Preparation method of novel TBC solar cell

Abstract

The invention discloses a preparation method of a novel TBC solar cell. The preparation method comprises the production steps of pretreatment, deposition crystallization, boron doping, laser grooving, phosphorus doping, annealing oxidation, removal of winding plating layers on the front face and the side face of a silicon wafer, cleaning and texturing, removal of a film layer structure on a doping layer on the back face, and preparation of an antireflection layer and a passivation layer on the front face and the back face. Compared with the prior art, the preparation method of the novel TBC solar cell has the advantages that the dependence on high-temperature equipment can be greatly reduced, so that the energy loss is reduced, the doping effect is improved, and the problems of insufficient doping concentration or uniformity, structural defects and the like in the prior art can be effectively solved, so that the occurrence of the electric leakage phenomenon of the cell is prevented; meanwhile, the technological process is simplified, waste water and waste gas are reduced, so that the environmental burden is reduced, the production efficiency can be improved, the production cost of an enterprise is effectively reduced, the competitiveness of the enterprise is improved, and meanwhile, the development of the photovoltaic technology is promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cell preparation, and in particular relates to a preparation method of a novel TBC solar cell. Background Art

[0002] TBC battery: Passivated contact back contact battery (TOPCon Back Contact), the full name is the battery formed by combining TOPCon and IBC technology, also known as POLO-IBC battery. TBC battery adopts tunnel oxide layer passivation contact (TOPCon) technology and applies it to the back contact structure. This design takes advantage of the high passivation quality and good contact characteristics of TOPCon technology. TBC battery has high efficiency potential due to its excellent passivation performance and back contact design. The theoretical conversion efficiency upper limit of TBC battery is 29.56%, which is about to become the mainstream battery technology.

[0003] TBC batteries are widely used due to their good passivation effect. However, the current mainstream TBC battery preparation process has some obvious defects. First, its process is complicated, with many steps, and there is leakage, which leads to low yield rate and low production efficiency of TBC batteries.

[0004] Secondly, the configuration of the back electrode in the traditional back-doped emitter process is the most complicated part, which usually needs to be realized through screen printing, photolithography, inkjet printing and other technologies. This production process has cumbersome steps and complicated processes, which greatly reduces production efficiency and is not conducive to the development of photovoltaic companies.

[0005] In addition, the wastewater and waste gas generated by mask cleaning and photolithography processes will seriously pollute the environment, making it difficult to achieve green and environmentally friendly low-cost production. This not only leads to a significant increase in production costs, but is also not conducive to the low-cost industrial promotion of back-contact solar cells.

[0006] Therefore, in view of the above technical problems, it is necessary to provide a method for preparing a new TBC solar cell.

[0007] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0008] The purpose of the present invention is to provide a novel method for preparing TBC solar cells, which can greatly reduce the dependence on high-temperature equipment, thereby reducing energy loss, and at the same time improve the doping effect, and can effectively solve the problems of insufficient doping concentration or uniformity, structural defects, etc. in the prior art, thereby preventing the occurrence of battery leakage; at the same time, it simplifies the process flow, reduces the generation of wastewater and waste gas, thereby reducing the environmental burden, which can not only improve production efficiency, but also effectively reduce the production cost of the enterprise, enhance the competitiveness of the enterprise, but also is conducive to promoting the development of photovoltaic technology.

[0009] In order to achieve the above object, a specific embodiment of the present invention provides a method for preparing a novel TBC solar cell, comprising the following steps:

[0010] S1, pretreatment, cleaning and polishing the silicon wafer to remove organic dirt, metal impurities and surface damage layer on the surface of the silicon wafer;

[0011] S2, deposition crystallization, coating silicon oxide on the cell as a tunneling oxide layer, preparing an intrinsic amorphous silicon layer on the back of the cell, and using laser irradiation to crystallize the amorphous silicon, so that the amorphous silicon on the horizontal surface is converted into polycrystalline silicon;

[0012] S3, boron doping, while preparing the BSG layer, using a laser process to dope the P-type region with boron for multiple times, using the BSG layer as a boron source to dope the polysilicon in the P-type region with boron;

[0013] S4, laser grooving, removing the BSG layer above the polysilicon where the N region is located, preparing a silicon nitride layer as a P / N type region isolation layer and a P type protection layer, and using laser to separate and groove the P type region and the N type region;

[0014] S5, doping with phosphorus to prepare an N-type doping source layer, using the doping source layer as a phosphorus source, performing laser phosphorus doping to dope the polysilicon in the N-type region with phosphorus, preparing a polysilicon structure in the N-type region and performing laser phosphorus doping;

[0015] S6, annealing and oxidation, repairing laser damage, reducing the surface concentration of non-laser areas, and increasing junction depth;

[0016] S7, removing the plating layers on the front and side surfaces of the silicon wafer, and etching the silicon wafer with a chain machine to remove the plating layers on the front and side surfaces of the silicon wafer;

[0017] S8, cleaning and texturing, forming a suede layer on the front side of the silicon wafer;

[0018] S9, removing the film structure on the back doping layer to completely expose the P and N type polysilicon;

[0019] S10, preparing front and back anti-reflection layers and passivation layers, wherein the refractive index of the passivation layer decreases from the inner side of the silicon wafer substrate to the outer side.

[0020] In one or more embodiments of the present invention, in S1, the cleaning includes pre-cleaning the crystalline silicon substrate with a pre-cleaning solution formed by a mixture of an alkaline solution and hydrogen peroxide, the volume proportion of the alkaline solution in the alkaline solution is 5%, the volume proportion of the hydrogen peroxide is 8%, the concentration range of the alkaline solution is 15mol / L to 25mol / L, the concentration range of hydrogen peroxide in the hydrogen peroxide is 5mol / L to 12mol / L, the pre-cleaning process temperature is 45°C to 85°C, the process time is 40s to 150s, the polishing solution includes an alkali, an additive and water, the concentration of the alkali in the polishing solution is 0.1% to 10%, and the concentration of the additive in the polishing solution is 0.5% to 5%; the polishing temperature is 50 to 150°C.

[0021] In one or more embodiments of the present invention, in S2, the amorphous silicon layer has a thickness of 80 to 300 nm, the process temperature during preparation is 200 to 550° C., and the process gas is SiH 4 , H 2 , gas flow ratio is SiH 4 :H 2 =0.25~0.75, the laser irradiation power density is 5KW / cm 2 ~30KW / cm 2 , the laser irradiation time is 5ms-200ms, and the laser wavelength is 300~600nm.

[0022] In one or more embodiments of the present invention, in S3, the BSG layer is deposited to a thickness of 30 to 50 nm, the laser power during laser doping is 50 to 100 W, and the pulse energy density range is 0.5 J / cm 2 ≤Hp≤4.5J / cm 2 .

[0023] In one or more embodiments of the present invention, in S4, the silicon nitride layer has a thickness of 30 to 50 nm, the laser grooving is laser patterned grooving, the groove width is 20 to 150 μm, and the groove depth matches the inward concave length of the silicon wafer.

[0024] In one or more embodiments of the present invention, the parameters of the laser patterning grooving are: laser wavelength 300-600 nm, power 30-70 W, and processing time 5-30 s.

[0025] In one or more embodiments of the present invention, in S5, an N-type doping source layer is prepared before phosphorus doping, and the N-type doping source layer is a PSG layer, and the thickness of the PSG layer is 45-80 nm.

[0026] In one or more embodiments of the present invention, the laser power during phosphorus doping is 5 to 50 W, the doping times are 1 to 3 times, and the pulse energy density range is 0.3 J / cm 2 ≤Hp≤1J / cm 2 .

[0027] In one or more embodiments of the present invention, in S6, the oxidation temperature is 650°C-800°C.

[0028] In one or more embodiments of the present invention, metal contacts are formed on the N / P type regions on the back of the silicon wafer by screen printing, and Ag-Si ohmic contacts are formed by sintering at a temperature of 680-880°C to form electrodes, which correspond to the doped polysilicon regions crystallized by laser.

[0029] Compared with the prior art, the preparation method of a new TBC solar cell of the present invention can greatly reduce the dependence on high-temperature equipment, thereby reducing energy loss, while improving the doping effect, and can effectively solve the problems of insufficient doping concentration or uniformity, structural defects and the like in the prior art, thereby preventing the occurrence of battery leakage; at the same time, it simplifies the process flow, reduces the generation of wastewater and waste gas, thereby reducing the environmental burden, which can not only improve production efficiency, but also effectively reduce the production cost of the enterprise, enhance the competitiveness of the enterprise, but also is conducive to promoting the development of photovoltaic technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments recorded in the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 The figure is a process flow chart of a method for preparing a novel TBC solar cell in one embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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 should fall within the scope of protection of the present invention.

[0033] like Figure 1As shown, a method for preparing a novel TBC solar cell in one embodiment of the present invention comprises the following steps:

[0034] S1. Pretreatment: cleaning and polishing the silicon wafer to remove organic dirt, metal impurities and surface damage layers on the surface of the silicon wafer. Specifically, the cleaning process uses a pre-cleaning solution mixed with an alkaline solution and hydrogen peroxide to pre-clean the crystalline silicon substrate.

[0035] The alkaline solution is one of potassium hydroxide solution or sodium hydroxide solution, and the volume proportion of the alkaline solution in the pre-cleaning solution is 5%, and the volume proportion of hydrogen peroxide is 8%. Preferably, the concentration range of the alkaline solution potassium hydroxide solution or sodium hydroxide is 15mol / L to 25mol / L, and the concentration range of hydrogen peroxide in hydrogen peroxide is 5mol / L to 12mol / L. The pre-cleaning process temperature is 45℃ to 85℃, and the process time is 40s to 150s.

[0036] The crystalline silicon substrate is polished using a polishing solution, the polishing solution comprising an alkali, an additive and water. The alkali includes but is not limited to a sodium hydroxide or potassium hydroxide solution, and the concentration of the alkali in the polishing solution is 0.1% to 10%. The concentration of the additive in the polishing solution is 0.5% to 5%; the polishing temperature is 50 to 150°C.

[0037] Preferably, the silicon wafer is an N-type single crystal silicon wafer with a thickness of 80 to 180 microns.

[0038] S2, deposition crystallization, coating silicon oxide on the cell as a tunneling oxide layer, preparing an intrinsic amorphous silicon layer on the back of the cell, using laser irradiation to crystallize the amorphous silicon, and converting the amorphous silicon on the horizontal surface into polycrystalline silicon.

[0039] Specifically, silicon oxide is plated on the cell as a tunneling oxide layer by PECVD technology, and the film performance can be affected by adjusting the nitrogen doping amount. The film thickness is 0.5-2.5nm, the process temperature is 150-400℃, and the process gas includes at least SiH 4 With N2 / NH 3 One of the oxygen sources is O 2 or N 20 .

[0040] Preferably, the process gas is SiH 4 、N 2 、N 20 The gas flow ratio is N 2 O:SiH 4 :N 2 =1~3:1:30~40.

[0041] The intrinsic amorphous silicon layer is prepared on the back side using PECVD technology, with a film thickness of 80-300nm, a process temperature of 200-550℃, and a process gas of SiH 4 , H 2 , gas flow ratio is SiH 4 :H 2 =0.25~0.75.

[0042] Amorphous silicon is crystallized by laser, and the laser power density is 5KW / cm 2 ~30KW / cm 2 , laser irradiation time is 5ms-200ms, and laser wavelength is 300~600nm.

[0043] Preferably, the laser wavelength is 308, 458 nm or 514 nm.

[0044] Furthermore, crystallization is performed twice, with the power density of the first crystallization not exceeding 15KWcm 2 , laser irradiation time is 30ms-150ms. The second power density is not less than 15KW / cm 2 The laser irradiation time is 5ms-50ms. The secondary crystallization area corresponds to the location of the later electrode. Laser crystallization is used to increase the crystallization rate of polysilicon and reduce the high temperature process time.

[0045] S3, boron doping, while preparing the BSG layer, use a laser process to dope the P-type region with boron multiple times, use the BSG layer as a boron source, and dope the polysilicon in the P-type region with boron.

[0046] Specifically, a borosilicate glass layer is prepared with a deposition thickness of 30 to 50 nm, and light doping is performed during the preparation.

[0047] Using laser technology to dope the P-type region can easily control the doping concentration and doping depth, thereby improving the doping quality, greatly reducing production time, reducing dependence on high-temperature equipment, and reducing energy loss. At this time, set the laser wavelength to 300-600nm and the power to 50-100W. The doping times are 1 to 3 times, and the pulse energy density range is 0.5J / cm 2 ≤Hp≤4.5J / cm 2 The final P-type polysilicon doping concentration is 2.5 to 8×1019 cm-3, the junction depth is 0.25 to 0.3 μm, and the square resistance is 50 to 180 Ω / □.

[0048] Preferably, the laser power is 55-80W.

[0049] S4, laser grooving, removing the BSG layer above the polysilicon where the N region is located, preparing a silicon nitride layer as a P / N type region isolation layer and a P type protective layer, and using laser to separate and groove the P type region and the N type region.

[0050] Specifically, the BSG layer is removed, and the BSG layer above the polysilicon where the N region is located is removed. A silicon nitride layer is prepared as a P / N type region isolation layer and a P type protection layer to prevent leakage. Preferably, the thickness of the silicon nitride layer is 30 to 50 nm.

[0051] Laser patterning is used to create grooves to separate the P-type area from the N-type area. The groove width is 20 to 150 μm, and the groove depth is the inward concave length of the silicon wafer, which is less than or equal to 50 μm.

[0052] Specifically, the laser wavelength of the laser patterning grooving is 300-600 nm, the power is 30-70 W, and the processing time is 5-30 s.

[0053] S5, doping with phosphorus, preparing an N-type doping source layer, using the doping source layer as a phosphorus source, performing laser phosphorus doping, doping the polysilicon in the N-type region with phosphorus, preparing a polysilicon structure in the N-type region and performing laser phosphorus doping.

[0054] Specifically, repeat step S2 to prepare the required polysilicon structure in the N-type region. The thickness of the polysilicon film in the N-type region is not greater than that in the P-type region, which can optimize the TBC battery structure. Then prepare an N-type doping source layer, preferably phosphorus silicon glass PSG, with a thickness of 45 to 80 nm, and lightly dope it at the same time. During doping, the N-type region is laser doped with a laser process, with a wavelength of 300 to 600 nm and a laser power of 5 to 50 W. The preferred laser power is 15 to 30 W, and the number of doping times is 1 to 3. Among them, the pulse energy density range is 0.3 J / cm 2 ≤Hp≤1J / cm 2 The final N-type polysilicon doping concentration is not less than 5×1019cm -3 .

[0055] The traditional high-temperature process requires a temperature of more than 800°C for doping, and generates a large amount of waste gas. The above method uses laser doping, which saves costs and shortens the process time. It also abandons high-temperature doping and greatly reduces waste gas emissions.

[0056] S6, annealing and oxidation, repair laser damage, reduce the surface concentration of non-laser area, and increase junction depth. The temperature of post-oxidation treatment is 650℃-800℃.

[0057] S7, removing the wrap-around coating on the front and side surfaces of the silicon wafer, and using a chain machine to etch the silicon wafer to remove the wrap-around coating on the front and side surfaces of the silicon wafer. Using a wet process, using a chain machine to etch the silicon wafer to remove the wrap-around coating on the front and side surfaces of the silicon wafer.

[0058] S8. After cleaning, texturing is performed to form a texturing layer on the front of the silicon wafer. The texturing liquid is a potassium hydroxide solution with a volume ratio of 2% to 8%, a texturing additive of 0.2% to 2%, and the rest is deionized water; the texturing temperature is 70℃ to 90℃, and the texturing time is 400s to 800s. The concentration range of the potassium hydroxide solution for preparing the texturing liquid is 15mol / L to 25mol / L, and the texturing additive solution is a mixture of 0.05% to 2.5% potassium polyacrylate, 0051% to 2.5% potassium sorbate, 2% to 7% polyethylene glycol, 0.05% to 2.5% potassium hydroxide, and the rest is deionized water. The circulation flow rate of the texturing tank is 50L / m, and the discharge factor is 0.065 to 0.095.

[0059] S9. Remove the film structure above the back doping layer to completely expose the P and N type polysilicon.

[0060] S10, prepare the front and back anti-reflection layers and passivation layers, the refractive index decreases from the inner side of the silicon wafer substrate to the outer side. First, prepare the front passivation layer, preferably prepare the aluminum oxide layer by ALD technology, and the aluminum oxide layer has a thickness of 5 to 10 nm.

[0061] Then, the front and back anti-reflection layers are prepared, and the reflective layer includes silicon nitride, silicon oxynitride or other passivation layers. The refractive index decreases from the inner side of the silicon wafer substrate to the outside, and the total film thickness is 50-100nm.

[0062] Electrodes are prepared for the products obtained in the above steps. Specifically, metal contacts are formed on the N / P type areas on the back of the silicon wafer by screen printing, and then sintered at 680-880°C to form Ag-Si ohmic contacts to form electrodes, which correspond to the doped polysilicon areas crystallized by the secondary laser.

[0063] Compared with the prior art, the preparation method of a new TBC solar cell of the present invention can greatly reduce the dependence on high-temperature equipment, thereby reducing energy loss, while improving the doping effect, and can effectively solve the problems of insufficient doping concentration or uniformity, structural defects and the like in the prior art, thereby preventing the occurrence of battery leakage; at the same time, it simplifies the process flow, reduces the generation of wastewater and waste gas, thereby reducing the environmental burden, which can not only improve production efficiency, but also effectively reduce the production cost of the enterprise, enhance the competitiveness of the enterprise, but also is conducive to promoting the development of photovoltaic technology.

[0064] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0065] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a novel TBC solar cell, characterized in that: The following steps are involved: S1, pretreatment, cleaning and polishing the silicon wafer to remove organic dirt, metal impurities and surface damage layer on the surface of the silicon wafer; S2, deposition crystallization, coating silicon oxide on the cell as a tunneling oxide layer, preparing an intrinsic amorphous silicon layer on the back of the cell, and using laser irradiation to crystallize the amorphous silicon, so that the amorphous silicon on the horizontal surface is converted into polycrystalline silicon; S3, boron doping, while preparing the BSG layer, using a laser process to dope the P-type region with boron for multiple times, using the BSG layer as a boron source to dope the polysilicon in the P-type region with boron; S4, laser grooving, removing the BSG layer above the polysilicon where the N region is located, preparing a silicon nitride layer as a P / N type region isolation layer and a P type protection layer, and using laser to separate and groove the P type region and the N type region; S5, doping with phosphorus to prepare an N-type doping source layer, using the doping source layer as a phosphorus source, performing laser phosphorus doping to dope the polysilicon in the N-type region with phosphorus, preparing a polysilicon structure in the N-type region and performing laser phosphorus doping; S6, annealing and oxidation, repairing laser damage, reducing the surface concentration of non-laser areas, and increasing junction depth; S7, removing the plating layers on the front and side surfaces of the silicon wafer, and etching the silicon wafer with a chain machine to remove the plating layers on the front and side surfaces of the silicon wafer; S8, cleaning and texturing, forming a suede layer on the front side of the silicon wafer; S9, removing the film structure on the back doping layer to completely expose the P and N type polysilicon; S10, preparing front and back anti-reflection layers and passivation layers, wherein the refractive index of the reflective layer decreases from the inner side of the silicon wafer substrate to the outer side.

2. The method for preparing a novel TBC solar cell according to claim 1, characterized in that: In S1, the cleaning includes pre-cleaning the crystalline silicon substrate with a pre-cleaning solution formed by a mixture of an alkaline solution and hydrogen peroxide, the volume proportion of the alkaline solution in the alkaline solution is 5%, the volume proportion of the hydrogen peroxide is 8%, the concentration range of the alkaline solution is 15mol / L to 25mol / L, the concentration range of hydrogen peroxide in the hydrogen peroxide is 5mol / L to 12mol / L, the pre-cleaning process temperature is 45°C to 85°C, the process time is 40s to 150s, the polishing solution includes an alkali, an additive and water, the concentration of the alkali in the polishing solution is 0.1% to 10%, and the concentration of the additive in the polishing solution is 0.5% to 5%; the polishing temperature is 50 to 150°C.

3. The method for preparing a novel TBC solar cell according to claim 1, characterized in that: In S2, the thickness of the amorphous silicon layer is 80-300 nm, the process temperature during preparation is 200-550°C, the process gases are SiH4 and H2, the gas flow ratio is SiH4:H2=0.25-0.75, and the laser irradiation power density is 5KW / cm 2 ~30KW / cm 2 , the laser irradiation time is 5ms-200ms, and the laser wavelength is 300~600nm.

4. The method for preparing a novel TBC solar cell according to claim 1, characterized in that: In S3, the BSG layer is deposited to a thickness of 30 to 50 nm, the laser power is 50 to 100 W during laser doping, and the pulse energy density is in the range of 0.5 J / cm 2 ≤Hp≤4.5J / cm 2 .

5. The method for preparing a novel TBC solar cell according to claim 1, characterized in that: In S4, the silicon nitride layer has a thickness of 30 to 50 nm, the laser grooving is laser patterned grooving, the groove width is 20 to 150 μm, and the groove depth matches the inward concave length of the silicon wafer.

6. The method for preparing a novel TBC solar cell according to claim 5, characterized in that: The parameters of the laser patterning grooving are: laser wavelength 300-600nm, power 30-70W, and processing time 5-30s.

7. A method for preparing a novel TBC solar cell according to claim 1, characterized in that: In S5, an N-type doping source layer is prepared before phosphorus doping, and the N-type doping source layer is a PSG layer, and the thickness of the PSG layer is 45-80 nm.

8. The method for preparing a novel TBC solar cell according to claim 7, characterized in that: The laser power during phosphorus doping is 5-50W, the doping times are 1-3 times, and the pulse energy density range is 0.3J / cm 2 ≤Hp≤1J / cm 2 .

9. The method for preparing a novel TBC solar cell according to claim 1, characterized in that: In S6, the oxidation temperature is 650°C-800°C.

10. A method for preparing a novel TBC solar cell according to any one of claims 1 to 9, characterized in that: Metal contacts are formed on the N / P type areas on the back of the silicon wafer by screen printing, and Ag-Si ohmic contacts are formed by sintering at 680-880°C to form electrodes corresponding to the laser crystallized doped polysilicon areas.

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