WO2012162899A1 - Fabrication method for back-contacted crystalline silicon solar cell - Google Patents

Abstract

A fabrication method for the back-contacted crystalline silicon solar cell includes: texturing（S101） and diffusion（S102） on the surface of the semiconductor substrate, formation of vias in the semiconductor substrate after the diffusion（S103）, etching of the semiconductor substrate after vias formation（S104）, removal of the doped glass layer from the semiconductor substrate after the etching（S105）, film deposition on the light receiving side of the semiconductor substrate after the removal of the doped glass layer（S106）, and formation of electrodes and back surface fields on the semiconductor substrate after the film deposition（S107）. Consequently, the back-contacted crystalline silicon solar cell is obtained. In the method, the surface of the semiconductor substrate is diffused firstly, and the vias are formed in the semiconductor after the diffusion, so the inner walls of the through vias will not be diffused, namely there will be no emitter junctions in the through vias.

Description

 BACKGROUND OF THE INVENTION 1. Field of the Invention This application claims priority to Chinese Patent Application No. 201110141621.8, 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 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 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 embodiment of the present application provides a method for manufacturing a back contact crystalline silicon solar cell sheet, which is then opened after diffusing the surface of the semiconductor substrate, so that the inner wall of the through hole is not diffused, that is, in the solar cell. A conductive layer that shorts the PN junction is not formed between the backlight surface and the conductive via.

 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 sheet, comprising:

 Performing texturing and diffusion on the surface of the semiconductor substrate;

 Opening a hole in the semiconductor substrate after diffusion;

 Etching the semiconductor substrate after the opening;

 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;

 A back contact crystalline silicon solar cell sheet is obtained after preparing an electrode and a back electric field on the semiconductor substrate after coating.

Preferably, the process of diffusion on the surface of the semiconductor substrate is: Diffusion is performed on one or both sides of the semiconductor substrate.

 Preferably, after the diffusion of the semiconductor substrate, before removing the doped glass layer on the semiconductor substrate after etching, the method further includes:

 The backlight surface and the side surface of the semiconductor substrate are etched.

 Preferably, the opening in the semiconductor substrate after diffusion is:

 At least one through hole is opened in the semiconductor substrate after diffusion by a laser. 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 first diffuses the surface of the semiconductor substrate, and then opens the semiconductor substrate after diffusion, so that The inner wall of the through hole is not diffused, that is, there is no emission junction in the through hole, so the conductive layer which short-circuits the PN junction is not formed between the backlight surface of the finally obtained solar cell and the conductive hole, and 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.

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 being processed according to the first embodiment;

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

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

 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 an electrode and a back-field prepared silicon wafer according to the first embodiment; FIG. 8 is a flow chart 9 of the method for manufacturing a back contact crystalline silicon solar cell according to the second embodiment; Schematic diagram of the structure of the wafer after the velvet;

图 10为本实施例二提供的扩散后硅片的结构示意图；

FIG. 10 is a schematic structural view of a silicon wafer after diffusion according to Embodiment 2; FIG.

 11 is a schematic structural view of a silicon wafer after opening according to the second embodiment;

 12 is a schematic structural view of a silicon wafer after etching 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 can cause damage to the battery chip, and chipping may occur, so that the battery chip The defective product rate increases, increasing the production cost of the battery. To this end, the present invention proposes a solution. The basic idea is: first, the semiconductor substrate is subjected to texturing and diffusion, and then the semiconductor substrate is opened after diffusion, so that the inner wall of the through hole is not Diffusion, that is, a conductive layer that shorts the PN junction is not formed between the backlight surface of the solar cell 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: performing carding on one side of the silicon wafer to form a surface structure;

 In the embodiment of the present invention, the selection of the texturing is performed on one side of the silicon wafer 1. The purpose of the texturing is to form a convex and concave structure on the surface of the originally bright silicon wafer by chemical reaction to prolong the propagation path of the light on the surface thereof, thereby Increase the absorption of light by the silicon wafer. The structure diagram of the silicon wafer after the velvet is shown in Fig. 2. In the figure, 1 is a silicon wafer, 2 is a light receiving surface, 3 is a backlight surface, and 4 is a suede 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 S102: diffusing on a surface of the silicon wafer to form a P-N junction;

 The doping atoms are diffused onto the pile surface 4 and the side surface of the silicon wafer 1, as shown in Fig. 3, which is a schematic structural view of the silicon wafer after diffusion, and 5 is an 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 S103: 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 invention, the wavelength of the laser used for the opening may be 1064 nm, 1030 nm, 532 nm or 355 nm. In addition, in other embodiments of the present application, the drilling may be performed by mechanical drilling or chemical etching. The structure of the silicon wafer after opening is shown in Fig. 4. In the figure, 6 is a through hole, and 7 is an inner wall of the through hole. In the embodiment of the present application, since the process of first diffusing and re-perforating is adopted, there is no emitter junction in the through hole formed after the opening, so that there is no short circuit between the conductive hole and the backlight surface to form the PN junction. Conductive layer.

 Step S104: etching a side surface of the silicon wafer;

 The side of the silicon wafer 1 is etched, as shown in Fig. 5, for the purpose of removing the emitter junction formed on the side of the silicon wafer 1 during diffusion bonding.

 There are various etching methods, which may be wet etching or dry etching, wherein: wet etching includes: chemical liquid etching, chemical etching slurry etching, etc. Dry etching includes plasma gas etching Wait. In the embodiment of the present invention, when etching, the side of the silicon wafer 1 may be etched by a plasma gas for 15 min, wherein the flow rate of the SF6 in the plasma gas is 200 scm, the flow rate of the 02 is 30 scm, and the flow rate of the N2 is 300 scm. For lOOPa, the glow power is chosen to be 700W.

 Step S105: 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 S106: 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 functions to reduce the reflection of sunlight and 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, 8 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: 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. 7 is a schematic view showing the structure of the silicon wafer after the electrode and the back electric field are prepared. In the figure, 9 is the back electrode of the hole, 10 is the back electrode, 11 is the back electric field, 12 is the light receiving surface electrode, and 13 is the hole electrode. The light-receiving electrode 12, the hole electrode 13, and the hole back electrode 9 may be separately formed. The three electrodes may be of the same material or different materials. In other embodiments of the invention, It is also possible to attach the electrode and the back electric field to the silicon wafer 1 by vacuum evaporation, sputtering or the like. An ohmic contact is formed between the hole back surface electrode 9, the back electrode 10, the back electric field 11, the light receiving surface electrode 12, the hole electrode 13, and the silicon wafer 1 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 first diffuses the surface of the semiconductor substrate, and then opens the semiconductor substrate after diffusion, so that The inner wall of the through hole is not diffused, that is, there is no emission junction in the through hole, so the conductive layer which short-circuits the PN junction is not formed between the backlight surface of the finally obtained solar cell and the conductive hole, and 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. 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:

 Step S201: performing texturing on both surfaces of the silicon wafer to form a surface structure;

 A schematic view of the structure of the wafer after the pile is shown in Fig. 9, in which the pile 4 is formed on both surfaces of the wafer 1.

 Step S202: diffusing a P-N junction on the surface of the silicon wafer;

 A schematic diagram of the structure of the silicon wafer after diffusion is shown in Fig. 10. In the figure, 5, an emission junction is diffused on both surfaces and sides of the silicon wafer 1.

 The above two steps are compared with the steps S101 to 103, except that the process is performed on both sides of the silicon wafer, and the processes of the corresponding steps are the same.

 Step S203: opening a hole in the silicon wafer;

 The structure diagram of the silicon wafer after opening is shown in Fig. 11, in which 6 is a through hole, and 7 is an inner wall of the through hole. Step S204: etching the side surface of the silicon wafer and the backlight surface;

The side surface of the silicon wafer 1 and the backlight surface are etched, as shown in FIG. 12, which is a schematic structural view of the silicon wafer after etching, and the purpose thereof is to remove the emission junction formed on the side of the silicon wafer 1 during diffusion bonding. The backlight surface of the silicon wafer 1 is etched, and the purpose thereof is to form an emission formed on the backlight surface of the silicon wafer 1 during diffusion bonding. The knot is removed.

 The etching method is performed by wet etching. In the embodiment of the present invention, the side surface of the silicon wafer 1 and the backlight surface may be in contact with the chemical liquid phase during the etching, and the contact may be performed by using HF (hydrogen fluoride). The solution may infiltrate the backlight surface of the silicon wafer, or may be used to rinse the backlight surface of the silicon wafer with the HF (hydrogen fluoride) solution, or may be etched by spraying in a preferred manner in this embodiment.

 The steps S205 to S207 after the etching are the same as the steps 105 to 107 in the first embodiment, and will not be described herein. The silicon wafer obtained as shown in FIG. 13 has no emitter junction on the inner wall of the through hole.

 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  What is claimed is: 1. A method of manufacturing a back contact crystalline silicon solar cell, comprising: performing texturing and diffusion on a surface of a semiconductor substrate;  Opening a hole in the semiconductor substrate after diffusion;  Etching the semiconductor substrate after the opening;  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;  A back contact crystalline silicon solar cell sheet is obtained after preparing an electrode and a back electric field on the semiconductor substrate after coating.  The method according to claim 1, wherein the diffusion on the surface of the semiconductor substrate is:  Diffusion is performed on one or both sides of the semiconductor substrate.  The method according to claim 2, wherein after the diffusion of the semiconductor substrate, removing the doped glass layer on the semiconductor substrate after etching further comprises: facing the semiconductor substrate The backlight surface and the side surface are etched.  4. The method of claim 1 wherein the opening in the semiconductor substrate after diffusion is:  At least one through hole is opened in the semiconductor substrate after diffusion by a laser.