BC solar cell and preparation method thereof

Abstract

The invention provides a BC solar cell and a preparation method thereof, and relates to the technical field of solar cells. A back P region of the BC solar cell comprises a first patterned groove, and a back N region of the BC solar cell comprises a second patterned groove. Wherein the first patterned groove comprises a first alloy layer formed by annealing a first seed layer, and the first seed layer comprises nickel, vanadium and aluminum; wherein the second patterned groove comprises a second alloy layer formed by annealing a second seed layer, and the second seed layer comprises nickel and vanadium. Seed layers of the N region and the P region of the BC solar cell are separated, nickel, vanadium and aluminum are selected as the seed layers of the P region, nickel and vanadium are selected as the seed layers of the N region, grid line region passivation can be better optimized, meanwhile, good transmission contact of current is guaranteed, the grid line binding force is improved, the seed layers can be more compact and stable through the alloy layer formed through annealing treatment, and the service life of the BC solar cell is prolonged. Therefore, the electrical performance of the battery is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a BC solar cell and a preparation method thereof. Background Art

[0002] BC (Back Contact) cells are photovoltaic cells based on organic semiconductor materials. They boast high conversion efficiency and low manufacturing costs, and are considered a key development direction for the future photovoltaic industry. BC cells have no grid lines on the front, but rather on the back. They require minimal light shielding, but typically have wider grid lines and consume a high amount of silver paste, with data showing silver consumption of approximately 14mg / W. Furthermore, the silver paste sintering temperature reaches over 700°C, resulting in high energy consumption.

[0003] In order to reduce costs and improve efficiency, some researchers have further proposed using electroplating technology to prepare metal electrodes. Currently, BC batteries usually need to use magnetron sputtering to prepare the seed layer metal of the P and N regions on the back to improve the performance of the battery, and acidic chemicals are also used to remove the metal outside the pattern. This not only increases the preparation cost and complexity of the battery, but may also introduce additional pollution and defects, affecting the performance and life of the battery.

[0004] Therefore, it is of great significance to study and obtain a preparation method for BC batteries in which seed layers are prepared separately in the N / P regions to optimize battery performance.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The present invention provides a BC solar cell and a method for manufacturing the same. The BC solar cell employs a combination of Ni, V, and Al as the first seed layer in the P region on the back side, and a combination of Ni and V as the second seed layer in the N region. This optimizes gate passivation while ensuring good current transmission and contact, enhancing gate bonding strength. Furthermore, the N and P regions utilize an annealed alloy to make the seed layer denser and more stable, effectively improving the cell's electrical performance.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0008] In a first aspect, the present invention provides a BC solar cell, wherein a back P region of the BC solar cell includes a first patterned groove, and a back N region includes a second patterned groove;

[0009] Wherein, the first patterned groove includes a first alloy layer formed by annealing a first seed layer, and the first seed layer includes nickel, vanadium and aluminum;

[0010] The second patterned groove includes a second alloy layer formed by annealing a second seed layer, and the second seed layer includes nickel and vanadium.

[0011] Furthermore, the width of the first patterned groove is 30-100 μm; the depth of the first patterned groove is 70-120 nm.

[0012] Furthermore, the thickness of the first seed layer is 10-100 nm.

[0013] Furthermore, the thickness of the first alloy layer is 1 to 50 nm.

[0014] Furthermore, the mass ratio of nickel, vanadium and aluminum in the first seed layer is (90-95):(2-5):(3-5).

[0015] Furthermore, the width of the second patterned groove is 30-100 μm; and the depth of the second patterned groove is 70-120 nm.

[0016] Furthermore, the thickness of the second seed layer is 10-100 nm.

[0017] Furthermore, the thickness of the second alloy layer is 1 to 50 nm.

[0018] Furthermore, the mass ratio of nickel to vanadium in the second seed layer is (90-98):(2-10).

[0019] Furthermore, the surfaces of the first alloy layer and the second alloy layer further include a copper layer and a tin layer stacked in sequence.

[0020] Furthermore, the copper layer has a thickness of 3 to 20 nm.

[0021] Furthermore, the thickness of the tin layer is 3 to 20 nm.

[0022] In a second aspect, the present invention provides a method for preparing a BC solar cell according to the first aspect, the method comprising:

[0023] Forming a first patterned groove in the back P region of the BC cell silicon substrate to obtain a BC cell silicon substrate having the first patterned groove;

[0024] After plating a first seed layer on the back side of the BC cell silicon substrate having the first patterned groove, the substrate is annealed to form a first alloy layer in the first patterned groove, and then the first seed layer is removed from the back side of the substrate other than the first patterned groove to obtain a BC cell silicon substrate having a first alloy layer in the P region;

[0025] A second patterned groove is formed in the N region on the back side of the BC battery silicon substrate having the first alloy layer in the P region to obtain a BC battery silicon substrate having the second patterned groove;

[0026] After plating a second seed layer on the back side of the BC battery silicon substrate having the second patterned groove and annealing treatment, a second alloy layer is formed in the second patterned groove, and then the second seed layer at the non-second patterned groove on the back side is removed to obtain a BC battery silicon substrate with a second alloy layer in the N region.

[0027] Furthermore, the first patterned groove and the second patterned groove are formed by laser grooving.

[0028] Furthermore, the power of the laser grooving is 2 to 6 W, the pulse frequency of the laser grooving is 500 to 2000 kHz, and the speed of the laser grooving is 25 to 50 mm / s.

[0029] Furthermore, the first seed layer and the second seed layer are formed by PVD coating.

[0030] Furthermore, the gas introduced into the PVD coating method includes any one of Ar, He, Kr or Xe, or a combination of at least two of them.

[0031] Furthermore, the flow rate of the gas introduced into the PVD coating method is 100 to 10,000 sccm.

[0032] Furthermore, the process parameters of the PVD coating method include: vacuum degree of 1×10 -3 ~1×10 -2 Torr; the deposition temperature is 20-60°C; the deposition time is 5-30 min; the current is 4-12 A; and the target voltage is 300-600 V.

[0033] Furthermore, the annealing treatment includes vacuum annealing and / or atmospheric annealing.

[0034] Furthermore, the temperature of the annealing treatment is 200-400° C., and the time of the annealing treatment is 10-20 seconds.

[0035] Furthermore, the removal of the first seed layer and the second seed layer is performed by acid leaching.

[0036] Furthermore, the acid leaching includes: immersing the BC battery silicon substrate after the alloy layer is formed in a seed layer removal working solution to remove the seed layer at the non-patterned groove on the back side.

[0037] Furthermore, the seed layer removal working fluid includes: 184-552 g / L sulfuric acid, 290-1450 g / L hydrogen peroxide, and the solvent is pure water.

[0038] Furthermore, the acid leaching temperature is 40 to 80° C., and the acid leaching time is 3 to 20 minutes.

[0039] Furthermore, the preparation method of the BC solar cell also includes a copper electroplating step: electroplating copper on the BC cell silicon substrate having a second alloy layer in the N region to form a copper layer on the surface of the first seed layer and the second seed layer to obtain a BC cell silicon substrate having a copper layer.

[0040] Furthermore, the copper electroplating specifically includes: immersing the BC battery silicon substrate having the second alloy layer in the N region in an activation solution for activation, then immersing it in a copper electroplating solution for copper electroplating to form a copper layer, and then washing and drying to obtain a BC battery silicon substrate having a copper layer.

[0041] Furthermore, the activation solution comprises: 0.5-3 g / L HF and 0.05-0.3 g / L noble metal salt, and the solvent is water.

[0042] Furthermore, the activation temperature is 15 to 40° C.; and the activation time is 10 to 60 seconds.

[0043] Furthermore, the copper electroplating solution comprises: 20-50 g / L H2SO4, 150-250 g / L CuSO4, and the solvent is water.

[0044] Furthermore, the current density of the copper electroplating is 10 to 50 A / dm 2 ; The temperature of the copper electroplating is 25 to 70°C; The time of the copper electroplating is 1 to 8 minutes.

[0045] Furthermore, the preparation method of the BC solar cell also includes a step of chemical tin plating: chemically tin plating the BC cell silicon substrate with the copper layer to form a tin layer on the surface of the copper layer at the back P region and N region to obtain the BC solar cell.

[0046] Furthermore, the chemical tin plating specifically includes: immersing the BC cell silicon substrate with the copper layer in a tin plating solution, performing chemical tin plating to form a tin layer, and then washing and drying to obtain the BC solar cell.

[0047] Furthermore, the tin plating solution comprises: 10-50 g / L of SnSO4, 5-20 g / L of methanesulfonic acid, 0.2-2 g / L of tetrasodium iminodisuccinate, and the solvent is water.

[0048] Furthermore, the temperature of the chemical tin plating is 30-70° C.; and the time of the chemical tin plating is 0.5-5 min.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The back P region of the BC solar cell of the present invention uses a combination of Ni, V and Al as the first seed layer, and the N region uses a combination of Ni and V as the second seed layer, which can better optimize the passivation of the grid line area, while ensuring good current transmission contact and improving the grid line bonding force; and the seed layers in the P and N regions are both annealed to form alloy layers to make the seed layers more dense and stable, thereby significantly improving the electrical performance of the battery.

[0051] (2) The preparation method of the BC solar cell described in the present invention utilizes PVD coating combined with annealing treatment to prepare an alloy layer, and then prepares a metal electrode by electroplating copper and chemical tin plating to replace the original silver electrode, which not only reduces the production cost of the battery but also improves the electrical performance of the battery; in addition, the copper layer and tin layer obtained by electroplating copper and chemical tin plating have good density and low porosity, especially the tin layer has strong corrosion resistance and good solderability, thereby further improving the electrical performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0053] Figure 1 Schematic diagram of the structure of the BC solar cell of the present invention.

[0054] Among them, 10 is an N-type crystalline silicon substrate, 20 is a tunneling oxide layer, 30 is a P-type polysilicon layer, 31 is an N-type polysilicon layer, 40 is an aluminum oxide layer, 41 is a silicon nitride layer, 42 is a silicon oxide layer, 50 is a first patterned groove, 51 is a second patterned groove, 60 is a first alloy layer, 61 is a second alloy layer, 70 is a copper layer, and 80 is a tin layer. DETAILED DESCRIPTION

[0055] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear; however, in the event of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, the use of "or" means "and / or" unless otherwise stated. In addition, the use of the term "including" and other forms is non-limiting.

[0056] It should be noted that the following description sets forth specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways than those described herein, and those skilled in the art may make similar generalizations without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0057] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0058] First, as Figure 1 As shown, the present invention provides a BC solar cell, wherein the back P region of the BC solar cell includes a first patterned groove 50, and the back N region includes a second patterned groove 51;

[0059] The first patterned groove 50 includes a first alloy layer 60 formed by annealing a first seed layer, and the first seed layer includes nickel, vanadium and aluminum;

[0060] The second patterned groove 51 includes a second alloy layer 61 formed by annealing a second seed layer, and the second seed layer includes nickel and vanadium.

[0061] In the present invention, the P region on the back side of the BC solar cell of the present invention uses a combination of Ni, V and Al as the first seed layer, and the N region uses a combination of Ni and V as the second seed layer, which can better optimize the passivation of the grid line area, while ensuring good current transmission contact and improving the grid line bonding force; and the seed layers in the P and N regions are both annealed to form an alloy layer to make the seed layer denser and more stable, thereby significantly improving the electrical performance of the battery.

[0062] 1. Passivation optimization:

[0063] Nickel can form low-defect-density silicide with silicon, and its interface state density is low, which can effectively reduce surface recombination and improve the passivation effect; at the same time, the doping characteristics of nickel on silicon (such as boron doping in the P-type region) can form a good ohmic contact and reduce contact resistance; aluminum can form a local Al-Si alloy in the P-type region through high-temperature sintering, resulting in field-effect passivation and reducing the surface recombination rate; vanadium acts as a diffusion barrier layer, which can inhibit the diffusion of Al metal atoms into the silicon substrate, avoid contamination of the doped area or damage to the passivation layer, and maintain the stability of the passivation structure.

[0064] 2. Current transmission and contact optimization:

[0065] The conductivity of nickel is significantly higher than that of traditional silver paste, which can reduce series resistance and improve current collection efficiency, especially in the N-type region, where the Schottky barrier between nickel and silicon is low, which is conducive to electron transmission; vanadium forms a transition layer between nickel and silicon, reducing interface defects, improving the carrier transmission path, and enhancing the adhesion between metal and semiconductor; in the P-type region, aluminum, as a P-type dopant, can work synergistically with boron to form a highly doped P+ emitter, reducing contact resistance and enhancing carrier injection efficiency.

[0066] 3. Advantages of partition design:

[0067] P-type region (Ni / V / Al combination): Aluminum's field-effect passivation and nickel's chemical passivation combine to reduce surface recombination; vanadium blocks aluminum diffusion, maintaining the integrity of the passivation layer. Furthermore, aluminum's high doping properties optimize the ohmic contact in the P-type region, reducing resistive losses. Aluminum's ductility and nickel's mechanical strength enhance the bonding between the gate line and the passivation layer, reducing the risk of interface delamination caused by thermal stress.

[0068] N region (Ni / V combination): The low-resistance contact formed by nickel in N-type silicon is suitable for electron transmission, while the barrier effect of vanadium prevents nickel from diffusing into the passivation layer, avoiding passivation failure. The Ni / V combination is also more compatible with N-type phosphorus doping than other metals.

[0069] As an optional embodiment, the width of the first patterned groove 50 is 30 to 100 μm, for example, it can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0070] As an optional embodiment, the depth of the first patterned groove 50 is 70 to 120 nm, for example, it can be 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, etc.

[0071] As an optional embodiment, the thickness of the first seed layer is 10 to 100 nm, for example, it can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc.

[0072] As an optional embodiment, the thickness of the first alloy layer 60 is 1 to 50 nm, for example, 1 nm, 2 nm, 3 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc.

[0073] As an optional embodiment, the mass ratio of nickel, vanadium and aluminum in the first seed layer is (90-95):(2-5):(3-5);

[0074] Among them, "90-95" can be, for example, 90, 91, 92, 93, 94, 95, etc.;

[0075] Here, “2-5” can be, for example, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.;

[0076] Here, “3-5” can be, for example, 3, 3.5, 4, 4.5, 5, etc.

[0077] As an optional embodiment, the width of the second patterned groove 51 is 30 to 100 μm, for example, it can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0078] As an optional embodiment, the depth of the second patterned groove 51 is 70 to 120 nm, for example, it can be 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, etc.

[0079] As an optional embodiment, the thickness of the second seed layer is 10 to 100 nm, for example, it can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc.

[0080] As an optional embodiment, the thickness of the second alloy layer 61 is 1 to 50 nm, for example, 1 nm, 2 nm, 3 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc.

[0081] As an optional embodiment, the mass ratio of nickel to vanadium in the second seed layer is (90-98):(1-20);

[0082] Among them, "90-98" can be, for example, 90, 91, 92, 93, 94, 95, 96, 97, 98, etc.;

[0083] Here, “2 to 10” can be, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.

[0084] As an optional implementation, Figure 1 As shown, the surface of the first alloy layer 60 further includes a copper layer 70 and a tin layer 80 stacked in sequence.

[0085] As an optional implementation, Figure 1 As shown, the surface of the second alloy layer 61 further includes a copper layer 70 and a tin layer 80 stacked in sequence.

[0086] As an optional embodiment, the copper layer 70 has a thickness of 3 to 20 nm, for example, 3 nm, 4 nm, 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, etc.

[0087] As an optional embodiment, the thickness of the tin layer 80 is 3 to 20 nm, for example, 3 nm, 4 nm, 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, etc.

[0088] In a second aspect, the present invention provides a method for preparing a BC solar cell according to the first aspect, the method comprising:

[0089] Forming a first patterned groove in the back P region of the BC cell silicon substrate to obtain a BC cell silicon substrate having the first patterned groove;

[0090] After plating a first seed layer on the back side of the BC cell silicon substrate having the first patterned groove, the substrate is annealed to form a first alloy layer in the first patterned groove, and then the first seed layer is removed from the back side of the substrate other than the first patterned groove to obtain a BC cell silicon substrate having a first alloy layer in the P region;

[0091] A second patterned groove is formed in the N region on the back side of the BC battery silicon substrate having the first alloy layer in the P region to obtain a BC battery silicon substrate having the second patterned groove;

[0092] After plating a second seed layer on the back side of the BC battery silicon substrate having the second patterned groove and annealing treatment, a second alloy layer is formed in the second patterned groove, and then the second seed layer at the non-second patterned groove on the back side is removed to obtain a BC battery silicon substrate with a second alloy layer in the N region.

[0093] As an optional embodiment, the first patterned groove and the second patterned groove are formed by laser grooving.

[0094] As an optional implementation, the power of the laser grooving is 2 to 6 W, for example, 2 W, 2.5 W, 3 W, 3.5 W, 4 W, 4.5 W, 5 W, 5.5 W, 6 W, etc.

[0095] As an optional embodiment, the pulse frequency of the laser grooving is 500 to 2000 kHz, for example, it can be 500 kHz, 600 kHz, 800 kHz, 1000 kHz, 1200 kHz, 1400 kHz, 1500 kHz, 1600 kHz, 1800 kHz, 2000 kHz, etc.

[0096] As an optional implementation, the speed of the laser grooving is 25 to 50 mm / s, for example, 25 mm / s, 30 mm / s, 35 mm / s, 40 mm / s, 45 mm / s, 50 mm / s, etc.

[0097] As an optional embodiment, the first seed layer and the second seed layer are formed by PVD coating.

[0098] As an optional embodiment, the gas introduced into the PVD coating method includes any one of Ar, He, Kr or Xe, or a combination of at least two of them.

[0099] As an optional embodiment, the flow rate of the gas introduced into the PVD coating method is 100 to 10,000 sccm, for example, it can be 100 sccm, 200 sccm, 400 sccm, 500 sccm, 600 sccm, 800 sccm, 1,000 sccm, 2,000 sccm, 3,000 sccm, 4,000 sccm, 5,000 sccm, 6,000 sccm, 7,000 sccm, 8,000 sccm, 9,000 sccm, 10,000 sccm, etc.

[0100] As an optional embodiment, the process parameters of the PVD coating method include: vacuum degree of 1×10 -3 ~1×10 -2 Torr, for example, can be 1×10 -3 Torr, 2×10 -3 Torr, 3×10 -3 Torr, 4×10 -3 Torr, 5×10 -3 Torr, 6×10 -3 Torr, 7×10 -3 Torr, 8×10 -3 Torr, 9×10 -3 Torr, 1×10 -2 Torr et al.

[0101] As an optional embodiment, the process parameters of the PVD coating method include: a deposition temperature of 20 to 60°C, for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc.

[0102] As an optional embodiment, the process parameters of the PVD coating method include: a deposition time of 5 to 30 minutes, for example, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.

[0103] As an optional embodiment, the process parameters of the PVD coating method include: a current of 4 to 12 A, for example, it can be 4A, 5A, 6A, 7A, 8A, 9A, 10A, 11A, 12A, etc.

[0104] As an optional embodiment, the process parameters of the PVD coating method include: a target voltage of 300-600V, for example, it can be 300V, 350V, 400V, 450V, 500V, 550V, 600V, etc.

[0105] As an optional embodiment, the annealing treatment includes vacuum annealing and / or atmospheric annealing.

[0106] As an optional embodiment, the annealing temperature is 200-400°C, for example, it can be 200°C, 220°C, 240°C, 250°C, 260°C, 280°C, 300°C, 320°C, 340°C, 350°C, 360°C, 380°C, 400°C, etc.

[0107] As an optional embodiment, the annealing treatment time is 10 to 20 seconds, for example, it can be 10 seconds, 11 seconds, 12 seconds, 13 seconds, 14 seconds, 15 seconds, 16 seconds, 17 seconds, 18 seconds, 19 seconds, 20 seconds, etc.

[0108] As an optional embodiment, the removal of the first seed layer and the second seed layer is performed by acid leaching.

[0109] As an optional embodiment, the acid immersion includes: immersing the BC battery silicon substrate after the alloy layer is formed in a seed layer removal working solution to remove the seed layer at the non-patterned groove on the back side.

[0110] As an optional embodiment, the seed layer removal working fluid includes: 184-552 g / L sulfuric acid, 290-1450 g / L hydrogen peroxide, and the solvent is pure water.

[0111] As an optional embodiment, the concentration of sulfuric acid in the deseeding layer working fluid is 184-552 g / L, for example, it can be 184 g / L, 190 g / L, 200 g / L, 250 g / L, 300 g / L, 350 g / L, 400 g / L, 450 g / L, 500 g / L, 552 g / L, etc.

[0112] As an optional embodiment, the concentration of hydrogen peroxide in the de-seeding layer working fluid is 290-1450 g / L, for example, it can be 290 g / L, 300 g / L, 350 g / L, 400 g / L, 450 g / L, 500 g / L, 550 g / L, 600 g / L, 650 g / L, 700 g / L, 750 g / L, 800 g / L, 900 g / L, 1000 g / L, 1100 g / L, 1200 g / L, 1300 g / L, 1400 g / L, 1450 g / L, etc.

[0113] As an optional embodiment, the acid leaching temperature is 40-70°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc.

[0114] As an optional embodiment, the acid leaching time is 3 to 20 minutes, for example, it can be 3 minutes, 4 minutes, 6 minutes, 8 minutes, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, etc.

[0115] As an optional embodiment, the preparation method of the BC solar cell also includes a copper electroplating step: electroplating copper on the BC cell silicon substrate having a second alloy layer in the N region, forming a copper layer on the surface of the first seed layer and the second seed layer, and obtaining a BC cell silicon substrate having a copper layer.

[0116] As an optional embodiment, the copper electroplating specifically includes: immersing the BC battery silicon substrate having a second alloy layer in the N region in an activation solution for activation, then immersing it in a copper electroplating solution for copper electroplating to form a copper layer, and then washing and drying to obtain a BC battery silicon substrate having a copper layer.

[0117] As an optional embodiment, the activation solution includes: 0.5-3 g / L HF and 0.05-0.3 g / L noble metal salt, and the solvent is water.

[0118] As an optional embodiment, the concentration of HF in the activation solution is 0.5-3 g / L, for example, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, etc.

[0119] As an optional embodiment, the concentration of the precious metal salt in the activation solution is 0.05-0.3 g / L, for example, it can be 0.05 g / L, 0.08 g / L, 0.1 g / L, 0.12 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, 0.3 g / L, etc.

[0120] As an optional embodiment, the noble metal salt includes PdCl2 and / or AuCl.

[0121] As an optional embodiment, the activation temperature is 15-40°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, etc.

[0122] As an optional embodiment, the activation time is 10 to 60 s, for example, it can be 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, etc.

[0123] As an optional embodiment, the copper electroplating solution includes: 20-50 g / L H2SO4, 150-250 g / L CuSO4, and the solvent is water.

[0124] As an optional embodiment, the concentration of H2SO4 in the copper electroplating solution is 20-50 g / L, for example, it can be 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, etc.

[0125] As an optional embodiment, the concentration of CuSO4 in the copper electroplating solution is 150-250 g / L, for example, it can be 150 g / L, 160 g / L, 180 g / L, 200 g / L, 220 g / L, 240 g / L, 250 g / L, etc.

[0126] As an optional embodiment, the current density of the copper electroplating is 10 to 50 A / dm 2 , for example, it can be 10A / dm 2 、15A / dm 2 , 20A / dm 2 , 25A / dm 2 、30A / dm 2 、35A / dm 2 、40A / dm 2 、45A / dm 2 、50A / dm 2 wait.

[0127] As an optional embodiment, the temperature of the copper electroplating is 25-70°C, for example, it can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc.

[0128] As an optional embodiment, the copper electroplating time is 1 to 8 minutes, for example, it can be 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, etc.

[0129] As an optional embodiment, the preparation method of the BC solar cell also includes a step of chemical tin plating: chemically tin plating is performed on the BC cell silicon substrate having the copper layer to form a tin layer on the surface of the copper layer at the back P region and N region to obtain the BC solar cell.

[0130] As an optional embodiment, the chemical tin plating specifically includes: immersing the BC cell silicon substrate with the copper layer in a tin plating solution, performing chemical tin plating to form a tin layer, and then washing and drying to obtain the BC solar cell.

[0131] As an optional embodiment, the tin plating solution includes: 10-50 g / L of SnSO4, 5-20 g / L of methanesulfonic acid, 0.2-2 g / L of tetrasodium iminodisuccinate, and the solvent is water.

[0132] As an optional embodiment, the concentration of SnSO4 in the tin plating solution is 20-50 g / L, for example, it can be 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, etc.

[0133] As an optional embodiment, the concentration of methanesulfonic acid in the tin plating solution is 5-20 g / L, for example, it can be 5 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 14 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, etc.

[0134] As an optional embodiment, the concentration of tetrasodium iminodisuccinate in the tin plating solution is 0.2-2 g / L, for example, it can be 0.2 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.8 g / L, 1 g / L, 1.2 g / L, 1.4 g / L, 1.5 g / L, 1.6 g / L, 1.8 g / L, 2 g / L, etc.

[0135] As an optional embodiment, the temperature of the chemical tin plating is 30-70°C, for example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc.

[0136] As an optional embodiment, the time for the chemical tin plating is 0.5 to 5 minutes, for example, it can be 0.5 minutes, 1 minute, 1.5 minutes, 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes, 5 minutes, etc.

[0137] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0138] The following embodiments use a BC cell silicon substrate of uniform specifications: the front side of the BC cell silicon substrate has a pyramid velvet surface and includes an aluminum oxide layer 40, a silicon nitride layer 41 and a silicon oxide layer 42 stacked in sequence; the P region on the back side of the BC cell silicon substrate includes a tunneling oxide layer 20, a P-type polysilicon layer 30, an aluminum oxide layer 40 and a silicon nitride layer 41 stacked in sequence; the N region on the back side of the BC cell silicon substrate includes a tunneling oxide layer 20, an N-type polysilicon layer 31 and an aluminum oxide layer 40 stacked in sequence.

[0139] Example 1

[0140] This embodiment provides a BC solar cell, which is prepared by the following steps:

[0141] S1. First graphing:

[0142] The coating layer of the P (boron-doped) area on the back side of the BC cell silicon substrate is removed by laser grooving, and a first patterned groove is formed in the P area on the surface of the coating layer to obtain a BC cell silicon substrate having the first patterned groove;

[0143] The width of the first patterned groove is 65 μm; the depth of the first patterned groove is 95 nm; the power of the laser grooving is 3 W, the pulse frequency of the laser grooving is 1000 kHz, and the speed of the laser grooving is 40 mm / s.

[0144] S2. Preparation of the first seed layer:

[0145] Coating a first seed layer on the back side of the BC cell silicon substrate having the first patterned groove by a PVD coating method to obtain a BC cell silicon substrate having the first seed layer;

[0146] The first seed layer includes nickel, vanadium and aluminum in a mass ratio of 93:3:4, and the thickness of the first seed layer is 50 nm. The process parameters of the PVD coating method include: introducing Ar gas with a flow rate of 5×10 -3 Torr; the deposition temperature was 25°C; the deposition time was 20 min; the current was 8 A; and the target voltage was 400 V.

[0147] S3, first annealing treatment:

[0148] Performing a first annealing treatment on the BC battery silicon substrate having the first seed layer by vacuum annealing to form a first alloy layer in the first patterned groove (the first seed layer on the back side not in the first patterned groove remains as a seed layer and is not alloyed), thereby obtaining a BC battery silicon substrate that has undergone the first annealing treatment;

[0149] The annealing temperature is 300° C., and the annealing time is 100 s.

[0150] S4. Removing the first seed layer:

[0151] Immerse the BC battery silicon substrate that has undergone the first annealing treatment in a seed layer removal working solution to remove the seed layer at the non-patterned groove on the back side to obtain a BC battery silicon substrate with a first alloy layer in the P region;

[0152] The seed layer removal working solution includes: 300 g / L sulfuric acid, 500 g / L hydrogen peroxide, and the solvent is pure water; the immersion temperature is 50° C., and the immersion time is 15 minutes.

[0153] S5. Second graphing:

[0154] The coating layer of the back N (phosphorus-doped) region of the BC battery silicon substrate with the first alloy layer in the P region is removed by laser grooving, and a second patterned groove is formed in the N region on the surface of the coating layer to obtain a BC battery silicon substrate with the second patterned groove;

[0155] The width of the second patterned groove is 65 μm; the depth of the second patterned groove is 95 nm; the power of the laser grooving is 4 W, the pulse frequency of the laser grooving is 1000 kHz, and the speed of the laser grooving is 40 mm / s.

[0156] S6. Preparation of the second seed layer:

[0157] Coating a second seed layer on the back side of the BC cell silicon substrate having the second patterned groove by a PVD coating method to obtain a BC cell silicon substrate having the second seed layer;

[0158] The second seed layer includes nickel and vanadium in a mass ratio of 95:5, and the thickness of the second seed layer is 50 nm. The process parameters of the PVD coating method include: introducing Ar gas with a flow rate of 5×10 -3 Torr; the deposition temperature is 30℃; the deposition time is 15min; the current is 8A; and the target voltage is 400V.

[0159] S3, second annealing treatment:

[0160] The BC battery silicon substrate having the second seed layer is subjected to a second annealing treatment by vacuum annealing to form a second alloy layer in the second patterned groove (the second seed layer at the back side not in the second patterned groove is still a seed layer and is not alloyed), thereby obtaining a BC battery silicon substrate subjected to the second annealing treatment;

[0161] The annealing temperature is 320° C., and the annealing time is 120 seconds.

[0162] S4, removing the second seed layer:

[0163] Immerse the BC battery silicon substrate that has undergone the second annealing treatment in a seed layer removal working solution to remove the seed layer at the non-patterned groove on the back side to obtain a BC battery silicon substrate with a second alloy layer in the N region;

[0164] The seed layer removal working solution includes: 300 g / L sulfuric acid, 500 g / L hydrogen peroxide, and the solvent is pure water; the immersion temperature is 55° C., and the immersion time is 6 minutes.

[0165] S5. Electroplating copper:

[0166] The BC battery silicon substrate with the second alloy layer in the N region is placed horizontally in a copper electroplating device with the back side facing downward, immersed in an activation solution for activation, and then immersed in a copper electroplating solution for copper electroplating to form a copper layer, and then washed and dried to obtain a BC battery silicon substrate with a copper layer;

[0167] The activation solution includes: PdCl2 0.1g / L, HF 1g / L, and the solvent is pure water; the activation temperature is 25°C; the activation time is 10s; the copper electroplating solution includes: H2SO4 35g / L, CuSO4 200g / L, and the solvent is pure water; the current density of the copper electroplating is 30A / dm 2 ; The temperature of the copper electroplating is 40°C; The time of the copper electroplating is 5 minutes.

[0168] S6, chemical tin plating:

[0169] Immersing the BC cell silicon substrate with the copper layer in a tin plating solution to perform chemical tin plating to form a tin layer, and then washing and drying to obtain the BC solar cell;

[0170] The tin plating solution comprises: 30 g / L SnSO4, 12 g / L methanesulfonic acid, and 1 g / L tetrasodium iminodisuccinate, and the solvent is pure water; the temperature of the chemical tin plating is 50° C.; and the time of the chemical tin plating is 2 minutes.

[0171] Example 2

[0172] This embodiment provides a BC solar cell, which is prepared by the following steps:

[0173] S1. First graphing:

[0174] The coating layer of the P (boron-doped) area on the back side of the BC cell silicon substrate is removed by laser grooving, and a first patterned groove is formed in the P area on the surface of the coating layer to obtain a BC cell silicon substrate having the first patterned groove;

[0175] The width of the first patterned groove is 65 μm; the depth of the first patterned groove is 95 nm; the power of the laser grooving is 5 W, the pulse frequency of the laser grooving is 1100 kHz, and the speed of the laser grooving is 30 mm / s.

[0176] S2. Preparation of the first seed layer:

[0177] Coating a first seed layer on the back side of the BC cell silicon substrate having the first patterned groove by a PVD coating method to obtain a BC cell silicon substrate having the first seed layer;

[0178] The first seed layer includes nickel, vanadium and aluminum in a mass ratio of 91:4:5, and the thickness of the first seed layer is 40 nm. The process parameters of the PVD coating method include: introducing He gas with a flow rate of 6×10 -3 Torr; the deposition temperature is 30℃; the deposition time is 20min; the current is 8A; and the target voltage is 400V.

[0179] S3, first annealing treatment:

[0180] Performing a first annealing treatment on the BC battery silicon substrate having the first seed layer by vacuum annealing to form a first alloy layer in the first patterned groove (the first seed layer on the back side not in the first patterned groove remains as a seed layer and is not alloyed), thereby obtaining a BC battery silicon substrate that has undergone the first annealing treatment;

[0181] The annealing temperature is 250° C., and the annealing time is 150 seconds.

[0182] S4, removing the first seed layer:

[0183] Immerse the BC battery silicon substrate that has undergone the first annealing treatment in a seed layer removal working solution to remove the seed layer at the non-patterned groove on the back side to obtain a BC battery silicon substrate with a first alloy layer in the P region;

[0184] The seed layer removal working fluid includes: 200 g / L sulfuric acid, 600 g / L hydrogen peroxide, and the solvent is pure water; the immersion temperature is 60° C., and the immersion time is 12 minutes.

[0185] S5. Second graphing:

[0186] The coating layer of the back N (phosphorus-doped) region of the BC battery silicon substrate with the first alloy layer in the P region is removed by laser grooving, and a second patterned groove is formed in the N region on the surface of the coating layer to obtain a BC battery silicon substrate with the second patterned groove;

[0187] The width of the second patterned groove is 65 μm; the depth of the second patterned groove is 95 nm; the power of the laser grooving is 4 W, the pulse frequency of the laser grooving is 1100 kHz, and the speed of the laser grooving is 30 mm / s.

[0188] S6. Preparation of the second seed layer:

[0189] Coating a second seed layer on the back side of the BC cell silicon substrate having the second patterned groove by a PVD coating method to obtain a BC cell silicon substrate having the second seed layer;

[0190] The second seed layer includes nickel and vanadium in a mass ratio of 94:6, and the thickness of the second seed layer is 40 nm. The process parameters of the PVD coating method include: introducing He gas with a flow rate of 6×10 -3 Torr; deposition temperature is 30℃; deposition time; current is 7A; target voltage is 350V.

[0191] S3, second annealing treatment:

[0192] The BC battery silicon substrate having the second seed layer is subjected to a second annealing treatment by vacuum annealing to form a second alloy layer in the second patterned groove (the second seed layer at the back side not in the second patterned groove is still a seed layer and is not alloyed), thereby obtaining a BC battery silicon substrate subjected to the second annealing treatment;

[0193] The annealing temperature is 350° C., and the annealing time is 50 seconds.

[0194] S4, removing the second seed layer:

[0195] Immerse the BC battery silicon substrate that has undergone the second annealing treatment in a seed layer removal working solution to remove the seed layer at the non-patterned groove on the back side to obtain a BC battery silicon substrate with a second alloy layer in the N region;

[0196] The seed layer removal working fluid includes: 300 g / L sulfuric acid, 500 g / L hydrogen peroxide, and the solvent is pure water; the immersion temperature is 60° C., and the immersion time is 4 minutes.

[0197] S5. Electroplating copper:

[0198] The BC battery silicon substrate with the second alloy layer in the N region is placed horizontally in a copper electroplating device with the back side facing downward, immersed in an activation solution for activation, and then immersed in a copper electroplating solution for copper electroplating to form a copper layer, and then washed and dried to obtain a BC battery silicon substrate with a copper layer;

[0199] The activation solution includes: PdCl2 0.2g / L, HF 2g / L, and the solvent is pure water; the activation temperature is 25°C; the copper electroplating solution includes: H2SO4 40g / L, CuSO4 200g / L, and the solvent is pure water; the current density of the copper electroplating is 30A / dm 2 ; The temperature of the copper electroplating is 40°C; The time of the copper electroplating is 7 minutes.

[0200] S6, chemical tin plating:

[0201] Immersing the BC cell silicon substrate with the copper layer in a tin plating solution to perform chemical tin plating to form a tin layer, and then washing and drying to obtain the BC solar cell;

[0202] The tin plating solution comprises: 40 g / L SnSO4, 10 g / L methanesulfonic acid, and 12 g / L tetrasodium iminodisuccinate, and the solvent is pure water; the temperature of the chemical tin plating is 60° C.; and the time of the chemical tin plating is 1 minute.

[0203] Example 3

[0204] This embodiment provides a BC solar cell, which is prepared by the following steps:

[0205] S1. First graphing:

[0206] The coating layer of the P (boron-doped) area on the back side of the BC cell silicon substrate is removed by laser grooving, and a first patterned groove is formed in the P area on the surface of the coating layer to obtain a BC cell silicon substrate having the first patterned groove;

[0207] The width of the first patterned groove is 65 μm; the depth of the first patterned groove is 95 nm; the power of the laser grooving is 5 W, the pulse frequency of the laser grooving is 900 kHz, and the speed of the laser grooving is 45 mm / s.

[0208] S2. Preparation of the first seed layer:

[0209] Coating a first seed layer on the back side of the BC cell silicon substrate having the first patterned groove by a PVD coating method to obtain a BC cell silicon substrate having the first seed layer;

[0210] The first seed layer includes nickel, vanadium and aluminum in a mass ratio of 95:2:3, and the thickness of the first seed layer is 60 nm. The process parameters of the PVD coating method include: introducing Kr gas with a flow rate of 4×10 -3 Torr; deposition temperature is 30℃; deposition time is 10min; current is 8A; target voltage is 400V; auxiliary.

[0211] S3, first annealing treatment:

[0212] Performing a first annealing treatment on the BC battery silicon substrate having the first seed layer by vacuum annealing to form a first alloy layer in the first patterned groove (the first seed layer on the back side not in the first patterned groove remains as a seed layer and is not alloyed), thereby obtaining a BC battery silicon substrate that has undergone the first annealing treatment;

[0213] The annealing temperature is 200° C., and the annealing time is 200 s.

[0214] S4. Removing the first seed layer:

[0215] Immerse the BC battery silicon substrate that has undergone the first annealing treatment in a seed layer removal working solution to remove the seed layer at the non-patterned groove on the back side to obtain a BC battery silicon substrate with a first alloy layer in the P region;

[0216] The seed layer removal working fluid includes: 200 g / L sulfuric acid, 600 g / L hydrogen peroxide, and the solvent is pure water; the immersion temperature is 55° C., and the immersion time is 13 minutes.

[0217] S5. Second graphing:

[0218] The coating layer of the back N (phosphorus-doped) region of the BC battery silicon substrate with the first alloy layer in the P region is removed by laser grooving, and a second patterned groove is formed in the N region on the surface of the coating layer to obtain a BC battery silicon substrate with the second patterned groove;

[0219] The width of the second patterned groove is 65 μm; the depth of the second patterned groove is 95 nm; the power of the laser grooving is 4 W, the pulse frequency of the laser grooving is 1000 kHz, and the speed of the laser grooving is 35 mm / s.

[0220] S6. Preparation of the second seed layer:

[0221] Coating a second seed layer on the back side of the BC cell silicon substrate having the second patterned groove by a PVD coating method to obtain a BC cell silicon substrate having the second seed layer;

[0222] The second seed layer includes nickel and vanadium in a mass ratio of 98:2, and the thickness of the second seed layer is 60 nm. The process parameters of the PVD coating method include: introducing Kr gas with a flow rate of 4×10 -3 Torr; the deposition temperature was 35°C; the deposition time was 20 min; the current was 7 A; and the target voltage was 350 V.

[0223] S3, second annealing treatment:

[0224] The BC battery silicon substrate having the second seed layer is subjected to a second annealing treatment by vacuum annealing to form a second alloy layer in the second patterned groove (the second seed layer at the back side not in the second patterned groove is still a seed layer and is not alloyed), thereby obtaining a BC battery silicon substrate subjected to the second annealing treatment;

[0225] The annealing temperature is 250° C., and the annealing time is 150 seconds.

[0226] S4, removing the second seed layer:

[0227] Immerse the BC battery silicon substrate that has undergone the second annealing treatment in a seed layer removal working solution to remove the seed layer at the non-patterned groove on the back side to obtain a BC battery silicon substrate with a second alloy layer in the N region;

[0228] The seed layer removal working fluid includes: 300 g / L sulfuric acid, 500 g / L hydrogen peroxide, and the solvent is pure water; the immersion temperature is 55° C., and the immersion time is 5 minutes.

[0229] S5. Electroplating copper:

[0230] The BC battery silicon substrate with the second alloy layer in the N region is placed horizontally in a copper electroplating device with the back side facing downward, immersed in an activation solution for activation, and then immersed in a copper electroplating solution for copper electroplating to form a copper layer, and then washed and dried to obtain a BC battery silicon substrate with a copper layer;

[0231] The activation solution includes: AuCl 0.1g / L, HF 1g / L, and the solvent is pure water; the activation temperature is 20°C; the activation time is 13s; the copper electroplating solution includes: H2SO4 30g / L, CuSO4 200g / L, and the solvent is pure water; the current density of the copper electroplating is 35A / dm 2 ; The temperature of the copper electroplating is 45°C; The time of the copper electroplating is 6 minutes.

[0232] S6, chemical tin plating:

[0233] Immersing the BC cell silicon substrate with the copper layer in a tin plating solution to perform chemical tin plating to form a tin layer, and then washing and drying to obtain the BC solar cell;

[0234] The tin plating solution includes: 40 g / L SnSO4, 15 g / L methanesulfonic acid, 0.5 g / L tetrasodium iminodisuccinate, and the solvent is pure water; the temperature of the chemical tin plating is 45° C.; and the time of the chemical tin plating is 1.5 min.

[0235] Example 4

[0236] This embodiment provides a BC solar cell, which differs from the embodiment 1 only in that: in S2, the first seed layer includes nickel, vanadium and aluminum in a mass ratio of 90:6:4, and the other steps are completely consistent with the embodiment 1.

[0237] Example 5

[0238] This embodiment provides a BC solar cell, which differs from the embodiment 1 only in that: in S2, the first seed layer includes nickel, vanadium and aluminum in a mass ratio of 98:1:1, and the other steps are exactly the same as those in the embodiment 1.

[0239] Example 6

[0240] This embodiment provides a BC solar cell, which differs from the embodiment 1 only in that: in S6, the second seed layer includes nickel and vanadium in a mass ratio of 85:15, and the other steps are completely consistent with the embodiment 1.

[0241] Example 7

[0242] This embodiment provides a BC solar cell, which differs from the embodiment 1 only in that: in S6, the second seed layer includes nickel and vanadium in a mass ratio of 99:1, and the other steps are completely consistent with the embodiment 1.

[0243] Comparative Example 1

[0244] This comparative example provides a BC solar cell, which differs from Example 1 only in that the first seed layer no longer contains nickel, the first seed layer only includes vanadium and aluminum with a mass ratio of 60:40, the thickness of the first seed layer is 50 nm, and the other steps are exactly the same as Example 1.

[0245] Comparative Example 2

[0246] This comparative example provides a BC solar cell, which differs from Example 1 only in that the first seed layer no longer contains vanadium, the first seed layer only includes nickel and aluminum with a mass ratio of 95:5, the thickness of the first seed layer is 50 nm, and the other steps are exactly the same as Example 1.

[0247] Comparative Example 3

[0248] This comparative example provides a BC solar cell, which differs from Example 1 only in that the first seed layer no longer contains aluminum, and the first seed layer only includes nickel and vanadium with a mass ratio of 95:5. The thickness of the first seed layer is 50 nm, and the other steps are exactly the same as Example 1.

[0249] Comparative Example 4

[0250] This comparative example provides a BC solar cell, which differs from Example 1 only in that the second seed layer no longer contains nickel, the second seed layer only includes vanadium, the thickness of the second seed layer is 50 nm, and the other steps are exactly the same as Example 1.

[0251] Comparative Example 5

[0252] This comparative example provides a BC solar cell, which differs from Example 1 only in that the second seed layer no longer contains vanadium, the second seed layer only includes nickel, the thickness of the second seed layer is 50 nm, and the other steps are exactly the same as Example 1.

[0253] Test Case

[0254] Test samples: BC solar cells provided in Examples 1 to 7, and BC solar cells provided in Comparative Examples 1 to 5;

[0255] Test method:

[0256] (1) Electrical performance test: (photoelectric conversion efficiency, open circuit voltage, series resistance); specifically, IV test was used at a temperature of 25°C and an AM of 1.5G;

[0257] (2) Welding capability test: Perform welding tensile test (300-350°C) on the PAD points on the metal electrode (the tensile force on the back of the BC battery is qualified if the average value of the 24 PAD points tested is ≥0.8N).

[0258] The specific test results are shown in Table 1:

[0259] Table 1

[0260]

[0261] As shown in Table 1, the back P region of the BC solar cell of the present invention uses a combination of Ni, V, and Al as the first seed layer, and the N region uses a combination of Ni and V as the second seed layer, which can better optimize the passivation of the grid line area, while ensuring good current transmission contact and improving the grid line bonding strength; and the seed layers in the P and N regions are both annealed to form alloy layers to make the seed layers more dense and stable, thereby significantly improving the electrical performance of the battery. In addition, the preparation method of the BC solar cell of the present invention utilizes PVD coating combined with annealing to prepare the alloy layer, and then prepares the metal electrode by electroplating copper and chemical tin plating to replace the original silver electrode, which not only reduces the production cost of the battery, but also improves the electrical performance of the battery; in addition, the copper layer and tin layer obtained by electroplating copper and chemical tin plating have good density and low porosity, especially the tin layer has strong corrosion resistance and good solderability, thereby improving the electrical performance of the battery.

[0262] As can be seen from the comparison between Example 1 and Examples 4 to 5, the ratio of nickel, vanadium and aluminum in the first seed layer is preferably (90 to 95): (2 to 5): (3 to 5). The alloy layer formed by annealing within this ratio makes the seed layer denser and more stable, thereby further improving the open circuit voltage, conversion efficiency and welding tension, thereby further improving the electrical performance of the battery.

[0263] As can be seen from the comparison between Example 1 and Examples 6 to 7, the mass ratio of nickel and vanadium in the second seed layer is preferably (90 to 98): (1 to 20). The alloy layer formed by annealing within this ratio makes the seed layer denser and more stable, thereby further improving the open circuit voltage, conversion efficiency and welding tension, thereby further improving the electrical performance of the battery.

[0264] From the comparison between Example 1 and Comparative Examples 1 to 3, it can be seen that when the first seed layer lacks any one of nickel, vanadium and aluminum, the electrical properties of the prepared battery are significantly reduced.

[0265] From the comparison between Example 1 and Comparative Examples 4-5, it can be seen that when the second seed layer lacks either nickel or vanadium, the electrical properties of the prepared battery are significantly reduced.

[0266] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A BC solar cell, characterized in that: The back P region of the BC solar cell includes a first patterned groove, and the back N region includes a second patterned groove; Wherein, the first patterned groove includes a first alloy layer formed by annealing a first seed layer, and the first seed layer includes nickel, vanadium and aluminum; The second patterned groove includes a second alloy layer formed by annealing a second seed layer, and the second seed layer includes nickel and vanadium.

2. The BC solar cell according to claim 1, characterized in that The width of the first patterned groove is 30 to 100 μm; the depth of the first patterned groove is 70 to 120 nm; Preferably, the thickness of the first seed layer is 10 to 100 nm; Preferably, the thickness of the first alloy layer is 1 to 50 nm; Preferably, the mass ratio of nickel, vanadium and aluminum in the first seed layer is (90-95):(2-5):(3-5); Preferably, the width of the second patterned groove is 30 to 100 μm; the depth of the second patterned groove is 70 to 120 nm; Preferably, the thickness of the second seed layer is 10 to 100 nm; Preferably, the thickness of the second alloy layer is 1 to 50 nm; Preferably, the mass ratio of nickel to vanadium in the second seed layer is (90-98):(2-10).

3. The BC solar cell according to claim 1, characterized in that The surfaces of the first alloy layer and the second alloy layer further include a copper layer and a tin layer stacked in sequence; Preferably, the thickness of the copper layer is 3 to 20 nm; Preferably, the thickness of the tin layer is 3 to 20 nm.

4. A method for preparing a BC solar cell according to any one of claims 1 to 3, characterized in that: The preparation method comprises: Forming a first patterned groove in the back P region of the BC cell silicon substrate to obtain a BC cell silicon substrate having the first patterned groove; After plating a first seed layer on the back side of the BC cell silicon substrate having the first patterned groove, the substrate is annealed to form a first alloy layer in the first patterned groove, and then the first seed layer is removed from the back side of the substrate other than the first patterned groove to obtain a BC cell silicon substrate having a first alloy layer in the P region; A second patterned groove is formed in the N region on the back side of the BC battery silicon substrate having the first alloy layer in the P region to obtain a BC battery silicon substrate having the second patterned groove; After plating a second seed layer on the back side of the BC battery silicon substrate having the second patterned groove and annealing treatment, a second alloy layer is formed in the second patterned groove, and then the second seed layer at the non-second patterned groove on the back side is removed to obtain a BC battery silicon substrate with a second alloy layer in the N region.

5. The method for preparing a BC solar cell according to claim 4, characterized in that: The first patterned groove and the second patterned groove are formed by laser grooving; Preferably, the power of the laser grooving is 2 to 6 W, the pulse frequency of the laser grooving is 500 to 2000 kHz, and the speed of the laser grooving is 25 to 50 mm / s.

6. The method for preparing a BC solar cell according to claim 4, wherein: The first seed layer and the second seed layer are formed by PVD coating; Preferably, the gas introduced into the PVD coating method includes any one of Ar, He, Kr or Xe, or a combination of at least two thereof; Preferably, the flow rate of the gas introduced during the PVD coating method is 100 to 10,000 sccm; Preferably, the process parameters of the PVD coating method include: vacuum degree of 1×10 -3 ~1×10 -2 Torr; the deposition temperature is 20-60°C; the deposition time is 5-30 min; the current is 4-12 A; and the target voltage is 300-600 V.

7. The method for preparing a BC solar cell according to claim 4, wherein: The annealing treatment includes vacuum annealing and / or atmospheric annealing; Preferably, the temperature of the annealing treatment is 200-400° C., and the time of the annealing treatment is 10-20 seconds.

8. The method for preparing a BC solar cell according to claim 4, characterized in that: The first seed layer and the second seed layer are removed by acid leaching; Preferably, the acid leaching comprises: immersing the BC battery silicon substrate after the alloy layer is formed in a seed layer removal working solution to remove the seed layer at the non-patterned groove on the back side; Preferably, the seed layer removal working solution comprises: 184-552 g / L sulfuric acid, 290-1450 g / L hydrogen peroxide, and the solvent is pure water; Preferably, the acid leaching temperature is 40-70° C., and the acid leaching time is 3-20 minutes.

9. The method for preparing a BC solar cell according to claim 4, wherein: The method for preparing the BC solar cell further includes a copper electroplating step: electroplating copper on the BC cell silicon substrate having the second alloy layer in the N region to form a copper layer on the surfaces of the first seed layer and the second seed layer to obtain a BC cell silicon substrate having a copper layer; Preferably, the copper electroplating specifically includes: immersing the BC battery silicon substrate having the second alloy layer in the N region in an activation solution for activation, then immersing it in a copper electroplating solution for copper electroplating to form a copper layer, and then washing and drying to obtain a BC battery silicon substrate having a copper layer; Preferably, the activation solution comprises: 0.5-3 g / L HF and 0.05-0.3 g / L noble metal salt, and the solvent is water; Preferably, the noble metal salt comprises PdCl2 and / or AuCl; Preferably, the activation temperature is 15 to 40° C.; the activation time is 10 to 60 seconds; Preferably, the copper electroplating solution comprises: 20-50 g / L H2SO4, 150-250 g / L CuSO4, and the solvent is water; Preferably, the current density of the copper electroplating is 10 to 50 A / dm 2 ; The temperature of the copper electroplating is 25 to 70°C; The time of the copper electroplating is 1 to 8 minutes.

10. The method for preparing a BC solar cell according to claim 9, wherein: The method for preparing the BC solar cell further comprises the step of chemical tin plating: chemically plating tin on the BC cell silicon substrate having the copper layer to form a tin layer on the surface of the copper layer at the back P region and the N region to obtain the BC solar cell; Preferably, the chemical tin plating specifically comprises: immersing the BC cell silicon substrate with the copper layer in a tin plating solution, performing chemical tin plating to form a tin layer, and then washing and drying to obtain the BC solar cell; Preferably, the tin plating solution comprises: 10-50 g / L SnSO4, 5-20 g / L methanesulfonic acid, 0.2-2 g / L tetrasodium iminodisuccinate, and the solvent is water; Preferably, the temperature of the chemical tin plating is 30-70° C.; and the time of the chemical tin plating is 0.5-5 min.

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