an organic resin, silicon oxide, silicon nitride, titanium oxide or zinc oxide.

Preferably, the area around the through hole is: an area i or outside the through hole and having an edge of the through hole of O.lmm-lOcm.

Preferably, the semiconductor substrate after diffusion is processed as:

Etching the edge of the light receiving surface of the semiconductor substrate after diffusion;

Removing the doped glass layer on the semiconductor substrate after etching; coating the light-receiving surface of the semiconductor substrate after removing the doped glass layer;

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

It can be seen from the above technical solutions that the back contact crystalline silicon semiconductor substrate manufacturing method provided by the embodiment of the present application forms a barrier layer on the backlight surface of the semiconductor substrate before the semiconductor substrate is diffused, and the barrier layer can be avoided. Diffusion is performed on the backlight surface of the semiconductor substrate, and after the diffusion is completed, the barrier layer of the backlight surface is removed, so that a conductive layer short-circuiting the PN junction is not formed between the backlight surface of the finally obtained solar cell and the conductive hole. , the PN junction is disconnected.

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, reducing the laser isolation process makes the process more compact and reduces equipment costs, which is conducive to large-scale industrial production. In addition, before the diffusion of the semiconductor substrate, a barrier layer may be formed on the inner wall of the through hole on the semiconductor substrate, and the barrier layer on the inner wall of the through hole may prevent diffusion in the through hole, that is, no emission in the through hole. In the same manner, a conductive layer that short-circuits the PN junction is not formed between the backlight surface of the solar cell sheet and the conductive hole, and the PN junction is in an off state. 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 diffusion according to Embodiment 1; FIG.

6 is a schematic structural view of a silicon wafer after removing a barrier layer according to Embodiment 1;

7 is a schematic structural view of an etched silicon wafer according to Embodiment 1;

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

9 is a schematic structural view of a silicon wafer after preparation of an electrode and a back electric field according to Embodiment 1; FIG. 10 is a flow chart of a method for manufacturing a back contact crystalline silicon solar cell sheet according to Embodiment 2;

FIG. 11 is a schematic structural diagram of a silicon wafer after forming a barrier layer according to Embodiment 2;

12 is a schematic structural view of a silicon wafer after diffusion according to Embodiment 2;

FIG. 13 is a schematic structural view of an electrode and a silicon wafer prepared by the back electric field according to the second 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 production should include the three-dimensional dimensions of length, width and depth.

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 in which the basic idea is: before the diffusion of the semiconductor substrate, a barrier layer is formed on one surface of the semiconductor substrate, and the barrier layer is removed after diffusion, thus It is possible to avoid diffusion of the surface on which the barrier layer is located on the semiconductor substrate, and no diffusion layer is formed on the backlight surface, that is, a conductive layer that short-circuits the PN junction is not formed between the backlight surface of the obtained solar cell sheet and the conductive hole.

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 film reduces the shading rate of the front surface grid lines. In the embodiment of the 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. The light-receiving surface 2 and the backlight surface 3 are simultaneously subjected to texturing, and in the figure, 6 is a pile surface. 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 texturing, 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 of the silicon wafer and the inner wall of the through hole; forming a barrier layer on the entire surface of any surface of the silicon wafer 1 after the texturing, the purpose of which is to avoid blocking when spreading The surface on which the layer is located is diffused. As shown in Fig. 4, a schematic diagram of the structure of the silicon wafer after the barrier layer is formed, and 7 is a barrier layer. In the embodiment of the present application, preferably, when the barrier layer is formed, a barrier layer is formed on the inner wall of the through hole 4, so that a plurality of ways of diffusing the inner wall of the through hole to form a barrier layer during diffusion can be avoided, including : Printing paste, PECVD deposition, chemical oxidation,

RTP, magnetron sputtering or evaporation, etc., and the material of the barrier layer may be one or any combination of an organic resin, silicon oxide, silicon nitride, titanium oxide or zinc oxide.

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, and the flow rate of N ₂ 0 is 7 slm, SiH ₄ The flow rate was 200 sccm, the pressure was 10 mTorr, and the deposition time was 9 min. Step S104: diffusing on the other surface and the side surface of the silicon wafer to form a PN junction; diffusing the dopant atoms onto the textured surface of the silicon wafer 1, as shown in FIG. 5, is a schematic structural view of the silicon wafer after diffusion, In the figure, 8 is an N-type or P-type emitter 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 the solar cell sheet.

Step S105: removing the barrier layer on the semiconductor substrate; the layer affects the subsequent operation, as shown in FIG. 6, the structure of the silicon wafer after removing the barrier layer, and the backlight layer and the barrier layer in the via hole are removed. .

Step S106: etching 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. 7, it is a schematic diagram of the structure of the etched silicon wafer.

The etching method can be performed by plasma gas etching, wherein the flow rate of SF ₆ in the plasma gas is 200 scm, the flow rate of 0 ₂ is 30 scm, the flow rate of N ₂ is 300 scm, the pressure is selected to be 100 Pa, and the glow power is selected to be 700 W.

Step S107: 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 S108: 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. 8, 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 S109: 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 backlight surface electrode, the light-receiving surface electrode, and the backlight surface can be printed on the silicon wafer 1 by screen printing. Fig. 9 is a schematic view showing the structure of a silicon wafer after preparation of an electrode and a back electric field, wherein 10 is a back electrode of the hole, 11 is a back electrode, 12 is a back 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 can be separately formed, and the three electrodes The same material can be used or different materials can be used. 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.

The method for manufacturing the back contact crystalline silicon solar cell sheet provided by the embodiment of the present application, the method for forming a barrier layer on the backlight surface of the solar cell sheet before the solar cell sheet is diffused, the barrier layer It is possible to avoid diffusion on the backlight surface of the solar cell sheet, and after the diffusion is completed, the barrier layer of the backlight surface is removed, so that a conductive layer short-circuiting the PN junction is not formed between the backlight surface of the solar cell sheet and the conductive hole. , the PN junction is disconnected.

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, reducing the laser isolation process makes the process more compact and reduces equipment costs, which is conducive to large-scale industrial production. In addition, before the diffusion of the semiconductor substrate, a barrier layer is formed on the inner wall of the through hole on the semiconductor substrate, and the barrier layer on the inner wall of the through hole can avoid diffusion in the through hole, that is, there is no emission junction in the through hole. Also, a conductive layer that short-circuits the PN junction is not formed between the backlight surface of the solar cell sheet finally obtained and the conductive hole, and the PN junction is in an off state.

Embodiment 2:

Referring to FIG. 10, FIG. 10 is a flowchart of a method for manufacturing a back contact crystalline silicon solar cell according to Embodiment 2. As shown in FIG. 10, the method includes the following steps:

In the embodiment of the present invention, only step S203 and step S103 are different, and other steps, such as steps 201 to 202 are the same as steps 101 to 102 in the first embodiment, steps S205 to S209 and steps in the first embodiment. S104~Step S109 are the same, and are not described here.

Step S203: forming a barrier layer in a region around the via hole on either surface of the semiconductor substrate. As shown in FIG. 11, compared with the first embodiment, in the embodiment of the present application, when the barrier layer 7 is formed, a barrier layer is formed only in a region around the through hole on a certain surface. In addition, in the embodiment of the present application, the area around the through hole is preferably an area from the edge of the through hole of 0.1 mm to 10 cm. As shown in FIG. 12, it is a schematic structural view of the silicon wafer after diffusion, in which the area around the through hole on the surface of the barrier layer 7 is not diffused, and the barrier layer around the through hole is removed after diffusion. The effect of diffusing other areas on the surface except the area around the through hole. FIG. 13 is a schematic structural view of an electrode and a back silicon field prepared by the embodiment of the present application. It can be seen that the conductive layer which short-circuits the PN junction is not formed between the backlight surface of the solar cell sheet and the conductive hole, and the PN junction is in an off state. 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

Rights request

A method for fabricating a back contact crystalline silicon solar cell, comprising: diffusing a semiconductor substrate after opening and texturing, and processing the semiconductor substrate after diffusion to obtain a back contact crystalline silicon solar cell. The method further includes: before the diffusion, forming a barrier layer on any surface of the semiconductor substrate after the texturing to avoid diffusion on the surface where the barrier layer is dispersed during diffusion; after diffusion, after removing the diffusion a barrier layer on the semiconductor substrate.

The method according to claim 1, wherein a barrier layer is formed on the inner wall of the through hole of the semiconductor substrate after the flocking to prevent diffusion on the inner wall of the through hole during diffusion.

3. The method of claim 1 wherein the step of forming a barrier layer on either surface of said semiconductor substrate after texturing comprises: on the entire surface of either surface of said semiconductor substrate A barrier layer is formed, or a barrier layer is formed on a region around the via hole on either surface of the semiconductor substrate.

4. The method of claim 3, wherein the step of forming a barrier layer on either surface of the semiconductor substrate after texturing comprises: using a printing paste, PECVD deposition, chemical oxidation, RTP , magnetron sputtering or evaporation to form a barrier layer.

The method according to claim 4, wherein the main component of the barrier layer is: one or any combination of an organic resin, silicon oxide, silicon nitride, titanium oxide or zinc oxide.

The method according to claim 3, wherein the area around the through hole is: an area outside the through hole and having an edge of the through hole of O.lmm-lOcm.

The method according to any one of claims 1 to 6, wherein the semiconductor substrate after diffusion is processed as:

Etching the semiconductor substrate after diffusion;

Removing the doped glass layer on the semiconductor substrate after etching; A film is coated on the light-receiving surface of the semiconductor substrate after removing the doped glass layer; and an electrode and a back electric field are prepared on the silicon wafer after the coating to obtain a back-contact crystalline silicon solar cell sheet.