Heterojunction solar cell and preparation method thereof

Abstract

The invention discloses a heterojunction solar cell and a preparation method thereof. The heterojunction solar cell may include: a cell substrate; the transparent conducting layer is arranged on the main surface of the battery substrate; the metal seed layers are arranged on the transparent conductive layer at intervals, and the metal seed layers comprise stacked metal particles; the first dielectric layer is arranged on the transparent conductive layer and is positioned in an area outside the metal seed layer; the second dielectric layer is discontinuously distributed on the surface of the metal seed layer, so that the metal seed layer comprises a skip plating region which is not covered by the second dielectric layer; the fine grain layer is laminated on the second dielectric layer and the skip plating region; and an additional conductive layer laminated on the fine grain layer. According to the invention, tedious processes such as exposure and development can be prevented from being used in preparation of the heterojunction solar cell, the risk of yield loss caused by poor development and exposure processes can be avoided, the production cost is reduced, the reliability of the metal electrode arranged in the heterojunction solar cell can be improved, and the performance of the heterojunction solar cell can be improved.

Description

Technical Field

[0001] The invention relates to a heterojunction solar cell and a preparation method thereof. Background Art

[0002] Currently, the metal grid lines of heterojunction solar cells are primarily produced through screen printing. This involves depositing metal electrodes on the formed indium tin oxide (ITO) during the heterojunction solar cell fabrication process. Currently, screen printing of silver paste / silver-coated copper paste is the primary method for producing metal electrodes for heterojunction solar cells. Due to the relatively high costs of both ITO and silver paste, electroplating has been explored to reduce the cost of heterojunction solar cells.

[0003] Currently, electroplating is used to prepare metal electrodes for heterojunction solar cells. Either a metal seed layer is combined with a developer, a development process, and an exposure process to form a mask in the area outside the metal seed layer, or ink is used to make a mask for the area outside the metal seed layer so that the electroplating process only occurs in the metal seed layer.

[0004] The existing conventional exposure, development and electroplating method for preparing metal electrodes for heterojunction solar cells is not only complex and requires relatively high process precision, but also easily causes foreign matter (developer or ink) residue after the introduction of developer or ink, which has an adverse effect on the heterojunction solar cell. Summary of the Invention

[0005] In view of this, the present invention provides a heterojunction solar cell and a preparation method thereof. The preparation process of the heterojunction solar cell can avoid the use of cumbersome processes such as exposure and development. It can not only avoid the influence of residual foreign matter (developer or ink, etc.) in the exposure and development process, and avoid the risk of yield loss due to poor development and exposure process, but also reduce production costs, which is beneficial to improving the reliability of the metal electrodes set in the heterojunction solar cell, and is beneficial to improving the performance and yield of the heterojunction solar cell.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a heterojunction solar cell, comprising:

[0008] Battery matrix;

[0009] A transparent conductive layer provided on the main surface of the battery substrate;

[0010] a metal seed layer disposed on the transparent conductive layer at intervals, wherein the metal seed layer comprises accumulated metal particles;

[0011] a first dielectric layer, the first dielectric layer being disposed on the transparent conductive layer and located in a region outside the metal seed layer;

[0012] a second dielectric layer, wherein the second dielectric layer is discontinuously disposed on the surface of the metal seed layer, so that the metal seed layer includes a plating skip area not covered by the second dielectric layer;

[0013] a fine-grained layer stacked on the second dielectric layer and the plating leakage area;

[0014] and an additional conductive layer stacked on the fine-grained layer.

[0015] In a second aspect, an embodiment of the present invention provides a method for preparing a heterojunction solar cell provided in an embodiment of the first aspect, comprising:

[0016] Step 1: preparing a transparent conductive layer on a battery substrate;

[0017] Step 2: preparing a metal seed layer containing accumulated metal particles on the transparent conductive layer;

[0018] Step 3: forming a first dielectric layer in the transparent conductive layer outside the metal seed layer, and forming a discontinuously distributed second dielectric layer on the metal seed layer, so that the metal seed layer includes a plating-missing area not covered by the second dielectric layer;

[0019] Step 4: forming a fine-grained layer on the metal seed layer;

[0020] Step 5: forming an additional conductive layer on the fine-grained layer.

[0021] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects:

[0022] The heterojunction solar cell provided by the embodiment of the present invention cooperates with the stacked metal particles contained in the metal seed layer, the first dielectric layer set in the area outside the metal seed layer, and the second dielectric layer scattered on the surface of some metal particles, so that the transparent conductive layer can be completely covered by the first dielectric layer. The metal seed layer has a leakage plating area, which is then stacked on the second dielectric layer and the leakage plating area through the fine crystal layer, and can form a stable contact between the fine crystal layer and the transparent conductive layer through the leakage plating area, so that the additional conductive layer stacked on the fine crystal layer can form a stable contact and electrical connection with the metal seed layer through the fine crystal layer. There is no need to introduce a mask, and the use of cumbersome processes such as exposure and development can be avoided. It can also avoid the risk of introducing foreign matter into the heterojunction solar cell due to exposure and development, and the risk of yield loss due to poor exposure and development process.

[0023] In addition, the metal electrode is composed of a metal seed layer, a leakage-plating area, a fine-grained layer and an additional conductive layer, and the fine-grained layer can ensure a stable electrical connection between the metal seed layer and the additional conductive layer, thereby effectively improving the reliability of the metal electrode of the heterojunction solar cell and benefiting to improving the performance and yield of the heterojunction solar cell.

[0024] In addition, by introducing a fine crystal layer, the gaps between the metal particles contained in the metal seed layer can be filled, and the leakage plating area and the additional conductive layer can be better electrically connected, thereby increasing the indirect contact area between the additional conductive layer and the metal seed layer, and effectively reducing the line resistance and contact resistance of the metal electrode of the heterojunction solar cell, thereby improving the series resistance and photoelectric conversion efficiency of the heterojunction solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of a partial cross-sectional structure of a heterojunction solar cell provided according to an embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of a partial cross-sectional structure of a first structure of a heterojunction solar cell provided according to an embodiment of the present invention;

[0027] Figure 3 is a partial cross-sectional structural schematic diagram of a second structure of a heterojunction solar cell provided according to an embodiment of the present invention;

[0028] Figure 4 1 is a schematic diagram of the main process of a method for preparing a heterojunction solar cell according to an embodiment of the present invention;

[0029] Figure 5 is a schematic diagram of the structural changes of the metal electrode corresponding to the preparation steps according to an embodiment of the present invention;

[0030] Figure 6 1 is an SEM image of a metal seed layer provided according to an embodiment of the present invention.

[0031] Reference numerals:

[0032] 10-battery substrate; 11-silicon wafer, 12-front intrinsic amorphous silicon layer; 13-front doped amorphous silicon layer; 20-transparent conductive layer; 30-metal seed layer; 41-first dielectric layer; 42-second dielectric layer; 50-leak plating area; 60-fine crystal layer; 70-additional conductive layer; 80-conductive protective layer; 91-back intrinsic amorphous silicon layer; 92-back doped amorphous silicon layer; 93-back passivation layer; 94-back metal electrode. DETAILED DESCRIPTION

[0033] Compared to other types of solar cells (such as TOPCon cells), the high cost of heterojunction solar cells is primarily due to the relatively expensive and thick indium tin oxide (ITO) layer required (typically, the thickness of the ITO layer on a single side of a heterojunction solar cell is approximately 100nm, and the thickness of the ITO layer on both sides of a heterojunction solar cell is approximately 200nm), as well as the high consumption of low-temperature silver paste (which is more expensive than high-temperature silver paste and other metal pastes). Currently, to reduce the cost of heterojunction solar cells, a process is used to electroplate lower-cost copper onto a printed metal seed layer. During the electroplating process, copper inevitably forms on the ITO layer outside the metal seed layer. Currently, to prevent the formation of electroplated copper on the ITO layer outside the metal seed layer, a developer mask or other type of mask is prepared on the ITO layer outside the metal seed layer through a combination of developer, development process, and exposure process. This method of introducing a mask inevitably leaves mask residue during the mask removal process, which can affect the performance of heterojunction solar cells, such as photoelectric conversion efficiency, stability, reliability, and service life. In addition, the method of setting a mask with a developer also has problems such as complex process steps, high cost, and low production yield.

[0034] Further research found that in the existing electroplating process, copper is directly electroplated on the metal seed layer. Since the metal particles contained in the metal seed layer have a relatively large particle size (generally above 2μm), the copper particles formed by the currently used acid copper plating process are also relatively large (generally above 2μm). There will be a large number of stacking gaps between the metal particles contained in the metal seed layer and the copper particles formed by the electroplated copper, which will lead to higher line resistance of the metal electrode, poor tensile strength, and poor electrical stability and reliability of the metal electrode.

[0035] In order to solve the above problems existing in the existing heterojunction solar cells, an embodiment of the present invention provides a heterojunction solar cell with a novel structure and a preparation method thereof.

[0036] The embodiment of the present invention relates to a structure being arranged on another structure, which means that the structure is located on the side of the other structure away from the battery substrate 10, and does not specifically mean that the structure is located above the other structure. For example, for the metal seed layer 30 being arranged on the transparent conductive layer 20, if the metal seed layer 30 and the transparent conductive layer 20 are located on the back of the heterojunction solar cell, then during the use of the heterojunction solar cell, the metal seed layer 30 is located below the transparent conductive layer 20; if the metal seed layer 30 and the transparent conductive layer 20 are located on the front of the heterojunction solar cell, then during the use of the heterojunction solar cell, the metal seed layer 30 is located above the transparent conductive layer 20. In addition, when a structure is arranged on another structure, the one structure may be in direct contact or indirect contact with the other structure. Indirect contact between one structure and another structure generally means that other structures may exist between the one structure and the other structure.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. For example, the "first" and "second" in the first dielectric layer 41 and the second dielectric layer 42 involved in the embodiment of the present invention are used to distinguish the positions of the dielectric layers and the differences in the structures presented by the dielectric layers at different positions. It does not refer to the number of dielectric layers or the arrangement of the dielectric layers. In addition, in the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0038] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements or functional layers having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0039] in, Figures 1 to 3 A schematic cross-sectional structure diagram of a heterojunction solar cell provided by an embodiment of the present invention is shown; Figure 4 A schematic diagram showing the main process of a method for preparing a heterojunction solar cell; Figure 5 Schematic diagram showing the structural changes of the metal electrode corresponding to the preparation process; Figure 6 A scanning electron microscope (SEM) image showing a portion of the surface of a heterojunction solar cell including a metal electrode region.

[0040] like Figures 1 to 3 As shown, the heterojunction solar cell may include:

[0041] Battery substrate 10;

[0042] A transparent conductive layer 20 is provided on the main surface of the battery substrate 10;

[0043] A metal seed layer 30 is disposed on the transparent conductive layer 20 at intervals, wherein the metal seed layer 30 comprises accumulated metal particles;

[0044] A first dielectric layer 41 , which is disposed on the transparent conductive layer 20 and is located outside the metal seed layer 30 ;

[0045] A second dielectric layer 42 , wherein the second dielectric layer 42 is discontinuously disposed on the surface of the metal seed layer 30 , so that the metal seed layer 30 includes a plating skip area 50 not covered by the second dielectric layer 42 ;

[0046] A fine crystal layer 60 stacked on the second dielectric layer 42 and the leakage plating area 50;

[0047] and an additional conductive layer 70 stacked on the fine crystal layer 60 .

[0048] Among them, Figures 1 to 3 As shown, the battery substrate 10 generally includes a single crystal silicon wafer 11, a front intrinsic amorphous silicon layer 12 formed on the main surface of the single crystal silicon wafer 11, and a front doped amorphous silicon layer 13 stacked on the front intrinsic amorphous silicon layer 12. It can be understood that Figures 1 to 3 The main surface of the cell substrate 10 is shown as a polished surface structure for exemplary purposes only. The main surface of the cell substrate 10 included in the heterojunction solar cell provided by the embodiment of the present invention can also have a suede structure. In addition, the front intrinsic amorphous silicon layer 12 can also be replaced with a front intrinsic microcrystalline silicon layer, and correspondingly, the front doped amorphous silicon layer 13 can be replaced with a front doped microcrystalline silicon layer.

[0049] It is worth noting that the transparent conductive layer 20 provided on the main surface of the battery substrate 10 means that the transparent conductive layer 20 is located on the side of the front doped amorphous silicon layer 13 away from the front intrinsic amorphous silicon layer 12 .

[0050] The metal seed layer 30 , the fine-grained layer 60 and the additional conductive layer 70 constitute part or all of the metal electrode.

[0051] Generally speaking, if Figures 1 to 3 As shown, the transparent conductive layer 20, the metal seed layer 30, the first dielectric layer 41, the second dielectric layer 42, the leakage plating area 50, the fine crystal layer 60 and the additional conductive layer 70 belong to the front side of the heterojunction solar cell. The back side of the heterojunction solar cell may include: a back intrinsic amorphous silicon layer 91, a back doped amorphous silicon layer 92, a back passivation layer 93 and a back metal electrode 94, wherein the back side may be as shown in FIG. Figure 2As shown, the structure of the back metal electrode 94 is the same as that of the front metal electrode (including the metal seed layer 30, the first dielectric layer 41, the second dielectric layer 42, the plating leakage area 50, the fine grain layer 60 and the additional conductive layer 70); in addition, it can also be as shown in FIG. Figure 3 As shown, the back metal electrode 94 is an existing metal electrode formed by conventional means such as printing or conventional electroplating. The front surface of a heterojunction solar cell generally refers to the main surface facing sunlight during the use of the heterojunction solar cell; the back surface of a heterojunction solar cell refers to the main surface facing away from sunlight during the use of the heterojunction solar cell. It should be noted that the back intrinsic amorphous silicon layer 91 can be replaced with a back intrinsic microcrystalline silicon layer, and correspondingly, the back doped amorphous silicon layer 92 can be replaced with a back doped microcrystalline silicon layer.

[0052] against Figures 1 to 3 The provided heterojunction solar cell cooperates with the stacked metal particles contained in the metal seed layer 30, the first dielectric layer 41 set in the area outside the metal seed layer 30, and the second dielectric layer 42 scattered on the surface of some metal particles, so that the transparent conductive layer 20 can be completely covered by the first dielectric layer 41. The metal seed layer 30 has a leakage area 50, which is stacked on the second dielectric layer 42 and the leakage area 50 through the fine crystal layer 60, and can form a stable contact between the fine crystal layer 60 and the transparent conductive layer 20 through the leakage area 50, so that the additional conductive layer 70 stacked on the fine crystal layer 60 can form a stable contact and electrical connection with the metal seed layer 30 through the fine crystal layer 60. Complex processes such as exposure and development can be omitted, and there is no need to introduce masks in processes such as exposure and development. The risk of introducing foreign matter into the heterojunction solar cell due to exposure and development and the risk of yield loss due to poor exposure and development processes can also be avoided.

[0053] In addition, the metal electrode is composed of a metal seed layer, a leakage-plating area, a fine-grained layer and an additional conductive layer, and the fine-grained layer can ensure a stable electrical connection between the metal seed layer and the additional conductive layer, thereby effectively improving the reliability of the metal electrode of the heterojunction solar cell and benefiting to improving the performance and yield of the heterojunction solar cell.

[0054] In addition, for Figures 1 to 3 The provided heterojunction solar cell can fill the gaps between the metal particles contained in the metal seed layer 30 by introducing the fine crystal layer 60, and can relatively well electrically connect the leakage plating area 50 and the additional conductive layer 70, thereby increasing the indirect contact area between the additional conductive layer 70 and the metal seed layer 30, and can effectively reduce the line resistance and contact resistance of the metal electrode of the heterojunction solar cell, thereby improving the series resistance and photoelectric conversion efficiency of the heterojunction solar cell.

[0055] Further, for Figures 1 to 3The heterojunction solar cell provided by the invention introduces a fine crystal layer, so that the effective contact area between the additional conductive layer 70 and the fine crystal layer 60 and between the fine crystal layer 60 and the metal seed layer 30 is relatively large, thereby effectively improving the adhesion and tension of the metal electrode.

[0056] As described above, the functional layers, including the transparent conductive layer 20, metal seed layer 30, first dielectric layer 41, second dielectric layer 42, skipped-plating region 50, fine-grained layer 60, and additional conductive layer 70, work together to improve the performance of the heterojunction solar cell. The structure of each functional layer also affects how it works together. The following describes the structure of each functional layer separately.

[0057] The thickness of the transparent conductive layer 20 is generally set to 5 nm to 150 nm. For example, the thickness can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 90 nm, 100 nm, 120 nm, or 150 nm. Preferably, the thickness of the transparent conductive layer 20 is 5 nm to 100 nm. Furthermore, the transparent conductive layer 20 can be a tin-doped indium oxide (ITO) film layer, a fluorine-doped tin oxide (FTO) layer, a tin oxide layer, a tungsten-doped indium oxide (IWO), a cerium-doped indium oxide (ICO) layer, an aluminum-doped zinc oxide layer, or a cerium-doped zinc oxide layer. Compared to existing heterojunction solar cells that typically use a thickness of at least 100 nm, the first dielectric layer 41 in the embodiments of the present invention can reduce the thickness of the transparent conductive layer 20. This ensures uniform coverage of the transparent conductive layer 20 while reducing the cost of the transparent conductive layer and the amount of indium used, thereby lowering the cost of the heterojunction solar cell. Furthermore, the thinned transparent conductive layer, in combination with the first dielectric layer 41, can improve the light utilization efficiency of the solar cell.

[0058] Furthermore, for the above-mentioned metal seed layer 30, in order to enable the metal seed layer 30 to have appropriate roughness and make the surface of the metal seed layer 30 present relatively good granularity to ensure the density of the fine crystal layer 60, the embodiment of the present invention is obtained by adjusting the diameter of the metal particles contained in the metal seed layer 30 and / or the thickness of the metal seed layer 30.

[0059] Specifically, in the heterojunction solar cell provided by an embodiment of the present invention, the diameter of the metal particles included in the metal seed layer 30 is generally controlled to be 0.5 μm to 20 μm. For example, the diameter of the metal particles included in the metal seed layer 30 can be 0.5 μm, 1 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.3 μm, 3.5 μm, 3.7 μm, 4 μm, 4.1 μm, 4.3 μm, 4.5 μm, 4.8 μm, 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 15 μm, 18 μm, or 20 μm. By controlling the diameter of the metal particles, the surface roughness of the metal seed layer 30 can be effectively improved during the formation of the second dielectric layer 42. Furthermore, the metal particles on the surface of the metal seed layer 30 can be used to effectively control the area of ​​the skipped plating zone 50 during the formation of the second dielectric layer 42, thereby increasing the effective contact area between the fine-grained layer 60 and the metal seed layer 30. It is worth noting that, within the same metal electrode of the same heterojunction solar cell, the diameter of the metal particles contained in the metal seed layer 30 is not limited to a single type. That is, within the same metal electrode, the metal seed layer 30 can contain metal particles of multiple diameters, i.e., the metal particles contained in the metal seed layer 30 are of varying sizes. By controlling the metal seed layer 30 to contain metal particles of multiple diameters, on the one hand, the surface roughness of the metal seed layer 30 and the diversity of the curved surfaces contained on the surface of the metal seed layer 30 can be improved, thereby increasing the area of ​​the skipped plating zone 50. On the other hand, the metal seed layer 30 can have a wider process window, effectively reducing the difficulty of forming the metal seed layer 30.

[0060] In addition, the thickness of the metal seed layer 30 is generally controlled to be 0.5μm~20μm. For example, the thickness of the metal seed layer 30 can be 0.5μm, 1μm, 2μm, 2.5μm, 4μm, 5μm, 6μm, 8μm, 10μm, 12μm, 15μm, 18μm or 20μm, etc. In an embodiment of the present invention, the thickness of the metal seed layer 30 is matched with the diameter of most metal particles in the metal seed layer 30. Generally speaking, the number of stacked metal particles in the thickness direction of the metal seed layer 30 generally does not exceed 5, so as to effectively improve the surface roughness of the metal seed layer 30 and the area of ​​the skipped plating area 50 on the surface of the metal seed layer 30.

[0061] Furthermore, the embodiment of the present invention controls the width of the metal electrode of the heterojunction solar cell provided by the embodiment of the present invention by regulating the width of the metal seed layer 30 to ensure the conductivity and reliability of the metal electrode. Specifically, the width of the metal seed layer 30 is generally 5μm~80μm. Exemplarily, the width of the metal seed layer 30 may be 5μm, 10μm, 12μm, 15μm, 16μm, 18μm, 20μm, 25μm, 30μm, 40μm, 55μm, 70μm or 80μm, etc. Furthermore, the width of the metal seed layer 30 is matched with the diameter of the metal particles contained in the above-mentioned metal seed layer 30 and the thickness of the metal seed layer, which helps to reduce the resistance loss of the metal electrode formed based on the metal seed layer 30. It is worth noting that the width of the above-mentioned metal seed layer 30 is preferably in the range of 5μm~40μm. The width of the metal seed layer can be even wider. For example, the width of the metal seed layer 30 made by copper paste printing can be 70μm~80μm, such as 70μm, 72μm, 75μm or 80μm.

[0062] The metal seed layer 30 may include one or more of silver, copper, nickel, aluminum, and titanium. Specifically, the metal seed layer 30 may be formed by coating and curing a slurry containing one or more of silver, copper, nickel, aluminum, and titanium. Preferably, the metal seed layer 30 is formed by coating and curing a silver-coated copper slurry or a copper slurry. The metal seed layer 30 may also be formed by using a mask plate in combination with physical vapor deposition of a slurry containing one or more of silver, copper, nickel, aluminum, and titanium. For the selection of coating a silver-coated copper slurry to form the metal seed layer 30, a silver-coated copper slurry with a silver content of less than 30% is preferably used. The coating may be a printing process, spraying process, laser transfer process, thermal transfer process, or inkjet printing process used in existing solar cell production. The silver-coated copper slurry or copper slurry is a relatively low-cost and commonly used raw material for metal electrodes of solar cells, thereby effectively controlling the production cost of the metal seed layer 30. In addition, the metal seed layer 30 is formed by the process used in existing solar cell production, and can be directly completed using the existing solar cell production line or production equipment, effectively reducing the equipment investment cost of the heterojunction solar cell provided by the embodiment of the present invention.

[0063] Furthermore, the first dielectric layer 41 is generally formed of a material with high resistivity or insulation. For example, the first dielectric layer 41 may include one or more of the following materials:

[0064] Silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, titanium nitride, titanium oxide, fluorine-doped tin oxide (SnO2:F), cadmium stannate (Cd2SnO3), or tin oxide. Furthermore, the material included in the first dielectric layer 41 may also be a tantalum-based material. For example, the material of the first dielectric layer 41 containing tantalum-based materials and titanium oxide may be tantalum-doped titanium oxide (TiO2:Ta).

[0065] In addition, the second dielectric layer 42 is generally formed of a material with high resistivity or insulation. For example, the second dielectric layer 42 may include one or more of the following materials:

[0066] Silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, titanium nitride, titanium oxide, fluorine-doped tin oxide (SnO2:F), CdSnO4, or tin oxide. Furthermore, the material included in the first dielectric layer 41 may also be other tantalum-based materials. For example, the material of the second dielectric layer 42 containing tantalum-based materials and titanium oxide may be tantalum-doped titanium oxide (TiO2:Ta).

[0067] It is worth noting that when the first dielectric layer 41 and the second dielectric layer 42 are located on the front side of the heterojunction solar cell, the first dielectric layer 41 and the second dielectric layer 42 are transparent film layers to ensure light utilization of the heterojunction solar cell.

[0068] The thickness of the first dielectric layer 41 is generally between 5 nm and 200 nm. For example, the thickness of the first dielectric layer 41 can be 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 40 nm, 50 nm, 80 nm, 100 nm, 110 nm, 130 nm, 150 nm, 170 nm, 180 nm, 190 nm, or 200 nm. By controlling the thickness of the first dielectric layer 41, the first dielectric layer 41 can completely cover and isolate the area outside the metal seed layer 30 of the transparent conductive layer 20. This prevents the formation of conductive material outside the metal seed layer 30 of the transparent conductive layer 20 during the formation of the fine-grained layer 60 and the additional conductive layer 70. On the one hand, the first dielectric layer 41 can compensate for the reduced thickness of the transparent conductive layer 20, ensuring complete coverage of the main surface of the cell substrate 10. On the other hand, the first dielectric layer 41 has a passivation effect, which helps improve the photoelectric conversion efficiency of the heterojunction solar cell.

[0069] In addition, the thickness of the second dielectric layer 42 can be 5 nm to 200 nm. For example, the thickness of the first dielectric layer 41 can be 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 40 nm, 50 nm, 80 nm, 100 nm, 110 nm, 130 nm, 150 nm, 170 nm, 180 nm, 190 nm, or 200 nm. On the one hand, the thickness of the second dielectric layer 42 is determined by the thickness of the first dielectric layer 41; on the other hand, controlling the thickness of the second dielectric layer 42 can effectively ensure the presence of the missed plating area 50.

[0070] More specifically, the first dielectric layer 41 and the second dielectric layer 42 are formed simultaneously. The first dielectric layer 41 and the second dielectric layer 42 can be formed by physical vapor deposition (PVD), plasma-enhanced chemical vapor deposition (PECVD), atmospheric pressure chemical vapor deposition (APCVD), or evaporation. Preferably, the first dielectric layer 41 and the second dielectric layer 42 are deposited at a temperature between 60°C and 250°C. For example, the deposition temperature can be 60°C, 70°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, or 250°C. Because the surface roughness and state of the transparent conductive layer 20 and the metal seed layer 30 are completely different, during the simultaneous formation of the first dielectric layer 41 and the second dielectric layer 42, it is ensured that the first dielectric layer 41 completely covers the area of ​​the transparent conductive layer 20 outside the metal seed layer 30, and a plating skip area 50 can exist on the surface of the metal seed layer 30. In addition, by forming the first dielectric layer 41 and the second dielectric layer 42 simultaneously, the introduction of a mask can be avoided, the preparation process can be reduced, and the preparation complexity of the first dielectric layer 41 and the second dielectric layer 42 can be reduced, which helps to improve the photoelectric conversion rate of the heterojunction solar cell while effectively improving the yield rate of the heterojunction solar cell.

[0071] Furthermore, with respect to the fine crystal layer 60, the diameter of the grains contained in the fine crystal layer 60 is 0.03 μm to 1 μm. For example, the diameter of the grains contained in the fine crystal layer 60 may be 0.03 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.5 μm, 0.55 μm, 0.65 μm, 0.8 μm, 0.9 μm or 1 μm, etc. Preferably, the diameter of the grains is 0.03 μm to 0.1 μm. More preferably, the diameter of the grains is 0.03 μm to 0.05 μm. For example, the diameter of the grains may be 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm or 0.1 μm, etc. By controlling the diameter of the grains contained in the fine-grained layer 60 to ensure that the fine-grained layer 60 can relatively perfectly fill the gaps between the metal particles contained in the skipped plating area 50 and the metal seed layer 30, it helps to reduce the line resistance and contact resistance of the metal electrode formed based on the metal seed layer 30.

[0072] Furthermore, the thickness of the fine crystal layer 60 is generally greater than or equal to 0.1 μm, and the thickness of the fine crystal layer 60 is less than or equal to 2 μm. For example, the thickness of the fine crystal layer 60 may be 0.1 μm, 0.3 μm, 0.5 μm, 0.6 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 1.9 μm or 2 μm, etc. By controlling the thickness of the fine crystal layer 60, it is possible to ensure that the fine crystal layer 60 can completely cover the plating skip area 50 as much as possible, and the plating skip area 50 of the metal seed layer 30, the fine crystal layer 60 and the additional conductive layer 70 can be coordinated to improve the reliability of the metal electrode formed based on the metal seed layer 30 as well as the contact resistance and line resistance of the metal electrode, and the cost of the heterojunction solar cell can be effectively controlled.

[0073] The fine crystal layer 60 may be composed of one or more of copper, silver, tin, cobalt, nickel, and aluminum.

[0074] The above-mentioned fine-grained layer 60 is generally formed by chemical plating or electroplating. The metal ions contained in the solution used for the selected chemical plating or electroplating, after oxidation and reduction, form relatively small grains (diameter within the range of 0.03μm~1μm) and the grains are orderly stacked, and the solution used for chemical plating or electroplating is generally neutral, weakly acidic or weakly alkaline. For example, the plating type of the fine-grained layer 60 can be selected from any one or more combinations of chemical nickel plating, chemical copper plating, chemical silver plating, electroplated nickel, pyrophosphate copper plating, other alkaline copper plating or electroplated silver plating. Furthermore, the plating type used to form the fine-grained layer 60 may include a chelating agent, which coordinates with the metal ions to reduce the dissociation rate of the metal ions and reduce the rate at which the metal ions form grains, so as to effectively control the grain size of the fine-grained layer 60. Furthermore, for electroplating to form the fine-grained layer 60, a low current density is generally used. For example, the current density is higher than 0.1 ASD (amperes per square foot) and lower than 5 ASD. For example, the current density may be 0.5 ASD, 1ASD, 1.5ASD, 1.8ASD, 2ASD, 2.5ASD, 3ASD, 4ASD or 4.5ASD, etc. Preferably, the current density is higher than 0 ASD and lower than 2ASD. For example, the current density may be 0.1ASD, 0.2ASD, 0.5ASD, 0.8ASD, 1ASD, 1.2ASD, 1.5ASD or 1.8ASD, etc.

[0075] Furthermore, the thickness of the additional conductive layer 70 can be 2 μm to 40 μm. For example, the thickness of the additional conductive layer 70 can be 2 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 10 μm, 15 μm, 18 μm, 20 μm, 25 μm, 28 μm, 30 μm, 35 μm, 38 μm, or 40 μm. By controlling the thickness of the conductive layer 70, the contact area between the additional conductive layer 70 and the fine-grained layer 60 can be effectively ensured, the contact resistance of the metal electrode can be reduced, and the tensile strength, stability, and reliability of the metal electrode can be improved.

[0076] The grain size of the additional conductive layer 70 is generally larger than that of the fine-grained layer 60. By controlling the grain size of the additional conductive layer 70, the additional conductive layer 70 can have a wider process window, reducing the difficulty of operating the additional conductive layer 70, simplifying the process and reducing operating costs, thereby improving the yield of the heterojunction solar cell and effectively reducing the cost of the heterojunction solar cell. More specifically, the additional conductive layer 70 includes copper and / or silver.

[0077] Specifically, the additional conductive layer 70 can be formed by electroplating. More specifically, the electroplating current density generally used to form the additional conductive layer 70 can be 2ASD to 20ASD. For example, the electroplating current density can be 2ASD, 4ASD, 5ASD, 8ASD, 10ASD, 12ASD, 15ASD, 18ASD, or 20ASD. Furthermore, the temperature used to form the additional conductive layer 70 by electroplating is generally 20°C to 40°C. Exemplarily, the temperature can be 20°C, 22°C, 25°C, 28°C, 30°C, 35°C, 38°C, or 40°C. In combination with this electroplating current density, the additional conductive layer 70 can be formed using an existing, relatively low-cost plating species. Exemplarily, the plating species used to form the additional conductive layer 70 can be acid copper plating, such as acid copper sulfate, and the copper content contained in the plating species can be any content.

[0078] Furthermore, the heterojunction solar cell may further include a conductive protection layer 80 stacked outside the additional conductive layer 70. The conductive protection layer 80 can protect the additional conductive layer 70, prevent the additional conductive layer 70 from being oxidized, and effectively improve the conductivity of the metal electrode.

[0079] The conductive protective layer 80 may include tin grains, copper grains, or silver grains. Generally, the grain size of the conductive protective layer 80 is smaller than the grain size of the additional conductive layer 70, and the grain size of the conductive protective layer 80 is larger than the grain size of the fine-grained layer 60. This ensures that the conductive protective layer 80 completely covers the additional conductive layer 70 and reduces the difficulty of the production process of the conductive protective layer 80.

[0080] Exemplarily, the thickness of the conductive protective layer 80 is generally 0.5 μm to 5 μm. For example, the thickness of the conductive protective layer 80 can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm. More specifically, for the conductive protective layer 80 containing tin grains, if the conductive protective layer 80 is obtained by electroplating, its thickness is generally 0.5 μm to 5 μm; if the conductive protective layer 80 is obtained by chemical plating, its thickness is generally 0.5 μm to 1 μm. For example, the thickness of the conductive protective layer 80 can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm. The conductive protective layer 80 containing silver grains, whether obtained by electroplating or chemical plating, generally has a thickness of 0.5 μm to 3 μm. For example, the thickness of the conductive protective layer 80 can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm.

[0081] Furthermore, an embodiment of the present invention also provides a method for preparing a heterojunction solar cell. Figure 4As shown, the method for preparing the heterojunction solar cell may include the following steps:

[0082] Step S401 : preparing a transparent conductive layer 20 on the battery substrate 10 .

[0083] This step can use existing techniques (such as chemical vapor deposition) to prepare the transparent conductive layer 20. Unlike existing transparent conductive layers, the transparent conductive layer 20 prepared in this step is a thinned film layer, and its thickness can be 5nm to 150nm. For example, the thickness can be 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 32nm, 35nm, 40nm, 43nm, 45nm, 48nm, 50nm, 60nm, 65nm, 70nm, 80nm, 90nm, 100nm, 120nm, or 150nm. Preferably, the transparent conductive layer 20 prepared in this step has a thickness of 5nm to 100nm. The transparent conductive layer 20 may be a tin-doped indium oxide (ITO) film layer, a fluorine-doped tin oxide (FTO) layer, a tin oxide layer, a tungsten-doped indium oxide (IWO) layer, a cerium-doped indium oxide (ICO) layer, an aluminum-doped zinc oxide layer, or a cerium-doped zinc oxide layer. For example, if the transparent conductive layer 20 is an ITO film layer, it may include, but is not limited to, ITO991, ITO973, or ITO9010.

[0084] Step S402 : preparing a metal seed layer 30 containing accumulated metal particles on the transparent conductive layer 20 .

[0085] For example, the structure of the metal seed layer 30 obtained after this step is as follows: Figure 5 shown.

[0086] This step can be formed by coating the transparent conductive layer 20 at intervals and curing. It can also be formed by physical vapor deposition with a mask plate. For the coating method, it can be completed by currently commonly used coating methods such as inkjet printing, spraying, laser transfer, thermal transfer, etc. The slurry used for coating generally contains one or more of silver, copper, nickel, aluminum and titanium. Preferably, the slurry used for coating is silver-coated copper slurry or copper slurry. For silver-coated copper slurry, silver-coated copper slurry with a silver content of less than 30% can be selected. Furthermore, the coating process is generally coordinated with a steel mesh to control the coating position of the metal seed layer 30, the width and thickness of the metal seed layer 30. The wet weight of the slurry printed in this step generally decreases by more than 20% after curing, and the wet weight of the printed slurry decreases by less than 90% after curing. For example, the wet weight of the printed slurry decreases by 25%, 30%, 40%, 50%, 80% or 90% after curing. For forming the transparent conductive layer 20 by physical vapor deposition using a mask, the selected paste generally contains one or more of silver, copper, nickel, aluminum, and titanium.

[0087] Furthermore, the thickness of the slurry applied in this step is generally 1.5μm~30μm, preferably, the thickness of the slurry applied in this step is generally 1.5μm~5μm. The thickness of the metal seed layer 30 obtained after curing is generally 0.5μm~20μm. Preferably, the thickness of the metal seed layer 30 obtained after curing is 0.5μm~2μm. Exemplarily, the height of the applied slurry can be 1.5μm, 3μm, 4μm, 5μm, 10μm, 15μm, 20μm, 25μm or 30μm, etc. The thickness of the metal seed layer 30 obtained after curing can be 0.5μm, 1μm, 2μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm or 20μm, etc.

[0088] The width of the slurry printed in this step is generally 7μm~90μm. The width of the formed metal seed layer 30 can be 5μm~80μm. For example, the width of the slurry printed in this step is 7μm, 12μm, 17μm, 19μm, 22μm, 25μm, 28μm, 30μm, 35μm, 40μm, 43μm, 45μm, 50μm, 60μm, 80μm, 85μm or 90μm, etc. The width of the metal seed layer 30 can be 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 25μm, 30μm, 35μm, 40μm, 50μm, 55μm, 60μm, 70μm or 80μm, etc.

[0089] The metal seed layer 30 formed in this step comprises metal particles of uneven size, which effectively improves the surface roughness and surface diversity of the metal seed layer 30 , thereby reducing the area of ​​the second dielectric layer 42 prepared subsequently and increasing the area of ​​the subsequently obtained plating skip area 50 .

[0090] Furthermore, the curing temperature in this step is generally 80°C to 250°C. For example, the curing temperature may be 80°C, 90°C, 100°C, 110°C, 120°C, 140°C, 150°C, 180°C, 200°C, 220°C, or 250°C. The curing time may be 2 min to 30 min. Preferably, the curing time may be 2 min to 10 min. For example, the curing time may be 2 min, 4 min, 5 min, 7 min, 9 min, 10 min, 15 min, 18 min, 20 min, 25 min, 28 min, or 30 min.

[0091] Step S403 : forming a first dielectric layer 41 in the transparent conductive layer 20 outside the metal seed layer 30 , and forming a discontinuously distributed second dielectric layer 42 on the metal seed layer 30 , so that the metal seed layer 30 includes a plating skip area 50 not covered by the second dielectric layer 42 .

[0092] For example, the structures of the second dielectric layer 42 covering the metal seed layer 30 and the plating skip area 50 not covered by the second dielectric layer 42 obtained through this step are as follows: Figure 5 shown.

[0093] In this step, a second dielectric layer 42 is formed on the metal seed layer 30 by a deposition method (such as PECVD, PVD, APCVD or evaporation, etc.), and a first dielectric layer 41 is formed in the area outside the metal seed layer 30 in the transparent conductive layer 20. Due to the difference between the surface of the metal seed layer 30 and the surface of the transparent conductive layer 20, differentiated dielectric layers can be simultaneously deposited on the surface of the metal seed layer 30 and the surface of the transparent conductive layer 20 to form.

[0094] The materials used to form the first dielectric layer 41 and the second dielectric layer 42 in this step are generally high-resistance or insulating materials. For example, these materials may include silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, titanium nitride, titanium oxide, fluorine-doped tin oxide (SnO2:F), cadmium stannate (Cd2SnO3), or tin oxide. Furthermore, the material included in the first dielectric layer 41 may also be a tantalum-based material. For example, the material of the first dielectric layer 41 containing tantalum-based materials and titanium oxide may be tantalum-doped titanium oxide (TiO2:Ta).

[0095] The deposition temperature is generally in the range of room temperature to 250° C. For example, the deposition temperature can be 60° C., 70° C., 80° C., 100° C., 120° C., 150° C., 180° C., 200° C., 220° C., or 250° C.

[0096] Because the surface roughness and state of the transparent conductive layer 20 and the metal seed layer 30 are completely different, during the simultaneous formation of the first dielectric layer 41 and the second dielectric layer 42, it is ensured that the first dielectric layer 41 completely covers the area of ​​the transparent conductive layer 20 outside the metal seed layer 30, and a plating skip area 50 can exist on the surface of the metal seed layer 30. In addition, by simultaneously forming the first dielectric layer 41 and the second dielectric layer 42, the introduction of a mask can be avoided, the preparation process can be reduced, and the preparation complexity of the first dielectric layer 41 and the second dielectric layer 42 can be reduced, which helps to improve the photoelectric conversion efficiency of the heterojunction solar cell while effectively improving the production yield of the heterojunction solar cell.

[0097] In addition, the thickness of the first dielectric layer 41 and the second dielectric layer 42 formed in this step is generally 5 nm to 200 nm. For example, the thickness of the first dielectric layer 41 and the second dielectric layer 42 can be 5 nm, 7 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 40 nm, 50 nm, 80 nm, 100 nm, 110 nm, 130 nm, 150 nm, 170 nm, 180 nm, 190 nm, or 200 nm.

[0098] Step S404 : forming a fine grain layer 60 on the metal seed layer 30 .

[0099] For example, the structure of the fine crystal layer 60 covering the metal seed layer 30 obtained through this step is as follows: Figure 5 shown.

[0100] This step can form the fine-grained layer 60 by electroplating or chemical plating. Specifically, the metal ions contained in the chemical plating or electroplating solution used to form the fine-grained layer 60, after oxidation-reduction, form relatively small grains (diameters ranging from 0.03 μm to 1 μm) with orderly grain stacking. The chemical plating or electroplating solution is generally neutral, weakly acidic, or weakly alkaline. For example, the components of the fine-grained layer 60 may include one or more of copper, silver, tin, cobalt, nickel, and aluminum. Preferably, the chemical plating or electroplating solution can be any one or more of chemical nickel plating, chemical copper plating, chemical silver plating, electroplated nickel, pyrophosphate copper plating, other alkaline copper plating methods, or electroplated silver plating methods. Preferably, the plating seed used in this step is an alkaline copper seed, such as copper pyrophosphate or copper citrate. A chelating agent is introduced into the plating seed to slow the ionization of metal ions (such as copper ions), thereby facilitating the formation of small grains and achieving more refined crystallization.

[0101] Furthermore, in this step, a low current density is generally used for electroplating to form the fine crystal layer 60. For example, the current density is higher than 0.1ASD (amperes per square foot) and lower than 5ASD. For example, the current density may be 0.1ASD, 0.3ASD, 0.5ASD, 1ASD, 1.5ASD, 1.8ASD, 2ASD, 2.5ASD, 3ASD, 4ASD or 5ASD, etc. Preferably, the current density is higher than 0.1ASD and lower than 2ASD, for example, the current density may be 0.1ASD, 0.2ASD, 0.5ASD, 0.8ASD, 1ASD, 1.2ASD, 1.5ASD, 1.8ASD or 2ASD, etc.

[0102] In addition, the diameter of the grains contained in the fine-grained layer 60 formed in this step is generally 0.03 μm to 1 μm. For example, the diameter of the grains contained in the fine-grained layer 60 may be 0.03 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.5 μm, 0.55 μm, 0.65 μm, 0.8 μm, 0.9 μm or 1 μm. Preferably, the diameter of the grains is 0.03 μm to 0.1 μm. More preferably, the diameter of the grains is 0.03 μm to 0.05 μm. For example, the diameter of the grains may be 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm or 0.1 μm. By controlling the diameter of the grains contained in the fine-grained layer 60 to ensure that the fine-grained layer 60 can relatively perfectly fill the gaps between the metal particles contained in the skipped plating area 50 and the metal seed layer 30, it helps to reduce the line resistance and contact resistance of the metal electrode formed based on the metal seed layer 30.

[0103] Furthermore, the thickness of the fine crystal layer 60 formed in this step is generally greater than or equal to 0.1 μm, and the thickness of the fine crystal layer 60 is less than or equal to 2 μm. For example, the thickness of the fine crystal layer 60 may be 0.1 μm, 0.3 μm, 0.5 μm, 0.6 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 1.9 μm or 2 μm, etc. By controlling the thickness of the fine crystal layer 60, it can be ensured that the fine crystal layer 60 can completely cover the plating skip area 50 as much as possible, and the plating skip area 50 of the metal seed layer 30, the fine crystal layer 60 and the additional conductive layer 70 can be coordinated to improve the reliability of the metal electrode formed based on the metal seed layer 30 as well as the contact resistance and line resistance of the metal electrode, and the cost of the heterojunction solar cell can be effectively controlled.

[0104] For example, in an embodiment of the present invention, copper citrate is selected as the plating seed, and the solution formula used for electroplating may include 5g / L~20g / L of copper ions, 100g / L~200g / L of citric acid, 2mL / L~5ml / L of a complexing agent, and 5mL / L~10mL / L of an additive, wherein the complexing agent can be a conventional complexing agent on the market that can complex with copper ions, and the additive can be an additive commonly used in electroplating copper (such as brighteners such as sodium lauryl sulfate, hexadecyl trimethyl betaine or polyoxyethylene lauryl ether, surfactants such as alkyl aryl sulfonate series, anionic wetting agents such as sodium lauryl sulfate, degreasing agents, leveling agents, etc.). The type of complexing agent and the type of additive are not limited here. For example, the mass volume concentration of copper ions included in the solution formula used for electroplating can be 5g / L, 8g / L, 10g / L, 12g / L, 15g / L, 18g / L or 20g / L, etc. The mass volume concentration of citric acid included in the electroplating solution formula can be 100g / L, 120g / L, 130g / L, 150g / L, 170g / L, 180g / L or 200g / L, etc. The volume concentration of the complexing agent included in the electroplating solution formula can be 2mL / L, 3mL / L, 4mL / L or 5ml / L, etc. The volume concentration of the additive included in the electroplating solution formula can be 5mL / L, 6mL / L, 7mL / L or 10ml / L, etc.

[0105] The electroplating process of the present invention preferably uses pulse power electroplating to further control the grain size of the fine-grained layer 60. Specifically, a plating solution containing metal ions and a complexing agent is combined with pulse electroplating to form the fine-grained layer 60 on the metal seed layer 30 to regulate the grain size of the fine-grained layer 60.

[0106] Step S405 : forming an additional conductive layer 70 on the fine-grained layer 60 .

[0107] Specifically, in this step, an additional conductive layer 70 is formed on the fine crystal layer 60 by electroplating. For example, the structure of the additional conductive layer 70 covering the fine crystal layer 60 obtained by this step is as follows: Figure 5 The additional conductive layer 70 comprises copper and / or silver.

[0108] If the fine-grained layer 60 contains copper grains, copper electroplating is preferred for this step because copper has the closest electrical conductivity to copper and is a relatively inexpensive material. Furthermore, considering the tolerance of heterojunction solar cells, the complexity and cost of the process and operation, acid copper sulfate plating is preferred for this step because acid copper plating is a simple process with very low operating costs.

[0109] More specifically, the electroplating current density generally used to form the additional conductive layer 70 may be 2ASD to 20ASD. For example, the electroplating current density may be 2ASD, 4ASD, 5ASD, 8ASD, 10ASD, 12ASD, 15ASD, 18ASD, or 20ASD. Furthermore, the temperature used to electroplating the additional conductive layer 70 is generally 20°C to 40°C. For example, the temperature may be 20°C, 22°C, 25°C, 28°C, 30°C, 35°C, 38°C, or 40°C. In combination with this electroplating current density, the additional conductive layer 70 may be formed using an existing, relatively low-cost plating species. For example, the plating species used to form the additional conductive layer 70 may be an acidic copper plating species such as acid copper sulfate, and the copper content in the plating species may be any amount.

[0110] in addition, Figure 5 It also shows that after omitting step S404, after the second dielectric layer 42 and the plating skip area 50 not covered by the second dielectric layer 42 are formed on the metal seed layer 30 formed in step S402 through step S403, step S405 is directly entered to form an additional conductive layer 70. Since the fine crystal layer 60 is omitted, a relatively large gap will exist between the metal seed layer 30 and the additional conductive layer 70, which will cause the metal electrode line resistance and contact resistance to be higher.

[0111] Furthermore, after step S405, the process may further include forming a conductive protective layer 80 on the outer side of the additional conductive layer 70 by electroplating. The conductive protective layer 80 generally comprises tin grains, copper grains, or silver grains. Generally, the grain size of the conductive protective layer 80 is smaller than the grain size of the additional conductive layer 70, and the grain size of the conductive protective layer 80 is larger than the grain size of the fine-grained layer 60. This ensures that the conductive protective layer 80 completely covers the additional conductive layer 70 and reduces the difficulty of the production process of the additional conductive layer 70.

[0112] Exemplarily, the thickness of the conductive protective layer 80 is generally 0.5 μm to 5 μm. For example, the thickness of the conductive protective layer 80 can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm. More specifically, for the conductive protective layer 80 containing tin grains, if the conductive protective layer 80 is obtained by electroplating, its thickness is generally 0.5 μm to 5 μm; if the conductive protective layer 80 is obtained by chemical plating, its thickness is generally 0.5 μm to 1 μm. For example, the thickness of the conductive protective layer 80 can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm. The conductive protective layer 80 containing silver grains, whether obtained by electroplating or chemical plating, generally has a thickness of 0.5 μm to 3 μm. For example, the thickness of the conductive protective layer 80 can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm.

[0113] According to the method for preparing a heterojunction solar cell provided in an embodiment of the present invention, the prepared heterojunction solar cell is provided with a metal seed layer 30 containing accumulated metal particles, a first dielectric layer 41 provided in an area outside the metal seed layer 30, and a second dielectric layer 42 scattered on the surface of some metal particles, so that the transparent conductive layer 20 can be completely covered by the first dielectric layer 41. The metal seed layer 30 has a plating skip area 50, and the fine crystal layer 60 can be accurately stacked on the second dielectric layer 42 and the plating skip area 50 by electroplating or chemical plating, and the fine crystal layer 60 can be accurately stacked on the second dielectric layer 42 and the plating skip area 50 ... A stable contact is formed between the layer 60 and the transparent conductive layer 20 through the leakage plating area 50, so that the additional conductive layer 70 stacked on the fine-grained layer 60 can form a stable contact and electrical connection with the metal seed layer 30 through the fine-grained layer 60. The preparation process of the heterojunction solar cell can avoid the use of cumbersome processes such as exposure and development. It can not only avoid the influence of residual foreign matter (developer or ink, etc.) in the exposure and development process, and avoid the risk of yield loss caused by poor development and exposure process, but also the preparation method can reduce production costs, does not require the introduction of a mask, and can avoid the presence of foreign matter in the heterojunction solar cell.

[0114] In addition, the heterojunction solar cell prepared by this preparation method is composed of a metal electrode through a metal seed layer 30, a leakage plating area 50, a fine crystal layer 60 and an additional conductive layer 70, and the fine crystal layer 60 can ensure a stable electrical connection between the metal seed layer 30 and the additional conductive layer 70, thereby effectively improving the reliability of the metal electrode of the heterojunction solar cell and being beneficial to improving the performance of the heterojunction solar cell.

[0115] In addition, by introducing the fine crystal layer 60, the preparation method can fill the gaps between the metal particles contained in the metal seed layer 30, and can better electrically connect the leakage plating area 50 and the additional conductive layer 70, thereby increasing the indirect contact area between the additional conductive layer 70 and the metal seed layer 30, and can effectively reduce the line resistance and contact resistance of the metal electrode of the heterojunction solar cell, thereby improving the series resistance and photoelectric conversion efficiency of the heterojunction solar cell.

[0116] Furthermore, compared with the existing method of preparing heterojunction solar cells by exposure and development with a developer and then preparing a mask in conjunction with an electroplating process, the preparation method provided by the embodiment of the present invention omits these tedious process steps, reduces production costs, and the entire preparation process does not require the introduction of other materials for the battery, and there is no need to align and introduce a mask during the electroplating process. The electroplating process can be targeted to only electroplate the fine crystal layer 60 and the additional conductive layer 70 on the metal seed layer 30, and can effectively improve the production yield.

[0117] The above steps are merely provided to help understand the structure, method, and core concept of the present invention. It will be apparent to those skilled in the art that various improvements and modifications may be made to the present invention without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the claims of the present invention.

Claims

1. A heterojunction solar cell, characterized in that: include: Battery substrate (10); A transparent conductive layer (20) provided on the main surface of the battery substrate (10); a metal seed layer (30) spaced apart on the transparent conductive layer (20), the metal seed layer (30) comprising accumulated metal particles; a first dielectric layer (41), the first dielectric layer (41) being disposed on the transparent conductive layer (20) and located in a region outside the metal seed layer (30); a second dielectric layer (42), wherein the second dielectric layer (42) is discontinuously disposed on the surface of the metal seed layer (30), so that the metal seed layer (30) includes a plating leakage area (50) not covered by the second dielectric layer (42); a fine-grained layer (60) stacked on the second dielectric layer (42) and the plating leakage area (50); and an additional conductive layer (70) stacked on the fine-grained layer (60).

2. The heterojunction solar cell according to claim 1, wherein: The thickness of the transparent conductive layer (20) is 5 nm to 150 nm.

3. The heterojunction solar cell according to claim 1, wherein: The metal seed layer (30) contains metal particles with a diameter of 0.5 μm to 20 μm; and / or, The thickness of the metal seed layer (30) is 0.5 μm to 20 μm; and / or, The width of the metal seed layer (30) is 5 μm to 80 μm; and / or, The metal seed layer (30) comprises one or more components selected from the group consisting of silver, copper, nickel, aluminum and titanium.

4. The heterojunction solar cell according to claim 1, wherein: The thickness of the first dielectric layer (41) and the second dielectric layer (42) are independently 5 nm to 200 nm; and / or, The materials of the first dielectric layer (41) and the second dielectric layer (42) are independently selected from one or more of the following materials: Silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, titanium nitride, titanium oxide, fluorine-doped tin oxide, cadmium stannate, tin oxide, or tantalum-based materials.

5. The heterojunction solar cell according to claim 1, characterized in that: The composition of the fine crystal layer (60) includes one or more of copper, silver, tin, cobalt, nickel and aluminum; and / or, The diameter of the grains contained in the fine-grained layer (60) is 0.03 μm to 1 μm, preferably, the diameter of the grains is 0.03 μm to 0.1 μm; and / or, The thickness of the fine crystal layer (60) is greater than or equal to 0.1 μm, and the thickness of the fine crystal layer (60) is less than or equal to 2 μm.

6. The heterojunction solar cell according to claim 1, characterized in that: The thickness of the additional conductive layer (70) is 2 μm to 40 μm; and / or, The additional conductive layer (70) comprises grains having a size greater than that of the fine-grained layer (60); and / or, The composition of the additional conductive layer (70) includes copper and / or silver.

7. The heterojunction solar cell according to claim 1, characterized in that: Also includes: A conductive protective layer (80) is stacked on the outside of the additional conductive layer (70).

8. The heterojunction solar cell according to claim 7, characterized in that: The conductive protective layer (80) comprises tin grains, copper grains or silver grains; and / or, The grain size of the conductive protective layer (80) is smaller than the grain size of the additional conductive layer (70), and the grain size of the conductive protective layer (80) is larger than the grain size of the fine-grained layer (60); and / or, The thickness of the conductive protective layer (80) is 0.5 μm to 5 μm.

9. The method for preparing a heterojunction solar cell according to any one of claims 1 to 8, characterized in that: include: Step 1: preparing a transparent conductive layer (20) on a battery substrate (10); Step 2: preparing a metal seed layer (30) containing accumulated metal particles on the transparent conductive layer (20); Step 3: forming a first dielectric layer (41) in an area outside the metal seed layer (30) in the transparent conductive layer (20), and forming a discontinuously distributed second dielectric layer (42) on the metal seed layer (30), so that the metal seed layer (30) includes a plating skip area (50) not covered by the second dielectric layer (42); Step 4: forming a fine-grained layer (60) on the metal seed layer (30); Step 5: forming an additional conductive layer (70) on the fine-grained layer (60).

10. The method for preparing a heterojunction solar cell according to claim 9, wherein: In step 2, the metal seed layer (30) is prepared by coating or physical vapor deposition; or, In step 4, the fine-grained layer (60) is prepared by electroplating or chemical plating; or, In step 5, the additional conductive layer (70) is prepared by electroplating; or, The preparation method further comprises: Step 6: forming a conductive protective layer (80) on the outside of the additional conductive layer (70) by electroplating.

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