Preparation method of solar cell
Patterned electrodes can be fabricated on crystalline silicon solar cells by using laser selective irradiation and etching processes, which solves the problems of high material cost and poor conductivity in existing technologies and achieves efficient and low-cost electrode fabrication.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN DR LASER TECH CORP LTD
- Filing Date
- 2024-11-21
- Publication Date
- 2026-05-22
AI Technical Summary
In the existing technology, silver is mainly used as the electrode material for preparing crystalline silicon solar cells, but it is costly and consumes a lot of resources. Other metal materials, such as aluminum, have insufficient conductivity and oxidation resistance, making it difficult to meet production requirements.
A patterned electrode structure is formed by selectively irradiating the electrode protective layer with laser and combining it with an etching process. Various metal materials such as copper, aluminum, and magnesium are used, combined with an antireflection film to improve laser energy utilization and etching efficiency.
High-precision electrode patterning was achieved, reducing electrode costs, decreasing silver consumption, and improving electrode conductivity and oxidation resistance, while avoiding the risk of leakage.
Smart Images
Figure CN122073884A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of photovoltaics, and specifically relates to a method for preparing a solar cell. Background Technology
[0002] In the manufacturing process of crystalline silicon solar cells, there are various metallization methods. One such method involves fabricating an electrode layer and an electrode protective layer on a semi-finished solar cell that has already undergone P-region and / or N-region doping and passivation layer fabrication. Existing technology can fabricate electrode grid lines using photolithography, masking, and etching, but this method is costly and cannot meet the cost and yield requirements of actual production.
[0003] Existing technologies commonly employ screen printing to prepare electrodes, which can create electrode grid lines on the surface of P and N regions. However, this requires the use of fine metal powder mixed with a slurry of complex composition, resulting in low metal purity and poor conductivity in the finished electrode. Furthermore, the thickness of electrodes produced by screen printing is difficult to meet process requirements.
[0004] In addition, since silver is currently the mainstream electrode material, but silver consumption is extremely high, there is an urgent need to use other metal materials in conjunction with other processes to prepare electrodes. Summary of the Invention
[0005] In view of this, this application provides a method for preparing a solar cell, comprising:
[0006] S100. A continuous electrode layer and a continuous electrode protective layer are sequentially prepared on the first side of the semi-finished solar cell; wherein the semi-finished solar cell includes a semiconductor substrate, a semiconductor layer and a passivation layer located on the first side of the semiconductor substrate;
[0007] S200, Prepare an antireflection film on the electrode protective layer;
[0008] S300: A laser is used to irradiate part of the electrode protective layer through the antireflection film, so that the electrode protective layer in the laser irradiation area forms a micro-pore structure; wherein, the laser irradiation area is the area outside the location of the target electrode structure;
[0009] S400, Etching: An etching solution is used to penetrate the pores and etch the electrode layer. This causes the electrode layer corresponding to the laser irradiation area in step S300 to react with the etching solution and be removed. The electrode protective layer corresponding to the laser irradiation area detaches, while the electrode protective layer and electrode layer corresponding to the non-laser irradiation area remain after etching, forming a target electrode structure including a separated positive electrode and / or negative electrode.
[0010] Wherein, the refractive index of the antireflective film is n1, the refractive index of the electrode protective layer is n2, and n1 < n2; the thickness of the antireflective film is [1 / 4 + (1 / 2) × a] × λ / n1, where λ is the wavelength of the laser used in step S300, and a is 0 or a natural number.
[0011] Preferably, in the semi-finished solar cell, a portion of the passivation layer has an opening that exposes the semiconductor layer, and the opening position of the passivation layer corresponds to the location of the target electrode structure.
[0012] Preferably, the reflectivity of the antireflective film is less than 12% at the laser wavelength used in step S300, and the absorption coefficient of the antireflective film is less than 10000 cm⁻¹ at the laser wavelength used in step S300. -1 .
[0013] Preferably, the antireflective membrane is a single-layer membrane or a multi-layer membrane.
[0014] Preferably, the electrode layer can react with an acidic etching solution; in step S400, the etching solution is an acidic etching solution, and the acidic etching solution is used to react with the antireflection membrane and the electrode layer corresponding to the laser irradiation area.
[0015] Alternatively, the electrode layer can react with an alkaline etching solution. The etching process in step S400 includes: first, using an acidic etching solution to etch away the antireflective film, and then using an alkaline etching solution to react with the electrode layer corresponding to the laser irradiation area.
[0016] Preferably, the antireflective film can reduce the reflectivity of laser incident on the electrode protective layer and the electrode layer from more than 80% to less than 60%.
[0017] Preferably, the solar cell is a back-contact solar cell, the semiconductor layer includes a first doped semiconductor layer and a second doped semiconductor layer, and the first side of the semi-finished solar cell includes a first semiconductor region and a second semiconductor region arranged in an interdigitated pattern and an isolation region located between adjacent first semiconductor regions and second semiconductor regions; the first doped semiconductor layer is disposed in the first semiconductor region, the second doped semiconductor layer is disposed in the second semiconductor region, and the first doped semiconductor layer and the second doped semiconductor layer have opposite conductivity types.
[0018] Preferably, the laser used in step S300 is a picosecond laser or a femtosecond laser.
[0019] Preferably, the resistivity of the electrode layer is in the range of 1.5 × 10⁻⁶. -8 Ω·m~20.0×10 -8 Ω·m; the melting point temperature range of the electrode protective layer is 600℃~3500℃, and the resistivity range is 3.5×10 Ω·m.-8 Ω·m~30.0×10 -8 Ω·m.
[0020] Preferably, the etching solution is an acidic etching solution, the electrode layer comprises any one of copper, aluminum, magnesium, zinc, cadmium, indium, and tin or an alloy thereof, and the electrode protective layer comprises any one of beryllium, molybdenum, tungsten, cobalt, nickel, iron, and platinum or an alloy thereof.
[0021] Preferably, the etchant is an alkaline etchant, and the electrode layer comprises any one of aluminum, beryllium, molybdenum, tungsten, zinc, indium, iron, platinum, and tin or an alloy thereof; the electrode protective layer comprises any one of silver, copper, gold, magnesium, cobalt, nickel, cadmium, molybdenum, tungsten, indium, iron, and platinum or an alloy thereof.
[0022] Preferably, the thickness of the electrode protective layer ranges from 2nm to 200nm.
[0023] Preferably, the thickness of the electrode protective layer ranges from 20 nm to 120 nm.
[0024] Preferably, in step S100, at least a portion of the passivation layer outside the target electrode structure region is a textured structure, or the entire passivation layer is a textured structure.
[0025] Preferably, the solar cell is a back-contact solar cell, the semiconductor layer includes a first doped semiconductor layer and a second doped semiconductor layer, and the first side of the semi-finished solar cell includes a first semiconductor region and a second semiconductor region arranged in an interdigitated pattern and an isolation region located between adjacent first semiconductor regions and second semiconductor regions; the first doped semiconductor layer is disposed in the first semiconductor region, the second doped semiconductor layer is disposed in the second semiconductor region, and the first doped semiconductor layer and the second doped semiconductor layer have opposite conductivity types;
[0026] In step S100, the portion of the passivation layer corresponding to the isolation region has a textured structure, or the portion of the passivation layer outside the target electrode structure region has a textured structure, or the entire passivation layer has a textured structure.
[0027] Preferably, the laser used in step S300 is a pulsed laser or a continuous laser.
[0028] Preferably, in step S100, the method for preparing the continuous electrode layer and the continuous electrode protective layer includes any one of physical vapor deposition, chemical deposition, or electroplating.
[0029] Preferably, in step S400, after the etching is completed, the electrode protective layer that has not been peeled off in the laser irradiation area of the first side of the semi-finished solar cell is cleaned and removed by a brush.
[0030] Alternatively, in step S400, ultrasonic cleaning is used simultaneously with corrosion to assist in the removal of the electrode protective layer corresponding to the laser irradiation area.
[0031] The solar cell fabrication method proposed in this application involves selective laser irradiation combined with an etching process on a continuous electrode layer and a continuous electrode protective layer to create patterned electrodes. This method offers high fabrication precision and causes no damage to the substrate. Furthermore, the resulting metal electrode grid lines have neat edges, eliminating the risk of leakage. In addition, this patented method is applicable to various metal electrode materials, reducing electrode costs and minimizing silver consumption in the photovoltaic industry. Attached Figure Description
[0032] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0033] The structures, proportions, sizes, etc., shown in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.
[0034] Figure 1 This is a process flow diagram of a method for fabricating a solar cell according to an embodiment of this application;
[0035] Figure 2 This is a schematic diagram of the structure of a semi-finished solar cell according to an embodiment of this application;
[0036] Figure 3 This is a schematic diagram of the battery structure after step S110 is completed in one embodiment of this application.
[0037] Figure 4 This is a schematic diagram of the battery structure after completing step S120 in one embodiment of this application.
[0038] Figure 5 This is a schematic diagram of the battery structure after step S200 is completed according to one embodiment of this application.
[0039] Figure 6This is a schematic diagram of the battery structure after step S300 is completed in one embodiment of this application.
[0040] Figure 7 This is a schematic diagram of the battery structure after completing step S400 in one embodiment of this application.
[0041] Figure 8 This is a schematic diagram of the structure of a semi-finished solar cell according to another embodiment of this application;
[0042] Figure 9 This is a schematic diagram of the structure of a semi-finished solar cell according to another embodiment of this application;
[0043] Figure 10 This is a schematic diagram of the structure of a semi-finished solar cell according to another embodiment of this application;
[0044] Figure 11 This is a schematic diagram of the structure of a semi-finished solar cell according to another embodiment of this application;
[0045] Figure 12 This is a schematic diagram of the battery structure after step S100 is completed in another embodiment of this application.
[0046] Figure 13 This is a schematic diagram of the battery structure after step S200 is completed in another embodiment of this application.
[0047] Figure 14 This is a schematic diagram of the battery structure after step S300 is completed in another embodiment of this application.
[0048] Figure 15 This is a schematic diagram of the battery structure after step S400 is completed in another embodiment of this application.
[0049] Figure 16 This is a scanning electron microscope image of the electrode protective layer after a laser is used to irradiate part of the electrode protective layer through the antireflection film in this application. Detailed Implementation
[0050] The embodiments of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0051] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0052] In existing technologies, silver is commonly used as the electrode material in solar cells, which is costly and global silver reserves are insufficient. Early solar cells used inexpensive and conductive metals such as aluminum as electrode materials, but aluminum is easily oxidized and has poor corrosion resistance. Conductive metals such as nickel are also potential electrode materials due to their oxidation and corrosion resistance, but their high melting points make them difficult to process. This patent combines the characteristics of various electrode materials with a laser-selective irradiation process to form the desired patterned metal electrode through an etching process.
[0053] This invention proposes a method for preparing a solar cell, such as... Figure 1 , Figure 4 , Figure 12 As shown, the method includes:
[0054] S100. A continuous electrode layer 6 and a continuous electrode protective layer 7 are sequentially prepared on the first side of the semi-finished solar cell. The semi-finished solar cell includes a semiconductor substrate 1, a semiconductor layer and a passivation layer 4 located on the first side of the semiconductor substrate 1. Further, a portion of the passivation layer 4 has an opening that exposes the semiconductor layer. The opening position of the passivation layer 4 corresponds to the location range of the target electrode structure. The target electrode structure is the electrode structure prepared on the final solar cell, which includes a separate positive electrode and / or negative electrode. The target electrode structure and its position pattern are conventional electrode structures in existing solar cells and will not be described in detail here. Specifically, it can be considered that a continuous electrode layer 6 and a continuous electrode protective layer 7 are sequentially prepared on the surface of the passivation layer 4 on the first side, and the electrode layer 6 prepared at the opening position of the passivation layer 4 is prepared on the surface of the semiconductor layer.
[0055] S200, Prepare an antireflection film 8 on the electrode protective layer 6;
[0056] S300: A laser is used to irradiate part of the electrode protective layer 7 through the antireflection film 8, so that the electrode protective layer 7 in the laser irradiation area forms a micro-pore structure; wherein, the laser irradiation area is the area outside the location of the target electrode structure;
[0057] S400, Etching: The electrode layer 6 is etched by entering the micropores with an etchant, so that the electrode layer 6 corresponding to the laser irradiation area in step S300 is removed after reacting with the etchant. The electrode protective layer 7 corresponding to the laser irradiation area is removed from the battery, and the electrode protective layer 7 and the electrode layer 6 corresponding to the non-laser irradiation area are retained after etching, forming a target electrode structure including a separated positive electrode and / or negative electrode.
[0058] The antireflection film 8 has a refractive index of n1, and the electrode protective layer 7 has a refractive index of n2, where n1 < n2. The thickness of the antireflection film 8 is [1 / 4 + (1 / 2) × a] × λ / n1, where λ is the wavelength of the laser used in step S300, and a is 0 or a natural number. Preferably, a = 0, in which case the thickness of the antireflection film 8 is λ / 4n1, which is the thinnest part of the antireflection film 8 and the laser absorption loss is minimized. Of course, a can also be equal to 1, 2, 3, etc. The antireflection film 8 is composed, for example, a uniform unidirectional solid layer or a porous film layer such as silicon dioxide, magnesium fluoride, silicon nitride, aluminum oxide, or titanium dioxide. In addition, the antireflection film 8 can be a single-layer film or a multi-layer film. By first fabricating the antireflection film 8 on the electrode protective layer 7, the incident laser can be absorbed more, improving the utilization rate of laser energy and significantly increasing production efficiency.
[0059] The semiconductor substrate 1 has a front (light-facing) and a back (light-reflecting) side. This solar cell can be a bifacial electrode cell, such as a TOPCON cell, or a back-contact cell, such as a BC cell. When it is a bifacial electrode cell, the first side can be either the front or back side of the cell; when it is a back-contact cell, the first side is the back side of the cell. When it is a TOPCON cell, the semiconductor layer can be phosphorus- or boron-doped amorphous silicon and / or microcrystalline silicon, or phosphorus- or boron-doped crystalline silicon. When it is a back-contact cell, the specific semiconductor layer structure is described in detail below.
[0060] In step S300, the size range of the laser irradiation area depends on the final desired size of the electrode layer 6 and the electrode protective layer 7.
[0061] The solar cell fabrication method proposed in this patent involves selective laser irradiation combined with an etching process on a continuous electrode layer and a continuous electrode protective layer to create patterned electrodes. This method offers high precision and causes no damage to the substrate. Furthermore, the resulting metal electrode grid lines have neat edges, eliminating the risk of leakage. In addition, this patented method is applicable to various metal electrode materials, reducing electrode costs and minimizing silver consumption in the photovoltaic industry.
[0062] Furthermore, the reflectivity of the antireflective coating 8 is less than 12% at the laser wavelength used in step S300, preferably less than 6%. The absorption coefficient of the antireflective coating 8 is less than 10000 cm⁻¹ at the laser wavelength used in step S300. -1 Preferably, the absorption coefficient of the antireflective coating 8 is less than 6000 cm⁻¹ at the laser wavelength used in step S300. -1 .
[0063] When the electrode protective layer 7 is irradiated by a laser, it can form a microporous structure, which tends to be honeycomb-like. By preparing an antireflection film 8 on the electrode protective layer 7 and using the antireflection film 8 within the above-mentioned parameter range, the depth and size of the micropores can be increased, which is more conducive to the subsequent wetting of the etching solution into the electrode layer 6. At the same time, using the antireflection film 8 within the above-mentioned preferred parameter range results in a higher energy density of laser bombardment of the electrode protective layer 7, and more high temperature is conducted to the lower layer, causing the electrode layer 6 to produce micro-explosions. This causes the electrode protective layer 7 to flip upward, forming a honeycomb structure, while the edges produce an outward curl structure. (See Appendix) Figure 16 The outward-rolled structure is also more easily corroded by the corrosive liquid, and reduces the influence of the surface structure near the honeycomb holes on the wetting tension of the corrosive liquid, making it easier for the corrosive liquid to enter the internal area from the honeycomb openings, rather than forming droplet aggregation in the surface area.
[0064] Furthermore, the antireflective coating 8 can reduce the laser reflectivity incident on the electrode protective layer 7 (and electrode layer 6) from more than 80% to less than 60%, thereby improving the utilization rate of laser energy.
[0065] For example, in one case, metallic nickel was chosen as the electrode protective layer 7 material and magnesium fluoride as the antireflection film 8 material. Under the laser wavelength of 1064nm, the refractive index of the magnesium fluoride antireflection film was 1.37, and the refractive index of metallic nickel was 2.89+5.33i. The required thickness of the magnesium fluoride antireflection film was 194nm. After the magnesium fluoride antireflection film was deposited, the reflectivity decreased from 73.45% to 57.57%, and the absorptivity increased from 26.55% to 42.43%, an increase of 1.60 times. For another example, cobalt metal is chosen as the electrode protective layer 7 material and silicon dioxide as the antireflection film 8 material. Under the condition of 355nm laser wavelength, the refractive index of silicon dioxide is 1.48 and the refractive index of cobalt metal is 1.63+3.43i. The required thickness of the silicon dioxide antireflection film is 60nm. After the silicon dioxide antireflection film is deposited, the reflectivity decreases from 65.10% to 45.82%, and the absorptivity increases from 34.90% to 55.18%, which is an increase of 1.55 times.
[0066] Example 1 (The solar cell is a back-contact solar cell)
[0067] S100. A continuous electrode layer 6 and a continuous electrode protective layer 7 are sequentially prepared on the first side of the semi-finished solar cell. The semi-finished solar cell includes a semiconductor substrate 1, a semiconductor layer and a passivation layer 4 located on the first side of the semiconductor substrate 1. A portion of the passivation layer 4 is open to expose the semiconductor layer. The opening position of the passivation layer 4 corresponds to the location of the target electrode structure. The opening area also corresponds to the electrode connection area. The electrode layer 6 in the electrode connection area is in direct contact with the semiconductor layer.
[0068] More specifically, step S100 includes:
[0069] S110, an opening is made in the passivation layer 4 on the back of the semi-finished solar cell, such as... Figure 3 As shown, the opening area of the passivation layer 4 corresponds to the alternately arranged first electrode connection area D and second electrode connection area E. In this embodiment, the solar cell is a back-contact solar cell, with the first side being the back of the cell. The first electrode connection area D and the second electrode connection area E together correspond to the electrode connection area. The area on the passivation layer 4 other than the first electrode connection area D and the second electrode connection area E is called the non-electrode connection area. The first electrode connection area D and the second electrode connection area E are the locations of the final first and second electrodes, which are the positive and negative electrodes of the solar cell.
[0070] Among them, such as Figure 2 The diagram shown is a schematic diagram of a semi-finished solar cell with an unopened passivation layer 4 according to an embodiment of this application. More specifically, the semi-finished solar cell includes a semiconductor substrate 1, a first doped semiconductor layer 2, and a second doped semiconductor layer 3. The semiconductor substrate 1 has a front side and a back side. The back side, also known as the first side, includes a first semiconductor region A and a second semiconductor region B arranged in an interdigitated pattern, and an isolation region C located between adjacent first semiconductor regions A and second semiconductor regions B. The first doped semiconductor layer 2 is disposed in the first semiconductor region A, and the second doped semiconductor layer 3 is disposed in the second semiconductor region B. The first doped semiconductor layer 2 and the second doped semiconductor layer 3 have opposite conductivity types. The opening area of the passivation layer 4 is located within the range of the first semiconductor region A and the second semiconductor region B, and the non-opening area of the passivation layer 4 is continuous. The passivation layer 4 covers the first semiconductor region A, the second semiconductor region B, and the isolation region C. The first electrode connection region D is located in the first semiconductor region A, and the second electrode connection region E is located in the second semiconductor region B. The first doped semiconductor layer 2 and the second doped semiconductor layer 3 arranged in an interdigitated pattern together constitute a semiconductor layer. The first electrode connection region D exposes the first doped semiconductor layer 2, and the second electrode connection region E exposes the second doped semiconductor layer 3.
[0071] There are multiple first semiconductor regions A and multiple second semiconductor regions B, such as Figure 2As shown, the first semiconductor region A and the second semiconductor region B can be considered as arranged in an interdigitated pattern along the X direction in the figure, with the first semiconductor region A and the second semiconductor region B spaced apart. The isolation region C is the area between the first semiconductor region A and the second semiconductor region B. Generally, the semi-finished solar cell also includes at least a first passivation layer disposed in the first semiconductor region A and a second passivation layer disposed in the second semiconductor region B. The first passivation layer and the first doped semiconductor layer 2 are arranged sequentially along the direction away from the semiconductor substrate 1, and the second passivation layer and the second doped semiconductor layer 3 are arranged sequentially along the direction away from the semiconductor substrate 1.
[0072] The semiconductor substrate 1 may include materials such as monocrystalline silicon, germanium, or gallium arsenide. The specific materials and fabrication methods of the first doped semiconductor layer 2 and the second doped semiconductor layer 3 depend on the specific structure of the back-contact solar cell, such as a TBC cell, an HBC cell, or an HTBC cell containing both TOPCON and HJT structures. When it is an HBC cell, the first doped semiconductor layer 2 may be phosphorus-doped amorphous silicon and / or microcrystalline silicon, and the second doped semiconductor layer 3 may be boron-doped amorphous silicon and / or microcrystalline silicon. The first passivation layer and the second passivation layer include intrinsic amorphous silicon. The passivation layer 4 may be a transparent conductive layer, such as at least one of indium tin oxide, zinc aluminum oxide, indium hydroxide, and indium tungsten oxide.
[0073] It should be noted that although the back contact battery structure in this patent example is based on a back side including a first semiconductor region A and a second semiconductor region B arranged in an interdigitated pattern and an isolation region C located between adjacent first semiconductor regions A and second semiconductor regions B, the back contact battery is not limited to this structure, and other back contact batteries are also within the scope of protection of this patent.
[0074] This application uses a TBC battery as an example for illustration. In this case, the first passivation layer and the second passivation layer are tunneling oxide 5, the first doped semiconductor layer 2 and the second doped semiconductor layer 3 can each be one of phosphorus-doped polycrystalline silicon and boron-doped polycrystalline silicon, and the passivation layer 4 can be silicon nitride.
[0075] like Figure 3 The diagram shown is a schematic representation of the battery structure after step S110 in one embodiment of this application. There are many ways to open the passivation layer 4 on the back of the semi-finished solar cell, such as laser removal or photolithography. Preferably, laser irradiation is used to connect the first electrode connection area D and the second electrode connection area E, which is more precise and simpler. How to obtain the partially open passivation film 4 is not the focus of this patent; it is sufficient to prepare a semi-finished solar cell with this structure to facilitate the following step S120.
[0076] S120. A continuous electrode layer 6 and a continuous electrode protective layer 7 are sequentially prepared on the passivation film 4, which includes the opening region.
[0077] Specifically, such as Figure 4 The diagram shown is a schematic representation of the battery structure after step S120 is completed in one embodiment of this application.
[0078] Furthermore, the methods for preparing electrode layer 6 and electrode protective layer 7 include any one of physical vapor deposition, chemical deposition, or electroplating. Physical vapor deposition methods include evaporation, sputtering, arc plasma deposition, ion plating, and molecular beam epitaxy. Using these methods, metal layers of arbitrary thickness can be prepared with uniform thickness, good contact, and high matching degree. Even on uneven battery surfaces, the metal layer and substrate can be completely bonded without voids. Moreover, the metal electrode has good conductivity, neat edges, and no risk of leakage.
[0079] Furthermore, the electrode layer 6 and electrode protective layer 7 prepared on the surface of the passivation layer 4 using the above preparation method are both continuous. "Continuous" means that the area of the electrode layer 6 and electrode protective layer 7 covers the entire area on the back of the back contact battery where the electrode needs to be made.
[0080] Furthermore, electrode layer 6 is made of a metal with good conductivity and relatively poor corrosion resistance, with a resistivity range of 1.5 × 10⁻⁶. -8 Ω·m~20.0×10 -8 The electrode layer 6 is preferably made of a readily available and inexpensive metal with good electrical conductivity (Ω·m). The electrode protective layer 7 is made of a corrosion-resistant and oxidation-resistant metal with a melting point range of 600℃ to 3500℃ and a resistivity range of 3.5 × 10⁻⁶ Ω·m. -8 Ω·m~30.0×10 -8 Ω·m. That is, the electrode protective layer 7 must be both corrosion-resistant and have a certain degree of conductivity. After completing the selective laser irradiation in step S200 and the corrosion in step S300, the electrode protective layer 7 is still retained in the non-laser irradiated areas to protect the electrode layer 6 from oxidation or corrosion.
[0081] The electrode layer 6 and electrode protective layer 7 can be made of a variety of materials, depending on the type of etching solution used. For example, when the etching solution is acidic, the electrode layer 6 can include any one of copper, aluminum, magnesium, zinc, cadmium, indium, and tin, or alloys containing these metals, such as brass or copper-tin alloys. These metals not only have good electrical conductivity but are also inexpensive. The electrode protective layer 7 can include any one of beryllium, molybdenum, tungsten, cobalt, nickel, iron, and platinum, or alloys containing these metals, such as nickel-cobalt alloys or tungsten steel. These metals are not easily oxidized and can effectively protect the electrode layer from oxidation or corrosion.
[0082] When the etchant is alkaline, electrode layer 6 comprises any one of aluminum, beryllium, molybdenum, tungsten, zinc, indium, iron, platinum, and tin, or an alloy containing them, such as an aluminum-copper-magnesium alloy, preferably aluminum, beryllium, zinc, or tin; electrode protective layer 7 comprises any one of silver, copper, gold, magnesium, cobalt, nickel, cadmium, molybdenum, tungsten, indium, iron, and platinum, or an alloy containing them, such as brass, preferably copper, magnesium, cobalt, nickel, or cadmium. Further, the thickness of the electrode layer ranges from 0.1 μm to 30 μm, and the thickness of the electrode protective layer 7 ranges from 2 nm to 200 nm. Within this thickness range, the electrode protective layer 7 can absorb most of the incoming laser energy. When the electrode protective layer is less than 2 nm, the thickness is insufficient to absorb laser energy and cannot provide adequate protection; when the thickness of the electrode protective layer is greater than 200 nm, high electrical loss leads to reduced battery efficiency, and the high energy required for the laser process results in energy waste and reduced production efficiency. Preferably, the thickness of the electrode protective layer 7 is in the range of 20nm to 120nm. Within this range, the laser absorption performance and protective performance of the electrode protective layer 7 are optimal.
[0083] The electrode layer 6 remaining after corrosion and the electrode protective layer 7 together constitute the first electrode and the second electrode of this patent. This can achieve good conductivity of the battery electrode and avoid easy oxidation. Moreover, the choice of materials for both facilitates the patterning of the electrode by combining selective laser irradiation and corrosion.
[0084] S200. Prepare an antireflection film 8 on the electrode protective layer 7.
[0085] Among them, such as Figure 5 The diagram shown is a schematic representation of the battery structure after step S200 in one embodiment of this application. The method for preparing the antireflective coating 8 can employ conventional methods from the prior art; however, since this preparation method is not the focus of this patent, it will not be described in detail here.
[0086] S300, A laser is used to irradiate part of the electrode protective layer through the antireflection film 8, so that the electrode protective layer 7 in the laser irradiation area F forms a micro-pore structure; wherein, the laser irradiation area F is the area outside the location of the target electrode structure; at this time, the laser irradiation area is the isolation area C and part of the first semiconductor area A and part of the second semiconductor area B near the isolation area C.
[0087] Specifically, the size range of the portion of the first semiconductor region A and the portion of the second semiconductor region B near the isolation region C depends on the size of the electrode layer 6 and the electrode protective layer 7 that are ultimately expected to be retained in the first electrode connection region D and the second electrode connection region E in the X direction, for example, 40 μm to 160 μm. Within this range, the electrode layer 6 and the electrode protective layer 7 are wide enough to ensure a small resistance, and not so wide that the ambient light received on the back side is blocked by the electrodes, thereby reducing the bifaciality.
[0088] Among them, such as Figure 6 The diagram shown is a schematic representation of the battery structure after step S300 is completed in one embodiment of this application.
[0089] Laser irradiation can induce micropore structures in the electrode protective layer 7. These micropore structures are laser-induced periodic surface structures (LIPSS or ripples), possessing both near-wavelength (micrometer or submicrometer) low spatial frequency (LSFL) structures and nanometer-scale high spatial frequency (HSFL) structures. This structure is typically obtained through a multi-pulse laser process, gradually forming as laser pulses are successively superimposed, and the resulting micropore structures tend to be honeycomb-like. Both incomplete and complete structures obtained using this phenomenon can induce ultrafine pores in nanometer-thick metal films, thereby connecting with the underlying structure.
[0090] In step S300, the laser used is a picosecond laser or a femtosecond laser, that is, the laser used in this patent is a laser with a pulse width in the ps or fs range.
[0091] S400, Etching: An etchant is used to enter the pores to etch the electrode layer 6, so that the electrode layer 6 corresponding to the laser irradiation area F in step S300 is removed after reacting with the etchant. The electrode protective layer 7 corresponding to the laser irradiation area F is removed from the battery, and the electrode protective layer 7 and the electrode layer 6 corresponding to the non-laser irradiation area are retained after etching, forming a target electrode structure including a separated positive electrode and a negative electrode. The positive electrode and the negative electrode are the first electrode and the second electrode mentioned above. The first electrode is one of the positive electrode and the negative electrode, and the second electrode is the other of the positive electrode and the negative electrode.
[0092] Specifically, such as Figure 7 The diagram shown is a schematic representation of the battery structure after step S400 is completed in one embodiment of this application.
[0093] After the etchant enters the micropore structure formed by the electrode protective layer 7 corresponding to the laser irradiation area F, it erodes the underlying electrode layer 6. After etching, the electrode layer 6 corresponding to the laser irradiation area F is removed, and the electrode protective layer 7 corresponding to the laser irradiation area F is peeled off. That is, in step 300, the electrode layer 6 and electrode protective layer 7 in the laser irradiation area F are completely removed, while the electrode layer 6 and electrode protective layer 7 in the non-laser irradiation area are retained. The electrode layer 6 and electrode protective layer 7 retained in the first semiconductor region A constitute the first electrode, and the electrode layer 6 and electrode protective layer 7 retained in the second semiconductor region B constitute the second electrode.
[0094] The etching solution used during etching, which reacts with electrode layer 6, can be either acidic or alkaline. Acidic etching solutions can be any one of dilute hydrochloric acid, dilute nitric acid, or dilute sulfuric acid, or a mixture thereof, or a mixture including these acids. They can also be non-oxidizing concentrated acids, such as concentrated hydrochloric acid. Alkaline etching solutions include alkaline aqueous solutions with sodium hydroxide or potassium hydroxide as the main solute.
[0095] Considering that some of the metals used in the electrode layer 6 can be corroded by acidic solutions and some by alkaline solutions, after preparing a continuous antireflection film 8 on the continuous electrode protective layer 7, step S400 is divided into two cases. First, the electrode layer 6 can react with the acidic etching solution. In step S400, the etching solution is an acidic etching solution, which reacts with the antireflection film 8 and the electrode layer 6 corresponding to the laser irradiation area. In this way, the preparation of the first electrode and the second electrode can be completed in one step of etching. The acidic etching solution is, for example, hydrofluoric acid solution.
[0096] The reaction process is as follows: Generally speaking, the acidic etchant will first corrode the antireflection membrane 8, and then the etchant will flow through the holes of the electrode protective layer 7 to the electrode layer 6 to corrode the electrode layer 6. Finally, the electrode layer 6 corresponding to the laser irradiation area F will react with the etchant and be removed. The electrode protective layer 7 corresponding to the laser irradiation area F will be peeled off. The electrode protective layer 7 and the electrode layer 6 corresponding to the non-laser irradiation area will be retained after corrosion. When the tensile strength of the antireflective membrane 8 is low, during the process of laser irradiation in step S300 to form holes in the electrode protective layer 7, heat or force may be transferred to the antireflective membrane 8, causing the antireflective membrane 8 to tear or form holes. Therefore, for the antireflective membrane 8 corresponding to the laser irradiation area F, the acidic etching solution can flow through the holes in the antireflective membrane 8 to the electrode protective layer 7, and then flow to the electrode layer 6 to corrode the electrode layer 6. The acidic etching solution will also corrode the antireflective membrane 8 in the laser irradiation area F and the non-laser irradiation area at the same time, and eventually corrode the entire antireflective membrane 8. The electrode layer 6 corresponding to the laser irradiation area F is removed after reacting with the etching solution, and the electrode protective layer 7 corresponding to the laser irradiation area F is peeled off. After corrosion, the electrode protective layer 7 and the electrode layer 6 corresponding to the non-laser irradiation area are retained.
[0097] The second method involves the electrode layer 6 reacting with an alkaline etching solution. The etching process in step S400 consists of two steps: first, an acidic etching solution is used to remove the antireflective membrane 8; then, an alkaline etching solution is used to react with the electrode layer 6 corresponding to the laser irradiation area F. This method allows for the selection of a metal material easily corroded by an alkaline etching solution as the electrode layer 6, thus broadening the choice of material for the electrode layer 6. For example, the alkaline solution could be a sodium hydroxide solution.
[0098] Furthermore, if necessary, ultrasonic cleaning can be used during corrosion to assist in peeling off the electrode protective layer 7 corresponding to the laser irradiation area F. Alternatively, after corrosion, the electrode protective layer 7 that has not been peeled off in the laser irradiation area F on the back of the semi-finished solar cell can be cleaned and removed with a brush. This helps to completely remove the electrode layer 6 and electrode protective layer 7 in the laser irradiation area F.
[0099] Example 2 (The solar cell is a bifacial electrode cell)
[0100] Let's take TOPCON batteries as an example.
[0101] S100. A continuous electrode layer 6 and a continuous electrode protective layer 7 are sequentially prepared on the first side of the semi-finished solar cell. The semi-finished solar cell includes a semiconductor substrate 1, a semiconductor layer and a passivation layer 4 located on the first side of the semiconductor substrate 1. A portion of the passivation layer 4 is open to expose the semiconductor layer, and the opening position of the passivation layer 4 corresponds to the location of the target electrode structure.
[0102] like Figure 11 The diagram shown is a schematic representation of the structure of a semi-finished TOPCON solar cell according to another embodiment of this application. In this case, it is assumed that the first side is the back side of the TOPCON cell, and the semiconductor layer is phosphorus-doped amorphous silicon and / or microcrystalline silicon, or boron-doped amorphous silicon and / or microcrystalline silicon; the passivation layer 4 covers the back semiconductor layer. The back side of the semi-finished TOPCON cell also includes a tunneling oxide layer disposed between the semiconductor substrate 1 and the semiconductor layer. Figure 11 The drawing is shown but not labeled. The material selection and preparation methods for electrode layer 6 and electrode protective layer 7 can refer to Example 1, such as... Figure 12 The diagram shown is a schematic of the battery structure after completing step S100 in this embodiment.
[0103] S200, Prepare an antireflection film 8 on the electrode protective layer 6;
[0104] like Figure 13 The diagram shown is a schematic representation of the battery structure after step S200 is completed in one embodiment of this application.
[0105] S300, A laser is used to irradiate a portion of the electrode protective layer 7 through the antireflection film 8, causing a microporous structure to form in the electrode protective layer 7 in the laser irradiation area F; wherein, the laser irradiation area is the region outside the location of the target electrode structure; for example... Figure 14 The diagram shown is a schematic of the battery structure after completing step S300 in this embodiment.
[0106] The laser used for laser irradiation is also a picosecond laser or a femtosecond laser. Similarly, the size of at least part of the non-opening area irradiated by the laser depends on the size of the electrode layer 6 and the electrode protective layer 7 that are ultimately expected to be retained. This size range is wide enough to ensure low resistance, but not so wide that it would block the ambient light received on the back side, thereby reducing the bifaciality.
[0107] S400, Etching: An etching solution is used to penetrate the pores and etch the electrode layer 6. This removes the electrode layer 6 corresponding to the laser irradiation area F from step S300 after reacting with the etching solution. The electrode protective layer 7 corresponding to the laser irradiation area F is peeled off, while the electrode protective layer 7 and electrode layer 6 remain in the non-laser irradiation areas after etching, forming a target electrode structure including a separated positive or negative electrode. The etching method can also refer to Example 1. Figure 15 The diagram shown is a schematic of the battery structure after completing step S400 in this embodiment.
[0108] As another embodiment, considering that when the surface of the electrode protective layer 7 is smooth, the reflectivity to laser is high and the light utilization rate is low; furthermore, in order to make the electrode protective layer 7 have oxidation resistance, the melting point of the electrode protective layer 7 is generally high, for example, the melting point of Ni reaches 1453°C. Therefore, in step S100, at least a portion of the passivation layer outside the target electrode structure region is a textured structure. That is, the portion of the passivation layer outside the target structure region can be entirely textured, or a portion of the portion outside the target structure region can be textured, or the entire passivation layer 4 can be textured. Specifically, the textured structure can be formed, for example, by laser irradiation at the corresponding location on the silicon substrate to form a textured structure, and then the corresponding region is textured when the passivation layer 4 is fabricated in the subsequent step. Of course, other methods can also be used.
[0109] Furthermore, when the solar cell is a back-contact solar cell, the semiconductor layer includes a first doped semiconductor layer 2 and a second doped semiconductor layer 3. The first side of the semi-finished solar cell includes a first semiconductor region A and a second semiconductor region B arranged in an interdigitated pattern, and an isolation region C located between adjacent first semiconductor regions A and second semiconductor regions B. The first doped semiconductor layer 2 is disposed in the first semiconductor region A, and the second doped semiconductor layer 3 is disposed in the second semiconductor region B, and the conductivity types of the first doped semiconductor layer 2 and the second doped semiconductor layer 3 are opposite. The opening region of the passivation layer 4 is located within the range of the first semiconductor region A and the second semiconductor region B, and the non-opening region of the passivation layer 4 is continuous. The isolation region C is located within the non-opening region of the passivation layer 4. At this time, the part of the passivation layer 4 corresponding to the isolation region C in the cell structure is a textured structure, or the part of the passivation layer 4 outside the target electrode structure region is a textured structure, or the entire passivation layer 4 is a textured structure. In this way, the light-trapping effect of the textured structure can be used to make the incident laser absorb and reflect multiple times, improve the utilization rate of laser energy, thereby reducing the energy consumption of the laser and greatly reducing the cost.
[0110] More specifically, such as Figure 8 , Figure 9 and Figure 10 The diagram shown is a schematic representation of a semi-finished solar cell with a passivation layer according to another embodiment of this application. Figure 7 The portion of the intermediate passivation layer corresponding to isolation region C has a textured surface. Figure 8 The portion of the passivation layer other than the positive and negative electrodes has a textured surface. Figure 9 The first semiconductor region A, the second semiconductor region B, and the isolation region C all have textured structures. These textured structures can improve the utilization rate of laser energy. Regarding the formation of the textured structures, for example, the textured structures corresponding to the first semiconductor region A and the second semiconductor region B corresponding to the passivation layer 4 can be obtained during the preparation of the first semiconductor region A and the second semiconductor region B, or the textured structure can be formed on the semiconductor substrate 1, and then the first semiconductor region A and the second semiconductor region B can be prepared on it. The textured structure of the isolation region C can be obtained during the fabrication of the isolation region C. Considering that the focus of this patent is that the textured structure is already present before the laser irradiation electrode protective layer 7, and how the textured structure is prepared is not the focus of this application, it will not be elaborated here.
[0111] Furthermore, the applicant's research found that when at least a portion of the passivation layer 4 outside the target electrode structure region is a textured structure, or when the entire passivation layer 4 is a textured structure, the pyramidal tips of the textured surface have a tip effect. Under the action of the laser photoelectric field, the air at the tip generates plasma, which improves the absorption efficiency of laser energy in this region and reduces the requirement for laser peak power. Moreover, an uneven thermal field is generated under textured conditions, causing the metal protective layer to tear and form tiny gaps. In this case, the laser used in step S200 can be either a continuous laser or a pulsed laser. When using a pulsed laser, a picosecond laser, a femtosecond laser, or a nanosecond laser can be used.
[0112] Furthermore, this patent also compares the laser processing energy consumption with and without a velvety surface. When there is no velvety surface, the required laser energy consumption using a green leather laser reaches 2051.28 mJ / cm². 2 The above. Furthermore, when using a textured surface, laser energy consumption across multiple wavelengths is significantly reduced, reaching as low as 80 mJ / cm². 2 the following.
[0113] Furthermore, the thickness of the semiconductor substrate 1 is 110 μm to 165 μm. This thickness range is beneficial for maximizing the absorption of sunlight while maintaining low cost; it also helps reduce the distance that carriers generated by light travel in the silicon substrate, thereby reducing bulk recombination.
[0114] The various embodiments in this specification are described in a progressive, parallel, or combined manner. Each embodiment focuses on its differences from other embodiments, and similar or identical parts between embodiments can be referred to interchangeably. For the apparatuses disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.
[0115] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for preparing a solar cell, characterized in that, include: S100. A continuous electrode layer and a continuous electrode protective layer are sequentially prepared on the first side of the semi-finished solar cell; wherein the semi-finished solar cell includes a semiconductor substrate, a semiconductor layer and a passivation layer located on the first side of the semiconductor substrate; S200, Prepare an antireflection film on the electrode protective layer; S300: A laser is used to irradiate part of the electrode protective layer through the antireflection film, so that the electrode protective layer in the laser irradiation area forms a micro-pore structure; wherein, the laser irradiation area is the area outside the location of the target electrode structure; S400, corrosion: using an etchant to enter the pores and corrode the electrode layer, so that the electrode layer corresponding to the laser irradiation area in step S300 reacts with the etchant and is removed, the electrode protective layer corresponding to the laser irradiation area is detached, and the electrode protective layer and electrode layer corresponding to the non-laser irradiation area are retained after corrosion, forming a target electrode structure including a separated positive electrode and / or negative electrode. Wherein, the refractive index of the antireflective film is n1, the refractive index of the electrode protective layer is n2, and n1 < n2; the thickness of the antireflective film is [1 / 4 + (1 / 2) × a] × λ / n1, where λ is the wavelength of the laser used in step S300, and a is 0 or a natural number.
2. The method for preparing a solar cell according to claim 1, characterized in that, In step S100, a portion of the passivation layer in the semi-finished solar cell has an opening that exposes the semiconductor layer, and the opening position of the passivation layer corresponds to the location of the target electrode structure.
3. The method for preparing a solar cell according to claim 1, characterized in that, The reflectivity of the antireflective coating is less than 12% at the laser wavelength used in step S300, and the absorption coefficient of the antireflective coating is less than 10000 cm⁻¹ at the laser wavelength used in step S300. -1 .
4. The method for preparing a solar cell according to claim 1, characterized in that, The antireflective membrane is a single-layer membrane or a multi-layer membrane.
5. The method for preparing a solar cell according to claim 1, characterized in that, The electrode layer can react with the acidic etching solution; in step S400, the etching solution is an acidic etching solution, and the acidic etching solution is used to react with the antireflection membrane and the electrode layer corresponding to the laser irradiation area. Alternatively, the electrode layer can react with an alkaline etching solution. The etching process in step S400 includes: first, using an acidic etching solution to etch away the antireflective film, and then using an alkaline etching solution to react with the electrode layer corresponding to the laser irradiation area.
6. The method for preparing a solar cell according to claim 1, characterized in that, The antireflective coating can reduce the reflectivity of laser incident on the electrode protective layer and the electrode layer from more than 80% to less than 60%.
7. The method for preparing a solar cell according to claim 1, characterized in that, The solar cell is a back-contact solar cell. The semiconductor layer includes a first doped semiconductor layer and a second doped semiconductor layer. The first side of the semi-finished solar cell includes a first semiconductor region and a second semiconductor region arranged in an interdigitated pattern, as well as an isolation region located between adjacent first semiconductor regions and second semiconductor regions. The first doped semiconductor layer is disposed in the first semiconductor region, and the second doped semiconductor layer is disposed in the second semiconductor region. The first doped semiconductor layer and the second doped semiconductor layer have opposite conductivity types.
8. The method for preparing a solar cell according to claim 1, characterized in that, The laser used in step S300 is a picosecond laser or a femtosecond laser.
9. The method for preparing a solar cell according to claim 1, characterized in that, The resistivity of the electrode layer is in the range of 1.5 × 10⁻⁶. -8 Ω·m~20.0×10 -8 Ω·m; the melting point temperature range of the electrode protective layer is 600℃~3500℃, and the resistivity range is 3.5×10 Ω·m. -8 Ω·m~30.0×10 -8 Ω·m.
10. The method for preparing a solar cell according to claim 1, characterized in that, The corrosive liquid is an acidic corrosive liquid, the electrode layer includes any one of copper, aluminum, magnesium, zinc, cadmium, indium, and tin or an alloy containing them, and the electrode protective layer includes any one of beryllium, molybdenum, tungsten, cobalt, nickel, iron, and platinum or an alloy containing them.
11. The method for preparing a solar cell according to claim 1, characterized in that, The corrosive liquid is an alkaline corrosive liquid, and the electrode layer includes any one of aluminum, beryllium, molybdenum, tungsten, zinc, indium, iron, platinum, and tin or an alloy thereof; the electrode protective layer includes any one of silver, copper, gold, magnesium, cobalt, nickel, cadmium, molybdenum, tungsten, indium, iron, and platinum or an alloy thereof.
12. The method for preparing a solar cell according to claim 1, characterized in that, The thickness of the electrode protective layer ranges from 2 nm to 200 nm.
13. The method for preparing a solar cell according to claim 1, wherein the thickness of the electrode protective layer ranges from 20 nm to 120 nm.
14. The method for preparing a solar cell according to claim 1, characterized in that, In step S100, at least a portion of the passivation layer outside the target electrode structure region is a textured structure, or the entire passivation layer is a textured structure.
15. The method for preparing a solar cell according to claim 1, characterized in that, The solar cell is a back-contact solar cell. The semiconductor layer includes a first doped semiconductor layer and a second doped semiconductor layer. The first side of the semi-finished solar cell includes a first semiconductor region and a second semiconductor region arranged in an interdigitated pattern, as well as an isolation region located between adjacent first semiconductor regions and second semiconductor regions. The first doped semiconductor layer is disposed in the first semiconductor region, and the second doped semiconductor layer is disposed in the second semiconductor region. The first doped semiconductor layer and the second doped semiconductor layer have opposite conductivity types. In step S100, the portion of the passivation layer corresponding to the isolation region has a textured structure, or the portion of the passivation layer outside the target electrode structure region has a textured structure, or the entire passivation layer has a textured structure.
16. The method for preparing a solar cell according to claim 14 or 15, characterized in that, The laser used in step S300 is a pulsed laser or a continuous laser.
17. The method for preparing a solar cell according to claim 1, characterized in that, In step S100, the method for preparing a continuous electrode layer and a continuous electrode protective layer includes any one of physical vapor deposition, chemical deposition, or electroplating.
18. The method for preparing a solar cell according to claim 1, characterized in that, In step S400, after etching, the electrode protective layer that has not been peeled off in the laser irradiation area of the first side of the semi-finished solar cell is cleaned and removed by a brush; or, in step S400, ultrasonic cleaning is used simultaneously with etching to assist in peeling off the electrode protective layer corresponding to the laser irradiation area.