Back contact heterojunction solar cell and preparation method thereof

Abstract

The present invention relates to the field of semiconductor technology, in particular, to a back-contact heterojunction solar cell and a preparation method thereof, the preparation method comprising: adsorbing a mask with a grid line pattern groove on the back of a battery precursor, depositing a metal seed layer on the back of the battery precursor, and removing the mask; filling a first ink layer at a position other than the metal seed layer on the back of the battery precursor, exposing the grid line-shaped metal seed layer after the first curing; first electroplating the metal seed layer to form a linear first electrode grid line; filling a second ink layer at a position other than the main grid of the first electrode grid line on the back of the battery precursor, exposing the main grid after the second curing; second electroplating or printing the main grid to form a pier-shaped second electrode grid line; third electroplating the second electrode grid line to form a tin covering layer; removing the second ink layer and the first ink layer, and washing and drying. The method can reduce the probability of positive and negative short circuits and improve the yield of the product.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a back-contact heterojunction solar cell and a preparation method thereof. Background Art

[0002] Solar cells are optoelectronic semiconductors that use sunlight to generate electricity, also known as "solar chips" or "photovoltaic cells."

[0003] The preparation method of the back-contact heterojunction solar cell provided by the related technology includes: subjecting the silicon wafer to the back-contact heterojunction solar cell process to form a cell precursor for making the grid line; then printing silver paste fine grids on the cell precursor to form alternating positive electrode fine grids and negative electrode fine grids; then printing insulating ink at intervals on the positive and negative electrode fine grids, and then printing the silver paste main grid.

[0004] When the solar cells are serially soldered, since the positive grid lines and the negative grid lines need to be serially soldered with soldering ribbons, and the positive grid lines and the negative grid lines are alternately distributed in sequence, it is necessary to print insulating ink on the electrode grid lines of the other polarity under the soldering ribbons; however, during serial soldering, the tin on the surface of the soldering ribbon (i.e., tin-plated copper ribbon) will also melt, and the molten tin can easily pierce the insulating ink when it cools and solidifies, causing a short circuit between the positive and negative electrodes. Summary of the invention

[0005] The object of the present invention is to provide a back-contact heterojunction solar cell and a preparation method thereof, wherein the preparation method can reduce the probability of positive and negative electrode short circuits and improve the yield of the product.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides a method for preparing a back-contact heterojunction solar cell, comprising:

[0008] Adsorbing a mask with a grid line pattern groove on the back of the battery precursor, depositing a metal seed layer on the back of the battery precursor, and removing the mask;

[0009] Filling a first ink layer at a position other than the metal seed layer on the back of the battery precursor, and exposing the metal seed layer in a grid line shape after the first curing;

[0010] First electroplating the metal seed layer to form a linear first electrode grid line;

[0011] Filling a second ink layer at a position other than the main grid of the first electrode grid line on the back of the battery precursor, and exposing the position of the main grid after the second curing;

[0012] Performing a second electroplating or printing at the position of the main grid to form a second electrode grid line in the shape of a bridge pier;

[0013] forming a tin covering layer on the second electrode grid line by third electroplating;

[0014] The second ink layer and the first ink layer are removed, and then washed and dried.

[0015] In an optional embodiment, the deposition thickness of the metal seed layer is 10-1000 nm, the material of the metal seed layer includes at least one of silver, copper, nickel and aluminum, the thickness of the mask is 0.02-1 mm, and the width of the gate line pattern groove of the mask is 0.02-0.5 mm;

[0016] The material of the first electrode grid line includes at least one of copper, nickel, silver and aluminum;

[0017] The material of the second electrode grid line includes at least one of copper, nickel, silver and aluminum.

[0018] In an optional embodiment, the material of the metal seed layer is silver; and the material of the first electrode grid line and the second electrode grid line is copper.

[0019] In an optional embodiment, the first ink layer formed by filling has a linear groove, and the width of the linear groove is 0.02-0.5 mm, and the thickness of the first ink layer is 0.01-1 mm;

[0020] After filling the second ink layer, the exposed main grid is in a square or triangle shape; when the main grid is in a square shape, the width of the main grid is 0.45-0.55 mm and the length is 1.1-1.3 mm.

[0021] In an optional embodiment, the first electroplating is horizontal electroplating or vertical electroplating;

[0022] The current density of the first electroplating is 2-10ASD, and the electroplating time is 1-60min;

[0023] The height of the first electrode grid lines is 0.01-0.05 mm, and the height of the first electrode grid lines is less than or equal to the thickness of the first ink layer.

[0024] In an optional embodiment, the second electroplating is horizontal electroplating or vertical electroplating;

[0025] The current density of the second electroplating is 0.5-2ASD, and the electroplating time is 1-20min;

[0026] The height of the second electrode grid line is 0.05-1 mm.

[0027] In an optional embodiment, the height of the second electrode grid line is less than or equal to the height of the second ink layer, and the height of the second ink layer is greater than the height of the first ink layer.

[0028] In an optional embodiment, the third electroplating is horizontal electroplating or vertical electroplating;

[0029] The current density of the third electroplating is 0.1-1ASD, and the electroplating time is 1-10min;

[0030] The thickness of the tin covering layer is 0.005-0.01 mm.

[0031] In an optional embodiment, a welding strip is welded to the second electrode grid line to form a bridge-shaped structure;

[0032] The welding tape is copper tape.

[0033] In a second aspect, the present invention provides a solar cell, which is prepared by the method for preparing a back-contact heterojunction solar cell according to any one of the aforementioned embodiments.

[0034] The present invention has the following beneficial effects:

[0035] The method for preparing a back-contact heterojunction solar cell provided by an embodiment of the present invention forms a pier-shaped second electrode grid line on the first electrode grid line formed by electroplating, and electroplates a tin covering layer on the second electrode grid line, thereby reducing the probability that the other polarity electrode at the bottom of the welding strip contacts the corresponding welding strip when welding the welding strip, thereby eliminating the use of insulating ink on the other polarity electrode at the bottom of the welding strip, thereby reducing the probability of the welding strip piercing the insulating ink, reducing the risk of short circuit between the positive and negative electrodes, and improving the yield of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a schematic diagram of the structure of the battery precursor in the present invention;

[0038] Figure 2 It is a schematic diagram of the mask result in the present invention;

[0039] Figure 3 It is a schematic diagram of the structure in which a metal seed layer is deposited on a battery precursor in the present invention;

[0040] Figure 4 It is a schematic diagram of the structure filled with the first ink layer in the present invention;

[0041] Figure 5 It is a schematic diagram of the structure of forming the first electrode grid line by electroplating in the present invention;

[0042] Figure 6It is a schematic diagram of the structure filled with a second ink layer in the present invention;

[0043] Figure 7 It is a schematic diagram of the structure in which the main grid is exposed after the second ink layer is filled in the present invention;

[0044] Figure 8 The structure diagram of the second electrode grid line formed by electroplating in the present invention is shown in FIG. Figure 1 ;

[0045] Fig. 9 The structure diagram of the second electrode grid line formed by electroplating in the present invention is shown in FIG. Figure 2 ;

[0046] Fig.10 This is a diagram of EL detection results in Example 1 of the present invention;

[0047] Fig.11 This is a diagram of EL detection results in Example 2 of the present invention;

[0048] Fig.12 This is a diagram of EL detection results in Example 3 of the present invention;

[0049] Fig.13 This is a diagram of EL detection results in Example 4 of the present invention;

[0050] Fig.14 This is a diagram of EL detection results in Example 5 of the present invention;

[0051] Fig.15 This is a diagram of EL detection results in Example 6 of the present invention;

[0052] Fig.16 This is a diagram of EL detection results in Example 7 of the present invention;

[0053] Fig.17 This is a diagram of EL detection results in Example 8 of the present invention;

[0054] Fig.18 This is a diagram of EL detection results in Example 9 of the present invention;

[0055] Fig.19 This is a diagram of EL detection results in Example 10 of the present invention;

[0056] Fig. 20 This is a diagram of EL detection results in Example 11 of the present invention;

[0057] Fig.21 This is a diagram of EL detection results in Example 12 of the present invention;

[0058] Fig. 22 This is a diagram of EL detection results in Example 13 of the present invention;

[0059] Fig.23This is a diagram of EL detection results in Example 14 of the present invention;

[0060] Fig.24 This is a diagram of the EL test results in Comparative Example 1 of the present invention;

[0061] Fig.25 This is a diagram of the EL detection results in Comparative Example 2 of the present invention.

[0062] Icon: 100 - battery precursor; 110 - mask; 111 - grid line pattern groove; 120 - metal seed layer; 130 - first ink layer; 140 - first electrode grid line; 141 - main grid; 150 - second ink layer; 160 - second electrode grid line. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0064] The positive and negative grid lines of the back-contact heterojunction solar cell are both on the back, and the positive and negative grid lines are alternately distributed in sequence. When the related technology uses a soldering ribbon to solder the positive and negative grid lines separately, it is necessary to print insulating ink on the electrode grid line of the other polarity below the soldering ribbon. For example, when the positive electrode is soldered with a soldering ribbon, it is necessary to print insulating ink on the negative grid line below the soldering ribbon. Moreover, the soldering ribbons of the related technology are all tin-plated copper ribbons. The surface of the tin-plated copper ribbon has a layer of tin and copper inside. During welding, the tin melts and contacts the silver grid, and then solidifies and connects. Since the tin on the surface of the tin-plated copper ribbon will melt, the molten tin will contact the electrode grid line of the other polarity below the soldering ribbon. The soldering ribbon can easily pierce the insulating ink, causing a short circuit between the positive and negative electrodes.

[0065] Please combine Figure 1-Figure 9In order to improve the above problems, the present invention provides a method for preparing a back-contact heterojunction solar cell, comprising: adsorbing a mask 110 with a grid line pattern groove 111 on the back side of a cell precursor 100, depositing a metal seed layer 120 on the back side of the cell precursor 100, and removing the mask 110; filling a first ink layer 130 at a position other than the metal seed layer 120 on the back side of the cell precursor 100, and exposing the metal seed layer 120 in a grid line shape after a first curing; first electroplating the metal seed layer 120 to form a linear first electrode grid line 140; filling a second ink layer 150 at a position other than the main grid 141 of the first electrode grid line 140 on the back side of the cell precursor 100, and exposing the position of the main grid 141 after a second curing; performing a second electroplating or printing at the position of the main grid 141 to form a pier-shaped second electrode grid line 160; performing a third electroplating on the second electrode grid line 160 to form a tin covering layer; removing the second ink layer 150 and the first ink layer 130, and washing and drying.

[0066] The preparation method of the present invention forms a pier-shaped second electrode grid line 160 by electroplating again on the first electrode grid line 140 formed by electroplating, and electroplates a tin covering layer on the second electrode grid line 160, thereby reducing the probability that the other polarity electrode at the bottom of the welding strip contacts the corresponding welding strip when welding the welding strip, thereby eliminating the use of insulating ink on the other polarity electrode at the bottom of the welding strip, thereby reducing the probability of the welding strip piercing the insulating ink, reducing the risk of short circuit between the positive and negative electrodes, and improving the yield of the product.

[0067] Moreover, by forming the first electrode grid line 140 and the second electrode grid line 160 by electroplating, a densely crystallized metal grid line can be formed, which has a small resistance and a higher conductivity than printed silver paste (printed silver paste contains non-conductive organic matter), and can improve the electrical properties of the solar cell such as FF (fill factor) and Eff (conversion efficiency).

[0068] It should be noted that the preparation method of the cell precursor 100 is similar to the related technology, for example: the cell precursor 100 for the gate line to be manufactured is formed after the silicon wafer undergoes a back contact heterojunction solar cell process.

[0069] Optionally, the mask 110 is a metal plate mask, and its material includes one of a copper plate, an aluminum plate, a stainless steel plate, and an aluminum alloy plate; the thickness of the mask 110 is 0.02-1mm, for example: 0.02mm, 0.05mm, 0.1mm, 0.15mm, 0.2mm, 0.5mm, 0.7mm, 1.0mm, etc.

[0070] Optionally, the gate line pattern grooves 111 on the mask 110 can be obtained by laser grooving, and the groove width is 0.02-0.5 mm, for example: 0.02 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.5 mm, etc., which is not specifically limited here.

[0071] Optionally, the deposition thickness of the metal seed layer 120 is 10-1000 nm, for example, 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc., which is not specifically limited here.

[0072] Optionally, the material of the metal seed layer 120 includes at least one of silver, copper, nickel and aluminum; the material of the first electrode grid line 140 includes at least one of copper, nickel, silver and aluminum; the material of the second electrode grid line 160 includes at least one of copper, nickel, silver and aluminum.

[0073] In a preferred embodiment, the metal seed layer 120 is made of silver, and the first electrode grid lines 140 and the second electrode grid lines 160 are made of copper. This not only reduces the use of silver and reduces costs, but also ensures good electrical properties such as FF (fill factor) and Eff (conversion efficiency).

[0074] It should be noted that the method of forming the second electrode grid lines 160 by printing will lead to an increase in the amount of silver paste used and an increase in cost compared to the second electroplating method.

[0075] Optionally, the metal seed layer 120 is deposited by a PVD (Physical Vapor Deposition) sputtering method, a PVD evaporation method or a PVD ion plating method.

[0076] Optionally, the first ink layer 130 is filled by a screen printing method, and the first ink layer 130 formed by filling has a straight line groove, and the width of the straight line groove is 0.02-0.5mm (for example: 0.02mm, 0.05mm, 0.1mm, 0.12mm, 0.15mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, etc., not specifically limited here), and the thickness of the first ink layer 130 is 0.01-1mm (for example: 0.01mm, 0.02mm, 0.05mm, 0.1mm, 0.12mm, 0.15mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.8mm, 1mm, etc., not specifically limited here).

[0077] Optionally, the ink used to fill the first ink layer 130 is one of photocurable ink, thermal curable ink and UV curable ink, and the ink curing method is photocurable, thermal curable or UV curable corresponding to the ink used.

[0078] Optionally, after filling the second ink layer 150, the exposed position of the main grid 141 is square or triangular, that is, when the second ink layer 150 is filled on the first electrode grid line 140 except the position of the main grid 141, the first ink layer 130 is covered at the same time to form the main grid 141 pores to be plated, which can be square or triangular.

[0079] In a preferred embodiment, the main grid 141 is square, the width of the main grid 141 is 0.45-0.55mm (for example: 0.45mm, 0.5mm, 0.55mm, etc., not specifically limited here), and the length is 1.1-1.3mm (for example: 1.1mm, 1.2mm, 1.3mm, etc., not specifically limited here); in this way, subsequent welding can be facilitated and the stability of welding can be ensured.

[0080] It should be noted that the filling method, ink selection, and corresponding curing method of the second ink layer 150 may all refer to the first ink layer 130 , and will not be described in detail herein.

[0081] Optionally, the first electroplating is horizontal electroplating or vertical electroplating; the current density of the first electroplating is 2-10ASD (for example: 2ASD, 3ASD, 4ASD, 5ASD, 6ASD, 7ASD, 8ASD, 9ASD, 10ASD, etc., which are not specifically limited here), and the electroplating time is 1-60min (for example: 1min, 5min, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc., which are not specifically limited here). The purpose of the first electroplating is to form the first electrode grid line 140 to conduct current. The use of high current density for electroplating can quickly grow the metal grid line; and, since the area to be plated during the first electroplating is large, the use of high current density for electroplating the first electrode grid line 140 can ensure the efficiency and reliability of the electroplating; if a low-density current is used to grow the first electrode grid line 140, it will take longer and be inefficient.

[0082] It should be noted that the density of the metal grid lines grown with high current density is relatively low, and the resistance of the first electrode grid lines 140 is relatively large. However, when the solar cell is in use, the first electrode grid lines 140 function to conduct current, and the current it conducts is small, so the corresponding electrical loss (calculated as I 2R, I is current, and R is resistance) is small, so a high current density is used to electroplate the first electrode grid line 140, which improves efficiency without reducing the electrical performance of the solar cell.

[0083] Furthermore, the height of the first electrode grid line 140 is 0.01-0.05 mm (for example: 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, etc., which are not specifically limited here), and the height of the first electrode grid line 140 is less than or equal to the thickness of the first ink layer 130. During electroplating, the metal will grow in all directions. The function of the first ink layer 130 is to limit the growth position of the metal so that the metal can only grow in the grooves of the first ink layer 130. After growing beyond the grooves of the first ink layer 130, it will grow in all directions on the surface of the first ink layer 130, so that the metal covers the first ink layer 130, forming a sandwich state, which makes it difficult to remove the film in the subsequent process. Therefore, making the height of the first electrode grid line 140 less than or equal to the height of the first ink layer 130 can improve the problem of difficulty in stripping due to the growth of metal on the surface of the first ink layer 130.

[0084] Optionally, the second electroplating is horizontal electroplating or vertical electroplating; the current density of the second electroplating is 0.5-2ASD (for example: 0.5ASD, 0.7ASD, 1ASD, 1.2ASD, 1.5ASD, 1.8ASD, 2ASD, etc., not specifically limited here), and the electroplating time is 1-20min (for example: 1min, 5min, 7min, 10min, 12min, 15min, 18min, 20min, etc., not specifically limited here). The purpose of the second electroplating is to form a bridge-shaped second electrode grid line 160 to collect current. Using a small current density for electroplating growth can grow a denser metal grid line. The dense metal has a small internal resistance, which can reduce losses when collecting current, thereby ensuring the electrical performance of the prepared solar cell.

[0085] Furthermore, the height of the second electrode grid line 160 is 0.05-1 mm, for example: 0.05 mm, 0.07 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, etc., which are not specifically limited here. It should be noted that, generally speaking, the maximum thickness of the tin layer on the surface of the tin-plated copper strip as the welding strip is 0.04 mm. Therefore, setting the height of the second electrode grid line 160 to at least 0.05 mm can improve the problem of the tin that is melted and then cooled and solidified contacting the electrode of the other polarity below when the tin-plated copper strip is serially soldered, thereby reducing the probability of short circuit after serial soldering.

[0086] Furthermore, the height of the second electrode grid line 160 is less than or equal to the height of the second ink layer 150, and the height of the second ink layer 150 is greater than the height of the first ink layer 130. The height of the second ink layer 150 needs to be greater than that of the first ink layer 130 because the first electrode grid line 140 prepared corresponding to the first ink layer 130 mainly plays the role of transmitting current, while the bridge-shaped second electrode grid line 160 plays the role of collecting current to the welding strip bus bar, and the height of the second electrode grid line 160 should be relatively large, so the second ink layer 150 required for the preparation of the second electrode grid line 160 is configured to be thicker; the height of the second electrode grid line 160 is less than or equal to the height (thickness) of the second ink layer 150, which can avoid the problem of metal electroplating on the surface of the second ink layer 150, resulting in difficulty in stripping.

[0087] Optionally, the third electroplating is horizontal electroplating or vertical electroplating; the thickness of the tin covering layer is 0.005-0.01 mm (for example: 0.005 mm, 0.006 mm, 0.007 mm, 0.008 mm, 0.009 mm, 0.01 mm, etc., not specifically limited herein); the current density of the third electroplating is 0.1-1 ASD (for example: 0.1 ASD, 0.2 ASD, 0.3 ASD, 0.4 ASD, 0.5 ASD, 0.6 ASD, 0.7 ASD, 0.8 ASD, 0.9 ASD, 1 ASD, etc., not specifically limited herein), and the electroplating time is 1-10 min (for example: 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc., not specifically limited herein). The tin covering layer only needs to cover the second electrode grid line 160, and the electroplating coverage area is small and the thickness is moderate, so a smaller current density can be used for electroplating; moreover, the electroplating forms a tin covering layer of moderate thickness, which is conducive to welding and can help improve the risk of short circuit.

[0088] Optionally, a welding strip is welded on the second electrode grid line 160 to form a bridge-like structure; the welding strip is a copper strip. The second electrode grid line 160 is directly electroplated to form a tin covering layer, and a copper strip is used as the welding strip, which can ensure that the welding strip will not melt and contact the grid line of another polarity below it during string welding, effectively improving the risk of short circuit caused by welding.

[0089] It should be noted that when the bridge-pier-shaped second electrode grid line 160 of the present invention is serially welded, the welding strip forms a bridge-like structure, and the tension between the grid line column and the welding strip is sufficient to resist the lamination pressure so that the bridge-like structure does not collapse. Therefore, there is a gap between the welding strip and the second electrode grid line 160 thereunder, and there is no need to print insulating ink on the second electrode grid line 160 of the other polarity thereunder, so as to prevent the welding strip from easily piercing the insulating ink and causing a short circuit between the positive and negative poles.

[0090] Optionally, the reagent used to remove the first ink layer 130 and the second ink layer 150 may be a NaOH solution, a KOH solution or an organic stripping solution.

[0091] The present invention is further described in detail below in conjunction with embodiments.

[0092] Example 1

[0093] Preparation of solar cells:

[0094] 1. Adsorb a mask with a grid pattern groove on the back of the battery precursor, deposit a metal seed layer on the back of the battery precursor, and remove the mask.

[0095] The mask is a copper plate with a thickness of 1 mm, and the width of the gate line pattern groove is 0.1 mm; the thickness of the metal seed layer is 1000 nm, and the deposition material is silver.

[0096] 2. Filling the first ink layer at the position outside the metal seed layer on the back of the battery precursor, and exposing the gate line-shaped metal seed layer after the first curing.

[0097] The thickness of the first ink layer is 1 mm, and the width of the line groove formed by the first ink layer is 0.1 mm.

[0098] 3. Perform a first electroplating on the metal seed layer to form a linear first electrode grid line.

[0099] The current density of the first electroplating is 10 ASD, the time is 1 min, the height of the first electrode grid line is 0.05 mm, and the electroplating material of the first electrode grid line is copper.

[0100] 4. Fill the back of the battery precursor with a second ink layer except for the main grid of the first electrode grid line, and expose the main grid after the second curing.

[0101] The thickness of the second ink layer is 1.5 mm, and the exposed main grid is square with a width of 0.5 mm and a length of 1.2 mm.

[0102] 5. Perform a second electroplating on the main grid to form a bridge-shaped second electrode grid line.

[0103] The current density of the second electroplating is 2ASD, and the time is 5 minutes; the thickness of the second electrode grid line is 1 mm, and the electroplating material of the second electrode grid line is copper.

[0104] 6. A third electroplating process is performed on the second electrode grid line to form a tin covering layer.

[0105] The current density of the third electroplating is 1 ASD, the time is 3 min, and the thickness of the tin covering layer is 0.01 mm.

[0106] 7. Remove the second ink layer and the first ink layer, clean and dry; perform serial welding, and use a copper strip as the welding strip.

[0107] 8. Test the battery electrical performance (short circuit current Isc (mA), open circuit voltage Voc (V), fill factor FF (%), conversion efficiency Eff (%)), the results are shown in Table 1; the battery string EL (Electroluminescence) test results after string welding are as follows Fig.10 .

[0108] Table 1

[0109]

[0110] Example 2

[0111] 1. Adsorb a mask with a grid pattern groove on the back of the battery precursor, deposit a metal seed layer on the back of the battery precursor, and remove the mask.

[0112] The mask is an aluminum plate with a thickness of 0.02 mm, and the width of the gate line pattern groove is 0.3 mm; the thickness of the metal seed layer is 10 nm, and the deposition material is silver.

[0113] 2. Filling the first ink layer at the position outside the metal seed layer on the back of the battery precursor, and exposing the gate line-shaped metal seed layer after the first curing.

[0114] The thickness of the first ink layer is 0.01 mm, and the width of the line groove formed by the first ink layer is 0.3 mm.

[0115] 3. Perform a first electroplating on the metal seed layer to form a linear first electrode grid line.

[0116] The current density of the first electroplating is 2 ASD, the time is 30 min, the height of the first electrode grid line is 0.01 mm, and the electroplating material of the first electrode grid line is copper.

[0117] 4. Fill the back of the battery precursor with a second ink layer except for the main grid of the first electrode grid line, and expose the main grid after the second curing.

[0118] The thickness of the second ink layer is 0.05 mm, and the exposed main grid is square with a width of 0.45 mm and a length of 1.3 mm.

[0119] 5. Perform a second electroplating on the main grid to form a bridge-shaped second electrode grid line.

[0120] The current density of the second electroplating is 0.5 ASD, and the time is 20 min. The thickness of the second electrode grid line is 0.05 mm, and the electroplating material of the second electrode grid line is copper.

[0121] 6. A third electroplating process is performed on the second electrode grid line to form a tin covering layer.

[0122] The current density of the third electroplating is 0.1 ASD, the time is 10 min, and the thickness of the tin covering layer is 0.005 mm.

[0123] 7. Remove the second ink layer and the first ink layer, clean and dry; perform serial welding, and use a copper strip as the welding strip.

[0124] 8. Test the battery electrical performance, the results are shown in Table 2; the battery string EL test results after string welding are as follows Fig.11 .

[0125] Table 2

[0126]

[0127] Example 3

[0128] 1. Adsorb a mask with a grid pattern groove on the back of the battery precursor, deposit a metal seed layer on the back of the battery precursor, and remove the mask.

[0129] The mask is a copper plate with a thickness of 0.5 mm, and the width of the gate line pattern groove is 0.5 mm; the thickness of the metal seed layer is 500 nm, and the deposition material is silver.

[0130] 2. Filling the first ink layer at the position outside the metal seed layer on the back of the battery precursor, and exposing the gate line-shaped metal seed layer after the first curing.

[0131] The thickness of the first ink layer is 0.5 mm, and the width of the line groove formed by the first ink layer is 0.5 mm.

[0132] 3. Perform a first electroplating on the metal seed layer to form a linear first electrode grid line.

[0133] The current density of the first electroplating is 5 ASD, the time is 30 min, the height of the first electrode grid line is 0.01 mm, and the electroplating material of the first electrode grid line is copper.

[0134] 4. Fill the back of the battery precursor with a second ink layer except for the main grid of the first electrode grid line, and expose the main grid after the second curing.

[0135] The thickness of the second ink layer is 1 mm, and the exposed main grid is square with a width of 0.45 mm and a length of 1.1 mm.

[0136] 5. Perform a second electroplating on the main grid to form a bridge-shaped second electrode grid line.

[0137] The current density of the second electroplating is 1 ASD, and the time is 10 min. The thickness of the second electrode grid line is 0.5 mm, and the electroplating material of the second electrode grid line is copper.

[0138] 6. A third electroplating process is performed on the second electrode grid line to form a tin covering layer.

[0139] The current density of the third electroplating was 0.5 ASD, and the time was 5 min; the thickness of the tin covering layer was 0.008 mm.

[0140] 7. Remove the second ink layer and the first ink layer, clean and dry; perform serial welding, and use a copper strip as the welding strip.

[0141] 8. Test the battery electrical performance, the results are shown in Table 3; the battery string EL test results after string welding are as follows Fig.12 .

[0142] Table 3

[0143]

[0144] Example 4

[0145] The difference between Example 4 and Example 1 is that the height of the first electrode grid line and the second electrode grid line are the same, both 0.05 mm; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 4; the EL test results of the battery string after string welding are shown in Table 4. Fig.13 .

[0146] Table 4

[0147]

[0148] Example 5

[0149] The difference between Example 5 and Example 1 is that the height of the first electrode grid line is 0.07 mm; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 5; the EL test results of the battery string after string welding are shown in Fig.14 .

[0150] Table 5

[0151]

[0152] Example 6

[0153] The difference between Example 6 and Example 1 is that the height of the first electrode grid line is 0.005 mm; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 6; the EL test results of the battery string after string welding are shown in Table 6. Fig.15 .

[0154] Table 6

[0155]

[0156] Example 7

[0157] The difference between Example 7 and Example 1 is that the height of the second electrode grid line is 0.02 mm, and the second electrode grid line is formed by printing; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 7; the EL test results of the battery string after string welding are shown in Table 7. Fig.16 .

[0158] Table 7

[0159]

[0160] Example 8

[0161] The difference between Example 8 and Example 1 is that the height of the second electrode grid line is 1.2 mm; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 8. The EL test results of the battery string after string welding are shown in Table 8. Fig.17 .

[0162] Table 8

[0163]

[0164] Example 9

[0165] The difference between Example 9 and Example 1 is that the current density of the second electroplating is 3ASD; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 9; the EL test results of the battery string after string welding are shown in Fig.18 .

[0166] Table 9

[0167]

[0168] Example 10

[0169] The difference between Example 10 and Example 1 is that the current density of the second electroplating is 0.2ASD; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 10; the EL test results of the battery string after string welding are shown in Fig.19 .

[0170] Table 10

[0171]

[0172] Embodiment 11

[0173] The difference between Example 11 and Example 1 is that the current density of the first electroplating is 12ASD; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 11. The EL test results of the battery string after string welding are shown in Fig. 20 .

[0174] Table 11

[0175]

[0176] Example 12

[0177] The difference between Example 12 and Example 1 is that the material of the metal seed layer is copper, and the electroplating material of the first electrode grid line and the second electrode grid line is silver; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 12. The EL test results of the battery string after string welding are shown in Fig.21 .

[0178] Table 12

[0179]

[0180] Example 13

[0181] The difference between Example 13 and Example 1 is that the height of the first electrode grid line is 0.07 mm, the current density of the first electroplating is 12 ASD, the height of the second electrode grid line is 0.02 mm, and the current density of the second electroplating is 0.2 ASD; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 13. The EL test results of the battery string after string welding are shown in Fig. 22 .

[0182] Table 13

[0183]

[0184] Embodiment 14

[0185] The difference between Example 14 and Example 1 is that the height of the first electrode grid line is 0.005 mm, the height of the second electrode grid line is 1.2 mm, and the current density of the second electroplating is 3ASD; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 14. The EL test results of the battery string after string welding are shown in Fig.23 .

[0186] Table 14

[0187]

[0188] Comparative Example 1

[0189] The difference between Comparative Example 1 and Example 1 is that after forming the first electrode grid line, the second electrode grid line is not prepared, the ink layer is directly removed, cleaned and dried, and insulating ink is printed on the first electrode grid line, and then soldered with tinned copper strip; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 15; the EL test results of the battery string after soldering are shown in Fig.24 .

[0190] Table 15

[0191]

[0192] Comparative Example 2

[0193] The difference between Comparative Example 2 and Example 1 is that there is no electroplated tin covering layer on the second electrode grid line, and tinned copper strip is used for string welding; other process parameters refer to Example 1. The battery electrical performance is tested, and the results are shown in Table 16. The EL test results of the battery string after string welding are shown in Fig.25 .

[0194] Table 16

[0195]

[0196] According to the test results of the above-mentioned embodiments and comparative examples, the solar cell prepared by the preparation method of the present invention not only has good electrical performance, but also can effectively reduce the probability of short circuit.

[0197] In summary, the back-contact heterojunction solar cell prepared by the preparation method of the present invention can reduce the probability of positive and negative electrode short circuits and improve the yield of the product.

[0198] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a back contact heterojunction solar cell, characterized in that: include: Adsorbing a mask with a grid line pattern groove on the back of a battery precursor, depositing a metal seed layer on the back of the battery precursor, and removing the mask; Filling a first ink layer at a position other than the metal seed layer on the back side of the battery precursor, and exposing the metal seed layer in a grid line shape after first curing; Performing a first electroplating on the metal seed layer to form a linear first electrode grid line; Filling a second ink layer at a position other than the main grid of the first electrode grid line on the back side of the battery precursor, and exposing the position of the main grid after the second curing; Performing a second electroplating at the position of the main grid to form a bridge-shaped second electrode grid line; forming a tin covering layer on the second electrode grid line by third electroplating; removing the second ink layer and the first ink layer, and washing and drying; The first electroplating is horizontal electroplating or vertical electroplating; The current density of the first electroplating is 2-10ASD, and the electroplating time is 1-60min; The height of the first electrode grid line is 0.01-0.05 mm, and the height of the first electrode grid line is less than or equal to the thickness of the first ink layer; The second electroplating is horizontal electroplating or vertical electroplating; The current density of the second electroplating is 0.5-2ASD, and the electroplating time is 1-20min; The height of the second electrode grid lines is 0.05-1 mm.

2. The method for preparing a back contact heterojunction solar cell according to claim 1, characterized in that: The deposition thickness of the metal seed layer is 10-1000nm, the material of the metal seed layer includes at least one of silver, copper, nickel and aluminum, the thickness of the mask is 0.02-1mm, and the width of the gate line pattern groove of the mask is 0.02-0.5mm; The material of the first electrode grid line includes at least one of copper, nickel, silver and aluminum; The material of the second electrode grid line includes at least one of copper, nickel, silver and aluminum.

3. The method for preparing a back contact heterojunction solar cell according to claim 2, characterized in that: The material of the metal seed layer is silver; the material of the first electrode grid line and the second electrode grid line is copper.

4. The method for preparing a back-contact heterojunction solar cell according to claim 1, characterized in that: The first ink layer formed by filling has a linear groove, and the width of the linear groove is 0.02-0.5 mm, and the thickness of the first ink layer is 0.01-1 mm; After filling the second ink layer, the exposed position of the main grid is a square or a triangle; when the main grid is a square, the width of the main grid is 0.45-0.55 mm and the length is 1.1-1.3 mm.

5. The method for preparing a back-contact heterojunction solar cell according to claim 1, characterized in that: The height of the second electrode grid line is less than or equal to the height of the second ink layer, and the height of the second ink layer is greater than the height of the first ink layer.

6. The method for preparing a back-contact heterojunction solar cell according to claim 1, characterized in that: The third electroplating is horizontal electroplating or vertical electroplating; The current density of the third electroplating is 0.1-1ASD, and the electroplating time is 1-10min; The thickness of the tin covering layer is 0.005-0.01 mm.

7. The method for preparing a back contact heterojunction solar cell according to claim 1, characterized in that: Welding a welding strip to the second electrode grid line to form a bridge structure; The welding strip is a copper strip.

8. A back contact heterojunction solar cell, characterized in that: It is prepared by the method for preparing a back-contact heterojunction solar cell according to any one of claims 1 to 7.

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