Back contact solar cell, preparation method thereof and application of back contact solar cell in preparation of photovoltaic module

Abstract

The invention provides a back contact solar cell, a preparation method thereof and application of the back contact solar cell in preparation of a photovoltaic module, and relates to the technical field of solar cells. According to the back contact solar cell, a photosensitive mask layer is formed on a TCO layer, at least two independent patterning operations are carried out on the mask layer, an insulation window used for wet etching and a pattern window used for electroplating gate forming are sequentially defined, local removal of the TCO layer between a P-type region and an N-type region is achieved, and an insulation channel is formed. And meanwhile, electroplating forming of the metal grid line electrode is completed under the same mask system. According to the method, the use frequency of the mask is reduced, and the interface pollution and alignment error risk are reduced. And meanwhile, a functional structure for preventing electroplate liquid from permeating is arranged in the insulating channel, so that the electrolyte is effectively prevented from diffusing to a semiconductor interface, and the prepared back contact solar cell has excellent high-temperature and high-humidity aging performance.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a back-contact solar cell, its preparation method, and its use in the preparation of photovoltaic modules. Background Technology

[0002] As an important component of clean energy, solar cells have seen continuous development in recent years in terms of efficiency improvement and cost reduction. Back-contact solar cells (BC cells), because all their electrodes are located on the back of the cell, avoid light loss due to shading of the front electrodes and have high potential for photoelectric conversion efficiency. They are widely used in high-efficiency photovoltaic devices, such as interdigitated back contact (IBC) and passivated emitter back contact (HBC) structures.

[0003] In the fabrication of back-contact solar cells, P-type and N-type doped regions are typically formed sequentially on the back side, and current is collected through metal electrodes. To improve carrier collection efficiency, a transparent conductive oxide (TCO), such as indium tin oxide (ITO), is often introduced between the semiconductor layer and the metal electrode to improve ohmic contact and reduce contact resistance.

[0004] However, in back-contact cell structures containing a TCO layer, if the TCO layer between the P-region and the N-region is not effectively disconnected, a lateral conduction path will form at the P / N junction, leading to increased leakage current and consequently reducing the open-circuit voltage (Voc) and fill factor (FF), thus affecting the overall photoelectric conversion performance of the cell. Therefore, the TCO layer must be locally removed at the P / N junction to achieve electrical isolation between the P-region and the N-region.

[0005] Currently, selective etching of the TCO layer typically relies on masking processes. A common approach is to use screen printing or photoresist as a mask, combined with wet or dry etching techniques to remove TCO from specific areas. These methods often involve multiple independent mask fabrication and removal steps, resulting in complex processes, increased production costs, and the potential for interface damage or contamination due to repeated processing, impacting device efficiency and reliability. In particular, when using copper plating, the electrolyte may penetrate into sensitive interface regions near the P / N junction (such as amorphous silicon / crystalline silicon heterojunctions), causing metal ion contamination, increasing recombination centers, and reducing long-term stability. Existing tests have shown that such structures may exhibit significant performance degradation under high-temperature and high-humidity aging conditions.

[0006] To address the aforementioned issues, existing technologies have attempted to use etching paste or specific etching solutions for localized removal of the TCO layer. However, these methods still require additional cleaning steps, are difficult to precisely control the etched area, and cannot meet the requirements for fine patterning of subsequent electrodes.

[0007] Therefore, it is imperative to provide a new back-contact solar cell and its electrode fabrication method that can organically combine P / N region TCO isolation with electrode patterning process, reduce the number of mask uses and process steps, and reduce the risk of material damage.

[0008] In view of this, the present invention is hereby proposed. Summary of the Invention

[0009] The primary objective of this invention is to provide a method for fabricating a back-contact solar cell. This method integrates TCO insulating etching and electroplated grid line formation by performing multiple independent patterning processes on the same photosensitive mask layer, and sets an anti-permeation functional structure within the insulating channel. This not only significantly simplifies the process flow but also improves the electrical performance of the cell.

[0010] A second objective of this invention is to provide a back-contact solar cell.

[0011] A third objective of this invention is to provide an application of a back-contact solar cell in the fabrication of a photovoltaic module.

[0012] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: This invention provides a method for fabricating a back-contact solar cell, the method comprising the following steps: S1: A photosensitive mask layer is formed on the TCO layer on the back of the battery; S2: Perform at least two independent patterning operations using the same photosensitive mask layer in a time-division manner, sequentially forming multiple patterning windows, wherein: At least one graphical window exposes the TCO layer region at the junction of the P-type region and the N-type region, which is used to perform wet etching on the TCO layer in this region to cut off the conductive path between the P-type region and the N-type region and achieve electrical insulation. At least one other graphical window exposes the TCO region in the P-type region and / or N-type region for forming metal gate lines, which are then used to form metal gate line electrodes by electroplating. The photosensitive mask layer is not stripped or recoated between two independent graphical operations.

[0013] Furthermore, the preparation method further includes: removing the photosensitive mask layer after completing the process corresponding to the graphical window; or, retaining the photosensitive mask layer after completing the process corresponding to the graphical window.

[0014] Furthermore, before wet etching the TCO layer, the process also includes: using the window formed by the first patterning as a barrier layer to selectively expose the TCO layer at the P / N junction; Preferably, when the wet etching is used to etch the TCO layer, the etching stops at the surface of the second passivation layer. After the wet etching, the TCO layer between the P-type region and the N-type region is partially removed, forming an insulating channel.

[0015] Furthermore, after wet etching to form the insulating channel and before electroplating, the process also includes: A functional structure is provided within the insulating channel to prevent the electroplating solution from penetrating into the semiconductor interface.

[0016] Furthermore, the functional structure is a protective coating obtained by printing or spraying inorganic or organic materials.

[0017] Furthermore, the functional structure is composed of a portion of a permanent photosensitive mask, referred to as the second mask; The second mask is screen-printed inside and above the insulating channel after the first patterning, and plays a physical barrier role during the electroplating process.

[0018] Furthermore, the TCO layer includes one of ITO, VTTO, and SnOx.

[0019] The present invention provides a back-contact solar cell, comprising: The substrate is N-type single-crystal silicon, with P-type and N-type regions on its back side; The second passivation layer is located on the P-type and N-type regions; A first silicon doped layer disposed in the P-type region and a second silicon doped layer disposed in the N-type region; A TCO layer is applied over the first silicon doped layer and the second silicon doped layer, wherein: the TCO layer between the P-type region and the N-type region is partially removed to form an insulating channel; a functional structure for preventing electroplating solution from penetrating into the semiconductor interface is provided within or above the insulating channel. Metal grid electrodes (008) formed by electroplating on the P-type region and N-type region respectively. And the first passivation layer and the outermost antireflection layer are disposed on the front; The metal gate electrode is formed by defining the same photosensitive mask layer through at least two independent patterning methods.

[0020] The present invention provides an application of the above-mentioned back-contact solar cell in the fabrication of photovoltaic modules.

[0021] The present invention provides a photovoltaic module, wherein the photovoltaic module comprises a plurality of the above-mentioned back-contact solar cells connected in series or in parallel and integrated using half-cell or shingled technology.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for fabricating a back-contact solar cell provided by this invention involves performing at least two independent patterning operations on the same photosensitive mask layer in a time-division manner, sequentially defining the TCO layer etching region and the metal grid plating region, thus achieving multi-functional reuse of the patterning mask. Compared to the traditional process that requires separate masks for insulating channel etching and electrode patterning, this method significantly reduces the number of mask coating, alignment, and removal operations, effectively shortening the overall process flow and reducing material consumption and equipment costs. Simultaneously, it avoids the overlay errors and interface contamination risks introduced by multiple masking operations, improving process stability and product yield. Furthermore, since there is no need to peel off the mask after the first patterning, the retained mask structure can provide temporary protection for subsequent processes, helping to maintain the passivation quality of the semiconductor surface.

[0023] The back-contact solar cell provided by this invention effectively cuts off the lateral conductive path between the P / N regions by setting an insulating channel formed by partial removal in the TCO layer between the P-type and N-type regions, thus avoiding the problem of increased leakage current caused by continuous TCO coverage. Simultaneously, this application provides a functional structure within or above the insulating channel to prevent electroplating solution penetration. This structure, as a physical barrier layer, effectively inhibits the diffusion of electrolyte to the semiconductor interface during subsequent electroplating processes, preventing metal ion contamination and the formation of interface recombination centers, thereby significantly improving the long-term stability and reliability of the battery under high temperature and high humidity environments. Furthermore, the metal grid lines of this invention are formed by defining the same photosensitive mask layer through at least two independent patterning steps, achieving a highly integrated manufacturing mode of "one-time coating, multi-step patterning," which not only simplifies the process flow and reduces production costs but also improves patterning accuracy and overlay consistency.

[0024] The back-contact solar cell provided by this invention can be widely used in the manufacturing process of photovoltaic modules. The photovoltaic module is composed of several back-contact solar cells connected in series or parallel and integrated using half-cell or shingled technology. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of a back-contact solar cell provided in Embodiment 1 of the present invention; Figure 2 This is a process flow diagram of the fabrication process of the back contact solar cell provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the structure of a back-contact solar cell provided in Embodiment 2 of the present invention; Figure 4 This is a process flow diagram of the fabrication process of the back contact solar cell provided in Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of the structure of the back-contact solar cell provided in Embodiment 3 of the present invention; Figure 6 This is a process flow diagram of the fabrication process of the back-contact solar cell provided in Embodiment 3 of the present invention; Figure 7 This is a schematic diagram of the structure of the back-contact solar cell provided in Embodiment 4 of the present invention; Figure 8 This is a process flow diagram of the fabrication process of the back contact solar cell provided in Embodiment 4 of the present invention; Figure 9 This is a process flow diagram of the fabrication process of the back contact solar cell provided in Embodiment 5 of the present invention; Figure 10 This is a process flow diagram of the fabrication process of the back-contact solar cell provided in Embodiment 6 of the present invention.

[0027] Icons: 001-N-monocrystalline silicon; 002-first passivation layer; 003-second passivation layer; 004-first silicon doped layer; 005-second silicon doped layer; 006-TCO layer; 007-antireflection layer; 008-metal gate electrode; 009-photosensitive mask layer; 010-functional structure; 011-seed layer; 012-second mask. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] According to one aspect of the present invention, a method for fabricating a back-contact solar cell includes the following steps: S1: A photosensitive mask layer 009 is formed on the TCO layer 006 on the back of the battery; S2: Perform at least two independent graphical operations using the same photosensitive mask layer (009 time division) to sequentially form multiple graphical windows, where: At least one graphical window exposes the TCO layer 006 region at the junction of the P-type region and the N-type region, which is used to perform wet etching on the TCO layer 006 in this region to cut off the conductive path between the P-type region and the N-type region and achieve electrical insulation. At least one other graphical window exposes the TCO region in the P-type region and / or N-type region for forming metal gate lines, which are then used to form metal gate line electrodes 008 by electroplating. The photosensitive mask layer 009 is not stripped or recoated between two independent graphical operations.

[0030] The method for fabricating a back-contact solar cell provided by this invention involves performing at least two independent patterning operations on the same photosensitive mask layer 009 in a time-division manner, sequentially defining the TCO layer 006 etching region and the metal grid plating region, thus achieving multi-functional reuse of the patterning mask. Compared to the traditional process that requires separate masks for etching the insulating channel and patterning the electrodes, this method significantly reduces the number of mask coating, alignment, and removal operations, effectively shortening the overall process flow and reducing material consumption and equipment costs. Simultaneously, it avoids the overlay errors and interface contamination risks introduced by multiple masking operations, improving process stability and product yield. Furthermore, since it eliminates the need to peel off the mask after the first patterning, the retained mask structure can provide temporary protection for subsequent processes, helping to maintain the passivation quality of the semiconductor surface.

[0031] It should be noted that the patterning operations described in this application include at least one of the following: photolithography exposure and development, screen printing, inkjet printing, laser direct writing, or microcontact printing. Furthermore, the specific implementation method of the patterning operation needs to be flexibly selected based on the type of the selected photosensitive mask layer 009, with the core being the utilization of the differences in the photochemical properties of the materials.

[0032] (i) When the photosensitive mask layer 009 is a negative photoresist, its characteristic is that the exposed area undergoes cross-linking and solidification, and does not dissolve in the developer; while the unexposed area can be dissolved and removed by the developer. The preferred method for the two patterning operations includes: 1. First patterning: The first patterned window is directly formed on the negative adhesive layer (photosensitive mask layer 009) through screen printing, inkjet printing and other methods; 2. Second patterning: Expose and develop the same negative resist layer. The exposed area corresponds to the electrode area where the second patterning window needs to be formed, thus forming the second patterning window.

[0033] (ii) When the photosensitive mask layer 009 is a positive photoresist, its characteristic is that the exposed area undergoes a photodissolution reaction and can be dissolved and removed in the developer; while the unexposed area is retained. The preferred method for the two patterning operations includes: 1. First pattern definition: The positive resist layer (photosensitive mask layer 009) is selectively exposed for the first time through a photomask with a first pattern, so that the area corresponding to the first pattern window is exposed. Then, development is performed to remove the exposed area, forming the first pattern window.

[0034] 2. Second Patterning: Replace the mask with one bearing the second pattern, or use a different area of ​​the same mask to selectively expose the same positive resist layer a second time, exposing the area corresponding to the second patterning window. Subsequently, development can be performed again to remove the newly exposed area, thus forming the second patterning window. Because the unexposed areas of the positive resist are always preserved, the two exposure patterns can be precisely superimposed without interference.

[0035] In a preferred embodiment of the present invention, the preparation method further includes: removing the photosensitive mask layer 009 after completing the process corresponding to the graphical window; or retaining the photosensitive mask layer 009 after completing the process corresponding to the graphical window.

[0036] In a preferred embodiment of the present invention, before wet etching the TCO layer 006, the method further includes: using the window formed by the first patterning as a barrier layer to selectively expose the TCO layer 006 at the P / N junction. Preferably, when the wet etching is performed on the TCO layer 006, the etching stops at the surface of the second passivation layer 003. After the wet etching, the TCO layer 006 between the P-type region and the N-type region is partially removed, forming an insulating channel.

[0037] In a preferred embodiment of the present invention, after wet etching to form an insulating channel and before electroplating, the method further includes: providing a functional structure 010 in the insulating channel to prevent the electroplating solution from penetrating into the semiconductor interface.

[0038] In a preferred embodiment, after forming an insulating channel between the P-type and N-type regions using wet etching, the present invention provides a functional structure 010 within the channel to prevent the electroplating solution from penetrating into the semiconductor interface. This effectively blocks direct contact between the electrolyte and the sensitive semiconductor interface during subsequent electroplating. By pre-constructing this functional structure 010 within the insulating channel, the present invention creates a dual physical and chemical barrier, significantly suppressing the risk of electrolyte erosion of the passivation layer and doped regions, and ensuring the electrical isolation stability at the P / N interface. Simultaneously, this structure helps maintain the quality of the back-side passivation, reduces interface defect generation, and thus improves the long-term reliability and environmental tolerance of the device.

[0039] In a preferred embodiment of the present invention, the functional structure 010 is a protective coating printed or sprayed from inorganic or organic materials.

[0040] In a preferred embodiment of the present invention, the functional structure 010 is composed of a portion of a permanent photosensitive mask, referred to as the second mask 012; The second mask 012 is screen-printed inside and above the insulating channel after the first patterning, and plays a physical barrier role during the electroplating process.

[0041] In a preferred embodiment of the present invention, the material of the TCO layer 006 may be selected from, but is not limited to: indium tin oxide (ITO), indium tungsten oxide (IWO / VTTO), and tin oxide (SnOx).

[0042] According to one aspect of the present invention, a back-contact solar cell comprises: The substrate is N-type single crystal silicon 001, with P-type and N-type regions on its back side; The second passivation layer 003 is located on the P-type and N-type regions; A first silicon doped layer 004 is disposed in the P-type region and a second silicon doped layer 005 is disposed in the N-type region; A TCO layer 006 is covered on the first silicon doped layer 004 and the second silicon doped layer 005, wherein: the TCO layer 006 between the P-type region and the N-type region is partially removed to form an insulating channel; a functional structure 010 for preventing electroplating solution from penetrating into the semiconductor interface is provided in or above the insulating channel. Metal grid line electrodes 008 formed by electroplating are located on the P-type region and N-type region, respectively; And the first passivation layer 002 and the outermost antireflection layer 007 are disposed on the front side; The metal gate electrode 008 is formed by defining the same photosensitive mask layer 009 through at least two independent patterning methods.

[0043] The back-contact solar cell provided by this invention effectively cuts off the lateral conductive path between the P / N regions by setting an insulating channel formed by partial removal in the TCO layer 006 between the P-type and N-type regions, thus avoiding the problem of increased leakage current caused by continuous TCO coverage. Simultaneously, this application provides a functional structure 010 within or above the insulating channel to prevent electroplating solution penetration. This structure, as a physical barrier layer, effectively suppresses the diffusion of electrolyte to the semiconductor interface during subsequent electroplating processes, preventing metal ion contamination and the formation of interface recombination centers, thereby significantly improving the long-term stability and reliability of the battery under high temperature and high humidity environments. Furthermore, the metal grid lines of this invention are formed by defining the same photosensitive mask layer 009 through at least two independent patterning steps, achieving a highly integrated manufacturing mode of "one-time coating, multi-step patterning," which not only simplifies the process flow and reduces production costs but also improves patterning accuracy and overlay consistency.

[0044] According to one aspect of the present invention, the above-described back-contact solar cell is used in the fabrication of a photovoltaic module.

[0045] The back-contact solar cell provided by this invention can be widely used in the manufacturing process of photovoltaic modules.

[0046] According to one aspect of the present invention, a photovoltaic module is provided, wherein a plurality of the aforementioned back-contact solar cells are connected in series or in parallel and integrated using half-cell or shingled technology.

[0047] The technical solution of the present invention will be further described below with reference to the embodiments.

[0048] Example 1 Figure 1 This is a schematic diagram of the structure of a back-contact solar cell provided in Embodiment 1 of the present invention.

[0049] Figure 2 This is a process flow diagram of the fabrication process of the back contact solar cell provided in Embodiment 1 of the present invention.

[0050] See Figure 1 , Figure 2 The method for fabricating a back-contact solar cell in this embodiment includes the following steps: (1) Preparation of XBC blue film: We provide XBC cell substrates with completed front texturing, back passivation layer, doped layer, and TCO layer 006 deposition.

[0051] (2) Mask fabrication: A patternable negative photosensitive resin is uniformly coated on the TCO layer 006 on the back of the battery, and the photosensitive mask layer 009 is formed after pre-baking treatment.

[0052] The photosensitive mask layer 009 is the single carrier for subsequent two patterning operations.

[0053] (3) First patterning and TCO etching: The photosensitive mask layer 009 formed in step (2) is subjected to a first patterning operation. In this embodiment, a first patterned window is directly formed on the photosensitive mask layer 009 using a screen printing process, exposing the underlying TCO layer 006; The exposed TCO layer 006 is wet-etched to remove the conductive material at the P / N junction, thereby forming an insulating channel and severing the lateral electrical connection between the P and N regions.

[0054] (4) Filling + Drying (Ditch Insulation Treatment): After TCO etching is completed, without removing the mask, a dense inorganic silicon oxide protective layer, namely functional structure 010, is deposited in the channel region within the first opening (i.e., the insulating channel) to cover the disconnected TCO edge interface and achieve P / N region insulation isolation.

[0055] (5) Second graphical representation: While retaining and continuing to use the same photosensitive mask layer 009, a second patterning is performed: through exposure and development processes, a second set of openings is formed on the photosensitive mask layer 009; The second set of openings is located at predetermined positions in the P-type and N-type regions, respectively exposing the TCO regions below for forming the metal gate lines. Thus, the same photomask layer 009, through two independent patterning processes, defines the insulating channel and the electroplating window, achieving multiple uses for a single mask.

[0056] (6) Electroplating: In the second opening, copper seed layer 011 is deposited and DC electroplating is performed sequentially to thicken it, forming a low-resistance, fine-lined metal gate electrode 008. Optionally, after electroplating, the photosensitive mask layer 009 is removed by ashing or wet stripping processes to obtain the back contact solar cell structure.

[0057] Example 2 The difference between this embodiment and embodiment 1 is that the XBC blue film in step (1) is replaced with the XBC yellow film.

[0058] Note: The yellow film refers to a battery semi-finished product on the basis of the "blue film" with the back seed layer 011 deposited. Therefore, this embodiment has a seed layer 011 compared to embodiment 1.

[0059] Figure 3 This is a schematic diagram of the structure of a back-contact solar cell provided in Embodiment 2 of the present invention.

[0060] Figure 4 This is a process flow diagram of the fabrication process of the back contact solar cell provided in Embodiment 2 of the present invention.

[0061] Example 3 The difference from Example 1 is that the protective layer is not included, and a permanent second mask 012 is used instead of the protective layer.

[0062] Figure 5 This is a schematic diagram of the structure of a back-contact solar cell provided in Embodiment 3 of the present invention.

[0063] Figure 6 This is a process flow diagram of the fabrication process of the back contact solar cell provided in Embodiment 3 of the present invention.

[0064] See Figure 5 , Figure 6 The method for fabricating a back-contact solar cell in this embodiment includes the following steps: (1) Preparation of XBC blue film: Same as in Example 1; (2) First mask fabrication: Same as in Example 1; (3) First patterning and TCO etching: Same as in Example 1; (4) Second mask 012 for screen printing: like Figure 6 As shown, after TCO etching, a layer of insulating paste (negative ink) is printed on the entire back of the battery as a second mask 012 using a screen printing process. The insulating paste (negative ink) fills the insulating channels formed in step (3). After printing, it is pre-dried for subsequent patterning.

[0065] (5) Second graphical representation: Using photolithography equipment, selective exposure and development are performed on the first and second masks using a mask template corresponding to the predetermined electroplating pattern (i.e., the future gate line position), precisely forming a second set of openings on the second mask 012. The pattern of this set of openings is consistent with the arrangement of the future metal gate lines, and is located directly above the TCO layer 006 in the P-type and N-type regions, respectively, thereby fully exposing the TCO region for electroplating.

[0066] (6) Electroplating: On the TCO region exposed at the opening formed in step (5), a copper seed layer 011 is deposited and then thickened by DC electroplating to form a low-resistance, fine-line metal grid electrode 008. After electroplating, the second mask 012 does not need to be removed and is retained as part of the final battery structure.

[0067] Example 4 The difference between this embodiment and embodiment 3 is that the XBC blue film in step (1) is replaced with the XBC yellow film.

[0068] Note: The yellow film refers to a battery semi-finished product on the basis of the "blue film" with the back seed layer 011 deposited. Therefore, this embodiment has a seed layer 011 compared to embodiment 3.

[0069] Figure 7 This is a schematic diagram of the structure of a back-contact solar cell provided in Embodiment 4 of the present invention.

[0070] Figure 8 This is a process flow diagram of the fabrication process of the back-contact solar cell provided in Embodiment 4 of the present invention.

[0071] Example 5 In Example 5, only one mask is used in the fabrication process, but the grid lines are made first, and the final back-contact solar cell structure is the same as in Example 1.

[0072] Figure 9 This is a process flow diagram of the fabrication process of the back contact solar cell provided in Embodiment 5 of the present invention.

[0073] See Figure 9 The method for fabricating a back-contact solar cell in this embodiment includes the following steps: (1) Preparation of XBC blue film: Same as in Example 1; (2) Mask fabrication: A patternable negative photosensitive resin is uniformly coated on the TCO layer 006 on the back of the battery, and after pre-baking treatment, a photosensitive mask layer 009 is formed.

[0074] This photosensitive mask layer 009 will serve as a single mask shared by the subsequent electroplating and etching patterning processes.

[0075] (3) Electroplating: The photosensitive mask layer 009 formed in step (2) is first patterned, and the first patterned window is directly formed by screen printing, exposing the underlying TCO layer 006.

[0076] Subsequently, using the same patterned photosensitive mask layer 009 as the electroplating mask, a copper seed layer 011 was deposited and then DC electroplating was performed sequentially on the exposed TCO region to form a low-resistance, fine-lined metal gate electrode 008. At this point, the fabrication of the gate electrode was completed.

[0077] (4) Exposure and development (second patterning): Without stripping the same photomask layer 009, it is patterned a second time, and through re-exposure and development, a second set of openings is formed on the photomask layer 009.

[0078] The second set of openings is precisely located at the boundary between the P-type and N-type regions, exposing the TCO region that needs to be etched to achieve electrical isolation between the P / N regions. At this time, the photomask layer 009 simultaneously contains the first set of openings for defining the gate lines and the second set of openings for defining the insulating channels.

[0079] (5) Etching: Using the same photosensitive mask layer 009 that has been patterned a second time as an etching barrier layer, wet etching is performed on the TCO layer 006 exposed in step (4). This step selectively removes the ITO-type TCO material at the P / N junction, thereby forming an insulating channel and completely cutting off the lateral conductive path between the P region and the N region.

[0080] (6) Filling protective layer: After TCO etching is completed, the photosensitive mask layer 009 is retained. In the insulating channel formed in step (5), a dense inorganic insulating material is filled and deposited by spraying or other suitable processes as a channel protective layer. Subsequently, a curing process is performed to make the protective layer firmly cover the disconnected TCO edge interface, achieving permanent insulation isolation of the P / N region.

[0081] (7) Remove the mask: After the protective layer is filled and cured, the same photosensitive mask layer 009 coated and used in step (2) is completely removed by ashing, wet stripping or chemical dissolution, exposing the underlying metal grid electrode 008 and the cured protective layer and other structures, thus obtaining a complete back contact solar cell.

[0082] It should be noted that, depending on the actual application scenario, the above step (7) of removing the mask may not be included in this embodiment.

[0083] This embodiment utilizes a single photosensitive mask layer 009 to sequentially complete two key patterning processes: gate line definition and electroplating, and insulating channel definition and etching. Its advantages are: 1. This embodiment also uses a single mask, patterned twice, to complete the fabrication of all key structures (gate lines and insulating channels), significantly reducing the cost of mask materials and the complexity of the process.

[0084] 2. In this embodiment, complete metal grid lines are fabricated first, and then wet etching is performed, which increases the uniformity of electroplating and the electroplating capability.

[0085] Example 6 The difference between this embodiment and embodiment 5 is that the XBC blue film in step (1) is replaced with the XBC yellow film.

[0086] Note: The yellow film refers to a battery semi-finished product on the basis of the "blue film" with the back seed layer 011 deposited. Therefore, this embodiment has a seed layer 011 compared to embodiment 5.

[0087] Figure 10 This is a process flow diagram of the fabrication process of the back-contact solar cell provided in Embodiment 6 of the present invention.

[0088] Comparative Example 1 The difference between this comparative example and Example 1 is that in Example 1, the PN insulating region was etched away using a mask and etching solution, and then the mask was removed to screen print silver paste. The comparative method for fabricating a back-contact solar cell includes the following steps: (1) Preparation of XBC blue film: Same as in Example 1; (2) First mask fabrication and graphics: A first photoresist mask is coated on the TCO layer 006 on the back of the battery.

[0089] The first photoresist mask is patterned through the first exposure and development process, forming an opening only at the junction of the P-type and N-type regions to expose the TCO region that needs to be etched underneath.

[0090] (3) TCO etching: Using the patterned first mask as a barrier layer, wet etching is performed on the exposed TCO layer 006 to remove the TCO material at the P / N interface, thereby forming an insulating channel and achieving electrical isolation between the P region and the N region.

[0091] (4) Remove the first mask: After the TCO etching is completed, the first photoresist mask used in step (2) is completely removed by ashing or wet stripping processes. At this time, only the TCO layer 006 and the disconnected insulating channel in it are on the back of the battery, and the insulating channel and the TCO etching edge are directly exposed.

[0092] (5) Screen-printed silver paste electrode: After the battery has been insulated, cleaned, and dried, conductive silver paste is directly printed onto the surface of the TCO layer 006 above the P-type and N-type regions using a screen printing process, forming a finger-shaped intersecting grid pattern. The silver paste pattern must avoid the insulating trench formed in step (3).

[0093] Subsequently, the printed silver paste is sintered at high temperature, which melts the glass material in the silver paste and forms an ohmic contact with the TCO layer 006, while the organic carrier is volatilized, and finally solidifies to form the silver paste grid line electrode.

[0094] Comparative Example 1 is the traditional method, which involves first using a first mask to complete the insulating etching and then immediately removing it, and then using a second set of tools (screen printing) to form the electrode. This involves two independent patterning systems (photolithography + screen printing) and two independent pattern alignments.

[0095] Comparative Example 2 The difference between this comparative example and Example 1 is that in Example 1, after etching away the PN insulating region with etching paste, the etching paste was removed with alkaline solution, and then silver paste was screen printed. The comparative method for fabricating a back-contact solar cell includes the following steps: (1) Preparation of XBC blue film: Same as in Example 1; (2) Etching: Instead of using a photoresist mask, a paste or gel-like chemical etching paste is precisely applied to the interface between the P-type and N-type regions on the TCO layer 006 on the back of the battery using methods such as screen printing, dispensing, or coating. This etching paste contains acidic or alkaline components that react with the TCO material (such as ITO). Within a set reaction time, the etching paste selectively dissolves the TCO material in the underlying contact area, thereby forming a physically insulating trench.

[0096] (3) Remove residual etching paste: After reaching the predetermined etching depth, the back of the battery is sprayed or soaked in an alkaline solution to thoroughly neutralize and remove all residual etching paste and its reaction byproducts.

[0097] (4) Screen-printed silver paste electrode: After cleaning and drying, conductive silver paste is directly printed onto the surface of the complete TCO layer 006 above the P-type and N-type regions using a screen printing process to form a grid pattern. During printing, it is necessary to ensure that the silver paste pattern avoids the insulating trench formed in step (2) to prevent short circuits in the P / N regions.

[0098] Subsequently, the printed silver paste is sintered at high temperature (peak temperature >700°C). At high temperature, the glass floc in the silver paste melts and forms an ohmic contact with the TCO layer 006, the organic carrier volatilizes, and finally solidifies into silver paste grid line electrodes.

[0099] Comparative Example 2 is a traditional manufacturing method that relies on etching paste and high-temperature silver paste. Compared with this application, it has inherent limitations in terms of accuracy, cost, temperature compatibility, process integration and final device performance.

[0100] Experimental Example 1 To verify the long-term reliability of the back-contact solar cell provided by the present invention under harsh conditions, 10 back-contact solar cell samples prepared by the methods of Examples 1-6 and Comparative Examples 1 and 2 were selected and subjected to high-temperature and high-humidity aging tests (HTHH, 85% relative humidity, 85°C, for 120 hours). The specific results are shown in Table 1.

[0101] Table 1:

[0102] As shown in Table 1 above, the photoelectric conversion efficiency (ETA) degradation of all sample examples was controlled within 1% (0.30%–0.89%), with an average degradation of only about 0.63%, indicating that the devices have excellent environmental tolerance. In contrast, the efficiency degradation of Comparative Example 1 and Comparative Example 2 reached 8.5% and 8.3% respectively, which is more than 10 times that of the examples, showing a significant trend of performance degradation.

[0103] The significant differences between the embodiments of this application and the comparative examples 1 and 2 mentioned above mainly stem from the fact that the present invention incorporates a functional structure 010 within the insulating channel of the TCO layer 006 between the P-type and N-type regions to prevent electroplating solution penetration. Furthermore, it utilizes a single photosensitive mask layer 009 to achieve multiple patterned integration processes, effectively avoiding damage caused by repeated cleaning and interface exposure. The functional structure 010 acts as a dual physical and chemical barrier, blocking the diffusion path of moisture and electrolyte to the semiconductor sensitive interface, suppressing metal ion contamination and the formation of interface recombination centers, thereby significantly improving the long-term stability of the device.

[0104] Further comparison of different embodiments reveals that: Examples 1 and 2, which use dense inorganic materials to fill the channels (attenuation of approximately 0.3%), perform best; while Examples 3 and 4, which use an organic second mask 012, are slightly better (approximately 0.55%); Examples 5 and 6, which use electroplating followed by etching, have relatively large attenuation (approximately 0.88%), but are still far superior to the comparative examples. This gradient variation confirms that the material selection and process sequence of the functional structure 010 have a regulatory effect on reliability, and also demonstrates the overall synergistic effect and optimization potential of the technical solution of this invention.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a back-contact solar cell, characterized in that, The preparation method includes the following steps: S1: A photosensitive mask layer (009) is formed on the TCO layer (006) on the back of the battery. S2: At least two independent graphical operations are performed time-division multiple times using the same photosensitive mask layer (009) to sequentially form multiple graphical windows, wherein: At least one graphical window exposes the TCO layer (006) region at the junction of the P-type region and the N-type region, which is used to perform wet etching on the TCO layer (006) in this region to cut off the conductive path between the P-type region and the N-type region and achieve electrical insulation; At least one other graphical window exposes the TCO region in the P-type region and / or N-type region for forming metal grid lines, which are then used to form metal grid line electrodes (008) by electroplating. The photosensitive mask layer (009) is not stripped or recoated between two independent graphical operations.

2. The method according to claim 1, characterized in that, The preparation method further includes: removing the photosensitive mask layer (009) after completing the process corresponding to the graphical window. Alternatively, after completing the process corresponding to the graphical window, the photosensitive mask layer (009) can be retained.

3. The method according to claim 1, characterized in that, When the wet etching process etches the TCO layer (006), the etching stops at the surface of the second passivation layer (003). After the wet etching process, the TCO layer (006) between the P-type region and the N-type region is partially removed, forming an insulating channel.

4. The method according to claim 3, characterized in that, After wet etching to form the insulating channel and before electroplating, the process also includes: A functional structure (010) is provided in the insulating channel to prevent the electroplating solution from penetrating into the semiconductor interface.

5. The method according to claim 4, characterized in that, The functional structure (010) is a permanent insulating layer formed in the insulating channel by screen printing, inkjet printing or coating, and serves as an electroplating barrier layer in subsequent patterning.

6. The method according to claim 4, characterized in that, The functional structure (010) is a protective coating printed or sprayed from inorganic or organic materials; Alternatively, the functional structure (010) is composed of a portion of a photosensitive mask, referred to as the second mask (012). The second mask (012) is screen-printed inside and above the insulating channel after the first patterning and plays a physical barrier role during the electroplating process.

7. The method according to claim 1, characterized in that, The TCO layer (006) includes one of indium tin oxide, tungsten-doped indium oxide, and tin oxide.

8. A back-contact solar cell, characterized in that, include: The substrate is N-type monocrystalline silicon (001), with P-type and N-type regions on its back side; The second passivation layer (003) is located on the P-type region and the N-type region. A first silicon doped layer (004) is disposed in the P-type region and a second silicon doped layer (005) is disposed in the N-type region; A TCO layer (006) is covered on the first silicon doped layer (004) and the second silicon doped layer (005), wherein: the TCO layer (006) between the P-type region and the N-type region is partially removed to form an insulating channel; a functional structure (010) for preventing electroplating solution from penetrating into the semiconductor interface is provided in or above the insulating channel. Metal grid electrodes (008) formed by electroplating on the P-type region and N-type region respectively. And a first passivation layer (002) and an outermost antireflection layer (007) disposed on the front. The metal gate electrode (008) is formed by defining the same photosensitive mask layer (009) through at least two independent patternings.

9. Use of a back-contact solar cell according to claim 8 in the fabrication of a photovoltaic module.

10. A photovoltaic module, characterized in that, The photovoltaic module is composed of several back-contact solar cells as described in claim 8 connected in series or in parallel, and integrated using half-cell or shingled technology.

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