IBC photovoltaic cell and preparation method thereof

Abstract

The invention discloses an IBC photovoltaic cell and a preparation method thereof, and relates to the technical field of cell preparation, the IBC photovoltaic cell comprises a silicon substrate, the back surface of the silicon substrate is provided with a plurality of back surface first doped regions, back surface second doped regions and isolation groove regions which are alternately arranged, the isolation groove regions are groove isolation G regions, and the groove isolation G regions are arranged on the back surface of the silicon substrate. The back metallization circuit pattern of the IBC photovoltaic cell adopts an 0BB connection circuit pattern without a main grid connection line. According to the invention, an 0BB electrocoppering line without a main grid connecting line is adopted, so that a large number of trench isolation G regions do not need to be arranged at the positions of the patterned main grids I and II, the processing flow is simplified, and a cylindrical contact channel is formed through processes such as laser film opening and acid cleaning. The aluminum-titanium alloy barrier layer, the copper seed layer, the copper conductive layer and the antioxidant tin layer are adopted to construct the metal electrode, so that the non-silicon cost of the IBC photovoltaic cell is further reduced, meanwhile, the contact resistance between aluminum and polycrystalline silicon is lower, and compared with a silver-coated copper wire screen printing process, the electrical property of the cell is optimized.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, specifically an IBC photovoltaic cell and its manufacturing method. Background Technology

[0002] IBC photovoltaic cells, with their full back junction design, have advantages in photoelectric conversion efficiency and have become one of the key development directions in the photovoltaic field. In terms of circuit structure design, traditional IBC photovoltaic cells use isolation trenches G to separate the N-region and P-region substrates. Main grid and fine grid metal electrodes are fabricated on the N-region and P-region substrates. The main grid metal electrodes are equipped with large PADs, small PADs, and main grid connection lines. The N-region main grid connection lines are perpendicularly connected to the N-region fine grids. The trenches G isolate the N-region main grids from the P-region fine grids, and the P-region main grid connection lines are perpendicularly connected to the P-region fine grids. The trenches G isolate the P-region main grids from the N-region fine grids. However, this conventional IBC patterning design requires a large number of spaced trenches at the N-region and P-region main grid positions to achieve isolation between the main grid connection lines and the irregular fine grids. This structural design makes the laser patterning process one and two complex, affecting the production capacity of the laser patterning process one and two.

[0003] Regarding the selection of metallization solutions, the current metallization technologies for IBC cells mainly include silver paste screen printing, copper electroplating, and silver-coated copper paste printing. Among these, the high price of silver paste raw materials leads to a high cost per watt for IBC photovoltaic cells, resulting in generally low overall competitiveness. Although the silver-coated copper paste printing process offers a slight cost improvement, the stability of the paste composition is poor, which can easily lead to a decrease in cell reliability and adversely affect photoelectric conversion efficiency. While the copper electroplating metallization solution has the potential for cost and performance optimization, further optimization of material selection and process design is still needed to achieve the goal of improving efficiency and reducing costs.

[0004] Based on this, we now provide an IBC photovoltaic cell and its preparation method, which can eliminate the drawbacks of existing technical solutions. Summary of the Invention

[0005] The purpose of this invention is to provide an IBC photovoltaic cell and its preparation method, so as to solve the problems in the background art where conventional IBC patterning design affects the production capacity of the first and second laser patterning processes and the shortcomings of IBC cell metallization technology.

[0006] To achieve the above objectives, the present invention provides the following technical solution: An IBC photovoltaic cell includes a silicon substrate. A first passivation layer and a first antireflection layer are stacked sequentially from the inside to the outside on the front side of the silicon substrate. A second passivation layer and a second antireflection layer are stacked sequentially from the inside to the outside on the side side of the silicon substrate. A plurality of back-side first doped regions, back-side second doped regions and isolation trench regions are arranged alternately on the back side of the silicon substrate. The isolation trench area is the trench isolation G area, and it is provided with a third passivation layer; The first doped region on the back side is a first doped semiconductor region, in which a first tunneling oxide layer, a first polysilicon doped layer, a third passivation layer, a first aluminum-titanium alloy barrier layer, a first copper seed layer, a first copper conductive layer and a first anti-oxidation tin layer are sequentially stacked from the surface of the silicon substrate. The first aluminum-titanium alloy barrier layer, the first copper seed layer, the first copper conductive layer and the first anti-oxidation tin layer together form the first fine gate metal electrode. The second doped region on the back side is a second doped semiconductor region, in which a second tunneling oxide layer, a second polysilicon doped layer, a third passivation layer, a second aluminum-titanium alloy barrier layer, a second copper seed layer, a second copper conductive layer, and a second anti-oxidation tin layer are sequentially stacked from the surface of the silicon substrate. The second aluminum-titanium alloy barrier layer, the second copper seed layer, the second copper conductive layer, and the second anti-oxidation tin layer together form the second fine gate metal electrode.

[0007] Preferably, the back metallization circuit pattern of the IBC photovoltaic cell adopts an OBB connection circuit pattern without main grid connection lines. The back metallization circuit pattern includes a main grid metal electrode and a fine grid metal electrode. The main grid metal electrode includes a large main grid metal PAD and a small main grid metal PAD that are spaced apart.

[0008] Preferably, along the positive X-axis direction, at the location where the main grid metal electrode connects to the non-standard fine grid metal electrode, the IBC photovoltaic cell is provided with a plurality of insulating adhesives arranged at intervals, the insulating adhesives being used to prevent the solder ribbon from connecting to the non-standard fine grid.

[0009] Preferably, solder paste is applied to both the large and small main gate metal PADs along the positive X-axis, so that the solder strips and the main gate PADs can form good electrical contact at low soldering temperatures.

[0010] A method for preparing an IBC photovoltaic cell specifically includes the following steps: Step S1: The photovoltaic cells that have undergone the front film and back film processes are subjected to a laser three-stage film-opening process, in which the passivation film is initially removed by ablation. The diameter of the circular spot in the laser three-stage film-opening process is 20~40um. Step S2: Low-temperature light-injection annealing and ultraviolet light irradiation are used to activate the hydrogen passivation inside the silicon substrate and the film layer. The peak temperature of the light-injection annealing is 450~650℃, and the temperature of the ultraviolet light irradiation is 50~100℃. Step S3: Cleaning operation using hydrofluoric acid, hydrochloric acid and hydrogen peroxide to further remove residual passivation film and form cylindrical contact channels. The volume ratio of hydrofluoric acid, hydrochloric acid and hydrogen peroxide is 1:2:1. Step S4: After cleaning the residual passivation film, deposit an aluminum-titanium alloy barrier layer and a copper seed layer through a PVD process. Step S5: After completing the PVD process, electrolytically prepare a copper conductive layer and an antioxidant tin layer to form the main gate and fine gate metal electrodes; Step S6: Use screen printing to print the protective film onto the metal electrode area, then cure the protective film at low temperature, and then use sulfuric acid and hydrogen peroxide to perform back etching to remove the non-electrode areas where the protective film was not printed.

[0011] Preferably, step S4 specifically includes: the PVD process uses PVD equipment, with aluminum-titanium alloy as target material 1 and copper as target material 2; When depositing the aluminum-titanium alloy barrier layer, the deposition power of the aluminum-titanium alloy barrier layer is 40-150W, the temperature is 50-200℃, the argon gas flow rate is 20-200sccm, and the deposition time is 10-30min. When depositing a copper seed layer, the deposition power of the copper seed layer is 30-250W, the temperature is 40-120℃, the argon gas flow rate is 20-120sccm, the deposition time is 10-30min, and the thickness of the copper seed layer is 20-220nm.

[0012] Preferably, the aluminum-titanium alloy barrier layer in step S4 has a 1-3 layer structure; When the aluminum-titanium alloy barrier layer has a three-layer structure, the aluminum-titanium alloy layer closest to the silicon substrate has an aluminum and titanium composition ratio of 90% and 10% respectively, and the thickness of the first aluminum-titanium alloy layer is 10~40nm; the aluminum-titanium alloy layer has an aluminum and titanium composition ratio of 50% each, and the thickness of the second aluminum-titanium alloy layer is 10~40nm; the aluminum-titanium alloy layer has an aluminum and titanium composition ratio of 10% and 90% respectively, and the thickness of the third aluminum-titanium alloy layer is 10~40nm; the total thickness of the aluminum-titanium alloy barrier layer is 30~120nm. When the aluminum-titanium alloy barrier layer has a two-layer structure, the aluminum and titanium components in the first aluminum-titanium alloy layer closest to the silicon substrate are 90% and 10% respectively, and the thickness of the first aluminum-titanium alloy layer is 10~60nm. The aluminum and titanium components in the second aluminum-titanium alloy layer are both 50%, and the thickness of the second aluminum-titanium alloy layer is 10~60nm. The total thickness of the aluminum-titanium alloy barrier layer is 20~120nm. When the aluminum-titanium alloy barrier layer is a single layer, the proportion of aluminum and titanium in the aluminum-titanium alloy barrier layer is 50% each, and the total thickness of the aluminum-titanium alloy barrier layer is 20~120nm.

[0013] Preferably, step S5 specifically includes: the copper conductive layer is prepared by electrolysis of copper sulfate pentahydrate, sulfuric acid and additive solution, and the antioxidant tin layer is prepared by electrolysis of tin methanesulfonate, methanesulfonic acid and additive solution.

[0014] Preferably, both the main grid metal electrode and the fine grid metal electrode are set according to the pattern of the screen printing stencil. A protective film is used to cover the preset metal electrode area, and then low-temperature curing is performed. The protective film protects the stacked metal electrodes at the main grid and fine grid positions. After curing, sulfuric acid and hydrogen peroxide are used for back-side etching to remove the non-electrode areas where the protective film is not printed. The protective film includes modified polyester resin, rosin resin and silica particles. The modified polyester resin is used to increase the crosslinking density, the rosin resin is used to increase the adhesion between the mask and the metal electrode, and the silica is used to increase the mechanical strength of the film layer.

[0015] Preferably, the first aluminum-titanium alloy barrier layer forms an electrical contact with the first polycrystalline silicon doped layer through a cylindrical contact channel, and the second aluminum-titanium alloy barrier layer forms an electrical contact with the second polycrystalline silicon doped layer through a cylindrical contact channel.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs an OBB electroplated copper route without main grid connection lines. Compared to conventional BC cells, eliminating the main grid connection lines eliminates the need for numerous trench isolation G-areas at the patterned first and second main grid positions, simplifying the number of marking lines in the laser patterning process and reducing the time cost and process losses associated with trench processing. Furthermore, this invention forms cylindrical contact channels through laser film opening and acid cleaning processes, using an aluminum-titanium alloy stack as a barrier layer, combined with a copper seed layer, a copper conductive layer, and an anti-oxidation tin layer to construct a metal electrode system. This replaces the silver paste in traditional processes, reducing the non-silicon cost of IBC photovoltaic cells. Simultaneously, the contact resistance between aluminum and polycrystalline silicon is lower, further optimizing the electrical performance of the cell compared to the silver-clad copper screen printing process. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the IBC battery structure in Embodiment 1 of the present invention.

[0018] Figure 2 This is a top view of the back of the IBC battery in Embodiment 1 of the present invention.

[0019] Figure 3 For the present invention Figure 2 An enlarged schematic diagram.

[0020] Figure 4 This is a schematic diagram of the preparation method of the present invention.

[0021] Figure 5 This is a top view of the back of the IBC battery in Comparative Example 1 of the present invention.

[0022] Figure reference numerals: 1. Silicon substrate; 2. First passivation layer; 3. First antireflection layer; 4. Second passivation layer; 5. Third passivation layer; 6. First fine gate metal electrode; 7. First aluminum-titanium alloy barrier layer; 71. First copper seed layer; 72. First copper conductive layer; 73. First anti-oxidation tin layer; 74. Second fine gate metal electrode; 8. Second aluminum-titanium alloy barrier layer; 81. Second copper seed layer; 82. Second copper conductive layer; 83. Second anti-oxidation tin layer; 84. First tunneling oxide layer; 9. First polysilicon doped layer; 10. Second tunneling oxide layer; 11. Second polysilicon doped layer; 12. First doped region on the back side; 20. Second edge main gate metal electrode; 21. Second edge main gate doped region; 22. First edge main gate metal electrode; 23. First edge main gate doped region; 24. Second main gate metal small PAD; 25. Second main gate metal large PAD; 26. First main gate metal small PAD; 27. First main gate metal large PAD. 28. Second doped region on the back side; 30. Isolation trench region; 40. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] Example 1 In this embodiment, as Figures 1-4 As shown, an IBC photovoltaic cell includes a silicon substrate 1. A first passivation layer 2 and a first antireflection layer 3 are stacked sequentially from the inside to the outside on the front side of the silicon substrate 1. A second passivation layer 4 and a second antireflection layer 5 are stacked sequentially from the inside to the outside on the side side of the silicon substrate 1. A plurality of back first doped regions 20, back second doped regions 30 and isolation trench regions 40 are arranged alternately on the back side of the silicon substrate 1. The isolation trench area 40 is the trench isolation G area, and a third passivation layer 6 is provided; The first doped region 20 on the back side is the first doped semiconductor region. A first tunneling oxide layer 9, a first polysilicon doped layer 10, a third passivation layer 6, a first aluminum-titanium alloy barrier layer 71, a first copper seed layer 72, a first copper conductive layer 73, and a first anti-oxidation tin layer 74 are sequentially stacked from the surface of the silicon substrate 1. The first aluminum-titanium alloy barrier layer 71, the first copper seed layer 72, the first copper conductive layer 73, and the first anti-oxidation tin layer 74 together form the first fine gate metal electrode 7. The second doped region 30 on the back side is a second doped semiconductor region. A second tunneling oxide layer 11, a second polysilicon doped layer 12, a third passivation layer 6, a second aluminum-titanium alloy barrier layer 81, a second copper seed layer 82, a second copper conductive layer 83, and a second anti-oxidation tin layer 84 are sequentially stacked from the surface of the silicon substrate 1. The second aluminum-titanium alloy barrier layer 81, the second copper seed layer 82, the second copper conductive layer 83, and the second anti-oxidation tin layer 84 together form the second fine gate metal electrode 8. The first doped region 20 on the back side and the second doped region 30 on the back side have different conductivity types. Among them, such as Figure 2 and Figure 3 As shown, the back metallization circuit pattern of the IBC photovoltaic cell adopts an 0BB connection circuit pattern without main grid connection lines. 0BB refers to no main grid. The back metallization circuit pattern includes main grid metal electrodes and fine grid metal electrodes. The main grid metal electrodes include large main grid metal PADs and small main grid metal PADs arranged at intervals, such as... Figure 1 The second main gate metal small PAD 25, the second main gate metal large PAD 26, the first main gate metal small PAD 27, and the first main gate metal large PAD 28 are included. The fine gate metal electrode also includes several fine gates perpendicular to the main gate and several fine gates parallel to the main gate. Compared with conventional BC batteries, the battery structure of this embodiment removes the main gate connection line and patterns the positions of the first and second main gates. It does not need to set up a trench G region similar to the main gate metal large PADs (second main gate metal large PAD 26 and first main gate metal large PAD 28) at both ends of the X-axis. Only the main gate metal small PAD is set in the trench G region, which improves the battery patterning capacity. Patterning one refers to the laser or mask process of forming an N-type doped region on the back of the silicon substrate 1, and patterning two refers to the laser or mask process of forming a P-type doped region on the back of the silicon substrate 1. Among them, such as Figures 1-3 As shown, along the positive X-axis (extending from X1 to X2), at the connection point between the main grid metal electrode and the opposite-shaped fine grid metal electrode, the IBC photovoltaic cell has several insulating adhesives arranged at intervals. These insulating adhesives are used to prevent the solder ribbon from connecting to the opposite-shaped fine grid. The opposite-shaped electrodes have different electrical types, such as N-type and P-type. Figure 2 and Figure 3 The device includes a second edge main gate metal electrode 21, a second edge main gate doped region 22, a first edge main gate metal electrode 23, and a first edge main gate doped region 24. Insulating adhesive is provided at the connection position between the second fine gate metal electrode 8 and the second edge main gate metal electrode 21 to prevent the solder ribbon from accidentally contacting adjacent fine gates of different polarities during soldering, which could cause a short circuit. Among them, such as Figures 1-3 As shown, solder paste is applied to both the large and small gate metal PADs along the positive X-axis (extending from X1 to X2), so that the solder ribbon and the gate PAD can form good electrical contact at low soldering temperature. Among them, such as Figure 4 As shown, this invention also provides a method for fabricating an IBC photovoltaic cell. The method involves using an electroplating process to prepare the main grid and fine grid metal electrodes, initially removing the passivation film beneath the fine grid using a circular laser spot, and further removing the residual passivation film using hydrofluoric acid to form a cylindrical contact channel. The main grid and fine grid metal electrodes are then fabricated, and the cylindrical channel connects the fine grid metal electrodes to the highly doped polycrystalline silicon semiconductor. This method offers cost advantages and specifically includes the following steps: Step S1: After the front and back film processes, the photovoltaic cell undergoes a laser three-stage film removal process. This process uses ablation to initially remove the passivation film. The diameter of the circular laser spot in this process is 20-40 μm. The photovoltaic cell can be a whole cell or a half cell, depending on the actual requirements. The circular laser spot initially removes the passivation film below the fine grid in the first doped region 20 and the second doped region 30 on the back side. The laser spot position is as follows... Figures 1-3 As indicated by the letter 'a', the laser three-stage opening process refers to the laser processing step of opening holes in the back passivation layer to form a contact channel. The laser spot is circular, and after acid pickling and hole enlargement, a cylindrical contact channel is formed to achieve electrical contact between the electrode and the polycrystalline silicon layer. Step S2: Low-temperature light-injection annealing and ultraviolet light irradiation are used to activate the hydrogen passivation inside the silicon substrate 1 and the film layer. The peak temperature of light-injection annealing is 450~650℃, and the temperature of ultraviolet light irradiation is 50~100℃. Step S3: Use hydrofluoric acid, hydrochloric acid and hydrogen peroxide to perform cleaning operations to further remove the residual passivation film and form a cylindrical contact channel. The volume ratio of hydrofluoric acid, hydrochloric acid and hydrogen peroxide is 1:2:1 to clean the residual passivation film affected by laser heat. Step S4: After cleaning the residual passivation film, deposit an aluminum-titanium alloy barrier layer and a copper seed layer through a PVD process. Step S5: After completing the PVD process, electrolytically prepare a copper conductive layer and an antioxidant tin layer to form the main gate and fine gate metal electrodes; Step S6: Use screen printing to print the protective film on the metal electrode area, then cure the protective film at low temperature, and then use sulfuric acid and hydrogen peroxide to perform back etching to remove the non-electrode areas where the protective film was not printed. In this embodiment, the diameter of the circular spot in the laser three-stage film-opening process is 28 μm, the peak temperature of the light injection annealing is 590°C, and the temperature of the ultraviolet irradiation is 60°C. Step S4 specifically includes: the PVD process uses PVD equipment, aluminum-titanium alloy as target material 1, copper as target material 2, the target material is connected to the cathode seat, the carrier plate carrying the battery is connected to the anode seat, the carrier plate busbar connects the second edge main grid doped region 22 and the first edge main grid doped region 24 of the battery, the first edge is the doped region close to the Y-axis Y2 direction, and the second edge is the doped region close to the Y-axis Y1 direction; When depositing the aluminum-titanium alloy barrier layer, the deposition power of the aluminum-titanium alloy barrier layer is 40~150W, the temperature is 50~200℃, the argon gas flow rate is 20~200sccm, and the deposition time is 10~30min. When depositing the copper seed layer, the deposition power of the copper seed layer is 30~250W, the temperature is 40~120℃, the argon gas flow rate is 20~120sccm, the deposition time is 10~30min, and the thickness of the copper seed layer is 20~220nm. In this embodiment, the deposition power of the aluminum-titanium alloy barrier layer is 120W, the temperature is 125℃, the argon gas flow rate is 35sccm, the deposition time is 15min, the deposition power of the copper seed layer is 145W, the temperature is 90℃, the argon gas flow rate is 50sccm, the deposition time is 23min, and the thickness of the copper seed layer is 100nm. The aluminum-titanium alloy barrier layer in step S4 has a 1-3 layer structure; When the aluminum-titanium alloy barrier layer has a three-layer structure, the aluminum-titanium alloy layer closest to the silicon substrate 1 has an aluminum and titanium composition ratio of 90% and 10% respectively, and the thickness of the first aluminum-titanium alloy layer is 10~40nm. The aluminum-titanium alloy layer has an aluminum and titanium composition ratio of 50% each, and the thickness of the second aluminum-titanium alloy layer is 10~40nm. The aluminum-titanium alloy layer has an aluminum and titanium composition ratio of 10% and 90% respectively, and the thickness of the third aluminum-titanium alloy layer is 10~40nm. The total thickness of the aluminum-titanium alloy barrier layer is 30~120nm. When the aluminum-titanium alloy barrier layer has a two-layer structure, the aluminum and titanium components in the first aluminum-titanium alloy layer closest to the silicon substrate 1 are 90% and 10% respectively, and the thickness of the first aluminum-titanium alloy layer is 10~60nm. The aluminum and titanium components in the second aluminum-titanium alloy layer are both 50%, and the thickness of the second aluminum-titanium alloy layer is 10~60nm. The total thickness of the aluminum-titanium alloy barrier layer is 20~120nm. When the aluminum-titanium alloy barrier layer is a single layer, the proportion of aluminum and titanium in the aluminum-titanium alloy barrier layer is 50% each, and the total thickness of the aluminum-titanium alloy barrier layer is 20~120nm. In this embodiment, the aluminum-titanium alloy barrier layer adopts a three-layer structure. The first aluminum-titanium alloy layer, which is close to the silicon substrate 1, has an aluminum and titanium composition ratio of 90% and 10%, respectively, and a thickness of 20 nm. The second aluminum-titanium alloy layer has an aluminum and titanium composition ratio of 50% each, and a thickness of 20 nm. The third aluminum-titanium alloy layer has an aluminum and titanium composition ratio of 10% and 90%, respectively, and a thickness of 20 nm. The total thickness of the aluminum-titanium alloy barrier layer is 60 nm. This gradient three-layer structure makes the aluminum-rich layer close to the silicon beneficial for forming a low-resistance contact with polycrystalline silicon, the middle layer balances performance, and the outermost layer is rich in titanium, which has excellent copper diffusion blocking ability and improves adhesion. Step S5 specifically includes: the copper conductive layer is prepared by electrolysis of copper sulfate pentahydrate, sulfuric acid and additive solution, and the antioxidant tin layer is prepared by electrolysis of tin methanesulfonate, methanesulfonic acid and additive solution; Specifically, both the main grid metal electrodes and the fine grid metal electrodes are set according to the pattern of the screen printing stencil. A protective film is used to cover the preset metal electrode area, and then low-temperature curing is performed. The protective film protects the stacked metal electrodes at the main grid and fine grid positions. After curing, sulfuric acid and hydrogen peroxide are used for back-side etching to remove the non-electrode areas where the protective film was not printed. The protective film includes modified polyester resin, rosin resin and silica particles. Modified polyester resin is used to increase the crosslinking density, rosin resin is used to increase the adhesion between the mask and the metal electrodes, and silica is used to increase the mechanical strength of the film layer. Modified polyester resin is used as acrylic acid, rosin resin is used as a tackifier, and silica is used as an inorganic filler. This protective film can be rapidly cured at low temperature to form a dense and corrosion-resistant mask, which protects the formed metal electrode pattern in the subsequent acid etching step. Specifically, the first aluminum-titanium alloy barrier layer 71 forms an electrical contact with the first polycrystalline silicon doped layer 10 through a cylindrical contact channel, and the second aluminum-titanium alloy barrier layer 81 forms an electrical contact with the second polycrystalline silicon doped layer 12 through a cylindrical contact channel. Specifically, this invention opens the passivation film through a laser three-stage film-opening process and hydrofluoric acid cleaning to form a cylindrical contact channel. An aluminum-titanium alloy stack is used as a barrier layer, and a metal electrode is prepared by electroplating. The cylindrical contact channel connects the fine grid metal electrode and the highly doped polycrystalline silicon together. In addition, inexpensive metals such as copper, aluminum, titanium, and tin are used to replace silver paste, thereby reducing the non-silicon cost of IBC photovoltaic cells. Compared with silver-clad copper screen printing, the contact resistance between aluminum and polycrystalline silicon is lower. High-temperature sintering of the paste is not required, resulting in lower thermal stress in the cell and thus good load resistance. Comparative Example 1 Unlike Example 1, this comparative example provides a conventional back-side metallization circuit pattern, such as... Figure 5As shown, the difference is that the comparative example uses a circuit pattern with main gate connection lines, and a large number of isolation trenches G regions are set at the position where the main gate and the heterogeneous fine gate electrode are connected in the X1 to X2 direction. The insulating adhesive is set on the isolation trenches G regions. In contrast, the insulating adhesive in Example 1 is set at the position where the main gate and the heterogeneous fine gate are connected in the first doped region 20 or the second doped region 30 on the back side. The heterogeneous fine gate is a fine gate metal electrode with a conductivity type opposite to that of the main gate metal electrode. This operation effectively avoids the need to set a large number of isolation trenches G regions at the intersection of the main gate connection lines and the heterogeneous fine gate, reduces the laser etching isolation trench process, and simplifies the process flow. This comparative example also provides a conventional method for preparing metallized electrodes for IBC photovoltaic cells. The metallization process is as follows: after the photovoltaic cell has undergone the front and back film processes, the main grid silver paste is printed, dried, N fine grid silver paste is printed, dried, P fine grid silver paste is printed, dried, sintered, cooled, and annealed for hydrogen passivation. The difference between the back metallized circuit pattern of this comparative example and Example 1 is that: Comparative example 1 uses printed silver paste and high-temperature sintering to form an electrical contact between the silver paste and the doped polycrystalline silicon semiconductor, while Example 1 uses electroplated electrodes, electrolytically deposited electrodes, and laser-drilled holes to form an electrical contact between the electrode material and the doped polycrystalline silicon semiconductor. Therefore, Example 1 can reduce the cost of non-silicon materials, and since the contact resistance between aluminum and polycrystalline silicon is lower, this operation can avoid the thermal stress caused by high-temperature sintering. In addition, Example 1 can reduce the contact area between the metal and the silicon substrate, which is beneficial to reduce carrier recombination and improve the open-circuit voltage of the cell. In summary, this invention simplifies the laser processing steps of patterning one and patterning two by adopting an OBB design and eliminating the main grid connection line, thereby improving production efficiency and capacity. Furthermore, this invention reduces the non-silicon cost of IBC batteries by using inexpensive metal materials. The inherent low contact resistance between aluminum and polycrystalline silicon optimizes the ohmic contact of the electrodes, which is beneficial to improving the fill factor and conversion efficiency of the battery. Thus, this invention can reduce costs and increase capacity while ensuring the electrical performance and reliability of the battery.

[0025] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An IBC photovoltaic cell, characterized in that, The silicon substrate (1) has a first passivation layer (2) and a first antireflection layer (3) stacked sequentially from the inside to the outside on the front side of the silicon substrate (1), a second passivation layer (4) and a second antireflection layer (5) stacked sequentially from the inside to the outside on the side side of the silicon substrate (1), and a plurality of back first doped regions (20), back second doped regions (30) and isolation trench regions (40) arranged alternately on the back side of the silicon substrate (1). The isolation trench area (40) is the trench isolation G area, and is provided with a third passivation layer (6). The first doped region (20) on the back side is a first doped semiconductor region. A first tunneling oxide layer (9), a first polysilicon doped layer (10), a third passivation layer (6), a first aluminum-titanium alloy barrier layer (71), a first copper seed layer (72), a first copper conductive layer (73), and a first anti-oxidation tin layer (74) are sequentially stacked from the surface of the silicon substrate (1). The first aluminum-titanium alloy barrier layer (71), the first copper seed layer (72), the first copper conductive layer (73), and the first anti-oxidation tin layer (74) together form the first fine gate metal electrode (7). The second doped region (30) on the back side is a second doped semiconductor region. A second tunneling oxide layer (11), a second polysilicon doped layer (12), a third passivation layer (6), a second aluminum-titanium alloy barrier layer (81), a second copper seed layer (82), a second copper conductive layer (83), and a second anti-oxidation tin layer (84) are sequentially stacked from the surface of the silicon substrate (1). The second aluminum-titanium alloy barrier layer (81), the second copper seed layer (82), the second copper conductive layer (83), and the second anti-oxidation tin layer (84) together form the second fine gate metal electrode (8).

2. The IBC photovoltaic cell according to claim 1, characterized in that, The back metallization circuit pattern of the IBC photovoltaic cell adopts an OBB connection circuit pattern without main grid connection lines. The back metallization circuit pattern includes a main grid metal electrode and a fine grid metal electrode. The main grid metal electrode includes a large main grid metal PAD and a small main grid metal PAD that are spaced apart.

3. The IBC photovoltaic cell according to claim 2, characterized in that, Along the positive X-axis direction, at the location where the main grid metal electrode connects to the opposite-shaped fine grid metal electrode, the IBC photovoltaic cell is provided with several insulating adhesives arranged at intervals. The insulating adhesives are used to prevent the solder ribbon from connecting to the opposite-shaped fine grid.

4. The IBC photovoltaic cell according to claim 3, characterized in that, Along the positive X-axis direction, solder paste is applied to both the large and small main gate metal PADs, enabling the solder strips to form good electrical contact with the main gate PADs at low soldering temperatures.

5. A method for preparing an IBC photovoltaic cell according to any one of claims 1-4, characterized in that, Specifically, the following steps are included: Step S1: The photovoltaic cells that have undergone the front film and back film processes are subjected to a laser three-stage film-opening process, in which the passivation film is initially removed by ablation. The diameter of the circular spot in the laser three-stage film-opening process is 20~40um. Step S2: Low-temperature light injection annealing and ultraviolet light irradiation are used to activate the hydrogen passivation inside the silicon substrate (1) and the film layer. The peak temperature of the light injection annealing is 450~650℃, and the temperature of the ultraviolet light irradiation is 50~100℃. Step S3: Cleaning operation using hydrofluoric acid, hydrochloric acid and hydrogen peroxide to further remove residual passivation film and form cylindrical contact channels. The volume ratio of hydrofluoric acid, hydrochloric acid and hydrogen peroxide is 1:2:

1. Step S4: After cleaning the residual passivation film, deposit an aluminum-titanium alloy barrier layer and a copper seed layer through a PVD process. Step S5: After completing the PVD process, electrolytically prepare a copper conductive layer and an antioxidant tin layer to form the main gate and fine gate metal electrodes; Step S6: Use screen printing to print the protective film onto the metal electrode area, then cure the protective film at low temperature, and then use sulfuric acid and hydrogen peroxide to perform back etching to remove the non-electrode areas where the protective film was not printed.

6. The method for preparing an IBC photovoltaic cell according to claim 5, characterized in that, The step S4 specifically includes: the PVD process uses PVD equipment, with aluminum-titanium alloy as target material 1 and copper as target material 2; When depositing the aluminum-titanium alloy barrier layer, the deposition power of the aluminum-titanium alloy barrier layer is 40-150W, the temperature is 50-200℃, the argon gas flow rate is 20-200sccm, and the deposition time is 10-30min. When depositing a copper seed layer, the deposition power of the copper seed layer is 30-250W, the temperature is 40-120℃, the argon gas flow rate is 20-120sccm, the deposition time is 10-30min, and the thickness of the copper seed layer is 20-220nm.

7. The method for preparing an IBC photovoltaic cell according to claim 6, characterized in that, The aluminum-titanium alloy barrier layer in step S4 has a 1-3 layer structure. When the aluminum-titanium alloy barrier layer is a three-layer structure, the aluminum and titanium components in the first aluminum-titanium alloy layer closest to the silicon substrate (1) are 90% and 10% respectively, and the thickness of the first aluminum-titanium alloy layer is 10~40nm. The aluminum and titanium components in the second aluminum-titanium alloy layer are both 50%, and the thickness of the second aluminum-titanium alloy layer is 10~40nm. The aluminum and titanium components in the third aluminum-titanium alloy layer are 10% and 90% respectively, and the thickness of the third aluminum-titanium alloy layer is 10~40nm. The total thickness of the aluminum-titanium alloy barrier layer is 30~120nm. When the aluminum-titanium alloy barrier layer is a two-layer structure, the aluminum and titanium components in the first aluminum-titanium alloy layer closest to the silicon substrate (1) are 90% and 10% respectively, and the thickness of the first aluminum-titanium alloy layer is 10~60nm. The aluminum and titanium components in the second aluminum-titanium alloy layer are both 50%, and the thickness of the second aluminum-titanium alloy layer is 10~60nm. The total thickness of the aluminum-titanium alloy barrier layer is 20~120nm. When the aluminum-titanium alloy barrier layer is a single layer, the proportion of aluminum and titanium in the aluminum-titanium alloy barrier layer is 50% each, and the total thickness of the aluminum-titanium alloy barrier layer is 20~120nm.

8. The method for preparing an IBC photovoltaic cell according to claim 5, characterized in that, Step S5 specifically includes: the copper conductive layer is prepared by electrolysis of copper sulfate pentahydrate, sulfuric acid and additive solution, and the antioxidant tin layer is prepared by electrolysis of tin methanesulfonate, methanesulfonic acid and additive solution.

9. The method for preparing an IBC photovoltaic cell according to claim 5, characterized in that, Both the main grid metal electrode and the fine grid metal electrode are set according to the pattern of the screen printing stencil. A protective film is used to cover the preset metal electrode area, and then low-temperature curing is performed. The protective film protects the stacked metal electrodes at the main grid and fine grid positions. After curing, sulfuric acid and hydrogen peroxide are used for back-side etching to remove the non-electrode areas where the protective film is not printed. The protective film includes modified polyester resin, rosin resin and silica particles. The modified polyester resin is used to increase the crosslinking density, the rosin resin is used to increase the adhesion between the mask and the metal electrode, and the silica is used to increase the mechanical strength of the film layer.

10. The method for preparing an IBC photovoltaic cell according to claim 5, characterized in that, The first aluminum-titanium alloy barrier layer (71) forms an electrical contact with the first polycrystalline silicon doped layer (10) through a cylindrical contact channel, and the second aluminum-titanium alloy barrier layer (81) forms an electrical contact with the second polycrystalline silicon doped layer (12) through a cylindrical contact channel.

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