P-type back contact solar cell and preparation process thereof

Abstract

The invention discloses a P-type back contact solar cell and a preparation process thereof, and relates to the field of semiconductor devices and photovoltaic power generation. The preparation process of the P-type back contact solar cell specifically comprises the steps of texturing, oxidation, silicon dioxide removal, alkali polishing, PECVD (Plasma Enhanced Chemical Vapor Deposition) poly, annealing, first laser treatment, RCA cleaning, double-sided aluminum oxide / silicon nitride treatment, second laser treatment and printing and sintering. According to the preparation process of the P-type back contact solar cell, a feasible process route is provided for a TOPCon cell of an existing PECVD (Plasma Enhanced Chemical Vapor Deposition) poly route, an existing production line is fully utilized to carry out differentiated upgrading, the situation that only TOPCon products can be produced by the PECVD poly route is avoided, and the production line of the TOPCon cell of the existing PECVD poly route does not need to add new equipment and transform equipment except necessary laser equipment, so that the production cost is reduced, and the production efficiency is improved. And the back contact battery can be produced.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices and photovoltaic power generation, and in particular to a P-type back-contact solar cell and a preparation process thereof. Background Art

[0002] Solar cells are usually composed of multiple layers, including silicon wafers, doping layers, passivation layers, electrodes, etc. Among them, the silicon wafer is the core part of the solar cell, which determines the photoelectric conversion efficiency of the solar cell. The doping layer is used to adjust the conductive properties of the silicon wafer to form a PN junction.

[0003] The current mainstream photovoltaic cell factories mainly produce TOPCon cells, with surplus production capacity. Back-contact cells are favored by high-end customers for their high efficiency and beautiful appearance. TOPCon cells are mainly produced by LPCVD and PECVD. It is relatively simple and feasible to upgrade the production line of the LPCVD route to the production line of back-contact cells, because its poly can be plated on both sides with a single insertion. However, the PECVD route has many problems to overcome when transforming the back-contact cell route because its poly is plated on one side and has a slight plating problem. For example, the transformation of the TOPCon cell line to the back-contact cell production line requires at least two lasers. In addition, some new processes or the troughs of some processes need to be added. There is currently no low-cost method. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a P-type back-contact solar cell and its preparation process, which solves the problem that TOPCon cells are mainly LPCVD and PECVD. It is relatively simple and feasible to transform and upgrade the production line of the LPCVD route to the production line of the back-contact cell, because its poy can choose single-insert double-sided plating, while the PECVD route is more difficult to transform the back-contact cell route because its plated Poly is single-sided and has a slight plating problem.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a P-type back-contact solar cell, comprising P-type silicon, wherein silicon dioxide is arranged on the back, both sides and front corners of the P-type silicon, a phosphorus-doped polysilicon layer is deposited on the outside of the silicon dioxide, the P-type silicon at the outside and the outside of the phosphorus-doped polysilicon layer are passivated to form an aluminum oxide / silicon nitride stack, the outside of the phosphorus-doped polysilicon layer at the back is printed and sintered to form a silver electrode, the back of the P-type silicon is printed and sintered to form an aluminum electrode, and an aluminum film layer is arranged between the aluminum electrode and the P-type silicon, and laser isolation layers are arranged on both side corners of the P-type silicon.

[0006] A preparation process of a P-type back-contact solar cell, the preparation process comprising the following steps: Step 1: Velvet making Step 2: Oxidation Step 3: Remove silica Step 4: Alkaline polishing Step 5: PECVD poly Step 6: Annealing Step 7: First laser treatment Step 8: RCA Cleaning Step 9: Double-sided aluminum oxide / silicon nitride Step 10: Second laser treatment Step 11: Printing and sintering.

[0007] Preferably, the texturing and oxidation steps are specifically as follows: The outer side of the P-type silicon is textured, and then the front side of the P-type silicon is oxidized outward at high temperature to form silicon dioxide.

[0008] Preferably, the desiliconization and alkali polishing steps are specifically: Use hydrofluoric acid from a chain-type PSG removal device to corrode and remove unnecessary silicon dioxide on the surface, and then use an alkaline polishing device to polish the P-type silicon back film.

[0009] Preferably, the PECVD poly step is specifically as follows: The back film is coated with a silicon dioxide tunneling layer, a phosphorus-doped polysilicon layer and silicon dioxide using PECVD coating equipment.

[0010] Preferably, the annealing step is specifically: Heat treatment is performed at high temperature facing outward to rearrange the atoms in the phosphorus-doped polysilicon layer. The P-type silicon is annealed at high temperature to crystallize the phosphorus-doped polysilicon layer.

[0011] Preferably, the first laser treatment step is specifically as follows: According to the back contact design, the phosphorus-doped polysilicon layer on the back is molded using laser equipment.

[0012] Preferably, the RCA cleaning step is specifically as follows: Entering the RCA equipment, its alkaline tank corrodes the laser-treated part to form a P area; the hydrofluoric acid in the post-cleaning acid tank corrodes and cleans the silicon dioxide on the front and back films to remove high-temperature by-products.

[0013] Preferably, the double-sided aluminum oxide / silicon nitride step is specifically as follows: The P-type silicon is double-sided passivated using aluminum oxide and silicon nitride to form an aluminum oxide / silicon nitride stack.

[0014] Preferably, the second laser processing and printing sintering steps are specifically as follows: The P area of ​​the back film is opened by laser equipment, and then the silver electrode and the aluminum electrode are printed and sintered on the phosphorus-doped polysilicon layer on the back and the back of the P-type silicon respectively.

[0015] The present invention discloses a P-type back-contact solar cell and a preparation process thereof, which has the following beneficial effects: The P-type back-contact solar cell and its preparation process provide a feasible process route for the TOPCon cell of the existing PECVD poly route, making full use of the existing production line for differentiated upgrades, avoiding the PECVD poly route being limited to producing TOPCon products; After the boron is expanded to oxidation in the poly processing route, the surface BSG, which was originally about 120nm, becomes silicon dioxide with a thickness of 10~50nm. After annealing, part of the phosphorus-doped polysilicon layer will be oxidized to silicon dioxide. Even if some phosphorus-doped polysilicon layer remains, it will not have much impact on the battery. After RCA cleaning, the hydrofluoric acid tank inside will clean the silicon dioxide on the front. The phosphorus-doped polysilicon layer plated around the edge is the same as the silicon base, but with a very thin silicon dioxide inserted in the middle; this does not affect the appearance of the battery and has little impact on efficiency; the phosphorus-doped polysilicon layer plated around the edge is relatively thin in itself, and becomes thinner after being oxidized by oxygen. After crystallization, the impact on efficiency is extremely limited. Therefore, the TOPCon battery production line of the PECVD route does not require new equipment or modified equipment except for the necessary laser equipment to produce back-contact batteries.

[0016] The P-type back-contact solar cell and its preparation process change the boron expansion in the existing processing steps to oxidation. The process of this process does not pass the boron source, and the temperature of high-temperature oxidation is reduced from about 1030°C to about 860°C; the duration is also greatly shortened; after this process is completed, the BSG on the front of the semi-finished product will become a thin silicon dioxide. At the same time, the original process formula of the annealing process must have oxygen, and the PSG removal process of the TOPCon process in the original technology needs to be skipped. At this time, there is no thick BSG protection on the front, so this process must be skipped and the RCA cleaning step is directly entered, otherwise the RCA alkaline tank will easily polish the velvet surface of the front. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2Schematic diagram of PECVD poly wrap plating to the front side of a conventional TOPCon cell of the present invention; Figure 3 Schematic diagram of the winding plating of a conventional TOPCon battery of the present invention; Figure 4 Schematic diagram of a battery after RCA cleaning and coating according to the present invention.

[0019] In the figure: 1. P-type silicon; 2. Silicon dioxide; 3. Phosphorus-doped polysilicon layer; 4. Aluminum oxide / silicon nitride stack; 5. Silver electrode; 6. Aluminum electrode; 7. Aluminum film layer; 8. Laser isolation layer. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The embodiment of the present application provides a P-type back-contact solar cell and its preparation process, which solves the problem that TOPCon cells are mainly LPCVD and PECVD. It is relatively simple and feasible to transform and upgrade the production line of the LPCVD route to the production line of the back-contact cell, because its poy can choose single-insert double-sided plating, while the PECVD route is more difficult to transform the back-contact cell route because its plated poly is single-sided and has a slight plating problem.

[0022] Provide a feasible process route for TOPCon batteries using the existing PECVD poly route, make full use of the existing production line for differentiated upgrades, and avoid the PECVD poly route being limited to producing TOPCon products; After the boron is expanded to oxidation in the poly processing route, the surface BSG, which was originally about 120nm, becomes silicon dioxide 2 with a thickness of 10~50nm. After annealing, part of the phosphorus-doped polysilicon layer 3 will be oxidized to silicon dioxide 2. Even if some phosphorus-doped polysilicon layer 3 remains, it will not have much impact on the battery. After RCA cleaning, the hydrofluoric acid tank inside will wash away the silicon dioxide 2 on the front. The phosphorus-doped polysilicon layer 3 around the edge is the same as the silicon base, but only a very thin silicon dioxide 2 is inserted in the middle; this does not affect the appearance of the battery and has little impact on the efficiency; the phosphorus-doped polysilicon layer 3 around the edge is relatively thin in itself, and it is even thinner after being oxidized by oxygen. After crystallization, the impact on efficiency is extremely limited. Therefore, the TOPCon battery production line of the PECVD route can produce back-contact batteries without adding or modifying equipment except for the necessary laser equipment. .

[0023] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0024] The embodiment of the present invention discloses a P-type back-contact solar cell and a preparation process thereof.

[0025] According to the attached Figure 1-4 As shown, it includes P-type silicon 1, silicon dioxide 2 is arranged on the back, both sides and front corners of the P-type silicon 1, a phosphorus-doped polysilicon layer 3 is deposited on the outside of the silicon dioxide 2, the outer part of the P-type silicon 1 and the outer side of the phosphorus-doped polysilicon layer 3 are passivated to form an aluminum oxide / silicon nitride stack 4, the outer side of the phosphorus-doped polysilicon layer 3 on the back is printed and sintered to form a silver electrode 5, the back of the P-type silicon 1 is printed and sintered to form an aluminum electrode 6, and an aluminum film layer 7 is arranged between the aluminum electrode 6 and the P-type silicon 1, and laser isolation layers 8 are arranged on both side corners of the P-type silicon 1.

[0026] A preparation process of a P-type back contact solar cell, the preparation process comprising the following steps: Step 1: Velvet making Step 2: Oxidation Step 3: Remove silica 2 Step 4: Alkaline polishing Step 5: PECVD poly Step 6: Annealing Step 7: First laser treatment Step 8: RCA cleaning Step 9: Double-sided aluminum oxide / silicon nitride Step 10: Second laser treatment Step 11: Printing and sintering.

[0027] Furthermore, the steps of texturing and oxidation are specifically as follows: The outer side of the P-type silicon 1 is textured, and then the front side of the P-type silicon 1 is oxidized outward at high temperature to form silicon dioxide 2.

[0028] Further, the steps of removing silicon dioxide 2 and alkali polishing are specifically as follows: The unnecessary silicon dioxide 2 on the surface is corroded and removed using hydrofluoric acid from a chain PSG removal device, and then the P-type silicon 1 back film is polished using an alkali polishing device.

[0029] Furthermore, the PECVD poly steps are as follows: The back film is coated with a silicon dioxide 2 tunneling layer, a phosphorus-doped polysilicon layer 3 and silicon dioxide 2 using PECVD coating equipment.

[0030] Furthermore, the annealing step is specifically as follows: The front side is heat treated outward at high temperature to rearrange the atoms in the phosphorus-doped polysilicon layer 3. The P-type silicon 1 is annealed at high temperature to crystallize the phosphorus-doped polysilicon layer 3.

[0031] Furthermore, the first laser treatment step is specifically as follows: According to the back contact design, the phosphorus-doped polysilicon layer 3 on the back is molded using laser equipment.

[0032] Furthermore, the RCA cleaning steps are specifically as follows: Entering the RCA equipment, its alkaline tank corrodes the laser-treated part to form a P area; the hydrofluoric acid in the post-cleaning acid tank corrodes and cleans the silicon dioxide 2 on the front and back films to remove high-temperature by-products.

[0033] Furthermore, the double-sided aluminum oxide / silicon nitride step is specifically as follows: The P-type silicon 1 is double-sided passivated using aluminum oxide and silicon nitride to form an aluminum oxide / silicon nitride stack 4 .

[0034] Furthermore, the second laser processing and printing sintering steps are specifically as follows: The back film P region is molded by laser equipment, and then the silver electrode 5 and the aluminum electrode 6 are printed and sintered on the back side of the phosphorus-doped polysilicon layer 3 and the back side of the P-type silicon 1 respectively.

[0035] Implementation Cases: Existing PECVD route TOPCon process route: texturing - boron diffusion - BSG removal - alkali polishing - PECVD poly - annealing - PSG removal - RCA - double-sided aluminum oxide / silicon nitride - printing sintering The specific steps of the present invention are: texturing → oxidation → removal of silicon dioxide 2 → alkali polishing → PECVD poly → annealing → first laser treatment → RCA cleaning → double-sided aluminum oxide / silicon nitride → second laser treatment → printing and sintering 1. Texturing of P-type silicon 1 2. High temperature oxidation: P-type silicon 1 is oxidized from the front to the outside, the temperature is 500~1030℃; the time length is 600S~9900S; the thickness of the oxide layer is 10nm~50nm 3. Remove silicon dioxide 2: Use hydrofluoric acid from the chain PSG removal equipment to corrode the silicon dioxide 2 that bypasses the back of the P-type silicon 1. 4. Use alkaline polishing equipment to polish the P-type silicon 1 back film. There should be no hydrofluoric acid in the post-cleaning tank to avoid corrosion of the thinner front silicon oxide. If there is hydrofluoric acid, the cleaning time should not exceed 50S. 5. Use PECVD coating equipment to coat the back film with a silicon dioxide 2 tunneling layer, a phosphorus-doped polysilicon layer 3 and silicon dioxide 2; the thickness of silicon dioxide 2 is 1~2nm, the thickness of phosphorus-doped polysilicon layer 3 is 80~300nm, and the thickness of the outer silicon dioxide 2 is 5~50nm 6. Annealing: With the front side facing outward, the P-type silicon 1 is annealed at high temperature, and the phosphorus-doped polysilicon layer 3 is crystallized. The temperature is 870~1000℃; the time is 1000S~10000S, and the oxygen flow rate is 1000sccm~10000sccm; the phosphorus-doped polysilicon layer 3 plated on the front side is partially oxidized, reducing the thickness of the phosphorus-doped polysilicon layer 3 7. First laser processing: According to the back contact design, the phosphorus-doped polysilicon layer 3 on the back is molded using laser equipment 8. The PSG equipment is not chained, but directly enters the RCA equipment. The alkaline tank corrodes the laser-treated part to form the P area. The hydrofluoric acid in the post-cleaning acid tank corrodes and cleans the silicon dioxide 2 on the front and back films to remove high-temperature by-products. 9. Double-layer coating is performed on the front and back. The inner layer is aluminum oxide 3~15nm, and the outer layer is silicon nitride. The thickness of the front layer is 60~90nm, and the thickness of the back layer is 60~250nm, forming an aluminum oxide / silicon nitride stack 4 10. Use laser equipment to open the silicon nitride mold in the P area of ​​the back film 11. Printing and sintering: The first pass is for the pad and silver main grid, which are dried and shaped; the second pass is for printing silver paste in the N area, which is dried and shaped; the third pass is for printing and covering the mold opening area in the P area with aluminum paste, which is dried and shaped; sintering 12. Conduct efficiency and appearance tests and sort the back contact batteries.

[0036] The boron expansion in the existing processing steps is changed to oxidation. The process of this process does not pass the boron source, and the temperature of high-temperature oxidation is reduced from about 1030℃ to about 860℃; the duration is also greatly shortened; after this process is completed, the BSG on the front of the semi-finished product will become a thin silicon dioxide 2. At the same time, the original process formula of the annealing process must have oxygen, and the PSG removal process of the TOPCon process in the original technology needs to be skipped. At this time, there is no thick BSG protection on the front, so this process must be skipped and the RCA cleaning step must be entered directly, otherwise the RCA alkaline tank will easily polish the velvet surface on the front.

[0037] Provide a feasible process route for TOPCon batteries using the existing PECVD poly route, make full use of the existing production line for differentiated upgrades, and avoid the PECVD poly route being limited to producing TOPCon products; After the boron is expanded to oxidation in the poly processing route, the surface BSG, which was originally about 120nm, becomes silicon dioxide 2 with a thickness of 10~50nm. After annealing, part of the phosphorus-doped polysilicon layer 3 will be oxidized to silicon dioxide 2. Even if some phosphorus-doped polysilicon layer 3 remains, it will not have much impact on the battery. After RCA cleaning, the hydrofluoric acid tank inside will wash away the silicon dioxide 2 on the front. The phosphorus-doped polysilicon layer 3 plated around the edge is the same as the silicon base, but with a very thin silicon dioxide 2 inserted in the middle; this does not affect the appearance of the battery and has little impact on the efficiency; the phosphorus-doped polysilicon layer 3 plated around the edge is relatively thin in itself, and becomes thinner after being oxidized by oxygen. After crystallization, the impact on efficiency is extremely limited. Therefore, the TOPCon battery production line of the PECVD route does not need to add or modify equipment except for the necessary laser equipment to produce back-contact batteries.

[0038] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A P-type back-contact solar cell, comprising P-type silicon (1), characterized in that: Silicon dioxide (2) is arranged on the back, both sides and front corners of the P-type silicon (1), a phosphorus-doped polysilicon layer (3) is deposited on the outside of the silicon dioxide (2), the outer part of the P-type silicon (1) and the outer side of the phosphorus-doped polysilicon layer (3) are passivated to form an aluminum oxide / silicon nitride stack (4), the outer side of the phosphorus-doped polysilicon layer (3) on the back is printed and sintered to form a silver electrode (5), the back side of the P-type silicon (1) is printed and sintered to form an aluminum electrode (6), and an aluminum film layer (7) is arranged between the aluminum electrode (6) and the P-type silicon (1), and laser isolation layers (8) are arranged on both side corners of the P-type silicon (1).

2. The process for preparing a P-type back contact solar cell according to claim 1, characterized in that: The preparation process comprises the following steps: Step 1: Velveting Step 2: Oxidation Step 3: Remove silica (2) Step 4: Alkaline polishing Step 5: PECVD poly Step 6: Annealing Step 7: First laser treatment Step 8: RCA Cleaning Step 9: Double-sided aluminum oxide / silicon nitride Step 10: Second laser treatment Step 11: Printing and sintering.

3. The process for preparing a P-type back contact solar cell according to claim 2, characterized in that: The texturing and oxidation steps are specifically as follows: The outer side of the P-type silicon (1) is textured, and then the front side of the P-type silicon (1) is oxidized outward at high temperature to form silicon dioxide (2).

4. The process for preparing a P-type back contact solar cell according to claim 2, characterized in that: The desiliconization (2) and alkali polishing steps are specifically as follows: The unnecessary silicon dioxide (2) on the surface is removed by etching using hydrofluoric acid in a chain-type PSG removal device, and then the P-type silicon (1) back film is polished using an alkaline polishing device.

5. The process for preparing a P-type back contact solar cell according to claim 2, characterized in that: The PECVD poly steps are specifically as follows: The back film is coated with a silicon dioxide (2) tunneling layer, a phosphorus-doped polysilicon layer (3) and silicon dioxide (2) using PECVD coating equipment.

6. The process for preparing a P-type back contact solar cell according to claim 2, characterized in that: The annealing step is specifically as follows: The front side is heat treated outward at a high temperature to rearrange the atoms in the phosphorus-doped polysilicon layer (3). The P-type silicon (1) is annealed at a high temperature to crystallize the phosphorus-doped polysilicon layer (3).

7. The process for preparing a P-type back contact solar cell according to claim 2, characterized in that: The first laser treatment step is specifically as follows: According to the back contact design, laser equipment is used to open the mold of the phosphorus-doped polysilicon layer (3) on the back side.

8. The process for preparing a P-type back contact solar cell according to claim 2, characterized in that: The RCA cleaning steps are specifically as follows: After entering the RCA equipment, the alkaline tank etches the laser-treated part to form the P zone; the hydrofluoric acid in the post-cleaning acid tank etches and cleans the silicon dioxide (2) on the front and back films to remove high-temperature byproducts.

9. The process for preparing a P-type back contact solar cell according to claim 2, characterized in that: The double-sided aluminum oxide / silicon nitride step is specifically as follows: Aluminum oxide and silicon nitride are used to perform double-sided passivation on P-type silicon (1), thereby forming an aluminum oxide / silicon nitride stack (4).

10. The process for preparing a P-type back contact solar cell according to claim 8, characterized in that: The second laser treatment and printing sintering steps are specifically as follows: The back film P region is molded using a laser device, and then a silver electrode (5) and an aluminum electrode (6) are respectively printed and sintered on the back side of the phosphorus-doped polysilicon layer (3) and the back side of the P-type silicon (1) to form a silver electrode (5) and an aluminum electrode (6).

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