A low-cost crystalline silicon heterojunction cell and a method of manufacturing the same

Abstract

The application provides a low-cost crystalline silicon heterojunction cell and a preparation method thereof, and particularly relates to a crystalline silicon heterojunction cell based on a tin oxide-based transparent electrode and a seedless copper electrochemical copper electrode and a preparation method thereof, and belongs to the technical field of solar cells. The seedless copper electrochemical copper electrode is prepared on the surface of a micro-nano structure tin oxide-based transparent conductive film with excellent hydrophilicity, so that the electrochemical copper electrode has characteristics such as high interface bonding force and low interface contact resistance. The low-cost crystalline silicon heterojunction cell of the application adopts a patterned seedless copper electrochemical copper electrode, which can effectively reduce the width of the grid lines and reduce the light-shielding area. Meanwhile, by constructing a micro-nano structure tin oxide-based transparent conductive film, the interface between the electrochemical copper electrode and the tin oxide-based transparent electrode has excellent electrical characteristics and bonding force, so that the efficiency of the crystalline silicon heterojunction cell is improved.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology and relates to a low-cost crystalline silicon heterojunction cell and its preparation method. Specifically, it relates to a crystalline silicon heterojunction cell based on a tin oxide-based transparent electrode and a seedless copper electrochemical copper electrode and its preparation method. Background Technology

[0002] Crystalline silicon heterojunction solar cells (HJTs) possess advantages such as high photoelectric conversion efficiency, high bifaciality, low temperature coefficient, and simple fabrication process, making them a focus of attention in next-generation crystalline silicon photovoltaic technology and showing broad application potential in both terrestrial and space-based photovoltaics. However, as photovoltaic installations grow towards the terawatt (TW) level, the use of silver (Ag), a rare element with high price and limited reserves, as the metal electrode material for crystalline silicon heterojunction solar cells has become a limiting factor for its development. It is estimated that photovoltaic installations will reach 3 TW by 2030. Based on silver reserves, assuming that silver used in photovoltaics accounts for 20% of total Ag reserves, the Ag consumption for photovoltaics needs to be reduced from the current 10 mg / W to 2 mg / W. Energy Environ. Sci. [2021, 14, 5587–5610]. Furthermore, the rare element Ag is expensive, costing as much as 15,000-20,000 yuan per kilogram. Therefore, conducting research on silver-free crystalline silicon heterojunction solar cells is of great significance for supporting the high-quality and healthy development of the photovoltaic industry.

[0003] Copper (Cu) is abundant and its price is only 1 / 100th that of Ag. Furthermore, Cu's resistivity is second only to Ag (1.68 μΩ•cm vs. 1.59 μΩ•cm). Electrochemical fabrication of copper electrodes can achieve superior performance, such as narrower linewidths and lower bulk resistivity. Therefore, crystalline silicon heterojunction solar cells based on electrochemical copper electrodes offer the dual benefits of cost reduction and efficiency improvement, and are considered the ultimate alternative to screen-printed silver metallization technology.

[0004] Current research includes studies such as the certified 26.6% efficiency of crystalline silicon heterojunction cells based on electroplated copper electrodes by Myvi and Sundrive. To further reduce costs and improve performance, researchers are working on seedless electrochemical copper electrode technology, building upon the traditional magnetron sputtering seed copper layer combined with electrochemical copper process. This avoids the seed copper layer etch-back process and the resulting increase in bottom gate line width, further reducing process costs and improving performance.

[0005] However, seedless electrochemical copper electrode technology suffers from problems such as poor interfacial mechanical and electrical properties between traditional indium tin oxide (ITO) transparent electrodes and electrochemical Cu electrodes. Summary of the Invention

[0006] To address the issues of poor interfacial bonding and electrical properties of existing seedless copper electrochemical copper electrodes in crystalline silicon heterojunction solar cells, this invention provides a low-cost crystalline silicon heterojunction solar cell and its fabrication method. Specifically, it describes a crystalline silicon heterojunction solar cell with a seedless copper electrochemical copper electrode deposited on a tin oxide-based transparent electrode. Compared to traditional ITO electrodes, the tin oxide-based transparent electrode has the advantage of strong hydrophilicity, which facilitates the fabrication of electrochemical copper electrodes with excellent interfacial properties. Furthermore, the tin oxide-based transparent electrode offers advantages such as excellent photoelectric properties, environmental stability, and low cost, thereby achieving a low-cost crystalline silicon heterojunction solar cell with superior photoelectric performance and stability.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A low-cost crystalline silicon heterojunction cell, which is also a crystalline silicon heterojunction cell based on a tin oxide-based transparent electrode and a seedless electrochemical copper electrode, has the following structure: an intrinsic amorphous silicon thin film is deposited on both sides of a textured silicon wafer, followed by the deposition of n-type and p-type doped silicon thin films on both sides respectively, then a tin oxide-based transparent electrode is deposited on both sides, and finally a patterned electrochemical copper electrode is deposited on the tin oxide-based transparent electrode to obtain a low-cost indium-less and silver-free crystalline silicon heterojunction cell; The tin oxide-based transparent electrode comprises at least one layer of tin oxide (SnO). x A transparent conductive film with SnO as its base and a SnO surface. x film; The tin oxide (SnO) x The transparent electrode is a single-layer SnO structure. x Thin film, or bilayer ITO / SnO x Thin film, or three-layer SnO x / ITO / SnO x film; The term "low indium" refers to the indium oxide (In2O3) content in the transparent electrode being 0 wt%-50 wt%.

[0009] The electrochemical copper electrode with patterned deposition on a tin oxide-based transparent electrode is an electrochemical copper electrode with seedless copper deposition on a tin oxide-based transparent electrode, which includes two steps: patterning and electrochemical deposition.

[0010] Furthermore, the single-layer SnO structure x The film thickness is 50 nm-500 nm; the described bilayer ITO / SnO structure x In the thin films, the ITO film thickness is 10 nm-50 nm, and the SnO film thickness is... x The film thickness is 50 nm-300 nm; the three-layer SnO structure x / ITO / SnO xIn the thin film, the thickness of the ITO thin film is 10 nm - 50 nm, and the thickness of the SnO x thin film is 50 nm - 100 nm.

[0011] Furthermore, the SnO x thin film is a pure SnO x thin film or a tantalum (Ta)-doped SnO x thin film. The SnO x thin film is a thin film with a low oxygen content, where 1 < x ≤ 2 and the O / Sn ratio is 1 - 2; Even further, the total mass of the tantalum oxide accounts for 0.5 - 10 wt% of the SnO x transparent conductive thin film.

[0012] Furthermore, the ITO thin film and the SnO x base thin film are prepared by a magnetron sputtering process; In the transparent electrode, the SnO x thin film is prepared by DC or RF sputtering, with a sputtering power density of 2 W / cm 2 -10 W / cm 2 , a gas pressure of 0.2 Pa - 1.0 Pa, a substrate temperature of room temperature - 150°C, an O2 / Ar ratio of 0 - 6%, and a thin film thickness of 50 nm - 500 nm; In the transparent electrode, the ITO thin film is prepared by DC or RF sputtering, with a sputtering power density of 2 W / cm 2 -10 W / cm 2 , a gas pressure of 0.2 Pa - 1.0 Pa, a substrate temperature of room temperature - 150°C, an O2 / Ar ratio of 0 - 6%, and a thin film thickness of 10 nm - 50 nm.

[0013] Furthermore, the In2O3 content in the ITO thin film is 90 wt% - 99 wt%.

[0014] Furthermore, the patterning is achieved by preparing a dielectric layer such as a dry film, ink, or photoresist on the surface of the transparent electrode, performing exposure treatment on the dielectric layer using methods such as laser direct writing or mask lithography, and then further removing the dielectric layer in the area where electrochemical deposition of metal is required through a developer; The surface of the patterned area generally needs to be cleaned with an acidic solution to remove residual oil stains on the surface for subsequent electrochemical deposition of the metal electrode.

[0015] Furthermore, the seedless copper electrochemical copper electrode includes a seed layer, an electroplated Cu electrode body, and a chemically deposited tin (Sn) layer; the seed layer is used to improve the interface characteristics between copper and the transparent electrode; the chemically deposited tin (Sn) layer is used to protect the Cu electrode from oxidation.

[0016] Furthermore, in order to improve the electrical and interfacial properties of seedless copper electrochemical copper electrodes, SnO... x The transparent electrode can be treated by electroreduction or chemical reduction to form a micro-nano structure on its surface, which is beneficial for the subsequent deposition of high-quality electrochemical electrodes; Furthermore, the SnO mentioned above... x The reduction process on the surface of the transparent electrode includes electroreduction or chemical reduction methods, which result in the precipitation of SnO / Sn particles with a characteristic size of 10 nm-1000 nm on the electrode surface.

[0017] Furthermore, the SnO x In the electroreduction process of the transparent electrode surface, the reducing solutions used include 0.1M-1M sodium aminosulfonate, 0.01M-0.1M sodium citrate, and 0.01M-0.1M sodium carbonate, etc. In the aforementioned electroreduction system, the working electrode is connected to SnO. x For the base transparent electrode sample, the auxiliary electrode is connected to a carbon plate or a platinum plate, and the reference electrode is connected to a silver chloride electrode or a calomel electrode. The SnO x Electroreduction process on the surface of a transparent electrode, solution temperature 15℃-55℃, current density 0.5mA / cm² 2 -3 mA / cm 2 Voltage -1 to -5V, reduction time 20 s to 200 s; In the chemical reduction process, the solution used includes 0.1M-0.5M ferrous sulfate solution and a small amount of zinc powder, and 0.1M-0.5M sodium citrate solution to adjust the pH to 2.5-4.5, with a reaction time of 3 min-12 min.

[0018] Furthermore, after the dielectric layer on the transparent electrode is patterned, the width of the fine gate opening is 5μm-30μm.

[0019] Furthermore, the preparation of the seedless copper electrochemical metal electrode involves electroplating a seed layer film of 0.5 μm-3 μm, electroplating a Cu film of 5 μm-20 μm, and finally electrolessly plating a Sn film.

[0020] Furthermore, the electroplating seed layer needs to be pretreated with acid. Commonly used solutions include 5 wt%-20 wt% phosphoric acid, 5 wt%-20 wt% hydrochloric acid, etc., with a solution temperature of 40℃-50℃ and a treatment time of 30s-120s. The electroplating seed layer includes alloy systems such as nickel (Ni) and Ni-Cu; The electroplating seed layer electrode uses a DC power supply, a solution temperature of 20℃-50℃, and a current density of 1 A / dm³. 2-3A / dm 2 Electroplating time: 100 s - 300 s; The electroplating Cu electrode uses a DC or pulsed power supply, with a solution temperature of 20℃-40℃ and a current density of 3 A / dm³. 2 -5 A / dm 2 Electroplating time: 300 s-1500 s; The commonly used stripping solution for removing the dielectric film before electroless Sn plating is 0.5 wt%-3 wt% NaOH, with a solution temperature of 35℃-45℃ and a processing time of 30 s-120 s. The electroless Sn plating process involves a solution temperature of 20℃-30℃ and a plating time of 30s-120s.

[0021] This invention describes a low-cost crystalline silicon heterojunction solar cell, ultimately fabricating a crystalline silicon heterojunction solar cell with a low-indium transparent electrode and a seedless copper-plated electrode; ITO / Ta doped SnO x The bulk resistivity of the seedless copper-plated electrode on the transparent electrode is 2.01 μΩ•cm-2.21 μΩ•cm, the specific contact resistivity is 0.240 mΩ•cm-0.310 mΩ•cm, and the pull-out force is 0.90 N / mm-1.31 N / mm; the photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 21.60%-22.32%, and it retains its initial efficiency of 95.6%-99.0% after being placed at 35%-40% relative humidity for 800 h. The bulk resistivity of the seedless copper-plated electrode on the micro / nano structured ITO / Ta-doped SnOx transparent electrode is 1.98 μΩ•cm, the specific contact resistivity is 0.847 mΩ•cm, and the pull-out force is 1.65 N / mm. The photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 22.63%, and it still maintains an initial efficiency of 97.5% after being placed at 35%-40% relative humidity for 800 h.

[0022] This invention also relates to a method for preparing a low-cost crystalline silicon heterojunction solar cell, comprising the following steps: S1. Hydrogenated intrinsic silicon thin films (ia-Si:H) are deposited on both sides of an n-type textured silicon wafer. Then, an n-type microcrystalline silicon oxide thin film (n-μc-SiOx) is deposited on the front side, and a p-type amorphous silicon thin film (pa-Si:H) is deposited on the back side. SnO is then prepared by double-sided magnetron sputtering. x Single-layer structure, or ITO / SnO x Double-layer structure, or SnO x / ITO / SnO x A three-layer transparent electrode with low indium content; wherein the ITO film thickness is 10 nm-50 nm, and SnO... x The film thickness is 50 nm-500 nm; S2, in the above SnO x The surface of the transparent electrode is partially treated with electroreduction or chemical reduction to form a micro-nano structure surface, thereby improving the interface characteristics between the transparent electrode and the electrochemical copper electrode. S3. A patterned surface with micron-scale feature size is obtained by depositing a patterned dielectric layer on the transparent electrode surface that has not undergone or has undergone reduction treatment, and then exposing and developing it. S4. On the above-mentioned patterned transparent electrode surface, a seed layer and a copper electrode are electrochemically deposited, then the dielectric layer is removed by a stripping process, and finally tin is electrochemically deposited to form the complete structure of the patterned metal electrode.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention discloses a low-cost crystalline silicon heterojunction solar cell, which prepares a seedless copper electrochemical copper electrode on the surface of a micro / nano-structured tin oxide-based transparent conductive film with excellent hydrophilicity, and can achieve the electrochemical copper electrode with characteristics such as high interfacial bonding force and low interfacial contact resistivity.

[0024] 2. The low-cost crystalline silicon heterojunction solar cell described in this invention employs a patterned combination of seedless copper electrochemical copper electrodes, which can effectively reduce the width of the grid lines and decrease the light-shielding area. At the same time, by constructing a micro-nano structured tin oxide-based transparent conductive film, the interface between the electrochemical copper electrode and the tin oxide-based transparent electrode has excellent electrical properties and bonding force, thereby improving the efficiency of the crystalline silicon heterojunction solar cell.

[0025] 3. The low-cost crystalline silicon heterojunction solar cell described in this invention uses a tin oxide-based transparent electrode and an electrochemical copper electrode, while reducing the indium and silver content. Combined with the seedless electrochemical copper electrode preparation technology, it is beneficial to reduce processes such as etching back the seed copper layer, thereby achieving low cost of crystalline silicon heterojunction solar cells.

[0026] 4. The present invention provides a low-cost crystalline silicon heterojunction solar cell, SnO x Compared to In2O3, which has higher stability in damp heat and solvent resistance, this structure of crystalline silicon heterojunction solar cells can achieve higher stability.

[0027] 5. The method for preparing a low-cost crystalline silicon heterojunction solar cell described in this invention uses magnetron sputtering to prepare a tin oxide-based transparent electrode, which is compatible with existing processes; it uses an electrochemical copper process without a seed copper layer, avoiding the preparation of the seed copper layer by magnetron sputtering and the etch-back process, which is simple, effective, and suitable for large-area industrial production. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure 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 disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 In Experiment 1 of this invention, ITO / Ta-doped SnO was used. x A schematic diagram of a crystalline silicon heterojunction cell with a double-layer transparent electrode structure, resulting in a low-indium transparent electrode and a seedless copper-plated copper electrode. Figure 2 Ta-doped SnO was used in Experimental Example 2 of this invention. x A schematic diagram of a crystalline silicon heterojunction cell with a single-layer transparent electrode, an indium-free transparent electrode, and a seedless copper-plated copper electrode. Figure 3 Ta-doped SnO was used in Experimental Example 3 of this invention. x / ITO / Ta doped SnO x A schematic diagram of a crystalline silicon heterojunction cell with a three-layer transparent electrode structure, resulting in a low-indium transparent electrode and a seedless copper-plated electrode. Figure 4 In Experimental Example 4 of this invention, ITO / Ta-doped SnO with surface electroreduction was used. x A schematic diagram of a crystalline silicon heterojunction cell with a double-layer transparent electrode structure, resulting in a low-indium transparent electrode and a seedless copper-plated copper electrode. Figure 5 The pull-out force curves of the electroplated copper electrodes obtained in Experimental Example 1, Example 4, and Comparative Example 1 of this invention are shown. Figure 6 The graphs show the photoelectric conversion efficiency of the crystalline silicon heterojunction solar cells obtained in Experimental Example 1, Example 4, and Comparative Example 1 of this invention. Figure 7 This is a graph showing the ratio of the photoelectric conversion efficiency to the initial photoelectric conversion efficiency of the crystalline silicon heterojunction solar cells obtained in Experimental Example 1, Example 4, and Comparative Example 1 of this invention after being placed at a relative humidity of 35-40% for 800 hours. Figure 8 The ITO / Ta-doped SnO in Example 4 of this invention x The surface of the double-layer transparent electrode is transformed into a micro-nano structure after electroreduction.

[0030] Explanation of the labels in the diagram: 1. n-type crystalline silicon; 2. Hydrogenated intrinsic silicon thin film (ia-Si:H); 3. n-type microcrystalline silicon oxide thin film (n-μc-SiO) x); 4. p-type amorphous silicon thin film (pa-Si:H); 5. Front-side ITO / SnO x 6. Double-layer transparent electrode; back side ITO / SnO x 7. Double-layer transparent electrode; 8. Ni seed layer; 9. Cu main body layer; 10. Sn protective layer; 11. Front-side SnO x Single-layer transparent electrode; 11. Backside SnO x Single-layer transparent electrode; 12. Front-side SnO x / ITO / SnO x Three-layer transparent electrode structure; 13. Backside SnO x / ITO / SnO x Three-layer transparent electrode structure; 14. SnO electroreduced on the front side x Thin film; 15. SnO electroreduced on the back side x film. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1: A low-cost crystalline silicon heterojunction solar cell, specifically a crystalline silicon heterojunction solar cell based on a low-indium transparent electrode and a seedless copper-plated electrode, is shown in the schematic diagram below. Figure 1 As shown, in n-μc-SiO x ITO / Ta-doped SnO was deposited on a double-sided magnetron sputtering substrate on / ia-Si:H / nc-Si / ia-Si:H / pa-Si. x A bilayer thin film, wherein the front side is composed of ITO and SnO. x Thicknesses are 30 nm and 70 nm, respectively; back side is ITO and SnO. x The thicknesses are 30 nm and 150 nm, respectively. A patterning process, such as attaching a dry film and exposure development, is used to form an opening width of 20-30 μm on the transparent electrode. The patterned metal electrode is prepared by electroplating 2 μm Ni and 10 μm Cu at the opening in sequence. The dry film is then removed by a demolding process. Finally, Sn metal is electrolessly plated to protect the Cu electrode from oxidation.

[0033] This embodiment describes a method for fabricating a crystalline silicon heterojunction solar cell based on a low-indium transparent electrode and a seedless copper-plated electrode, comprising the following steps: S1, in n-μc-SiO x 30 nm ITO / 70 nm Ta-doped SnO was deposited by magnetron sputtering on a / ia-Si:H / nc-Si / ia-Si:H / pa-Si substrate. x Thin film, 30 nm ITO / 150 nm Ta-doped SnO deposited on the back side by magnetron sputtering. x film; Sputtering cavity vacuum level 8×10 -4 Pa, substrate temperature 150℃; wherein the sputtering power density of the ITO thin film is 2.5 W / cm². 2 The gas pressure was 0.3 Pa, the O2 / Ar ratio was 1%, and the thickness of the ITO film on both the front and back sides was 30 nm; Ta-doped SnO was used. x Target material, sputtering power density 3 W / cm² 2 The O2 / Ar ratio is 1%, the gas pressure is 0.3 Pa, and the front and back sides are Ta-doped with SnO. x The thicknesses are 70 nm and 150 nm, respectively; S2. Patterning is performed on the transparent electrode. A 15 mm thick dry film dielectric layer is tightly attached to the surface of the transparent electrode, and laser direct writing exposure is used. The exposed sample is placed in a 1% Na2CO3 solution for 40 s to form a pattern with a fine grid line width of 20 μm on the front side of the battery and a pattern with a fine grid line width of 30 μm on the back side of the battery. S3. After acid pretreatment for 50 s, the patterned surface is sequentially electroplated with 1 μm Ni and 10 μm Cu metal. The Ni electroplating is performed using a DC power supply at 45℃ and a current density of 2 A / dm³. 2 Electroplating time was 120 s, resulting in a uniform Ni seed layer of 1 μm; Cu electroplating was performed using a pulsed power supply at 25℃ and a current density of 4 A / dm³. 2 With a pulse period of 0.9 s, a pulse width of 0.3 s (duty cycle of 33.3%), and an electroplating time of 720 s, a uniform Cu electrode with a thickness of 10 μm was obtained on the Ni seed layer. S4. The dry film is removed by a demolding process. The demolding solution is 3% NaOH solution, the solution temperature is 40℃, and the processing time is 60s, resulting in a battery with no dry film covering the front and back. S5. Protect the Cu electrode from oxidation by chemically depositing Sn metal; the Sn plating process uses chemical tin plating solution and passivation solution, the solution temperature is 25℃, the plating time is 120 s, and a battery with a Sn layer on the electrode surface is obtained. Finally, a crystalline silicon heterojunction cell with a low-indium transparent electrode and a seedless copper-plated electrode was prepared.

[0034] like Figure 5 As shown, in ITO / Ta-doped SnO x The bulk resistivity of the copper-plated electrode without seeded copper on the transparent electrode is 2.11 μΩ•cm, the specific contact resistivity is 0.266 mΩ•cm, and the pull-out force is 1.10 N / mm. like Figure 6 As shown, the photoelectric conversion efficiency of the crystalline silicon heterojunction solar cell is 22.10%. like Figure 7 As shown, it still maintains 98.3% of its initial efficiency after being placed at a relative humidity of 35%-40% for 800 hours.

[0035] Example 2: The difference from Example 1 is that SnO is used. x Single-layer transparent electrode.

[0036] Finally, a crystalline silicon heterojunction cell with a low-indium transparent electrode and a seedless copper-plated electrode was fabricated. A schematic diagram of the structure is shown below. Figure 2 As shown; In SnO x The bulk resistivity of the transparent electrode without seeded copper plating is 2.12 μΩ•cm, the specific contact resistivity is 0.310 mΩ•cm, and the pull-out force is 1.05 N / mm. The photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 22.00%, and it still maintains the initial efficiency of 99.0% after being placed at 35%-40% relative humidity for 800 h.

[0037] Example 3: The difference from Example 1 is that SnO is used. x / ITO / SnO x Three-layer transparent electrode structure.

[0038] Finally, a crystalline silicon heterojunction cell with a low-indium transparent electrode and a seedless copper-plated electrode was fabricated. A schematic diagram of the structure is shown below. Figure 3 As shown; In SnO x / ITO / SnO x The bulk resistivity of the seedless copper-plated electrode on the transparent electrode is 2.05 μΩ•cm, the specific contact resistivity is 0.240 mΩ•cm, and the pull-out force is 1.07 N / mm. The photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 22.20%, and it still maintains the initial efficiency of 98.5% after being placed at 35%-40% relative humidity for 800 h.

[0039] Example 4: The difference from Example 1 is that the bilayer ITO / Ta structure is doped with SnO. xThe transparent electrode surface is subjected to an electroreduction process to form a micro / nano structure surface, as shown in the schematic diagram below. Figure 4 As shown; The electroreduction process employs a three-electrode system, with the working electrode being ITO / Ta-doped SnO. x The thin film sample used a carbon plate as the auxiliary electrode and a silver chloride electrode as the reference electrode. The reduction solution was a 0.04 M sodium sulfamate solution, and the reduction process employed a multi-potential step method with a current density of 1 mA / cm². 2 The restoration time is 60 seconds. like Figure 5 As shown, the bulk resistivity of the seedless copper plated electrode on the micro / nano structure ITO / Ta-doped SnOx transparent electrode is 1.98 μΩ•cm, the specific contact resistivity is 0.847 mΩ•cm, and the pull-out force is 1.65 N / mm. like Figure 6 As shown, the photoelectric conversion efficiency of the crystalline silicon heterojunction solar cell is 22.63%. like Figure 7 As shown, it still maintains 97.5% of its initial efficiency after being placed at 35%-40% relative humidity for 800 hours.

[0040] Figure 8 ITO / Ta-doped SnO in Example 4 x After electroreduction, a micro-nano structure surface pattern is formed on the surface of the double-layer transparent electrode, that is, nano-scale particles are precipitated on the surface of the pyramid structure at the micrometer scale.

[0041] Example 5: The difference from Example 1 is that the SnO on the back side is different. x The layer thickness was increased to 250 nm.

[0042] Finally, a crystalline silicon heterojunction cell with a low-indium transparent electrode and a seedless copper electroplated electrode was prepared. ITO / Ta doped SnO x The bulk resistivity of the copper-plated electrode without seeded copper on the transparent electrode is 2.05 μΩ•cm, the specific contact resistivity is 0.251 mΩ•cm, and the pull-out force is 1.10 N / mm; the photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 22.05%, and it still maintains the initial efficiency of 98.1% after being placed at 35%-40% relative humidity for 800 h.

[0043] Example 6: The difference from Example 1 is that the patterning uses photosensitive anti-plating ink to achieve a fine grid width of 30 μm and an electrochemical Cu electrode with an aspect ratio of 0.6; Finally, a crystalline silicon heterojunction cell with a low-indium transparent electrode and a seedless copper-plated electrode was prepared; ITO / Ta-doped SnO xThe bulk resistivity of the copper-plated electrode without seeded copper on the transparent electrode is 2.10 μΩ•cm, the specific contact resistivity is 0.264 mΩ•cm, and the pull-out force is 1.10 N / mm; the photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 21.60%, and it still maintains the initial efficiency of 95.6% after being placed at 35%-40% relative humidity for 800 h.

[0044] Example 7: The difference from Example 1 is that the patterning uses photoresist material, and the main components of the photolithography are phenolic varnish resin and naphthoquinone diazide, to achieve a fine gate width of 20 mm and an electrochemical Cu electrode with an aspect ratio of 1. Finally, a crystalline silicon heterojunction cell with a low-indium transparent electrode and a seedless copper-plated electrode was prepared; ITO / Ta-doped SnO x The bulk resistivity of the copper-plated electrode without seeded copper on the transparent electrode is 2.08 μΩ•cm, the specific contact resistivity is 0.264 mΩ•cm, and the pull-out force is 1.10 N / mm; the photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 22.18%, and it still maintains the initial efficiency of 98.4% after being placed at 35%-40% relative humidity for 800 h.

[0045] Example 8: The difference from Example 1 is that the electroplating seed layer uses a Ni-Cu alloy seed layer, the main components of the electroplating solution are nickel sulfate hexahydrate and copper sulfate pentahydrate, with sodium citrate as a complexing agent; a DC power supply is used, the solution temperature is 30°C, and the current density is 1 A / dm³. 2 Electroplating time: 120 seconds; Finally, a crystalline silicon heterojunction cell with a low-indium transparent electrode and a seedless copper-plated electrode was prepared; ITO / Ta-doped SnO x The bulk resistivity of the copper-plated electrode without seeded copper on the transparent electrode is 2.01 μΩ•cm, the specific contact resistivity is 0.240 mΩ•cm, and the pull-out force is 1.31 N / mm; the photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 22.40%, and it still maintains the initial efficiency of 96.2% after being placed at 35%-40% relative humidity for 800 h.

[0046] Example 9: The difference from Example 1 is that the electroplated Ni seed layer deposition time is 180s and the thickness is 3μm; Finally, a crystalline silicon heterojunction cell with a low-indium transparent electrode and a seedless copper-plated electrode was prepared; ITO / Ta-doped SnO x The bulk resistivity of the copper-plated electrode without seeded copper on the transparent electrode is 2.21 μΩ•cm, the specific contact resistivity is 0.305 mΩ•cm, and the pull-out force is 0.90 N / mm; the photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 21.82%, and it still maintains the initial efficiency of 97.8% after being placed at 35%-40% relative humidity for 800 h.

[0047] Example 10: The difference from Example 1 is that the copper electrode electroplating time is 1000 s and the thickness is 15 μm; Finally, a crystalline silicon heterojunction cell with a low-indium transparent electrode and a seedless copper-plated electrode was prepared; ITO / Ta-doped SnO x The bulk resistivity of the copper-plated electrode without seeded copper on the transparent electrode is 2.01 μΩ•cm, the specific contact resistivity is 0.261 mΩ•cm, and the pull-out force is 1.22 N / mm; the photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 22.32%, and it still maintains the initial efficiency of 98.1% after being placed at 35%-40% relative humidity for 800 h.

[0048] Comparative Example 1: The difference from Example 1 is that the double-sided transparent electrode uses a 100 nm ITO thin film with an In2O3 content of 99%. A patterning process, such as dry film lamination, exposure and development, is used on the transparent electrode to form an opening width of 20-30 μm. The patterned metal electrode is then fabricated by electroplating 2 μm Ni and 10 μm Cu at the opening sequentially. The dry film is then removed by a demolding process, and finally, Sn metal is electrolessly plated to protect the Cu electrode from oxidation. Finally, a crystalline silicon heterojunction cell with an ITO transparent electrode and a seedless copper-plated electrode was prepared. like Figure 5 As shown, the bulk resistivity of the copper-plated electrode without seeded copper on the ITO transparent electrode is 2.14 μΩ•cm, the specific contact resistivity is 0.397 mΩ•cm, and the pull-out force is 0.75 N / mm. like Figure 6 As shown, the photoelectric conversion efficiency of the crystalline silicon heterojunction solar cell is 22.99%. like Figure 7 As shown, it still maintains an initial efficiency of 93.5% after being placed at a relative humidity of 35%-40% for 800 hours.

[0049] Results and Discussion: 1. As can be seen from the performance comparison of the examples and Comparative Example 1, compared with the ITO transparent electrode, SnO x Seedless copper electrochemical copper electrodes with transparent substrates exhibit lower bulk resistivity, lower specific contact resistivity, and higher pull-out force.

[0050] 2. Compared to crystalline silicon heterojunction cells with ITO transparent electrodes and seedless copper electrochemical copper electrodes, this application is based on SnO. x The photoelectric conversion efficiency of crystalline silicon heterojunction cells with transparent base electrodes and seedless copper electrochemical copper electrodes did not decrease significantly, while exhibiting higher humidity stability.

[0051] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A low-cost crystalline silicon heterojunction solar cell, characterized in that, It is also a crystalline silicon heterojunction cell based on a tin oxide-based transparent electrode and a seedless copper electrochemical copper electrode. Its structure is as follows: an intrinsic amorphous silicon thin film is deposited on both sides of a textured silicon wafer, and then n-type and p-type doped silicon thin films are deposited on both sides respectively. On this basis, a tin oxide-based transparent electrode is deposited on both sides, and finally a patterned electrochemical copper electrode is deposited on the tin oxide-based transparent electrode to obtain a low-cost indium-less and silver-free crystalline silicon heterojunction cell. The tin oxide-based transparent electrode comprises at least one tin oxide-based transparent conductive film, and its surface is SnO. x film; The tin oxide-based transparent electrode is a single-layer SnO structure. x Thin film, or bilayer ITO / SnO x Thin film, or three-layer SnO x / ITO / SnO x film; The term "low indium" refers to an indium oxide content of 0 wt%-50 wt% in the transparent electrode. The electrochemical copper electrode with patterned deposition on a tin oxide-based transparent electrode is an electrochemical copper electrode with seedless copper deposition on a tin oxide-based transparent electrode, including patterning and electrochemical deposition.

2. The low-cost crystalline silicon heterojunction solar cell according to claim 1, characterized in that, The single-layer SnO structure x The film thickness is 50 nm-500 nm; the described bilayer ITO / SnO structure x In the thin films, the ITO film thickness is 10 nm-50 nm, and the SnO film thickness is... x The film thickness is 50 nm-300 nm; the three-layer SnO structure x / ITO / SnO x In the thin films, the ITO film thickness is 10 nm-50 nm, and the SnO film thickness is... x The film thickness is 50 nm-100 nm.

3. A low-cost crystalline silicon heterojunction solar cell according to claim 2, characterized in that, The described SnO x thin film is pure SnO x thin film or tantalum-doped SnO x thin film. The SnO x thin film is a thin film with a low oxygen content, 1 < x ≤ 2, and the O / Sn ratio is 1 - 2.

4. A low-cost crystalline silicon heterojunction solar cell according to claim 3, characterized in that, The total mass of tantalum oxide as a percentage of SnO x The proportion of transparent conductive film is 0.5-10 wt%.

5. A low-cost crystalline silicon heterojunction solar cell according to claim 1, characterized in that, The ITO thin film and SnO x The base thin film was prepared using a magnetron sputtering process; SnO in the transparent electrode x The thin film was sputtered using DC or RF sputtering with a sputtering power density of 2 W / cm². 2 -10 W / cm 2 The atmospheric pressure was 0.2 Pa to 1.0 Pa, the substrate temperature was room temperature to 150°C, the O2 / Ar ratio was 0 to 6%, and the film thickness was 50 nm to 500 nm. The ITO thin film in the transparent electrode is sputtered using DC or RF sputtering with a sputtering power density of 2 W / cm². 2 -10 W / cm 2 The atmospheric pressure was 0.2 Pa to 1.0 Pa, the substrate temperature was room temperature to 150°C, the O2 / Ar ratio was 0 to 6%, and the film thickness was 10 nm to 50 nm.

6. A low-cost crystalline silicon heterojunction solar cell according to claim 1, characterized in that, The In2O3 content in the ITO film is 90 wt%-99 wt%.

7. A low-cost crystalline silicon heterojunction solar cell according to claim 1, characterized in that, The seedless copper electrochemical copper electrode comprises a seed layer, an electroplated Cu electrode body, and a chemically plated tin layer.

8. A low-cost crystalline silicon heterojunction solar cell according to claim 1, characterized in that, The preparation of the seedless copper electrochemical metal electrode involves electroplating a seed layer film of 0.5 μm-3 μm, electroplating a Cu film of 5 μm-20 μm, and finally electrolessly plating a Sn film.

9. A low-cost crystalline silicon heterojunction solar cell according to any one of claims 1-8, characterized in that, The aforementioned low-cost crystalline silicon heterojunction solar cell ultimately yields a crystalline silicon heterojunction solar cell with a low-indium transparent electrode and a seedless copper-plated electrode; ITO / Ta doped SnO x The bulk resistivity of the seedless copper-plated electrode on the transparent electrode is 2.01 μΩ•cm-2.21 μΩ•cm, the specific contact resistivity is 0.240 mΩ•cm-0.310 mΩ•cm, and the pull-out force is 0.90 N / mm-1.31 N / mm; the photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 21.60%-22.32%, and it retains its initial efficiency of 95.6%-99.0% after being placed at 35%-40% relative humidity for 800 h. The bulk resistivity of the seedless copper-plated electrode on the micro / nano structured ITO / Ta-doped SnOx transparent electrode is 1.98 μΩ•cm, the specific contact resistivity is 0.847 mΩ•cm, and the pull-out force is 1.65 N / mm. The photoelectric conversion efficiency of the crystalline silicon heterojunction cell is 22.63%, and it still maintains an initial efficiency of 97.5% after being placed at 35%-40% relative humidity for 800 h.

10. A method for preparing a low-cost crystalline silicon heterojunction solar cell according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Hydrogenated intrinsic silicon films are deposited on both sides of an n-type textured silicon wafer. Then, an n-type microcrystalline silicon oxide film is deposited on the front side, and a p-type amorphous silicon film is deposited on the back side. SnO is prepared by double-sided magnetron sputtering. x Single-layer structure, or ITO / SnO x Double-layer structure, or SnO x / ITO / SnO x A three-layer transparent electrode with low indium content; wherein the ITO film thickness is 10 nm-50 nm, and SnO... x The film thickness is 50 nm-500 nm; S2, in the above SnO x The surface of the transparent electrode is partially treated with electroreduction or chemical reduction to form a micro-nano structure surface, thereby improving the interface characteristics between the transparent electrode and the electrochemical copper electrode. S3. A patterned surface with micron-scale feature size is obtained by depositing a patterned dielectric layer on the transparent electrode surface that has not undergone or has undergone reduction treatment, and then exposing and developing it. S4. On the above-mentioned patterned transparent electrode surface, a seed layer and a copper electrode are electrochemically deposited, then the dielectric layer is removed by a stripping process, and finally tin is electrochemically deposited to form the complete structure of the patterned metal electrode.

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