Method for manufacturing a solar cell and solar cell

Abstract

This application provides a method for fabricating a solar cell and the solar cell itself. The method includes: sequentially forming an intrinsic amorphous silicon layer, an amorphous silicon layer, a transparent conductive layer, a seed layer, and a photosensitive adhesive layer on a first surface and / or a second surface of a substrate; covering the side of the photosensitive adhesive layer away from the substrate with an angle-selective anti-reflection film, and exposing the photosensitive adhesive layer to form a non-developable reaction area on the photosensitive adhesive layer; removing the angle-selective anti-reflection film, and developing the non-developable reaction area to expose the electroplating area of ​​the seed layer; electroplating metal grid lines on the exposed electroplating area of ​​the seed layer, and removing the remaining photosensitive adhesive layer and the non-electroplated area of ​​the seed layer to obtain the solar cell. This method prepares an angle-selective anti-reflection film on the surface of the photosensitive adhesive to be exposed, and uses the interference effect of light to control the reflection behavior, so that destructive interference is achieved when perpendicularly incident light passes through, thereby minimizing reflection and maximizing transmission, and avoiding the curing of the adhesive film in the grid line area by scattered light.

Description

Technical Field

[0001] This application relates to the field of solar cell fabrication technology, and more specifically, to a method for fabricating a solar cell and a solar cell. Background Technology

[0002] Heterojunction solar cells (HJTs) currently employ a method of printing silver paste to form silver grid lines on the surface of an indium tin oxide (ITO) transparent conductive film. To ensure a larger light-absorbing area in the cell, the linewidth printed during pattern transfer on the seed copper layer needs to be minimized as much as possible to increase the short-circuit current and thus improve cell efficiency. However, as the printed linewidth decreases, the scattering of printed light causes some grid line areas to be exposed. This limits the theoretical lower limit of the printed linewidth and makes cells with linewidths below the lower limit prone to residual adhesive after development, leading to poor contact during electroplating and potentially causing grid breakage. Summary of the Invention

[0003] The main objective of this application is to provide a method for preparing a solar cell and a solar cell, so as to at least solve the problem in the prior art that residual adhesive abnormalities easily exist at the bottom of the groove after development in the preparation of existing solar cells, resulting in poor performance of the solar cell.

[0004] To achieve the above objectives, according to one aspect of this application, a method for fabricating a solar cell is provided, comprising: providing a substrate; sequentially forming an intrinsic amorphous silicon layer, an amorphous silicon layer, a transparent conductive layer, a seed layer, and a photosensitive adhesive layer on a first surface and / or a second surface of the substrate; covering the side of the photosensitive adhesive layer away from the substrate with an angle-selective anti-reflection film, and exposing the photosensitive adhesive layer to form a non-developable reaction region on the photosensitive adhesive layer, wherein the refractive index difference of the angle-selective anti-reflection film is greater than a preset refractive index difference; removing the angle-selective anti-reflection film, and developing the non-developable reaction region to remove the non-developable reaction region, thereby exposing the electroplating area of ​​the seed layer; electroplating metal grid lines on the exposed electroplating area of ​​the seed layer, and removing the remaining photosensitive adhesive layer and the non-electroplated area of ​​the seed layer to obtain a solar cell.

[0005] Optionally, before covering the side of the photosensitive adhesive layer away from the substrate with an angle-selective anti-reflective film, the method further includes: providing a carrier; and sequentially forming a first thin film and a second thin film on the carrier using a magnetron sputtering process to obtain the angle-selective anti-reflective film, wherein the refractive index of the first thin film is greater than a first preset refractive index, the refractive index of the second thin film is less than a second preset refractive index, and the first preset refractive index is greater than the second preset refractive index.

[0006] Optionally, the angle-selective anti-reflection film is obtained by sequentially forming a first thin film and a second thin film on the carrier using a magnetron sputtering process, comprising: a first sputtering step, forming the first thin film on the carrier using a magnetron sputtering process; a second sputtering step, forming the second thin film on the surface of the first thin film away from the carrier using the magnetron sputtering process; and repeating the first sputtering step and the second sputtering step a predetermined number of times to form the first thin film and the second thin film spaced apart on the carrier, thereby obtaining the angle-selective anti-reflection film, wherein the angle-selective anti-reflection film comprises a plurality of first thin films and a plurality of second thin films.

[0007] Optionally, the angle-selective antireflective film is obtained by sequentially forming a first thin film and a second thin film on the carrier using a magnetron sputtering process, comprising: forming the first thin film on the carrier using the magnetron sputtering process according to a first process parameter; and forming the second thin film on the surface of the first thin film away from the carrier using the magnetron sputtering process according to a second process parameter, thereby obtaining the angle-selective antireflective film.

[0008] Optionally, the first process parameters include a first target sputtering power, a first pressure, and a first reaction gas. The first target sputtering power is 180W~220W, the first pressure is 0.4Pa~0.6Pa, the ratio of inert gas to oxygen in the first reaction gas is three to one, the first pressure is the working pressure of the first chamber where the carrier is currently located, and the first reaction gas is the reaction gas introduced into the first chamber.

[0009] Optionally, the second process parameters include the second target sputtering power, the second pressure, and the second reaction gas. The second target sputtering power is 330W~380W, the second pressure is 0.3Pa~0.5Pa, the ratio of inert gas to oxygen in the second reaction gas is four to one, the second pressure is the working pressure of the second chamber where the carrier is currently located, and the second reaction gas is the reaction gas introduced into the second chamber.

[0010] Optionally, the refractive index difference of the angle-selective antireflective film is 0.92 to 0.99.

[0011] Optionally, the first film is a titanium dioxide film, and the second film is a silicon dioxide film.

[0012] Optionally, the thickness of the first film is 65nm~75nm, and the thickness of the second film is 105nm~115nm.

[0013] According to another aspect of this application, a solar cell is provided, which is prepared using any of the solar cell preparation methods described above.

[0014] Applying the technical solution of this application, the above-mentioned method for fabricating a solar cell firstly involves sequentially forming an intrinsic amorphous silicon layer, an amorphous silicon layer, a transparent conductive layer, a seed layer, and a photosensitive adhesive layer on a first surface and / or a second surface of a substrate; then, an angle-selective anti-reflection film is applied to the side of the photosensitive adhesive layer away from the substrate, and the photosensitive adhesive layer is exposed to form a non-developable reaction area on the photosensitive adhesive layer; the angle-selective anti-reflection film is removed, and the non-developable reaction area is developed, exposing the electroplating area of ​​the seed layer; finally, metal grid lines are electroplated on the exposed electroplating area of ​​the seed layer, and the remaining photosensitive adhesive layer and the non-electroplated area of ​​the seed layer are removed to obtain a solar cell. This method prepares an angle-selective anti-reflection film on the surface of the photosensitive adhesive to be exposed, utilizing the interference effect of light to control the reflection behavior, so that destructive interference is achieved when perpendicularly incident light passes through, thereby minimizing reflection and maximizing transmission; when obliquely incident light passes through, the optical path difference changes with the increase of the incident angle, destroying the original destructive interference condition, resulting in a significant increase in reflectivity. This application utilizes an angle-selective antireflective film to ultimately block the incident light (tilted incident light), preventing the scattered light from curing the resist film in the grid line area. This avoids the influence of scattered light from the printing exposure on the resist film in the grid line area, resolving grid breakage and abnormal grid line morphology caused by abnormal resist residue during development. Furthermore, by blocking scattered light, the printed linewidth in the grid line area can be further reduced, widening the adjustment range for grid line fineness and further improving cell efficiency. This application solves the problem in existing solar cell fabrication where abnormal resist residue easily remains at the bottom of the groove after development, leading to poor solar cell performance. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0016] Figure 1 This diagram illustrates the appearance of an N-plane broken gate provided by the prior art;

[0017] Figure 2 This diagram illustrates a microstructure of an N-plane broken gate provided by the prior art;

[0018] Figure 3 A schematic flowchart of a method for fabricating a solar cell according to an embodiment of this application is shown;

[0019] Figure 4 This diagram illustrates light transmission during printing exposure in the prior art.

[0020] Figure 5 A schematic diagram of residual adhesive (gap) at the bottom of both sides of the gate line after electroplating is shown in the prior art;

[0021] Figure 6 A schematic diagram of printing after the coverage angle selective antireflective film is provided according to an embodiment of this application;

[0022] Figure 7 A schematic diagram of the grid lines after electroplating is shown in the cover angle selective antireflective film printing according to an embodiment of this application;

[0023] Figure 8 This illustration shows a schematic cross-sectional structure of the substrate after forming an intrinsic amorphous silicon layer, an amorphous silicon layer, and a transparent conductive layer following a method for fabricating a solar cell according to an embodiment of this application.

[0024] Figure 9 An embodiment of this application is shown, providing a method in... Figure 8 A schematic diagram of the matrix cross-sectional structure after the seed layer is formed on the basis of the above.

[0025] Figure 10 An embodiment of this application is shown, providing a method in... Figure 9 A schematic diagram of the cross-sectional structure of the substrate after the photosensitive adhesive layer is formed on the basis;

[0026] Figure 11 An embodiment of this application is shown, providing a method in... Figure 10 A schematic diagram of the substrate cross-sectional structure after the cover angle selective antireflective coating is applied.

[0027] Figure 12 An embodiment of this application is shown, providing a method in... Figure 11 A schematic diagram of the substrate cross-sectional structure after removing the angle-selective antireflective coating and the non-developable reaction zone;

[0028] Figure 13 An embodiment of this application is shown, providing a method in... Figure 12 A schematic diagram of the cross-sectional structure of the substrate after the edge-sealing adhesive is formed on the basis of the above.

[0029] Figure 14 An embodiment of this application is shown, providing a method in... Figure 13 A schematic diagram of the substrate cross-sectional structure after electroplating metal grid lines;

[0030] Figure 15 An embodiment of this application is shown, providing a method in... Figure 14 A schematic diagram of the cross-sectional structure of the substrate after removing the remaining photosensitive emulsion layer and the non-electroplated area;

[0031] Figure 16 An embodiment of this application is shown, providing a method in... Figure 15 A schematic diagram of the substrate cross-section structure after tin plating on the sidewalls of the metal grid lines.

[0032] The above figures include the following reference numerals:

[0033] 10. Substrate; 20. Intrinsic amorphous silicon layer; 30. Amorphous silicon layer; 40. Transparent conductive layer; 50. Seed layer; 51. Electroplated area; 52. Non-electroplated area; 60. Photosensitive adhesive layer; 61. Non-development reaction area; 70. Angle-selective anti-reflective film; 80. Edge-sealing adhesive; 90. Metal grid lines. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0036] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0037] For ease of description, the following explains some of the nouns or terms used in the embodiments of this application:

[0038] Heterojunction solar cell (HJT)

[0039] Indium Tin Oxide (ITO)

[0040] Physical vapor deposition (PVD)

[0041] Transparent Conductive Oxide (TCO)

[0042] Currently, HJT solar cells use a technique of printing silver paste to form silver grid lines on the surface of an ITO conductive film. However, due to the high cost of silver paste, copper interconnect technology is generally used instead of silver grid lines, achieving cost reduction and efficiency improvement. Copper interconnect technology first requires PVD sputtering to deposit a seed copper layer on the ITO (or Transparent Conductive Oxide, TCO) conductive film. Then, pattern transfer is performed on the seed copper layer, followed by electroplating of the grid lines. The electroplated copper grid lines are then coated with a protective tin layer using chemical tin plating. This is the solution of using electroplated copper and tin to replace screen-printed silver grid lines, i.e., copper interconnect solar cell technology.

[0043] To ensure a larger light-absorbing area in the solar cell, the linewidth printed during pattern transfer on the seed copper layer needs to be minimized to increase the short-circuit current and thus improve cell efficiency. However, as the linewidth decreases, light scattering causes some grid areas to be exposed. This limits the theoretical lower limit of the linewidth and makes cells with linewidths below the lower limit prone to residual adhesive after development. This can lead to poor contact during electroplating, resulting in grid breakage. Figure 1 and Figure 2 As shown. Figure 1 The area circled in red shows a broken grid line in the white grid. Figure 2 The enlarged image shows that the white grid lines are not neat grid lines, but have blurred edges, which can easily cause grid breakage anomalies.

[0044] To address the problem of residual adhesive abnormalities at the bottom of the groove after development in existing solar cell fabrication processes, which leads to poor solar cell performance, embodiments of this application provide a method for fabricating a solar cell and a solar cell.

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0046] This embodiment provides a method for fabricating a solar cell. It should be noted that although the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than that shown here.

[0047] Figure 3This is a flowchart of a method for fabricating a solar cell according to an embodiment of this application. Figure 3 As shown, the method includes the following steps:

[0048] Step S101, provide a substrate;

[0049] Specifically, the substrate is an N-type or P-type silicon wafer. Optionally, the surface of the substrate is texturized to form a pyramid-shaped microstructure to enhance light absorption; this substrate is the main structure of the heterojunction (HJT) solar cell, with a thickness of 150–180 μm, and has good carrier diffusion length and low defect density, making it suitable for subsequent low-temperature process integration.

[0050] Step S102: An intrinsic amorphous silicon layer, an amorphous silicon layer, a transparent conductive layer, a seed layer, and a photosensitive adhesive layer are sequentially formed on the first surface and / or the second surface of the substrate.

[0051] Optionally, an intrinsic amorphous silicon layer (ia-Si:H) with a thickness of 5-10 nm and a doped amorphous silicon layer (n-type or p-type a-Si:H) with a thickness of 5-15 nm are sequentially deposited on the substrate surface by plasma-enhanced chemical vapor deposition (PECVD) as a passivation contact layer to effectively reduce interfacial recombination. Subsequently, a transparent conductive oxide (TCO) layer with a thickness of 70-100 nm, preferably indium tin oxide (ITO), with a transmittance higher than 90%, is deposited on the surface of the amorphous silicon layer by magnetron sputtering (PVD). A copper seed layer with a thickness of 50-100 nm is then sputtered and deposited on the TCO layer for subsequent electroplating conduction. Finally, a negative photosensitive adhesive layer with a thickness of 1.5-2.5 μm is formed on the seed layer by spin coating or spray coating process as a pattern transfer medium.

[0052] Step S103: Cover the side of the photosensitive adhesive layer away from the substrate with an angle-selective anti-reflection film, and expose the photosensitive adhesive layer to form a non-developable reaction area on the photosensitive adhesive layer. The refractive index difference of the angle-selective anti-reflection film is greater than a preset refractive index difference.

[0053] Specifically, an angle-selective reflective film is a multilayer dielectric thin film structure whose optical reflectivity is strongly dependent on the angle of incident light: for perpendicular incident light (0°): low reflection and high transmission (achieving efficient transmission of the main beam); for oblique incident light (>0.3°): high reflection and low transmission (achieving effective blocking of scattered light). This "selective reflection" characteristic is called angle selectivity.

[0054] Step S104: Remove the angle-selective antireflective film and develop the non-developable reaction area to remove the non-developable reaction area, thereby exposing the electroplating area of ​​the seed layer.

[0055] Specifically, the developing reaction zone refers to the area where the negative photoresist layer solidifies due to a chemical cross-linking reaction after exposure to light. This area is not dissolved by the developer during subsequent development, thus remaining as a patterned "resist mask" to protect the underlying seed layer and ensure its integrity during electroplating. The unexposed area (non-developing reaction zone) is removed by the developer, exposing the underlying copper seed layer, which becomes the electroplating channel. The electroplating area of ​​the seed layer refers to the localized area exposed by the developing reaction zone (photoresist) after photolithography and development processes, where an ultrathin copper layer (50–100 nm thick) deposited on a transparent conductive oxide (TCO, such as ITO) layer via PVD is not covered by the photoresist film. This area, due to direct contact with the electroplating solution, becomes the sole site for copper ion reduction deposition, ultimately forming continuous, low-resistance, and highly adhesive copper grid lines.

[0056] Step S105: Electroplating metal grid lines in the exposed electroplating area of ​​the seed layer, and removing the remaining photosensitive adhesive layer and the non-electroplated area of ​​the seed layer to obtain a solar cell.

[0057] Specifically, after development, a pulse electroplating process is used on the structure to electroplat copper grid lines in a copper sulfate solution at a current density of 1.5~3.0A / dm², a pulse frequency of 50~200Hz, and a duty cycle of 30~50%, with a thickness of 8~12μm. Subsequently, the remaining photosensitive adhesive layer is removed using a stripping solution (NaOH solution), and the copper seed layer not protected by the electroplating layer is selectively removed by wet etching (H2SO4+H2O2 solution), retaining only the electroplated copper grid line structure. Finally, 10~100nm of tin (Sn) is chemically plated on the copper grid lines to form an anti-oxidation protective layer, resulting in an HJT solar cell with a copper interconnect structure.

[0058] The method for fabricating the solar cell described in this application firstly involves sequentially forming an intrinsic amorphous silicon layer, an amorphous silicon layer, a transparent conductive layer, a seed layer, and a photosensitive adhesive layer on a first surface and / or a second surface of a substrate. Then, an angle-selective anti-reflective film is applied to the side of the photosensitive adhesive layer away from the substrate, and the photosensitive adhesive layer is exposed to form a non-developable reaction area. The angle-selective anti-reflective film is removed, and the non-developable reaction area is developed, exposing the electroplated area of ​​the seed layer. Finally, metal grid lines are electroplated on the exposed electroplated area of ​​the seed layer, and the remaining photosensitive adhesive layer and the non-electroplated area of ​​the seed layer are removed to obtain the solar cell. This method prepares an angle-selective anti-reflective film on the surface of the photosensitive adhesive to be exposed, utilizing the interference effect of light to control the reflection behavior. When perpendicularly incident light passes through, destructive interference is achieved, thereby minimizing reflection and maximizing transmission. When obliquely incident light passes through, the optical path difference changes with the increase of the incident angle, disrupting the original destructive interference condition, resulting in a significant increase in reflectivity. This application utilizes an angle-selective antireflective film to ultimately block the incident light (tilted incident light), preventing the scattered light from curing the resist film in the grid line area. This avoids the influence of scattered light from the printing exposure on the resist film in the grid line area, resolving grid breakage and abnormal grid line morphology caused by abnormal resist residue during development. Furthermore, by blocking scattered light, the printed linewidth in the grid line area can be further reduced, widening the adjustment range for grid line fineness and further improving cell efficiency. This application solves the problem in existing solar cell fabrication where abnormal resist residue easily remains at the bottom of the groove after development, leading to poor solar cell performance.

[0059] The above embodiment involves preparing an angle-selective anti-reflective film on the surface of the photosensitive emulsion to be exposed. The reflection behavior is controlled by the interference effect of light, achieving destructive interference when perpendicularly incident light passes through, thereby minimizing reflection and maximizing transmission. When obliquely incident light passes through, the optical path difference changes with the increase of the incident angle, disrupting the original destructive interference condition and leading to a significant increase in reflectivity. Ultimately, this achieves the blocking of incident scattered light (obliquely incident light), preventing the scattered light from curing the emulsion film in the grid line area. This process can avoid the influence of scattered light from printing exposure on the emulsion film in the grid line area, solving the problems of grid breakage and abnormal grid line morphology caused by abnormal residual emulsion during development. Furthermore, by blocking scattered light, the printed linewidth in the grid line area can be further reduced, widening the adjustment range for grid line fineness and further improving the efficiency of the solar cell.

[0060] Figure 4 This is a schematic diagram of light transmission during printing exposure in the prior art, such as... Figure 4As shown, A is the exposed area, B is the semi-exposed area, and C is the unexposed area. The photosensitive emulsion used is negative photosensitive emulsion, meaning the exposed areas cannot be removed by the developer after printing. During printing, areas directly exposed to light will form exposed areas; due to light scattering, a small amount of light propagates to shaded areas, but because the light energy in these areas is lower, they ultimately form semi-exposed areas. These semi-exposed areas are prone to leaving residue after development, which can affect the contact at the bottom of the grid lines after electroplating (e.g., ...). Figure 5 (As shown); a non-exposed area is formed in the area not exposed to light. The scattering angle of the light from a specific wavelength printing light source is fixed, and the distance c from the printing mask to the solar cell is also fixed, so the size a of the non-exposed area is also fixed; the bottom width x of the non-exposed area is x = b - 2a (b is the mask linewidth), so the size of the non-exposed area will decrease or even become 0 as the mask linewidth decreases, and there is a clear lower limit requirement for printing.

[0061] During normal printing, a 650nm light source is used, and the distance c between the mask and the solar cell is about 70μm-190μm. The influence of different printing light intensities on the printing linewidth is shown in Table 1. The lower the mask linewidth, the greater the impact of increasing printing energy (which can also increase the scattering area) on the grid line area. The monitorable influence width a of exposure printing on the half-exposure area is greater than 2μm.

[0062] Table 1. Line width variation under different printing light intensities

[0063]

[0064] The embodiments of this application prepare an angle-selective antireflective film on the surface of the adhesive film before printing. When scattered light (oblique incident light) passes through the film layer, it is largely reflected, reducing the deterioration of the half-exposed area to the exposed area (preventing the increase of residual adhesive area), minimizing the presence of residual adhesive abnormalities at the bottom of the groove after development, and effectively ensuring that the printed linewidth is similar to the mask linewidth.

[0065] In some embodiments, the refractive index difference of the angle-selective antireflective coating is 0.92 to 0.99.

[0066] In this embodiment, by limiting the refractive index difference of the angle-selective antireflective film to 0.92~0.99, the reflectivity of the film to obliquely incident scattered light is significantly improved. This allows scattered light that might otherwise enter the photosensitive emulsion layer at a non-perpendicular angle to be efficiently reflected back into the environment, rather than penetrating or spreading to non-target areas of the photosensitive emulsion layer. This effectively suppresses the half-exposure phenomenon caused by scattered light during exposure. The precise control of this refractive index difference range, combined with the direct contact structure between the angle-selective antireflective film and the photosensitive emulsion layer and the process sequence of pre-exposure covering and pre-development removal, ensures that the photosensitive emulsion layer undergoes sufficient development reaction only in the target illumination area. This avoids residual emulsion accumulation and distortion of the grid line edge morphology, achieving a clear groove contour, uniform linewidth, and stable finer linewidth after development. Ultimately, this solves the technical problems of insufficient scattering light suppression, poor grid line morphology, and limited linewidth control caused by unrestricted refractive index difference.

[0067] In some embodiments, the first film is a titanium dioxide film and the second film is a silicon dioxide film.

[0068] In this embodiment, the angle-selective antireflective film is specifically defined as consisting of a titanium dioxide film as the first film and a silicon dioxide film as the second film. Utilizing the significant refractive index difference between titanium dioxide and silicon dioxide, this film layer, in direct contact with the photosensitive adhesive layer, can efficiently reflect scattered light at a large incident angle. This effectively suppresses unintended penetration into non-target areas of the photosensitive adhesive, avoiding half-exposure caused by scattered light. Consequently, it reduces residual adhesive and improves the uniformity and precision of the grid line morphology during development. This material combination achieves controllable blocking of the scattered light path without changing the exposure parameters, solving the technical problems of unstable reflection control and uncontrollable residual adhesive risk caused by unclear film material. Ultimately, it achieves the effect of stably obtaining a high-fidelity metal grid line structure under standard process conditions.

[0069] In some embodiments, the thickness of the first film is 65nm to 75nm, and the thickness of the second film is 105nm to 115nm.

[0070] In this embodiment, by limiting the thickness of the first thin film of the angle-selective antireflective film to 65nm~75nm and the thickness of the second thin film to 105nm~115nm, in synergy with the characteristic that the refractive index difference of the film layer is greater than a preset value, the film system can form precise optical path difference control under the action of obliquely incident scattered light, effectively destroying the destructive interference condition, significantly improving the reflection blocking ability of non-perpendicular incident light, thereby stably suppressing the half-exposure effect of scattered light on the non-target area of ​​the photosensitive adhesive grid line region during the exposure process, significantly reducing the probability of residual adhesive after development, improving the cleanliness of the bottom of the grid line groove, and ensuring that the linewidth of the electroplated metal grid line is highly consistent with the linewidth of the mask design. Ultimately, this solves the technical defects of unstable scattered light blocking, residual adhesive accumulation and uncontrolled linewidth caused by uncontrolled film thickness, and achieves precise control of solar cell grid line morphology and improved yield.

[0071] Optionally, an angle-selective anti-reflective film composed of alternating stacks of TiO2 / SiO2 is horizontally coated on the surface of the photosensitive adhesive layer. The thickness of the TiO2 layer is 70 nm (refractive index n≈2.40), the thickness of the SiO2 layer is 110 nm (refractive index n≈1.46), and the refractive index difference between adjacent layers is Δn=0.94, which meets the requirement of a preset refractive index difference greater than 0.92. This film system is formed by 5 to 10 cycles of PVD deposition. At an exposure wavelength of 365 nm, the reflectivity is ≤2.5% when the incident angle is 0° and ≥40% when the incident angle is ≥0.3°, achieving high transmission of the vertical main beam and high reflection of scattered light. Exposure is performed using a laser projection system with a wavelength of 365 nm, energy of 70~130 mW / cm², and a mask distance of 70~190 μm from the cell. Only the photosensitive adhesive in the directly exposed area undergoes cross-linking and curing, forming a non-development reaction area, while the tilted scattered light is reflected by the angle-selective anti-reflective film, effectively suppressing it from entering the non-exposure area below the adhesive layer.

[0072] Optionally, after exposure, the angle-selective antireflective film is peeled off entirely from the substrate surface to avoid its residue affecting the penetration of the developer. Subsequently, a sodium carbonate solution with a concentration of 10-15 g / L is used for development, with a development time of 60-90 seconds and a temperature of 25-55°C. Only the photosensitive emulsion in the unexposed area is dissolved, while the cross-linked and cured area is retained, forming a precise grid groove structure. The width of the bottom of the groove deviates from the mask linewidth by less than 0.5 μm, and there is no visible residual emulsion film at the bottom. At this time, the seed layer copper film is completely exposed in the groove area, forming an electroplating channel.

[0073] In some embodiments, before covering the side of the photosensitive adhesive layer away from the substrate with an angle-selective antireflective film, the method further includes the following steps:

[0074] Step S201: Provide a carrier;

[0075] In step S202, a first thin film and a second thin film are sequentially formed on the carrier using a magnetron sputtering process to obtain the angle-selective antireflective coating. The refractive index of the first thin film is greater than a first preset refractive index, the refractive index of the second thin film is less than a second preset refractive index, and the first preset refractive index is greater than the second preset refractive index.

[0076] The carrier is a transparent glass substrate, and the deposition of the first and second thin films on the carrier is generally carried out by plasma-enhanced chemical vapor deposition or physical vapor deposition.

[0077] In this embodiment, before covering the angle-selective antireflective film, a carrier is provided and a first thin film and a second thin film are sequentially deposited on it using a magnetron sputtering process. The refractive index of the first thin film is higher than a first preset refractive index, and the refractive index of the second thin film is lower than a second preset refractive index. At the same time, the first preset refractive index is ensured to be greater than the second preset refractive index. This allows for the precise construction of a multilayer film system with a high refractive index difference at the structural level. Under the precise control of the magnetron sputtering process, this film system forms an optical structure with a clear interface, uniform thickness, and stable refractive index gradient. This results in strong reflection suppression of obliquely incident scattered light during exposure, while maintaining high transmittance for vertically incident main exposure light. This effectively avoids half-exposure of non-target areas of the photosensitive adhesive layer, significantly reduces the risk of residual adhesive after development, and improves the consistency of the grid line morphology. This overcomes the technical defects of the original scheme, which only limited the "refractive index difference to a preset value" without providing a supportive fabrication path, leading to uncontrollable film performance and unstable angle selectivity. This achieves high repeatability of the exposure process and reliable improvement in the quality of grid line formation.

[0078] In some embodiments, a first thin film and a second thin film are sequentially formed on the above-mentioned carrier using a magnetron sputtering process to obtain the above-mentioned angle-selective antireflective film, including the following steps:

[0079] In the first sputtering step, the first thin film is formed on the carrier using a magnetron sputtering process.

[0080] In the second sputtering step, the second thin film is formed on the surface of the first thin film away from the carrier using the magnetron sputtering process described above.

[0081] The first sputtering step and the second sputtering step are repeated a predetermined number of times to form the first film and the second film spaced apart on the carrier, thereby obtaining the angle-selective anti-reflective film, which includes a plurality of the first film and a plurality of the second film.

[0082] In this embodiment, a magnetron sputtering process is used to alternately execute a first sputtering step and a second sputtering step on a carrier a predetermined number of times to form an angle-selective anti-reflection film composed of multiple high-refractive-index thin films and low-refractive-index thin films stacked alternately. The refractive index of the first thin film is higher than a preset threshold, and the refractive index of the second thin film is lower than another preset threshold, forming a significant refractive index difference. Through the interference superposition effect between the multilayer film system, the reflection suppression capability of obliquely incident scattered light is stably enhanced. This continuously shields the non-direct light in the non-target area of ​​the photosensitive adhesive layer during multiple exposure printing processes, effectively avoiding half-exposure and residual adhesive in development caused by scattered light. At the same time, because the number of sputtering steps and the film thickness are precisely controlled, the repeatability and consistency of the film system structure are significantly improved, ensuring the stability of angle-selective reflection performance in different batches of production. Ultimately, high-precision control of the grid line morphology and stable improvement of yield are achieved.

[0083] In some embodiments, a first thin film and a second thin film are sequentially formed on the above-mentioned carrier using a magnetron sputtering process to obtain the above-mentioned angle-selective antireflective film, including the following steps:

[0084] Step S2021: The first thin film is formed on the carrier using the magnetron sputtering process described above according to the first process parameters;

[0085] In step S2022, the second thin film is formed on the surface of the first thin film away from the carrier using the above-mentioned magnetron sputtering process according to the second process parameters, thereby obtaining the angle-selective antireflective film.

[0086] In this embodiment, a first thin film and a second thin film are sequentially deposited on a carrier using a magnetron sputtering process according to the first process parameters and the second process parameters, respectively. The material composition, thickness, and density of the two thin films are precisely controlled to form a stable and adjustable refractive index difference between them, thereby constructing an anti-reflective film structure with angle-selective reflectivity. During the exposure process, this structure can effectively suppress the lateral scattered light from the photosensitive adhesive layer from entering the non-target area, while ensuring that the vertically incident exposure light can pass through smoothly. This fundamentally solves the problems of refractive index difference fluctuation and scattered light control failure caused by the instability of the film preparation process, thereby avoiding half-exposure in the non-grid area of ​​the photosensitive adhesive layer, ensuring no residual adhesive after development, and clear and consistent metal grid line morphology, ultimately realizing the efficient and high-yield grid line patterning manufacturing of solar cells.

[0087] In some embodiments, the first process parameters include a first target sputtering power, a first pressure, and a first reaction gas. The first target sputtering power is 180W~220W, the first pressure is 0.4Pa~0.6Pa, the ratio of inert gas to oxygen in the first reaction gas is three to one, the first pressure is the working pressure of the first chamber where the carrier is currently located, and the first reaction gas is the reaction gas introduced into the first chamber.

[0088] In this embodiment, by limiting the magnetron sputtering process parameters of the first thin film to a first target sputtering power of 180W~220W, a first pressure of 0.4Pa~0.6Pa, and a ratio of inert gas to oxygen in the first reaction gas of 3:1, and with the pressure and reaction gas being the actual working parameters of the first chamber, the first thin film forms a high refractive index characteristic under stable and controllable deposition conditions, ensuring that its refractive index is reliably greater than the first preset refractive index. This allows it to work in conjunction with the subsequently formed low refractive index second thin film to construct an angle-selective antireflective film that meets the preset refractive index difference requirement. This structure can effectively reflect obliquely incident scattered light, blocking its unintended exposure to non-target areas of the photosensitive adhesive layer, avoiding unreacted photosensitive adhesive residue at the bottom of the grid groove after development, significantly improving the grid morphology consistency and electroplating accuracy, and ultimately achieving high yield and high performance fabrication of solar cell grid structures.

[0089] In some embodiments, the second process parameters include the second target sputtering power, the second pressure, and the second reaction gas. The second target sputtering power is 330W~380W, the second pressure is 0.3Pa~0.5Pa, the ratio of inert gas to oxygen in the second reaction gas is four to one, the second pressure is the working pressure of the second chamber where the carrier is currently located, and the second reaction gas is the reaction gas introduced into the second chamber.

[0090] In this embodiment, by limiting the magnetron sputtering process parameters of the second thin film to a second target sputtering power of 330W~380W, a second pressure of 0.3Pa~0.5Pa, and a ratio of inert gas to oxygen in the reaction gas introduced into the second chamber of four to one, the deposition kinetics of the second thin film are precisely controlled. This results in a SiO2 layer with a uniform and dense microstructure and stable low refractive index characteristics. The bilayer structure formed by this layer and the first thin film can achieve a preset refractive index difference, thereby forming efficient and consistent reflection suppression of scattered light under oblique incident conditions. This effectively blocks the half-exposure phenomenon in non-target areas, avoids the formation of residual photoresist in the photosensitive layer due to interference from scattered light, significantly improves the accuracy and yield of the metal grid morphology, and ultimately achieves active control of photolithography defects in the solar cell manufacturing process.

[0091] The above embodiments utilize PECVD or PVD to deposit a single-layer TiO2 film with a thickness of approximately 70 nm and a single-layer SiO2 film with a thickness of approximately 110 nm on the surface of a transparent glass (carrier) to prepare an angle-selective anti-reflective film. The PVD preparation process for the angle-selective anti-reflective film is as follows: 1. Clean the transparent glass carrier and preheat it to 250℃ for 2 min; 2. Transfer the preheated glass carrier to the TiO2 coating chamber, using a power of 200W, introducing a gas with an Ar:O2 ratio of 3:1, and sputtering for 130 s at a pressure of 0.5 Pa; 3. Transfer the glass carrier with the TiO2 film to the SiO2 coating chamber, using a power of 350W, introducing a gas with an Ar:O2 ratio of 4:1, and sputtering for 185 s at a pressure of 0.4 Pa, completing the preparation of the angle-selective anti-reflective film. To increase the reflectivity of obliquely incident light, steps 2 and 3 can be repeated for cyclic coating to increase the number of film layers. The reflectance of the coating at different incident angles after different coating cycles is shown in Table 2. The more coating cycles, the higher the reflectance of light incident at angles greater than 0.3°.

[0092] Table 2. Reflectance of angle-selective antireflective coatings at different incident light angles under different coating cycles

[0093]

[0094] The process described in the above embodiment involves conveying the coated film to the printing table, then horizontally covering the surface with an angle-selective anti-reflective film, followed by exposure printing (e.g., ...). Figure 6 As shown, Figure 6 In the diagram, A represents the exposed area, and C represents the unexposed area. During printing, the mask pattern was set 70μm from the solar cell, the printing energy was 70mW-130mW, the printing time was 300ms, and a 365nm wavelength light source was used. Table 3 shows the effect of different printing light intensities on the printed linewidth after applying the angle-selective anti-reflective coating, demonstrating a significant improvement compared to printing without the coating. A schematic diagram of the grid after electroplating following printing with the angle-selective anti-reflective coating is shown below. Figure 7 As shown.

[0095] Table 3. Linewidth variation under different printing light intensities after selective antireflective coating with coverage angle

[0096]

[0097] To enable those skilled in the art to better understand the technical solution of this application, the implementation process of the solar cell fabrication method of this application will be described in detail below with reference to specific embodiments.

[0098] This embodiment relates to a specific method for preparing a solar cell, such as... Figures 8 to 16As shown, the process includes the following steps: First, an intrinsic amorphous silicon layer 20, an amorphous silicon layer 30, and a transparent conductive layer 40 are sequentially formed on the first and / or second surfaces of a substrate 10. The substrate 10 is N-type silicon. The amorphous silicon layer 30 formed on one side of the first surface is an N-type amorphous silicon layer, and the amorphous silicon layer 30 formed on one side of the second surface is a P-type amorphous silicon layer. The transparent conductive layer 40 is a TCO transparent conductive film. A seed layer 50 is formed by PVD sputtering deposition on the TCO transparent conductive film for metallization. The seed layer 50 is a copper seed layer. Then, a photosensitive emulsion is coated on the copper seed layer to form a photosensitive emulsion layer 60. The photosensitive material is selectively exposed to create a pattern. Next, an angle-selective anti-reflective film 70 is applied to the side of the photosensitive adhesive layer 60 away from the substrate 10, and the photosensitive adhesive layer 60 is exposed to form a non-developable reaction area 61. Then, the angle-selective anti-reflective film 70 is removed, and the non-developable reaction area 61 is developed using an alkaline solution, exposing the electroplating area 51 of the seed layer 50. Insulating adhesive is applied to the side of the solar cell to form an edge-sealing adhesive 80. Then, metal grid lines 90 are electroplated on the exposed electroplating area 51 of the seed layer 50 to replace the silver paste for conductivity, and the remaining photosensitive adhesive layer 60 and the non-electroplated area 52 of the seed layer 50 are removed. A layer of tin is deposited on the sidewall of the metal grid lines 90 by displacement reaction to prevent copper oxidation, thus obtaining a solar cell.

[0099] The above process involves surface treatment of the photosensitive emulsion before printing, followed by exposure printing, to prevent or reduce the impact of scattered light on the grid line area during printing exposure, thereby further widening the theoretical lower limit of the printed line width and improving grid breakage anomalies.

[0100] Furthermore, by adding an angle-selective anti-reflective coating during printing, the curing of the grid line region by scattered light during exposure is effectively reduced. TiO2 and SiO2 were chosen as the angle-selective anti-reflective coating materials primarily because SiO2 is the lowest refractive index medium, while TiO2 is one of the highest refractive index media. The significant refractive index difference between the two materials (0.92-0.99) allows for a steeper angle selectivity. The application of the angle-selective anti-reflective coating in exposure printing avoids abnormal residual adhesive at the bottom of the grid line grooves after development due to scattered light. Furthermore, the absence of scattered light affecting the mask's occlusion position allows for further reduction in mask linewidth, enabling the fabrication of finer grid line grooves, reducing the surface occlusion area, and improving cell efficiency.

[0101] The process described in the above embodiment involves preparing an angle-selective anti-reflective film after coating. This film can be prepared using a wet process with a TiO2 pre-coating solution and a SiO2 pre-coating solution. The coated cell surface is then coated with the pre-coating solution using a lift-coating method, followed by printing. Before development, the angle-selective anti-reflective film is removed, and then development is performed to complete the fabrication of the grid grooves. This method suffers from poor control over the film thickness and uniformity, and the angle-selective anti-reflective film cannot be reused. It must be removed after printing to prevent the developer from obstructing the removal of the unexposed photosensitive emulsion. Overall, the process and cost are high.

[0102] This application also provides a solar cell, which is prepared using any of the above-described methods for preparing solar cells.

[0103] The solar cell is formed using the above-described preparation method, which makes the photosensitive adhesive development outline in the grid area clearer, significantly reduces the residual adhesive rate at the bottom of the groove, improves the contact integrity between the metal grid lines and the seed layer after electroplating, and effectively suppresses the exposure scattering effect, thereby achieving a more stable and narrower mask linewidth design. This reduces the grid line shading area, improves the short-circuit current and photoelectric conversion efficiency of the cell, and the overall process yield and consistency are better than the conventional process path without the use of angle-selective anti-reflective coating.

[0104] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0106] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0107] 1) The method for fabricating the solar cell described in this application firstly involves sequentially forming an intrinsic amorphous silicon layer, an amorphous silicon layer, a transparent conductive layer, a seed layer, and a photosensitive adhesive layer on a first surface and / or a second surface of a substrate; then, an angle-selective anti-reflection film is applied to the side of the photosensitive adhesive layer away from the substrate, and the photosensitive adhesive layer is exposed to form a non-developable reaction area; the angle-selective anti-reflection film is removed, and the non-developable reaction area is developed, exposing the electroplated area of ​​the seed layer; finally, metal grid lines are electroplated on the exposed electroplated area of ​​the seed layer, and the remaining photosensitive adhesive layer and the non-electroplated area of ​​the seed layer are removed to obtain the solar cell. This method prepares an angle-selective anti-reflection film on the surface of the photosensitive adhesive to be exposed, utilizing the interference effect of light to control the reflection behavior, so that destructive interference is achieved when perpendicularly incident light passes through, thereby minimizing reflection and maximizing transmission; when obliquely incident light passes through, the optical path difference changes with the increase of the incident angle, destroying the original destructive interference condition, resulting in a significant increase in reflectivity. This application utilizes an angle-selective antireflective film to ultimately block the incident light (tilted incident light), preventing the scattered light from curing the resist film in the grid line area. This avoids the influence of scattered light from the printing exposure on the resist film in the grid line area, resolving grid breakage and abnormal grid line morphology caused by abnormal resist residue during development. Furthermore, by blocking scattered light, the printed linewidth in the grid line area can be further reduced, widening the adjustment range for grid line fineness and further improving cell efficiency. This application solves the problem in existing solar cell fabrication where abnormal resist residue easily remains at the bottom of the groove after development, leading to poor solar cell performance.

[0108] 2) The solar cell of this application is formed by adopting the above-mentioned preparation method, which makes the photosensitive adhesive development outline of the grid line area clearer, significantly reduces the residual adhesive rate at the bottom of the groove, improves the contact integrity between the metal grid line and the seed layer after electroplating, and effectively suppresses the exposure scattering effect, so as to stably achieve a narrower mask linewidth design, thereby reducing the grid line shading area, improving the short-circuit current and photoelectric conversion efficiency of the cell, and the overall process yield and consistency are better than the conventional process path without the use of angle-selective anti-reflective film.

[0109] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a solar cell, characterized in that, include: Provide a base; An intrinsic amorphous silicon layer, an amorphous silicon layer, a transparent conductive layer, a seed layer, and a photosensitive adhesive layer are sequentially formed on the first and / or second surfaces of the substrate. An angle-selective anti-reflective film is applied to the side of the photosensitive adhesive layer away from the substrate, and the photosensitive adhesive layer is exposed to form a non-developable reaction area on the photosensitive adhesive layer. The refractive index difference of the angle-selective anti-reflective film is greater than a preset refractive index difference. Remove the angle-selective antireflective film and develop the non-developable reaction area to remove the non-developable reaction area, thereby exposing the electroplating area of ​​the seed layer; Metal grid lines are electroplated in the exposed electroplating area of ​​the seed layer, and the remaining photosensitive adhesive layer and the non-electroplated area of ​​the seed layer are removed to obtain a solar cell.

2. The preparation method according to claim 1, characterized in that, Before covering the side of the photosensitive adhesive layer away from the substrate with an angle-selective anti-reflective film, the method further includes: Provide a carrier; A first thin film and a second thin film are sequentially formed on the carrier using a magnetron sputtering process to obtain the angle-selective anti-reflective film. The refractive index of the first thin film is greater than a first preset refractive index, the refractive index of the second thin film is less than a second preset refractive index, and the first preset refractive index is greater than the second preset refractive index.

3. The preparation method according to claim 2, characterized in that, The angle-selective antireflective film is obtained by sequentially forming a first thin film and a second thin film on the carrier using a magnetron sputtering process, comprising: In the first sputtering step, the first thin film is formed on the carrier using a magnetron sputtering process; In the second sputtering step, the magnetron sputtering process is used to form the second film on the surface of the first film away from the carrier. The first sputtering step and the second sputtering step are repeated a predetermined number of times to form the first film and the second film spaced apart on the carrier, thereby obtaining the angle-selective anti-reflective film, which includes a plurality of the first film and a plurality of the second film.

4. The preparation method according to claim 2, characterized in that, The angle-selective antireflective film is obtained by sequentially forming a first thin film and a second thin film on the carrier using a magnetron sputtering process, comprising: The first thin film is formed on the carrier using the magnetron sputtering process according to the first process parameters; The second thin film is formed on the surface of the first thin film away from the carrier using the magnetron sputtering process according to the second process parameters, thereby obtaining the angle-selective antireflective film.

5. The preparation method according to claim 4, characterized in that, The first process parameters include the first target sputtering power, the first pressure, and the first reaction gas. The first target sputtering power is 180W~220W, the first pressure is 0.4Pa~0.6Pa, the ratio of inert gas to oxygen in the first reaction gas is three to one, the first pressure is the working pressure of the first chamber where the carrier is currently located, and the first reaction gas is the reaction gas introduced into the first chamber.

6. The preparation method according to claim 4, characterized in that, The second process parameters include the second target sputtering power, the second pressure, and the second reaction gas. The second target sputtering power is 330W~380W, the second pressure is 0.3Pa~0.5Pa, the ratio of inert gas to oxygen in the second reaction gas is four to one, the second pressure is the working gas pressure of the second chamber where the carrier is currently located, and the second reaction gas is the reaction gas introduced into the second chamber.

7. The method according to claim 1, characterized in that, The refractive index difference of the angle-selective antireflective coating is 0.92~0.

99.

8. The preparation method according to claim 2, characterized in that, The first film is a titanium dioxide film, and the second film is a silicon dioxide film.

9. The method according to claim 2, characterized in that, The thickness of the first film is 65nm~75nm, and the thickness of the second film is 105nm~115nm.

10. A solar cell, characterized in that, The solar cell is prepared by the method for preparing a solar cell according to any one of claims 1 to 9.

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