HJT solar cell and preparation method thereof
By eliminating the PVD sputtering and etching steps in the HJT solar cell fabrication process and using a grid line pre-plating method to form electrodes, the problem of copper seed layer etching in traditional processes is solved, improving cell performance and environmental friendliness while reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUZHOU MAXWELL TECH CO LTD
- Filing Date
- 2023-02-07
- Publication Date
- 2026-05-12
AI Technical Summary
Traditional HJT solar cells suffer from problems such as copper-containing wastewater discharge due to copper seed layer etching, TCO damage, and excessively large ineffective linewidth shading areas during the fabrication process, which limit their industrial application.
A method that eliminates the need for PVD sputtering of copper seed layers and etching is used to form electrodes on heterojunction cells through gate line pre-plating. This process includes roughening, pre-dip, metal activation, pre-plating, deoxidation, copper electroplating, and chemical tin plating. This improves the adhesion between the electroplated copper and the TCO film, reducing damage and wastewater discharge.
It reduces the area of ineffective linewidth obstruction, improves the photoelectric conversion efficiency of the battery, reduces battery failure caused by copper migration, and reduces cost and environmental risks.
Smart Images
Figure CN115842064B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of solar cell technology, and in particular to an HJT solar cell and its fabrication method. Background Technology
[0002] HJT solar cells, as a new type of solar cell, have become a hot topic in the solar energy field in recent years. Traditional HJT solar cells typically use screen printing technology to print the front and back electrodes and electric field on the silicon wafer surface using low-temperature silver-aluminum paste. However, the high resistivity of low-temperature silver paste leads to excessive silver paste consumption and high cost.
[0003] To reduce costs, researchers have proposed a copper seed plating process. Since direct electroplating of metals onto the transparent conductive oxide (TCO) layer results in poor adhesion and easy detachment, PVD sputtering is typically used to deposit a copper seed layer on the silicon wafer's TCO surface to improve contact characteristics. However, to prevent short circuits and exposure of the TCO layer, the excess copper seed layer must be removed in subsequent processes. Etching the copper seed layer often leads to problems such as the discharge of copper-containing wastewater, damage to the TCO, and an excessively large ineffective linewidth blocking area, limiting the industrial application of heterojunction solar cells. Summary of the Invention
[0004] Based on this, this application provides an HJT solar cell and its fabrication method. The cell does not require PVD sputtering of copper seed layers and etching on both sides, thus avoiding the discharge of copper-containing wastewater. It also reduces TCO damage caused by etching of copper seed layers, reduces the ineffective linewidth shading area, and overcomes the shortcomings of traditional technologies.
[0005] The first aspect of this application provides a method for fabricating an HJT solar cell, comprising the following steps:
[0006] A heterojunction solar cell substrate is provided, and a transparent conductive oxide layer is deposited on both sides of the heterojunction solar cell substrate;
[0007] A mask layer is fabricated on the surface of a transparent conductive oxide layer;
[0008] The mask layer is patterned with openings to form a mask layer with patterned openings;
[0009] In a dark environment, roughening, pre-dipping, and metal activation treatments are sequentially performed at the patterned openings of the mask layer to obtain a pretreated heterojunction battery substrate.
[0010] HJT solar cells were prepared by sequentially performing pre-plating, deoxidation, copper electroplating, film stripping, and chemical tin plating on the pretreated heterojunction cell substrate.
[0011] In some embodiments, the roughening process includes: placing the heterojunction battery substrate with patterned openings in an acid solution with a mass concentration of 3% to 15% and treating it at 35°C to 90°C for 30 to 200 seconds.
[0012] In some embodiments, the pre-immersion treatment includes: placing the roughened heterojunction battery substrate in a pre-immersion solution and treating it at 20°C to 30°C for 30s to 300s;
[0013] The pre-impregnation solution includes: sodium sulfate 150g / L~350g / L, 50% sulfuric acid solution 150mL / L~250mL / L, and sulfur compounds 2g / L~4g / L.
[0014] In some embodiments, the sulfur compound is selected from sodium propanesulfonate and thiourea.
[0015] In some embodiments, the metal activation treatment is selected from palladium activation treatment, platinum activation treatment, ruthenium activation treatment, silver activation treatment, or zinc activation treatment.
[0016] In some embodiments, the metal activation treatment includes placing the pre-impregnated heterojunction battery substrate in an activation solution and treating it at 20°C to 30°C for 30s to 300s.
[0017] In some embodiments, the activation solution comprises a stabilizer, an acid, and a metal salt of the corresponding acid radical ion;
[0018] The stabilizer is selected from one or more of malic acid, citric acid, lactic acid, propionic acid, glycolic acid, triethanolamine, glycine, thiourea, potassium iodide, 4-methylpyridine, and sodium dodecyl sulfate;
[0019] The acid is selected from one or more of nitric acid, sulfuric acid, hydrochloric acid, chloric acid, perchloric acid, and methanesulfonic acid.
[0020] In some embodiments, the activation solution comprises the following components: palladium sulfate 5 mg / L to 80 mg / L, 4-methylpyridine 3 mg / L to 25 mg / L, sodium dodecyl sulfate 1 mg / L to 40 mg / L, sodium sulfate 1 mg / L to 40 mg / L, and 50% sulfuric acid solution 18 mL / L to 22 mL / L.
[0021] In some embodiments, the pre-plating is pre-plating with nickel, silver, zinc, or copper.
[0022] In some implementations, the pre-plating is chemical pre-plating.
[0023] In some embodiments, the pre-plating of nickel is electroless nickel plating, and the specific process includes: placing the heterojunction battery substrate that has undergone metal activation treatment into an electroless nickel plating solution for electroless nickel plating treatment, controlling the temperature of the electroless nickel plating solution to be 80°C to 95°C, and the electroless nickel plating treatment time to be 30s to 900s.
[0024] The electroless nickel plating solution contains the following components: nickel sulfate 2g / L~10g / L, sodium hypophosphite 10g / L~100g / L, citric acid 1g / L~15g / L, lead nitrate 1mg / L~20mg / L. Ammonia water is used to adjust the pH of the electroless nickel plating solution, and the pH of the electroless nickel plating solution is stably controlled at about 4.8.
[0025] In some embodiments, the deoxidation process involves placing the pre-plated heterojunction battery substrate in a deoxidation solution and reacting it at 20°C–30°C for 30–200 seconds. The deoxidation solution is an HF solution.
[0026] In some embodiments, the copper electroplating process is as follows: the deoxidized heterojunction battery substrate is placed in the copper electroplating solution and reacted at 20°C to 30°C for 100s to 1200s to form a copper electrode.
[0027] The copper plating solution contains the following components: copper sulfate 90g / L-180g / L and sulfuric acid 90g / L-180g / L.
[0028] In a second aspect, this application provides an HJT solar cell, which is prepared by the aforementioned method for preparing an HJT solar cell. Attached Figure Description
[0029] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0030] Figure 1 This is a grid line electroplating pattern of Embodiment 1 of this application;
[0031] Figure 2 This is a grid line electroplating pattern of Comparative Example 1 of this application. Detailed Implementation
[0032] To facilitate understanding of this application, a more comprehensive description will be provided below, along with preferred embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.
[0033] Furthermore, the use of terms such as "first" and "second" is for descriptive purposes only and should not be interpreted as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Nor should it be interpreted as implicitly specifying the importance or quantity of the indicated technical features. Moreover, "first" and "second" serve only a non-exhaustive enumeration purpose and should be understood as not constituting a closed-ended limitation on quantity.
[0034] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.
[0035] The terms "preferred," "more preferably," etc., used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application.
[0036] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.
[0037] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means additional steps and components that may be added without affecting the final result. The compositions and methods / processes of this application comprise, consist of, and are substantially composed of the essential elements and limitations described herein, as well as any additional or optional components, parts, steps, or limitations described herein.
[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.
[0039] Those skilled in the art will understand that, as described in the background section, conventional techniques employ a copper seeding process to fabricate solar cells. Because direct electroplating of metal onto a transparent conductive oxide (TCO) layer results in poor adhesion and easy detachment, this process typically uses PVD sputtering to deposit a copper seed layer on the TCO surface of the silicon wafer to improve contact characteristics. However, to prevent short circuits and exposure of the TCO layer, subsequent processes require etching away excess copper seed layer. This etching process not only causes the discharge of copper-containing wastewater but also easily damages the TCO; furthermore, etching the copper seed layer results in an excessively large area of ineffective linewidth obstruction.
[0040] This paper proposes an improvement to the fabrication method of heterojunction (HJT) solar cells, addressing the shortcomings of traditional copper seeding techniques. The method provided in this application eliminates the PVD sputtering and etching steps, directly generating the grid lines of the front and back electrodes by pre-plating the grid lines before the copper electroplating step. This achieves copper electroplating on the heterojunction cell without the need for a PVD sputtering copper seed layer, improving the adhesion between the electroplated copper and the TCO film; reducing sputtering damage, copper removal damage, and copper-containing wastewater pollution; enhancing the pull-out force and electroplating uniformity of the grid line electrodes; and reducing the ineffective linewidth obstruction area, thereby improving the photoelectric conversion efficiency of the cell and effectively solving the aforementioned technical defects of traditional techniques. Furthermore, the pre-plating of a metal layer between the electroplated copper grid lines and the TCO film significantly reduces the problem of cell failure caused by copper migration under energized conditions.
[0041] A first aspect of this application provides a method for fabricating an HJT solar cell, comprising the following steps:
[0042] S1. Provide a heterojunction cell substrate, and deposit transparent conductive oxide layers on both sides of the heterojunction cell substrate;
[0043] S2. A mask layer is formed on the surface of the transparent conductive oxide layer;
[0044] S3. Perform patterned opening processing on the mask layer to form a mask layer with patterned openings;
[0045] S4. In a dark environment, roughening, pre-dipping and metal activation treatments are performed sequentially at the patterned opening of the mask layer to obtain a pretreated heterojunction battery substrate.
[0046] S5. The pretreated heterojunction cell substrate is subjected to pre-plating, deoxidation, copper electroplating, film stripping, and chemical tin plating in sequence to obtain HJT solar cells.
[0047] In some embodiments, the heterojunction cell substrate in step S1 is a solar cell substrate with a PN junction. The transparent conductive oxide (TCO) layer material deposited on both sides of the heterojunction cell substrate is selected from one or more of the following: indium tin oxide (ITO), tin oxide (TO), indium tungsten oxide (IWO), zinc aluminum oxide (AZO), zinc gallium oxide (GZO), VTTO target, SCOT target, and fluorine-doped tin oxide (FTO). The materials of the transparent conductive oxide layers on both sides of the heterojunction cell substrate can be the same or different. Preferably, the transparent conductive oxide layer material is ITO, VTTO, SCOT, or AZO. This heterojunction cell substrate can also be referred to as a blue film or a cell.
[0048] It is understood that the transparent conductive oxide layer material of this application can be any of the transparent conductive oxides commonly used in the art, and no particular limitation is made here.
[0049] In some embodiments, steps S2 and S3 mainly include: fabricating a mask layer by uniformly covering the surface of the heterojunction battery substrate after the transparent conductive oxide layer deposition treatment with photosensitive material; exposure by selectively photocuring the photosensitive material; and development by cleaning the uncured photosensitive material with a weak alkaline solution to expose the positions where long grid lines are required, thereby forming a mask layer with patterned openings.
[0050] In some embodiments, a photosensitive ink is uniformly coated onto the surface of the heterojunction solar cell substrate after the transparent conductive oxide layer has been deposited using an ink coating method. The ink coating method can include screen coating, roller coating, immersion coating, etc. The heterojunction solar cell substrate coated with the photosensitive ink is then dried, exposed, and developed to form a mask layer with patterned openings. It is understood that the mask in this application can also be a dry film or other methods, and is not specifically limited herein.
[0051] It should be noted that the embodiments of this application do not particularly limit the specific operation method for forming a mask layer with patterned openings, and conventional manufacturing methods in the art can be adopted.
[0052] In some embodiments, the process of forming a mask layer with patterned openings may include the following steps: coating a photoresist film, drying / curing the photoresist film, exposing and curing the photoresist film, developing the pattern, washing, and drying. The photoresist film can be coated using photosensitive ink / photoresist, and the coating method can be ultrasonic spraying, compressed air spraying, roller coating, screen printing, etc. The raw material for pattern development may include an aqueous solution of potassium carbonate with a mass concentration of 0.7%–1.5%, a temperature of 28°C–32°C, and a pressure of approximately 30 psi. The washing process can use deionized water at room temperature and a pressure of approximately 25 psi. The drying temperature can be 25°C–85°C.
[0053] In other embodiments, the process of forming a mask layer with patterned openings includes the following steps: obtaining a lamination using a photosensitive dry film, exposing and curing the photoresist film, developing the pattern, washing, and drying. The raw material for pattern development may include an aqueous solution of potassium carbonate with a mass concentration of 0.7%–1.5%, a temperature of 28°C–32°C, and a pressure of approximately 30 psi. Washing may be performed using deionized water at room temperature and a pressure of approximately 25 psi. Drying may be performed at a temperature of 25°C–85°C.
[0054] In some embodiments, step S4 may sequentially include roughening, water washing, pre-immersion, metal activation, and water washing. The water washing step is performed after roughening and metal activation, thereby improving the processing effect of subsequent processes. Specifically, the roughening treatment in step S4 includes: placing the heterojunction battery substrate with a patterned opening mask layer in an acid solution with a mass concentration of 3%–15% and treating it at 35°C–90°C for 30–200 seconds. The acid solution may be selected from one or more aqueous solutions of hydrochloric acid, sulfuric acid, nitric acid, citric acid, and oxalic acid. The etching time depends specifically on the acid concentration and etching temperature. Preferably, it is treated in a sulfuric acid solution with a mass concentration of 5%–12% at 50°C–80°C for 60–120 seconds. More preferably, it is treated in a sulfuric acid solution with a mass concentration of 7%–10% at 60°C–70°C for 70–100 seconds. This step roughens the exposed TCO surface at the patterned opening, which can increase the adhesion of the TCO surface and improve the problem of poor bonding between electroplated copper and the TCO surface.
[0055] In some embodiments, the pre-immersion treatment in step S4 includes: placing the roughened heterojunction battery substrate in a pre-immersion solution containing the following components: sodium sulfate 150 g / L to 350 g / L, 50% sulfuric acid solution 150 mL / L to 250 mL / L, and sulfur compounds 2 g / L to 4 g / L. The sulfur compounds are selected from sodium propanesulfonate and thiourea, and the pre-immersion treatment is performed at 20°C to 30°C for 30 s to 300 s.
[0056] This application employs a pre-immersion process before copper electroplating, which improves the potential difference on the battery substrate surface. By coupling the potential difference, the battery substrate surface can adsorb more sulfate ions, thereby achieving the effect of adsorbing metal ions. Considering the pre-immersion effect, such as the ability of the ITO surface to adsorb sulfate ions and the subsequent pre-plating effect, preferably, the pre-immersion treatment is carried out at 20℃~30℃ for 60s~120s. More preferably, the pre-immersion treatment is carried out at 20℃~30℃ for 70s~100s.
[0057] In some embodiments, the metal activation treatment in step S4 includes: placing the pre-immersion-treated heterojunction battery substrate in an activation solution and treating it at 20°C to 30°C for 30 to 300 seconds. Preferably, the battery substrate is placed in the activation solution and treated at 20°C to 30°C for 60 to 120 seconds. More preferably, the battery substrate is placed in the activation solution and treated at 20°C to 30°C for 70 to 100 seconds.
[0058] In some embodiments, the activation solution comprises a stabilizer, an acid, and a metal salt of the corresponding acid anion. The different metal salts used can represent different metals, such as palladium activation, platinum activation, ruthenium activation, silver activation, or zinc activation, employing the corresponding metal salt, such as palladium salt, platinum salt, ruthenium salt, silver salt, or zinc salt. The stabilizer is selected from one or more of malic acid, citric acid, lactic acid, propionic acid, glycolic acid, triethanolamine, glycine, thiourea, 4-methylpyridine, sodium dodecyl sulfate, and potassium iodide. The acid is selected from nitric acid, sulfuric acid, hydrochloric acid, chloric acid, perchloric acid, and methanesulfonic acid.
[0059] In some embodiments, palladium activation treatment is preferred based on the metal activation effect and its impact on subsequent pre-plating processes. Specifically, the activation solution contains the following components: palladium sulfate 5 mg / L to 80 mg / L, 4-methylpyridine 3 mg / L to 25 mg / L, sodium dodecyl sulfate 1 mg / L to 40 mg / L, sodium sulfate 1 mg / L to 40 mg / L, and 50% sulfuric acid solution 18 mL / L to 22 mL / L.
[0060] In addition, it should be noted that step S4 is performed in a dark environment. Compared with the traditional process, the photovoltaic cell is "dark-processed". This can avoid the problem that occurs when the positive electrode (P side) of the photovoltaic cell is separated from the palladium ions under light conditions, which prevents the palladium ions from adsorbing onto the blue film on the surface of the positive electrode (P side).
[0061] In some embodiments, step S5 may sequentially include: pre-plating, deoxidation, water washing, acid activation, water washing, copper electroplating, water washing, film removal, water washing, acid activation, water washing, and electroless tin plating. The pre-plating treatment includes pre-plating nickel, silver, zinc, or copper. All of the above pre-plating uses electroless plating. Considering the damage to the mask during electroless plating and cost considerations, electroless nickel plating is preferred. Electroless nickel plating is acidic and will not damage the mask, thus preventing metal deposition in the light-receiving area. Furthermore, electroless nickel plating is inexpensive and low-cost. In addition, it does not contain hazardous components such as formaldehyde or cyanide. Specifically, the pre-plating nickel is acidic electroless nickel plating, and the process includes: placing the metal-activated heterojunction battery substrate in an electroless nickel plating solution for electroless nickel plating treatment at 80℃~95℃ for 30s~900s. Preferably, the treatment is at 82℃~85℃ for 60s~300s. More preferably, the treatment is carried out at 82°C to 85°C for 100 to 150 seconds.
[0062] In some embodiments, the electroless nickel plating solution contains the following components: nickel sulfate 2 g / L to 10 g / L, sodium hypophosphite 10 g / L to 100 g / L, citric acid 1 g / L to 15 g / L, and lead nitrate 1 mg / L to 20 mg / L.
[0063] In some embodiments, the deoxidation process in step S5 includes: placing the pre-plated heterojunction battery substrate in a deoxidation solution for treatment. The deoxidation solution is an HF solution.
[0064] In one specific embodiment, the deoxidation process in step S5 includes: placing the pre-plated heterojunction battery substrate in an HF solution with a mass concentration of 3% to 15% and treating it at 20°C to 30°C for 30 to 200 seconds. Preferably, the battery substrate is placed in an HF solution with a mass concentration of 5% to 12% and treated at 20°C to 30°C for 60 to 120 seconds. More preferably, the battery substrate is placed in an HF solution with a mass concentration of 7% to 10% and treated at 20°C to 30°C for 70 to 90 seconds.
[0065] In some embodiments, the copper electroplating process in step S5 is as follows: the deoxidized heterojunction battery substrate is placed in a copper electroplating solution and treated at 20°C–30°C for 100–1200 s to form a copper electrode. Preferably, the deoxidized heterojunction battery substrate is placed in a copper electroplating solution and treated at 20°C–30°C for 300–900 s to form a copper electrode. More preferably, the deoxidized heterojunction battery substrate is placed in a copper electroplating solution and treated at 20°C–30°C for 500–700 s to form a copper electrode.
[0066] In some embodiments, the copper plating solution contains the following components: copper sulfate 90 g / L to 180 g / L and sulfuric acid 90 g / L to 180 g / L.
[0067] In some embodiments, a uniform copper layer is formed on the surface of the nickel layer, with a copper height of 8μm to 15μm and a line height uniformity controlled within 3%, within a single wafer.
[0068] It should be noted that the embodiments of this application do not particularly limit the specific operation method of the stripping process or the type of stripping solution, and conventional stripping solutions and manufacturing methods in the art can be used. For example, the stripping process in step S5 is as follows: the heterojunction battery substrate treated with electroplated copper is placed in the stripping solution and treated at 45℃~85℃ for 30s~300s. Preferably, the battery substrate is placed in the stripping solution and treated at 55℃~70℃ for 60s~200s. More preferably, the battery substrate is placed in the stripping solution and treated at 60℃~65℃ for 80s~150s. This stripping process is used to remove the photosensitive material that has been photocured during patterning. The stripping solution contains the following components: sodium hydroxide 30g / L~100g / L, and a surfactant 0.1g / L~1g / L, the surfactant being selected from Henkel DF-117, Taiyuan Zhuoneng ME53, Dow H-66, and BASF TO-4070.
[0069] In some embodiments, the chemical tin plating process in step S5 is as follows: the heterojunction battery substrate that has undergone film removal treatment is placed in a tin-plating solution and reacted at 20°C–30°C for 30–300 seconds, thereby depositing a tin film on the surface of the copper wires through the displacement of copper and tin. Preferably, the battery substrate is placed in a tin-plating solution and reacted at 20°C–30°C for 60–200 seconds. More preferably, the battery substrate is placed in a tin-plating solution and reacted at 20°C–30°C for 80–150 seconds.
[0070] In some embodiments, the tin melting solution contains the following components: 100 ppm thiourea, 100 mL / L to 200 mL / L H2SO4 (24.5%), 1 ppm ascorbic acid, and 50 g / L SnCl2 solution.
[0071] In some embodiments, the tin-melting solution contains the following components: tin methanesulfonate 10 g / L to 30 g / L, methanesulfonic acid 50 g / L to 120 g / L, sodium hypophosphite 50 g / L to 100 g / L, thiourea 20 g / L to 100 g / L, ethylenediaminetetraacetic acid (EDTA) 15 g / L to 20 g / L, and sodium dodecyl sulfate 0.1 g / L to 1 g / L.
[0072] In some embodiments, the washing step of this application may be washing with deionized water at a temperature of room temperature and a pressure of about 25 psi.
[0073] In some embodiments, the acid activation step of this application may include: treating with a sulfuric acid solution with a mass concentration of 3% to 15% at room temperature for 30 to 300 seconds. The purpose of acid activation is to remove the oxide layer, form a metallic elemental layer, improve the bonding surface and bonding resistance, and improve the bonding force. Preferably, the acid activation step is treating with a sulfuric acid solution with a mass concentration of 5% to 12% at room temperature for 60 to 120 seconds. More preferably, the activation step is treating with a sulfuric acid solution with a mass concentration of 7% to 10% at room temperature for 80 to 100 seconds.
[0074] In a second aspect, this application provides an HJT solar cell, which is prepared by the HJT solar cell preparation method described in the first aspect of this application.
[0075] The implementation scheme of this application will be described in detail below with reference to specific embodiments.
[0076] The following are the process parameters used in the specific embodiments:
[0077] The pre-soaking solution consists of sodium sulfate at 150 g / L to 350 g / L, 50% sulfuric acid solution at 150 mL / L to 250 mL / L, and thiourea at 2 g / L to 4 g / L.
[0078] The activation solution consisted of 20 mg / L palladium sulfate, 10 mg / L 4-methylpyridine, 5 mg / L sodium dodecyl sulfate, 5 mg / L sodium sulfate, and 20 mL / L 50% sulfuric acid solution.
[0079] The electroless nickel plating solution consists of nickel sulfate (2g / L~10g / L), sodium hypophosphite (10g / L~100g / L), citric acid (1g / L~15g / L), and lead nitrate (1mg / L~20mg / L).
[0080] The deoxidation solution is an 8% (w / w) HF solution.
[0081] The copper plating solution consists of 100g / L copper sulfate and 100g / L sulfuric acid.
[0082] The membrane removal solution consists of 50 g / L sodium hydroxide and 0.5 g / L surfactant.
[0083] The tin melting solution consisted of 100 ppm thiourea, 100 ml / L H2SO4 (24.5%), 1 ppm ascorbic acid, and 50 g / L SnCl2 solution.
[0084] Example 1
[0085] S1. An ITO transparent conductive oxide layer is sputtered on both sides of a battery substrate with a PN junction using a PVD method.
[0086] S2. Fabricate a mask layer on the surface of the transparent conductive oxide layer.
[0087] S3. Perform patterned opening processing on the mask layer to form a mask layer with patterned openings.
[0088] S4. Roughening in a dark environment: Immerse the battery substrate in a 10% sulfuric acid solution at 65°C for 90 seconds, then rinse with water. Pre-soaking: Place the battery substrate in a pre-soaking solution at 25°C for 90 seconds. The pre-soaking solution contains the following components: 200 g / L sodium sulfate, 200 mL / L 50% sulfuric acid solution, and 3 g / L thiourea. Palladium activation: Place the battery substrate in an activation solution at 25°C for 90 seconds. Rinse with water.
[0089] S5. Pre-plating: The battery substrate is placed in a chemical nickel plating solution for chemical nickel plating treatment at 85°C for 150 seconds. The chemical nickel plating solution contains the following components: nickel sulfate 5g / L; sodium hypophosphite 45g / L; citric acid 5g / L; lead nitrate 6mg / L; and the pH of the chemical nickel plating solution is kept stable at 4.8.
[0090] Deoxidation: The battery substrate was placed in an 8% (w / w) HF solution and treated at 25°C for 90 seconds. Then, it was washed with water, activated, and washed again.
[0091] Copper plating: The battery substrate is placed in a copper plating solution and treated at 25°C for 600 seconds to form a copper electrode. Rinse with water.
[0092] Film removal: Place the battery substrate in the film removal solution, treat at 60°C for 90 seconds, wash with water, activate, and wash with water again.
[0093] Chemical tin plating: The battery substrate is placed in a tin-plating solution and reacted at 25°C for 90 seconds. Through the replacement of copper and tin, a tin film is plated on the surface of the copper wire to obtain the HJT solar cell.
[0094] Example 2
[0095] S1. An ITO transparent conductive oxide layer is sputtered on both sides of a battery substrate with a PN junction using a PVD method.
[0096] S2. Fabricate a mask layer on the surface of the transparent conductive oxide layer.
[0097] S3. Perform patterned opening processing on the mask layer to form a mask layer with patterned openings.
[0098] S4. Roughening in a dark environment: Immerse the battery substrate in a 10% sulfuric acid solution at 65°C for 90 seconds. Rinse with water. Pre-immersion: Place the battery substrate in a pre-immersion solution at 25°C for 90 seconds. The pre-immersion solution contains the following components: 150 g / L sodium sulfate, 150 mL / L 50% sulfuric acid solution, and 2 g / L thiourea. Palladium activation: Place the battery substrate in an activation solution at 25°C for 90 seconds. Rinse with water.
[0099] S5. Pre-plating: The battery substrate is placed in a chemical nickel plating solution for chemical nickel plating treatment at 85°C for 150 seconds. The chemical nickel plating solution contains the following components: nickel sulfate 5g / L; sodium hypophosphite 45g / L; citric acid 5g / L; lead nitrate 6mg / L; and the pH of the chemical nickel plating solution is kept stable at 4.8.
[0100] Deoxidation: The battery substrate was placed in an 8% HF solution and treated at 25°C for 90 seconds. Then, it was washed with water, activated, and washed again.
[0101] Copper plating: The battery substrate is placed in a copper plating solution and treated at 25°C for 600 seconds to form a copper electrode. Rinse with water.
[0102] Stripping: Place the battery substrate in the stripping solution and treat at 60°C for 90 seconds. Rinse with water, activate, and rinse with water again.
[0103] Chemical tin plating: The battery substrate is placed in a tin-plating solution and reacted at 25°C for 90 seconds. Through the replacement of copper and tin, a tin film is plated on the surface of the copper wire to obtain the HJT solar cell.
[0104] Example 3
[0105] S1. An ITO transparent conductive oxide layer is sputtered on both sides of a battery substrate with a PN junction using a PVD method.
[0106] S2. Fabricate a mask layer on the surface of the transparent conductive oxide layer.
[0107] S3. Perform patterned opening processing on the mask layer to form a mask layer with patterned openings.
[0108] S4. Roughening in a dark environment: Immerse the battery substrate in a 10% sulfuric acid solution at 65°C for 90 seconds, then rinse with water. Pre-soaking: Place the battery substrate in a pre-soaking solution at 25°C for 90 seconds. The pre-soaking solution contains the following components: 350 g / L sodium sulfate, 250 mL / L 50% sulfuric acid solution, and 4 g / L thiourea. Palladium activation: Place the battery substrate in an activation solution at 25°C for 90 seconds. Rinse with water.
[0109] S5. Pre-plating: The battery substrate is placed in a chemical nickel plating solution for chemical nickel plating treatment at 85°C for 150 seconds. The chemical nickel plating solution contains the following components: nickel sulfate 5g / L; sodium hypophosphite 45g / L; citric acid 5g / L; lead nitrate 6mg / L; and the pH of the chemical nickel plating solution is kept stable at 4.8.
[0110] Deoxidation: The battery substrate was placed in an 8% (w / w) HF solution and treated at 25°C for 90 seconds. Then, it was washed with water, activated, and washed again.
[0111] Copper plating: The battery substrate is placed in a copper plating solution and treated at 25°C for 600 seconds to form a copper electrode. Rinse with water.
[0112] Stripping: Place the battery substrate in the stripping solution and treat at 60°C for 90 seconds. Rinse with water, activate, and rinse with water again.
[0113] Chemical tin plating: The battery substrate is placed in a tin-plating solution and reacted at 25°C for 90 seconds. Through the replacement of copper and tin, a tin film is plated on the surface of the copper wire to obtain the HJT solar cell.
[0114] Example 4
[0115] S1. An ITO transparent conductive oxide layer is sputtered on both sides of a battery substrate with a PN junction using a PVD method.
[0116] S2. Fabricate a mask layer on the surface of the transparent conductive oxide layer.
[0117] S3. Perform patterned opening processing on the mask layer to form a mask layer with patterned openings.
[0118] S4. Roughening in a dark environment: Immerse the battery substrate in a 10% sulfuric acid solution at 65°C for 90 seconds, then rinse with water. Pre-soaking: Place the battery substrate in a pre-soaking solution at 25°C for 90 seconds. The pre-soaking solution contains the following components: 200 g / L sodium sulfate, 200 mL / L 50% sulfuric acid solution, and 3 g / L thiourea. Palladium activation: Place the battery substrate in an activation solution at 25°C for 90 seconds. Rinse with water.
[0119] S5. Pre-plating: The battery substrate is placed in a chemical nickel plating solution for chemical nickel plating treatment at 85°C for 150 seconds. The chemical nickel plating solution contains the following components: nickel sulfate 2g / L; sodium hypophosphite 10g / L; citric acid 1g / L; lead nitrate 1mg / L; and the pH of the chemical nickel plating solution is kept stable at 4.8.
[0120] Deoxidation: The battery substrate was placed in an 8% (w / w) HF solution and treated at 25°C for 90 seconds. Then, it was washed with water, activated, and washed again.
[0121] Copper plating: The battery substrate is placed in a copper plating solution and treated at 25°C for 600 seconds to form a copper electrode. Rinse with water.
[0122] Film removal: Place the battery substrate in the film removal solution and treat at 60°C for 90 seconds. 。 Wash with water, activate, wash with water.
[0123] Chemical tin plating: The battery substrate is placed in a tin plating solution and reacted at 25°C for 90 seconds. ， HJT solar cells are produced by depositing a tin film on the surface of copper wires through the substitution of copper and tin.
[0124] Example 5
[0125] S1. An ITO transparent conductive oxide layer is sputtered on both sides of a battery substrate with a PN junction using a PVD method.
[0126] S2. Fabricate a mask layer on the surface of the transparent conductive oxide layer.
[0127] S3. Perform patterned opening processing on the mask layer to form a mask layer with patterned openings.
[0128] S4. Roughening in a dark environment: Immerse the battery substrate in a 10% sulfuric acid solution at 65°C for 90 seconds, then rinse with water. Pre-soaking: Place the battery substrate in a pre-soaking solution at 25°C for 90 seconds. The pre-soaking solution contains the following components: 200 g / L sodium sulfate, 200 mL / L 50% sulfuric acid solution, and 3 g / L thiourea. Palladium activation: Place the battery substrate in an activation solution at 25°C for 90 seconds. Rinse with water.
[0129] S5. Pre-plating: The battery substrate is placed in a chemical nickel plating solution for chemical nickel plating treatment at 85°C for 150 seconds. The chemical nickel plating solution contains the following components: nickel sulfate 10g / L; sodium hypophosphite 100g / L; citric acid 15g / L; lead nitrate 20mg / L; and the pH of the chemical nickel plating solution is kept stable at 4.8.
[0130] Deoxidation: The battery substrate was placed in an 8% (w / w) HF solution and treated at 25°C for 90 seconds. Then, it was washed with water, activated, and washed again.
[0131] Copper plating: The battery substrate is placed in a copper plating solution and treated at 25°C for 600 seconds to form a copper electrode. Rinse with water.
[0132] Stripping: Place the battery substrate in the stripping solution and treat at 60°C for 90 seconds. Rinse with water, activate, and rinse with water again.
[0133] Chemical tin plating: The battery substrate is placed in a tin-plating solution and reacted at 25°C for 90 seconds. Through the replacement of copper and tin, a tin film is plated on the surface of the copper wire to obtain the HJT solar cell.
[0134] Comparative Example 1
[0135] Traditionally, there is a seed copper electroplating process, the specific steps of which are as follows:
[0136] S1. An ITO transparent conductive oxide layer and a copper seed layer are sputtered on both sides of a battery substrate with a PN junction using a PVD method.
[0137] S2. Fabricate a mask layer on the surface of the transparent conductive oxide layer.
[0138] S3. Perform patterned opening processing on the mask layer to form a mask layer with patterned openings.
[0139] S4. Copper plating: Place the battery substrate in a copper plating solution and treat at 25°C for 600 seconds to form a copper electrode. Rinse with water.
[0140] Stripping: Place the battery substrate in the stripping solution and treat at 60°C for 90 seconds. Rinse with water, activate, and rinse with water again.
[0141] The seed copper on the battery surface was removed by horizontal chemical etching, followed by cleaning and drying.
[0142] Chemical tin plating: The battery substrate is placed in a tin-plating solution and reacted at 25°C for 90 seconds. Through the replacement of copper and tin, a tin film is plated on the surface of the copper wire to obtain the HJT solar cell.
[0143] Comparative Example 2
[0144] Compared with the embodiment, the comparative example is identical except that step S4 is performed in a light environment.
[0145] S1. An ITO transparent conductive oxide layer is sputtered on both sides of a battery substrate with a PN junction using a PVD method.
[0146] S2. Fabricate a mask layer on the surface of the transparent conductive oxide layer.
[0147] S3. Perform patterned opening processing on the mask layer to form a mask layer with patterned openings.
[0148] S4. Under light conditions, immerse the battery substrate in a 10% sulfuric acid solution and roughen it at 65°C for 90 seconds, then rinse with water. Pre-immersion: Place the battery substrate in a pre-immersion solution and treat it at 25°C for 90 seconds. The pre-immersion solution contains the following components: 200 g / L sodium sulfate, 200 mL / L 50% sulfuric acid solution, and 3 g / L thiourea. Palladium activation: Place the battery substrate in an activation solution and treat it at 25°C for 90 seconds. Rinse with water.
[0149] S5. Pre-plating: The battery substrate is placed in a chemical nickel plating solution for chemical nickel plating treatment at 85°C for 150 seconds. The chemical nickel plating solution contains the following components: nickel sulfate 5g / L; sodium hypophosphite 45g / L; citric acid 5g / L; lead nitrate 6mg / L; and the pH of the chemical nickel plating solution is kept stable at 4.8.
[0150] Deoxidation: The battery substrate was placed in an 8% (w / w) HF solution and treated at 25°C for 90 seconds. Then, it was washed with water, activated, and washed again.
[0151] Copper plating: The battery substrate is placed in a copper plating solution and treated at 25°C for 600 seconds to form a copper electrode. Rinse with water.
[0152] Stripping: Place the battery substrate in the stripping solution and treat at 60°C for 90 seconds. Rinse with water, activate, and rinse with water again.
[0153] Chemical tin plating: The battery substrate is placed in a tin-plating solution and reacted at 25°C for 90 seconds. Through the replacement of copper and tin, a tin film is plated on the surface of the copper wire to obtain the HJT solar cell.
[0154] Test case
[0155] Performance Test 1:
[0156] like Figure 1 , Figure 2 The diagram shows the measurement results of grid line plating width and ineffective line width / shading width for HJT solar cells obtained using the method of Example 1 and the conventional seeded copper electroplating process in Comparative Example 1, respectively. Figure 1 It can be seen that the copper grid line width of the HJT solar cell finally obtained using the method of Example 1 is 30.43 μm, the actual bottom shading width is 34.20 μm, and the ineffective area accounts for less than 10% of the overall line width. Figure 2 It can be seen that the HJT solar cell obtained by using the conventional seeded copper electroplating process in Comparative Example 1 has a copper grid line electroplating width of 30.70 μm. However, due to the etching factor and the "surface tension" of the etching solution itself during the copper etching process, the actual light blocking area at the bottom of the copper grid line is about 47.66 μm, the invalid line width is about 17 μm, and the invalid area accounts for more than 50% of the overall line width.
[0157] The results show that the HJT solar cells obtained by the method of this application can achieve a very small difference between the copper wire width and the actual illumination compared with HJT solar cells obtained by the traditional seeded copper electroplating process.
[0158] Performance Test 2:
[0159] The adsorption of palladium ions in the palladium activation step of solar cells prepared using the methods of Examples 1-5 of this application is compared with that of Comparative Example 2. The results are shown in Table 1 below:
[0160] Table 1
[0161] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 2 N-side 100％ 100％ 100％ 100％ 100％ 100％ P-side 100％ 100％ 100％ 100％ 100％ 0％
[0162] This application relates to the chemical plating of solar cell surfaces. Solar cells inherently possess positive and negative electrodes (anode and cathode, P-side and N-side), with the positive electrode carrying a positive charge and the negative electrode carrying a negative charge. During the metal activation process, metal ions carry a positive charge in solution. Given the characteristics of solar cells, they generate electricity in the presence of light. If a "dark treatment" is not performed during the fabrication process, the positive electrode (P-side) will be excluded from the metal ions, preventing them from adsorbing onto the blue film on the positive electrode surface. In the subsequent pre-nickel plating step, the metal ions are reduced by nickel. Without this "dark treatment," the positive electrode (P-side) surface cannot adsorb the metal ions, preventing reduction and thus hindering the pre-nickel plating process.
[0163] Performance Test 3:
[0164] The solar cells obtained using the methods of Examples 1-5 of this application have the following performance characteristics compared to those obtained using the processes of Comparative Example 1 and Comparative Example 2, as shown in Table 2 below.
[0165] Table 2
[0166] Process scheme Eta(%) Voc(V) Isc(A) FF (%) Example 1 25.866 0.7486 11.012 86.02 Example 2 25.952 0.7492 11.036 86.05 Example 3 26.014 0.7496 11.058 86.04 Example 4 26.053 0.7495 11.072 86.07 Example 5 26.142 0.7497 11.103 86.10 Comparative Example 1 25.798 0.7499 10.9603 86.05 Comparative Example 2 25.786 0.7489 10.9723 86.03
[0167] As shown in Table 2, in Comparative Example 1, the use of a seeded copper electroplating process resulted in an increased actual light-blocking area at the bottom of the copper grid lines during subsequent processes. Furthermore, the etching process to remove the copper seed layer damaged the TCO layer, leading to a cell conversion efficiency of only 25.798%, lower than that of the solar cells in Examples 1-5. In Comparative Example 2, because it was not processed in a dark environment, metal ions could not be adsorbed on the surface of the positive electrode (P-side) of the solar cell, preventing reduction. Consequently, the pre-nickel plating process could not be completed on the positive electrode, resulting in poor copper plating on the positive electrode surface, and its efficiency was also lower than that of the solar cells in Examples 1-5.
[0168] 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.
[0169] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.
Claims
1. A method for fabricating an HJT solar cell, characterized in that, The method includes the following steps: A heterojunction cell substrate is provided, wherein a transparent conductive oxide layer is deposited on both sides of the heterojunction cell substrate; A mask layer is fabricated on the surface of the transparent conductive oxide layer; The mask layer is patterned with openings to form a mask layer with patterned openings; In a dark environment, roughening, pre-dipping, and metal activation treatments are sequentially performed at the patterned openings of the mask layer to obtain a pretreated heterojunction battery substrate. The pretreated heterojunction solar cell substrate is subjected to pre-plating, deoxidation, copper electroplating, film stripping, and chemical tin plating in sequence to obtain HJT solar cells; The pre-plating is performed using chemical pre-plating.
2. The preparation method according to claim 1, characterized in that, The roughening process includes: placing the heterojunction battery substrate with patterned openings in an acid solution with a mass concentration of 3% to 15% and treating it at 35°C to 90°C for 30 to 200 seconds.
3. The preparation method according to claim 1, characterized in that, The pre-immersion treatment includes: placing the roughened heterojunction battery substrate in a pre-immersion solution and treating it at 20°C to 30°C for 30s to 300s. The pre-impregnation solution contains: sodium sulfate 150g / L~350g / L, 50% sulfuric acid solution 150mL / L~250mL / L, and sulfur compounds 2g / L~4g / L.
4. The preparation method according to claim 1, characterized in that, The metal activation treatment is palladium activation treatment, platinum activation treatment, ruthenium activation treatment, silver activation treatment, or zinc activation treatment.
5. The preparation method according to claim 4, characterized in that, The metal activation treatment includes placing the pre-impregnated heterojunction battery substrate in an activation solution, the activation solution containing a stabilizer, an acid, and a metal salt of the corresponding acid radical ion; The stabilizer is selected from one or more of malic acid, citric acid, lactic acid, propionic acid, glycolic acid, triethanolamine, glycine, thiourea, 4-methylpyridine, sodium dodecyl sulfate, and potassium iodide; The acid is selected from one or more of nitric acid, sulfuric acid, hydrochloric acid, chloric acid, perchloric acid, and methanesulfonic acid.
6. The preparation method according to claim 1, characterized in that, The pre-plating is pre-plating nickel, pre-plating silver, pre-plating zinc, or pre-plating copper.
7. The preparation method according to claim 1, characterized in that, The deoxidation process includes: placing the pre-plated heterojunction battery substrate in a deoxidation solution and reacting it at 20℃~30℃ for 30s~200s; The deoxidation solution is an HF solution.
8. The preparation method according to claim 1, characterized in that, The copper electroplating process includes: placing the deoxidized heterojunction battery substrate in a copper electroplating solution and reacting it at 20℃~30℃ for 100s~1200s to form a copper electrode; The copper plating solution contains the following components: copper sulfate 90g / L~180g / L and sulfuric acid 90g / L~180g / L.
9. An HJT solar cell, characterized in that, It is prepared by any one of the preparation methods according to claims 1 to 8.