Texturing additive for the preparation of large size topcon solar cells and process of use thereof

Abstract

The application discloses a texturing additive for preparing a large-size Topcon solar cell and a use process thereof, and the texturing additive comprises the following components: 1.0-2.0% of a non-ionic surfactant, 2.0-10.0% of an anionic polyacrylamide, 3.0-8.0% of a dispersant, 3.0-8.0% of an inorganic salt, and the balance of deionized water. The use process comprises the following steps: texturing additive preparation, preparation of an alkali solution, preparation of an alkaline texturing solution and texturing. The additive can etch out a pyramid with a height of 2.4-3 mu in a short time, greatly shortens the texturing time, improves the production capacity of a production line, and achieves the purpose of reducing cost and improving efficiency.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic technology, specifically relating to texturing additives for preparing large-size Topcon solar cells and their application process. Background Technology

[0002] Photovoltaic power generation is a process of converting solar energy into electrical energy. Improving the conversion efficiency of monocrystalline silicon cells is crucial, and this is generally achieved through two improvements. The first is by increasing the cell's light absorption, such as by texturing the silicon surface to create a pyramidal light-trapping structure. The second is by effectively separating photogenerated carriers, which reduces carrier recombination and improves efficiency. Common methods include increasing the back surface field, adding a passivation layer, and improving the substrate material, as seen in BSF solar cells, IBC solar cells, HIT solar cells, PERC solar cells, and Topcon solar cells.

[0003] The Topcon cell employs an ultrathin tunneling oxide layer and a highly doped polycrystalline silicon thin layer on the back side of the cell, which together form a passivation structure. This structure provides excellent surface passivation for the back side of the silicon wafer. The ultrathin oxide layer allows majority carrier electrons to tunnel into the polycrystalline silicon layer while blocking minority carrier hole recombination. Subsequently, electrons are laterally transported in the polycrystalline silicon layer and collected by the metal, thereby significantly reducing the metal-to-metal recombination current and improving the cell's open-circuit voltage and short-circuit current. Currently, Topcon solar cells are the mainstream solar cell technology after PERC cells. However, the process of depositing polycrystalline silicon on the back side of the cell can easily lead to parasitic polycrystalline silicon coatings around the edges of the front side of the silicon wafer. A step is needed to remove the polycrystalline silicon layer on the front side, which requires a large pyramid size on the front side. This is to prevent the pyramid from being too short and small due to the removal of the polycrystalline silicon layer, which would affect the light trapping effect. Therefore, this patent designs a large-size Topcon solar cell texturing additive to etch out a large-size pyramid to match the various processes of Topcon solar cells, thereby improving the photoelectric conversion efficiency. Currently, the pyramid size of PERC solar cells is 1.3-2.5μm, and the additive provided by this invention aims to control the pyramid size to 2.4-3.0μm. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a texturing additive for preparing large-size Topcon solar cells, comprising the following components by weight percentage:

[0005]

[0006] As a preferred embodiment of the above technical solution, the nonionic surfactant is one or a mixture of several of the following: fatty alcohol polyoxyethylene ether AEO-7, fatty alcohol polyoxyethylene ether AEO-9, alkylphenol polyoxyethylene ether OP-10, Tween 20, and Tween 80.

[0007] As a preferred embodiment of the above technical solution, the anionic polyacrylamide is one or a mixture of several of the following: polyacrylamide with a molecular weight of 5 million, polyacrylamide with a molecular weight of 8 million, polyacrylamide with a molecular weight of 10 million, and polyacrylamide with a molecular weight of 12 million.

[0008] As a preferred embodiment of the above technical solution, the dispersant is one or more of maleic acid-acrylic acid copolymer, sodium polyacrylate, hydrolyzed polymaleic anhydride, and polyepoxysuccinic acid.

[0009] As a preferred embodiment of the above technical solution, the inorganic salt is any one or more of sodium carbonate, sulfite, and sodium ethylenediaminetetraacetate.

[0010] The process for using texturing additives in the fabrication of large-size Topcon solar cells includes the following steps:

[0011] 1) Formulation of texturing additive: Nonionic surfactant, polyanionic acrylamide, dispersant, inorganic salt and deionized water are mixed according to weight percentage to form Topcon monocrystalline silicon texturing additive;

[0012] 2) Preparation of alkaline solution: Weigh a certain mass of alkali and add it to deionized water to prepare an alkaline solution with a concentration of 0.10-2.00 wt%. The alkali is sodium hydroxide or potassium hydroxide.

[0013] 3) Preparation of alkaline texturing solution: Add the Topcon monocrystalline silicon texturing additive mixed evenly in step 1) to the alkaline solution prepared in step 2), and stir evenly to obtain the alkaline texturing solution. The mass ratio of Topcon monocrystalline silicon texturing additive to alkaline solution is 1-6:100.

[0014] 4) Texturing: The monocrystalline silicon wafer is immersed in an alkaline texturing solution to etch a pyramidal textured surface onto the silicon surface.

[0015] As a preferred embodiment of the above technical solution, the flocking temperature in step 4) is 75-85℃ and the flocking time is 250-320s.

[0016] The beneficial effects of this invention are: compared with the existing Topcon texturing additives on the market, the additive of this invention can etch 2.4-3μm pyramids in a short time, which greatly shortens the texturing time, increases the production line capacity, and indirectly achieves the purpose of reducing costs and improving efficiency. Attached Figure Description

[0017] Figure 1 This is a SEM image of the silicon wafer surface after texturing in Example 1;

[0018] Figure 2 This is a SEM image of the silicon wafer surface after texturing in Example 2;

[0019] Figure 3 This is a SEM image of the silicon wafer surface after texturing in Example 3;

[0020] Figure 4 This is a SEM image of the silicon wafer surface after texturing, as shown in Comparative Example 1. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Example 1

[0024] 1) Preparation of texturing additive: A monocrystalline silicon texturing additive is prepared by mixing 1.0% (by mass) of fatty alcohol polyoxyethylene ether AEO-7, 2.0% (by mass) of anionic polyacrylamide with a molecular weight of 5 million, 4.0% of sodium polyacrylate, 1.5% of sodium carbonate, and the balance being water; 2) Preparation of alkaline texturing solution: The additive prepared in step 1) is added to an alkaline solution and mixed evenly, wherein the mass ratio of texturing additive to alkaline solution is 3:100; the alkaline solution is a 1 wt% sodium hydroxide aqueous solution; 3) Texturing: The monocrystalline silicon wafer is placed in the alkaline texturing solution prepared in step 2) for texturing. The texturing time is 250s and the texturing temperature is 80℃.

[0025] Example 2

[0026] 1) Preparation of texturing additive: A monocrystalline silicon texturing additive is prepared by mixing 1.0% (by mass) of fatty alcohol polyoxyethylene ether AEO-7, 2.0% (by mass) of anionic polyacrylamide with a molecular weight of 8 million, 3.0% of polyepoxysuccinic acid, 1.5% of sodium carbonate, and the balance being water; 2) Preparation of alkaline texturing solution: The additive prepared in step 1) is added to an alkaline solution and mixed evenly, wherein the mass ratio of texturing additive to alkaline solution is 3:100; the alkaline solution is a 1.5wt% sodium hydroxide aqueous solution; 3) Texturing: The monocrystalline silicon wafer is placed in the alkaline texturing solution prepared in step 2) for texturing. The texturing time is 270s and the texturing temperature is 80℃.

[0027] Example 3

[0028] 1) Preparation of texturing additive: A monocrystalline silicon texturing additive is prepared by mixing 1.5% (by mass) fatty alcohol polyoxyethylene ether AEO-9, 1.0% (by mass) anionic polyacrylamide with a molecular weight of 10 million, 3.0% polyepoxysuccinic acid, 1.5% sodium sulfite, and the balance water; 2) Preparation of alkaline texturing solution: The additive prepared in step 1) is added to an alkaline solution and mixed evenly, wherein the mass ratio of texturing additive to alkaline solution is 3:100; the alkaline solution is a 2.0 wt% sodium hydroxide aqueous solution; 3) Texturing: The monocrystalline silicon wafer is placed in the alkaline texturing solution prepared in step 2) for texturing. The texturing time is 270 s and the texturing temperature is 82 ℃.

[0029] Comparative Example 1

[0030] (1) Preparation of additives: The “K02(T30D)” monocrystalline silicon texturing additive produced by Jiaxing Xiaochen Photovoltaic Technology Co., Ltd. is used directly.

[0031] (2) Preparation of texturing solution: Add the additive from step (1) to the alkaline solution and mix evenly to prepare the texturing solution; the mass ratio of additive to alkaline solution is 0.6:100; the alkaline solution is a 1.2wt% sodium hydroxide aqueous solution;

[0032] (3) Immerse the single crystal silicon wafer in the texturing solution obtained in step (2) for a first texturing process. The texturing temperature for the first texturing process is 82°C and the texturing time for the first texturing process is 400s.

[0033] The texturized monocrystalline silicon wafers of Examples 1, 2, and 3, and Comparative Example 1, were analyzed by scanning electron microscopy (SEM). The SEM images are shown below. Figure 1-4 As shown. (See attached instruction manual) Figure 1-4A comparison shows that monocrystalline silicon wafers using the texturing additive and its application process of this application can have pyramids of 2.4-3 μm etched within 250-270 seconds. In contrast, using the applicant's earlier texturing additive, pyramids of 1.3-2.5 μm were etched within 400 seconds. Therefore, the texturing additive and its application process of this invention improve the pyramid size of solar cells and shorten the texturing time.

[0034] After the texturized monocrystalline silicon wafers of Examples 1, 2, 3 and Comparative Example 1 were processed into solar cells using the same subsequent processing techniques, a texturing test was performed. The photoelectric conversion test results are shown in the table below:

[0035] Pyramid size Pyramid height reflectivity Photoelectric conversion efficiency Example 1 2.41 1.11 9.5 23.01％ Example 2 2.52 1.25 9.3 23.02％ Example 3 2.61 1.30 9.0 23.03％ Comparative Example 1 1.82 0.82 10.2 22.99％

[0036] As shown in the table above, the single-crystal silicon wafers obtained using the texturing additive and its application process of this application exhibit a significant improvement in photoelectric conversion efficiency. This is because the large-size pyramidal texturing structure brings a better light-trapping effect, allowing more light to be absorbed, thereby improving the photoelectric conversion efficiency.

[0037] It is worth mentioning that the scanning electron microscope and other technical features involved in this patent application should be regarded as prior art. The specific structure, working principle, and possible control methods and spatial arrangement of these technical features can be adopted using conventional choices in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0038] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experimentation on the basis of the prior art should be within the scope of protection defined by the claims.

Claims

1. A texturing additive for preparing large-size Topcon solar cells, characterized in that, By weight percentage, it includes the following components: Nonionic surfactants 1.0-2.0% Anionic polyacrylamide 2.0-10.0% Dispersant 3.0-8.0% Inorganic salts 3.0-8.0% The remainder is deionized water. The nonionic surfactant is one or a mixture of several of the following: fatty alcohol polyoxyethylene ether AEO-7, fatty alcohol polyoxyethylene ether AEO-9, alkylphenol polyoxyethylene ether OP-10, Tween 20, and Tween 80. The anionic polyacrylamide is one or a mixture of several of the following: polyacrylamide with a molecular weight of 5 million, polyacrylamide with a molecular weight of 8 million, polyacrylamide with a molecular weight of 10 million, and polyacrylamide with a molecular weight of 12 million. The dispersant is one or more of maleic acid-acrylic acid copolymer, sodium polyacrylate, hydrolyzed polymaleic anhydride, and polyepoxysuccinic acid. The inorganic salt is any one or more of sodium carbonate, sulfite, and sodium ethylenediaminetetraacetate.

2. The process of using the texturing additive for preparing large-size Topcon solar cells as described in claim 1, characterized in that, It includes the following steps: 1) Formulation of texturing additive: Nonionic surfactant, anionic polyacrylamide, dispersant, inorganic salt and deionized water are mixed according to weight percentage to form Topcon monocrystalline silicon texturing additive; 2) Preparation of alkaline solution: Weigh a certain mass of alkali and add it to deionized water to prepare an alkaline solution with a concentration of 0.10-2.00wt%, wherein the alkali is sodium hydroxide or potassium hydroxide; 3) Preparation of alkaline texturing solution: Add the Topcon monocrystalline silicon texturing additive mixed evenly in step 1) to the alkaline solution prepared in step 2), and stir evenly to obtain the alkaline texturing solution. The mass ratio of Topcon monocrystalline silicon texturing additive to alkaline solution is 1-6:

100. 4) Texturing: The monocrystalline silicon wafer is immersed in an alkaline texturing solution to etch a pyramidal textured surface onto the silicon surface.

3. The process of using the texturing additive for preparing large-size Topcon solar cells as described in claim 2, characterized in that, The flocking temperature in step 4) is 75-85℃, and the flocking time is 250-320s.

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