Etching aid, method for preparing the same and method for using the same

Abstract

This invention discloses an etching aid, its preparation method, and its application method, relating to the field of photosensitive chemistry. The etching aid comprises: 0.1-2.0 wt% sodium methylene bis(naphthalene) sulfonate, 0.1-2.0 wt% textured catalyst, 0.005-0.05 wt% defoamer, 0.001-0.05 wt% appearance modifier, 0.1-2.0 wt% reaction regulator, with the balance being deionized water. The etching aid in this invention uses sodium methylene bis(naphthalene) sulfonate as the main component, combined with the textured catalyst, defoamer, appearance modifier, and reaction regulator, to ensure a continuous, stable, and uniform reaction during the etching of monocrystalline silicon surfaces. The resulting monocrystalline silicon surface forms a pyramidal structure with a base side length of 3-5 μm, enabling high-quality interface passivation of heterojunction structures, which is of great significance for promoting the industrialization of heterojunction solar cells.

Description

Technical Field

[0001] This invention relates to the field of photosensitive chemistry, and in particular to an etching aid, its preparation method, and its application method. Background Technology

[0002] Following silicon-based PERC and TOPcon solar cells, silicon-based heterojunction (HJT) solar cells have received increasing attention in recent years. They possess numerous advantages, including structural symmetry, low-temperature processing, high open-circuit voltage, high conversion efficiency, and good stability, making them a strong contender for next-generation photovoltaic technology. The process flow for heterojunction cells includes double-sided cleaning and surface texturing, followed by the sequential deposition of a 5-10 nm intrinsic amorphous Si layer and a 5-10 nm p-type amorphous Si layer on the front side using PECVD to form a pn junction.

[0003] The core design element of heterojunction solar cells lies in the heterojunction structure formed by a crystalline silicon substrate and amorphous silicon. Therefore, interface passivation of this heterojunction structure plays a crucial role. High-quality interface passivation can effectively reduce carrier recombination, improve minority carrier lifetime, and ultimately increase cell efficiency. After surface texturing, a dense pyramid-shaped light-trapping structure is formed on the silicon substrate. Traditional crystalline silicon solar cells use silicon nitride thin films for passivation, but the thickness of silicon nitride films is 80-100 nm. Therefore, controlling the size of the pyramid light-trapping structure to 1-2 μm is sufficient to achieve good film deposition quality and passivation effect. However, the 1-2µm pyramid light-trapping structure is not suitable for heterojunction solar cells, mainly for two reasons: First, the thickness of amorphous silicon films is 5-10nm. Due to stress, it is difficult to achieve good coverage on small textured structures, and even more cracks may be generated at the top and bottom of the pyramids. Second, major manufacturers are now trying to use doped microcrystal technology on amorphous silicon. The grain size of microcrystals can reach the micrometer level, and may even exceed the distance between some adjacent pyramid structures, making it difficult to achieve good film deposition quality and coverage.

[0004] Therefore, in current heterojunction surface texturing processes, there is an urgent need to increase the size of the pyramid structure. Currently, the pyramid structures prepared by mainstream monocrystalline silicon texturing additives are generally 2 μm or smaller, which cannot meet the requirements of silicon-based heterojunction solar cells. Summary of the Invention

[0005] The purpose of this invention is to provide an etching aid, its preparation method, and its application method, to overcome the problem that existing surface texturing additives cannot achieve large pyramid structures.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An etching aid comprises the following components: 0.1-2.0 wt% sodium methylene bis(naphthalene) sulfonate, 0.1-2.0 wt% textured catalyst, 0.005-0.05 wt% defoamer, 0.001-0.05 wt% appearance modifier, 0.1-2.0 wt% reaction regulator, and the balance being deionized water.

[0008] Beneficial Technical Effects: The etching aid provided by this invention comprises the following components: 0.1-2.0 wt% sodium methylene bis(naphthalene) sulfonate, 0.1-2.0 wt% texturing catalyst, 0.005-0.05 wt% defoamer, 0.001-0.05 wt% appearance modifier, 0.1-2.0 wt% reaction regulator, and the balance being deionized water. This invention uses sodium methylene bis(naphthalene) sulfonate as the main active ingredient, combined with the texturing catalyst, defoamer, appearance modifier, and reaction regulator, to ensure a continuous, stable, and uniform reaction during the etching of single-crystal silicon surfaces. The resulting single-crystal silicon surface forms a pyramidal structure with a base side length of 3-5 μm. In this invention, sodium methylene bis(naphthalene) sulfonate is primarily used to promote the reaction and generate a larger pyramid structure. The textured catalyst added in this invention increases the density of the pyramid structure, ensuring its compactness. Since the alkaline solution (KOH) generates hydrogen gas during etching, bubbles accumulate on the silicon wafer surface due to surface tension, preventing the reaction from proceeding normally. This invention eliminates these bubbles on the silicon surface by adding a degassing agent, ensuring the continuous reaction. The addition of an appearance modifier ensures a more uniform reaction across the silicon wafer surface and guarantees a uniform appearance after etching, meeting industrial production requirements. Furthermore, this invention adds a reaction regulator, whose main function is to synergistically adjust the reaction rate with other components, ensuring controllable etching and allowing for the acquisition of desired surface morphology. The etching aid claimed in this invention ensures a continuous, stable, and uniform reaction during the assisted etching process, ultimately resulting in a pyramid structure morphology on the single-crystal silicon surface with a base side length of 3-5 μm, far exceeding the size of currently achievable pyramid structures. This enables high-quality interface passivation of heterojunction structures, which is of great significance for promoting the industrialization of heterojunction solar cells. Attached Figure Description

[0009] Figure 1 This is a SEM image of the surface morphology of the sample obtained in Example 1;

[0010] Figure 2 This is a SEM image of the surface morphology of the sample obtained in Example 2;

[0011] Figure 3 This is a SEM image of the surface morphology of the sample (existing technology) prepared in Comparative Example 4. Detailed Implementation

[0012] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0013] This invention provides an etching aid comprising the following components: 0.1-2.0 wt% sodium methylene bis(naphthalene) sulfonate, 0.1-2.0 wt% textured catalyst, 0.005-0.05 wt% defoamer, 0.001-0.05 wt% appearance modifier, 0.1-2.0 wt% reaction regulator, and the balance being deionized water.

[0014] In this invention, the etching aid preferably comprises the following components: 0.5-1.0 wt% sodium methylene bis(naphthalene) sulfonate, 0.5-1.0 wt% textured catalyst, 0.01-0.02 wt% defoamer, 0.01-0.03 wt% appearance modifier, 0.8-1.2 wt% reaction regulator, and the balance being deionized water.

[0015] In this invention, the etching aid more preferably comprises the following components: 0.8 wt% sodium methylene bis(naphthalene) sulfonate, 0.8 wt% textured catalyst, 0.015 wt% defoamer, 0.02 wt% appearance modifier, 0.10 wt% reaction regulator, and the balance being deionized water.

[0016] In this invention, the source of the sodium methylene bis(naphthalene) sulfonate is not particularly required; commercially available products are acceptable. It should be understood that the sodium methylene bis(naphthalene) sulfonate can effectively promote the etching reaction and contribute to obtaining a larger pyramid-shaped light-trapping structure.

[0017] In this invention, the content of sodium methylene bis(naphthalene)sulfonate is preferably 0.1-2.0 wt%, more preferably 0.5-1.0 wt%, and most preferably 0.8 wt%.

[0018] In this invention, the textured catalyst is preferably one of polyepoxysuccinic acid, alkyl glycoside, sodium dodecyl sulfate, or sodium dodecylbenzenesulfonate; more preferably, it is polyepoxysuccinic acid. This invention does not have special requirements on the molecular weight of the textured catalyst; any commonly used catalyst in the art can be used. This invention also does not have special requirements on the source of the textured catalyst; commercially available products can be used. It should be understood that the function of the textured catalyst in this invention is to increase the density of the pyramid structure and ensure its compactness.

[0019] In this invention, the content of the textured catalyst is preferably 0.1-2.0 wt%, more preferably 0.5-1.0 wt%, and most preferably 0.8 wt%.

[0020] In this invention, the defoaming agent is preferably one of cyclodextrin, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, gum arabic, guar gum, or xanthan gum; more preferably, cyclodextrin. This invention does not have special requirements regarding the molecular weight of the defoaming agent; any commonly used agent in the art is acceptable. This invention also does not have special requirements regarding the source of the defoaming agent; commercially available products are acceptable. It should be understood that because the alkaline solution (KOH) generates hydrogen gas during etching, bubbles will accumulate on the silicon wafer surface due to surface tension, preventing the reaction from proceeding normally. By adding a defoaming agent, the bubbles generated on the silicon surface are eliminated, ensuring the continuous progress of the reaction.

[0021] In this invention, the content of the defoaming agent is preferably 0.005-0.05 wt%, more preferably 0.01-0.02 wt%, and most preferably 0.015 wt%.

[0022] In this invention, the appearance modifier is preferably one of polyethylene glycol, diethylene glycol methyl ether, diethylene glycol butyl ether, triethylene glycol butyl ether, or tetraethylene glycol butyl ether; more preferably, it is polyethylene glycol. Specifically, the polyethylene glycol is preferably polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, and polyethylene glycol 1000. When polyethylene glycol is selected as the appearance modifier, the smaller the molecular weight of the polyethylene glycol in this invention, the better the effect. This invention does not have special requirements regarding the source of the appearance modifier; commercially available products are sufficient. It should be understood that by adding the appearance modifier, the reaction on the silicon wafer surface is made more uniform, and the appearance of the silicon wafer is ensured to be without problems.

[0023] In this invention, the content of the appearance modifier is preferably 0.001-0.05 wt%, more preferably 0.01-0.03 wt%, and most preferably 0.02 wt%.

[0024] In this invention, the reaction regulator is preferably an inorganic sodium salt and / or an organic sodium salt; the inorganic sodium salt may be sodium carbonate and / or sodium silicate, and the organic sodium salt may be one or two of sodium tripolyphosphate, sodium citrate, sodium lactate, and sodium tartrate. The reaction regulator is more preferably sodium carbonate and sodium silicate. This invention does not have any special requirements regarding the source of the reaction regulator; commercially available products are sufficient. It should be understood that the main function of the reaction regulator in this invention is to regulate the reaction rate and ensure the controllability of the etching degree, thereby obtaining the desired surface morphology as needed.

[0025] In this invention, the content of the reaction regulator is preferably 0.1-2.0 wt%, more preferably 0.8-1.2 wt%, and most preferably 0.10 wt%.

[0026] In this invention, deionized water is used to avoid the reaction of compound ions present in non-deionized water with the etching solution or silicon surface, which could lead to inaccurate etching. Generally speaking, deionized water is required to have a resistivity of less than or equal to 1.0 MΩ.

[0027] The present invention also provides a method for preparing an etching aid, which includes the following steps:

[0028] The etching aid is obtained by sequentially adding 0.1-2.0 wt% sodium methylene bis(naphthalene) sulfonate, 0.1-2.0 wt% textured catalyst, 0.005-0.05 wt% defoamer, 0.001-0.05 wt% appearance modifier, and 0.1-2.0 wt% reaction regulator to deionized water while continuously stirring.

[0029] In this invention, the process of adding the five auxiliary components to deionized water has a specific order requirement, preferably in the order of sodium methylene bis(naphthalene) sulfonate, frosting catalyst, defoaming agent, appearance modifier, and regulator.

[0030] In this invention, it is preferable that adjacent components are added at a certain time interval; the interval is preferably 1-2 minutes, more preferably 1.5 minutes. It should be understood that the time interval between adjacent components is to allow time for the components to dissolve fully.

[0031] In this invention, the addition of the component also includes a stirring operation; the stirring is preferably carried out at a rate of 500-600 rpm, more preferably 550 rpm.

[0032] In this invention, the etching aid is obtained by adding the final reaction modifier to the water; preferably, after adding the final reaction modifier to the water, stirring can be continued for 5-10 minutes.

[0033] The present invention also provides a method for applying an etching aid, comprising: adding the etching aid to a KOH solution and stirring evenly to prepare an etching solution; and etching a single crystal silicon in the etching solution to obtain etched single crystal silicon.

[0034] In this invention, the mass ratio of the etching aid to the KOH solution is preferably (1.0-5.0):100; more preferably 2.5:100; the concentration of the KOH solution is preferably 0.5-2.0 wt%; more preferably 1 wt%; and the stirring speed is preferably 500-600 rpm; more preferably 550 rpm.

[0035] In this invention, the etching is preferably performed at 70-80°C, more preferably at 75°C; the etching time is preferably 900-1500s, more preferably 1200s.

[0036] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0037] In this invention, unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially available reagents.

[0038] Example 1

[0039] The etching aid in this embodiment includes the following components: 10g sodium methylene bisnaphthalene sulfonate, 10g polyepoxysuccinic acid, 0.5g cyclodextrin, 0.1g polyethylene glycol 200, 5g sodium silicate, 5g sodium carbonate and 969.4g deionized water.

[0040] Preparation method of etching aid:

[0041] (1) According to the raw material ratio, sodium methylene bisnaphthalene sulfonate, polyepoxysuccinic acid, cyclodextrin, polyethylene glycol, sodium silicate and sodium carbonate are added to deionized water at 1.5 min intervals and mixed at 550 rpm to prepare 1 L of etching aid.

[0042] (2) Add the etching aid to 40L KOH solution (1wt%) and prepare the etching solution by stirring at 550rpm.

[0043] (3) Heat the etching solution to 70°C, immerse the single-crystal silicon wafer in the etching solution and react for 1200 seconds. The surface morphology of the obtained product is as follows. Figure 1 As shown, the side length of the pyramid base is 3-5 micrometers (e.g., Figure 1 (Note: Since the pyramid structures obtained by etching are not uniform in size, the side length of the pyramid base here is a range value, meaning that more than 80% of the pyramid structures formed have a base side length in the range of 3-5 micrometers.)

[0044] Example 2

[0045] The etching aid in this embodiment includes the following components: 20g sodium methylene bis(naphthalene) sulfonate, 20g alkyl glycoside, 0.5g hydroxyethyl cellulose, 0.5g diethylene glycol methyl ether, 20g sodium tripolyphosphate, and 939g deionized water.

[0046] Preparation method of etching aid:

[0047] (1) According to the raw material ratio, sodium methylene bisnaphthalene sulfonate, polyepoxysuccinic acid, cyclodextrin, polyethylene glycol, sodium silicate and sodium carbonate are added to deionized water at time intervals of 2.0 min and prepared into 1 L of etching aid under stirring at 6000 rpm.

[0048] (2) Add the etching aid to 40L KOH solution (1.5wt%) and prepare the etching solution by stirring at 500rpm.

[0049] (3) Heat the etching solution to 75°C, immerse the single-crystal silicon wafer in the etching solution and react for 1500 seconds. The surface morphology of the obtained product is as follows. Figure 2 As shown, the side length of the pyramid base is 3-5 micrometers (e.g., Figure 2 ).

[0050] Example 3

[0051] The etching aid in this embodiment includes the following components: 8g sodium methylene bis(naphthalene) sulfonate, 8g sodium dodecyl sulfate, 0.15g hydroxypropyl methylcellulose, 0.2g polyethylene glycol 400, 1g sodium citrate, and 982.65g deionized water.

[0052] Preparation method of etching aid:

[0053] (1) According to the raw material ratio, sodium methylene bisnaphthalene sulfonate, sodium dodecyl sulfate, hydroxypropyl methylcellulose, polyethylene glycol 400, sodium silicate and sodium carbonate are added to deionized water at 1 min intervals and mixed at 500 rpm to prepare 1 L of etching aid.

[0054] (2) Add the etching aid to 20L KOH solution (0.5wt%) and prepare the etching solution by stirring at 600rpm;

[0055] (3) Heat the etching solution to 75°C, immerse the single crystal silicon wafer in the etching solution and react for 900 seconds. The pyramid base of the obtained product surface morphology has a side length of 3-4 micrometers.

[0056] Example 4

[0057] The etching aid in this embodiment includes the following components: 10g sodium methylene bis(naphthalene) sulfonate, 5g sodium dodecylbenzene sulfonate, 0.1g guar gum, 0.3g triethylene glycol butyl ether, 4g sodium lactate, 4g sodium tartrate, and 976.6g deionized water.

[0058] Preparation method of etching aid:

[0059] (1) According to the raw material ratio, sodium methylene bisnaphthalene sulfonate, polyepoxysuccinic acid, cyclodextrin, polyethylene glycol, sodium silicate and sodium carbonate are added to deionized water at 2-minute intervals and mixed at 600 rpm to prepare 1 L of etching aid.

[0060] (2) Add the etching aid to 100L KOH solution (2.0wt%) and prepare the etching solution by stirring at 600rpm;

[0061] (3) Heat the etching solution to 80°C, immerse the single crystal silicon wafer in the etching solution and react for 1500s. The pyramid base of the obtained product surface morphology has a side length of 3-4 micrometers.

[0062] Example 5

[0063] The etching aid in this embodiment includes the following components: 5g sodium methylene bis(naphthalene) sulfonate, 10g polyepoxysuccinic acid, 0.2g gum arabic, 0.1g polyethylene glycol 1000, 12g sodium lactate, and 972.7g deionized water.

[0064] Preparation method of etching aid:

[0065] (1) According to the raw material ratio, sodium methylene bisnaphthalene sulfonate, polyepoxysuccinic acid, cyclodextrin, polyethylene glycol, sodium silicate and sodium carbonate are added to deionized water at 2-minute intervals and mixed at 500 rpm to prepare 1 L of etching aid.

[0066] (2) Add the etching aid to 100L KOH solution (2.0wt%) and prepare the etching solution by stirring at 550rpm.

[0067] (3) Heat the etching solution to 80°C, immerse the single crystal silicon wafer in the etching solution and react for 1500s. The side length of the pyramid base in the surface morphology of the obtained product is 3-4 micrometers.

[0068] Example 6

[0069] The etching aid in this embodiment includes the following components: 7g sodium methylene bis(naphthalene) sulfonate, 8.5g polyepoxysuccinic acid, 0.14g xanthan gum, 0.21g tetraethylene glycol butyl ether, 9g sodium lactate, and 975.15g deionized water.

[0070] Preparation method of etching aid:

[0071] (1) According to the raw material ratio, sodium methylene bisnaphthalene sulfonate, polyepoxysuccinic acid, cyclodextrin, polyethylene glycol, sodium silicate and sodium carbonate are added to deionized water at 1 min intervals and mixed at 600 rpm to prepare 1 L of etching aid.

[0072] (2) Add the etching aid to 100L KOH solution (2.0wt%) and prepare the etching solution by stirring at 500rpm.

[0073] (3) Heat the etching solution to 75°C, immerse the single crystal silicon wafer in the etching solution and react for 1200s. The side length of the pyramid base in the surface morphology of the obtained product is 3-4 micrometers.

[0074] Example 7

[0075] The etching aid in this embodiment includes the following components: 9g sodium methylene bis(naphthalene) sulfonate, 8g polyepoxysuccinic acid, 0.17g xanthan gum, 0.25g diethylene glycol butyl ether, 10g sodium lactate, and 972.58g deionized water.

[0076] Preparation method of etching aid:

[0077] (1) According to the raw material ratio, sodium methylene bisnaphthalene sulfonate, polyepoxysuccinic acid, cyclodextrin, polyethylene glycol, sodium silicate and sodium carbonate are added to deionized water at 1.5 min intervals and mixed at 550 rpm to prepare 1 L of etching aid.

[0078] (2) Add the etching aid to 100L KOH solution (2.0wt%) and prepare the etching solution by stirring at 600rpm;

[0079] (3) Heat the etching solution to 70°C, immerse the single crystal silicon wafer in the etching solution and react for 900 seconds. The side length of the pyramid base in the surface morphology of the obtained product is 3-4 micrometers.

[0080] Comparative Example 1

[0081] Compared with Example 1, this example replaces sodium methylene bisnaphthalene sulfonate in Example 1 with polyether (the effective component of etching aids in the prior art) in an equal amount, while keeping other conditions unchanged. The resulting product has a sporadic pyramid structure on its surface, but it is not dense and does not meet the actual production requirements.

[0082] Comparative Example 2

[0083] Compared with Example 1, this example replaces sodium carbonate and sodium silicate in Example 1 with deionized water in equal amounts, while keeping other conditions unchanged. The side length of the pyramid base in the surface morphology of the obtained product is all below 2 micrometers. This is because the reaction regulators sodium carbonate and sodium silicate can effectively increase the size of the pyramid.

[0084] Comparative Example 3

[0085] Compared with Example 1, this example replaces the polyepoxysuccinic acid (textured catalyst) in Example 1 with tap water in an equal amount, while keeping other conditions unchanged. The resulting product has a pyramid base side length of 1-3 micrometers and a weak surface density.

[0086] Comparative Example 4

[0087] Compared to Example 1, this example replaces the etching aid of the present invention in Example 1 with an equal amount of commercially available mainstream additives (prior art; this comparative example uses the etching aid described in CN111117623A), resulting in a product with an edge length of less than 2 micrometers (e.g., Figure 3 ).

[0088] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An etching aid, characterized in that, It comprises the following components by weight percentage: 0.1-2.0 wt% sodium methylene bis(naphthalene) sulfonate, 0.1-2.0 wt% textured catalyst, 0.005-0.05 wt% defoamer, 0.001-0.05 wt% appearance modifier, 0.1-2.0 wt% reaction regulator, balance deionized water; The reaction regulator is an inorganic sodium salt and / or an organic sodium salt; the inorganic sodium salt includes sodium carbonate and / or sodium silicate; the organic sodium salt includes one or two of sodium tripolyphosphate, sodium citrate, sodium lactate and sodium tartrate. The textured catalyst is one of polyepoxysuccinic acid, alkyl glycoside, sodium dodecyl sulfate, or sodium dodecylbenzene sulfonate. The appearance modifier is a high-polymer alcohol or an oligomeric alcohol ether.

2. The etching aid according to claim 1, characterized in that, It comprises the following components by weight percentage: 0.5-1.0 wt% sodium methylene bis(naphthalene) sulfonate, 0.5-1.0 wt% textured catalyst, 0.01-0.02 wt% defoamer, 0.01-0.03 wt% appearance modifier, 0.8-1.2 wt% reaction regulator, balance deionized water.

3. The etching aid according to claim 1 or 2, characterized in that, The defoaming agent is one of cyclodextrin, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, gum arabic, guar gum, or xanthan gum.

4. The etching aid according to claim 1, characterized in that, The high-polyol substance is polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, or polyethylene glycol 1000; and / or, The oligomeric alcohol ethers are diethylene glycol methyl ether, diethylene glycol butyl ether, triethylene glycol butyl ether, or tetraethylene glycol butyl ether.

5. A method for preparing the etching aid according to any one of claims 1-4, characterized in that, Includes the following steps: The sodium methylene bis(naphthalene) sulfonate, the textured catalyst, the defoaming agent, the appearance modifier, and the reaction regulator are added sequentially to deionized water, with an interval of 1-2 minutes between the addition of two adjacent components in the etching aid; the etching aid is obtained by stirring at 500-600 rpm.

6. A method for applying the etching aid according to any one of claims 1-4, characterized in that, The etching aid is added to a KOH solution and stirred until homogeneous to prepare an etching solution; the monocrystalline silicon is then immersed in the etching solution to obtain etched monocrystalline silicon.

7. The application method according to claim 6, characterized in that, The mass ratio of the etching aid to the KOH solution is (1.0-5.0):100; the concentration of the KOH solution is 0.5-2.0 wt%; and the stirring rate is 500-600 rpm. The etching is performed at 70-80°C for 900-1500 seconds.

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