An additive, reaction solution, method and application for texturing silicon wafers

Abstract

The present invention belongs to the technical field of silicon wafer processing, and relates to an additive, a reaction solution, a method and an application for silicon wafer texturing. The present invention provides an additive for silicon wafer texturing. In terms of mass percentage, the additive consists of: 0.3 - 1.0% of a templating agent, 0.1 - 1.0% of an inhibitor, 0.1 - 1.0% of a surfactant, and the balance being deionized water; the templating agent is at least one of high molecular polymers with a molecular weight not less than 10,000 Da, and the surfactant is at least one of anionic surfactants and alkyl polyether surfactants. The additive provided by the present invention solves the technical problem that at least two reaction tanks must be used during silicon wafer texturing.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon wafer processing, and relates to an additive, a reaction solution, a method and an application for texturing silicon wafers. Background Art

[0002] Generally, the first step in the preparation of monocrystalline silicon solar cells is to form a pyramid structure on the surface of the silicon wafer. When light is incident on the pyramid structure, part of the light is directly absorbed, part of the light is refracted and then incident on the silicon wafer again and absorbed, while part of the light is reflected by the silicon wafer surface and cannot be utilized. The purpose of texturing is to form a textured surface on the silicon wafer surface to reduce the reflectivity of the cell. The uneven textured surface can increase secondary reflection, change the optical path and the incident mode.

[0003] Currently, the reflectivity of monocrystalline silicon wafers for solar cell texturing is basically about 10.0%. Increasing the light absorption is crucial. For example, CN202210584582.7 discloses using an alkali and an additive to secondarily prepare a terraced pyramid microstructure on a conventional textured silicon wafer, and the reflectivity can be reduced to 4 - 7%. This method requires two steps to achieve the preparation of the terraced pyramid microstructure and cannot be achieved in one step, that is, on the basis of the conventional texturing process, texturing is carried out again to obtain a lower reflectivity; similarly, CN202111532361.7 discloses that two-step texturing can improve the pyramid uniformity and enhance the efficiency; CN202010201512.X discloses a method for preparing a porous pyramid structure using two-step texturing. Therefore, the reflectivity can be reduced and the terminal efficiency can be improved through two-step texturing. For battery manufacturers, although two-step texturing can improve the efficiency, it requires an increase in production costs, and some manufacturers also need to modify the texturing machine to achieve it. Summary of the Invention

[0004] The purpose of the present invention is to optimize the conventional texturing process. By changing the additive, without changing the texturing effect, the conventional two-step texturing is changed into one-step texturing to prepare a silicon wafer with a terraced pyramid microstructure. For this, the present invention provides an additive, a reaction solution, a method and an application for texturing silicon wafers to solve this need in the art.

[0005] On the one hand, the present invention relates to an additive for texturing silicon wafers. By mass percentage, the additive consists of: 0.3 - 1.0% of a templating agent, 0.1 - 1.0% of an inhibitor, 0.1 - 1.0% of a surfactant, and the balance being deionized water;

[0006] The templating agent is at least one of high molecular polymers with a molecular weight of not less than 10000 Da, and the surfactant is at least one of anionic surfactants and alkyl polyether surfactants.

[0007] Further, in the additive for silicon wafer texturing provided by the present invention, the high molecular polymer with a molecular weight of not less than 10,000 Da is selected from polydimethyldiallylammonium chloride, polyacrylamide, polyethylene glycol, and arabic gum;

[0008] The corrosion inhibitor is selected from polyaspartic acid, sodium mercaptobenzothiazole, and catechol;

[0009] The anionic surfactant is selected from sodium dodecylbenzenesulfonate and sodium lignosulfonate;

[0010] The alkyl polyether surfactant is selected from alkyl glycoside and polyethylene glycol ether.

[0011] Further, in the additive for silicon wafer texturing provided by the present invention, the resistivity of the deionized water is greater than 18 MΩ.

[0012] On the other hand, the present invention relates to a reaction solution for silicon wafer texturing, which is obtained by mixing an alkali solution with a concentration of 1-3 wt% and the above-mentioned additive.

[0013] Further, in the reaction solution for silicon wafer texturing provided by the present invention, the volume ratio of the alkali solution to the additive is 100:0.1-5.

[0014] Further, in the reaction solution for silicon wafer texturing provided by the present invention, the alkali in the alkali solution is sodium hydroxide and / or potassium hydroxide.

[0015] On the other hand, the present invention relates to a method for silicon wafer texturing, including: pre-cleaning the silicon wafer, and then performing texturing after cleaning; the texturing includes: placing the silicon wafer in the above-mentioned reaction solution for reaction, the temperature of the reaction is 60-90 °C, and the time is 60 s-420 s.

[0016] On the other hand, the present invention relates to a silicon wafer with a terraced pyramid micro-structure, which is obtained by using the method for silicon wafer texturing.

[0017] Further, in the silicon wafer with a terraced pyramid micro-structure provided by the present invention, the reflectivity of the silicon wafer with a terraced pyramid micro-structure is 5-8%.

[0018] On the other hand, the present invention relates to the application of the above-mentioned additive or the above-mentioned reaction solution in silicon wafer texturing.

[0019] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0020] In the present invention, it is found that during the texturing of silicon wafers, since the adhesion ability of the adsorbent and inhibitor to the silicon wafer in pure water is less than that of water, the additives in the reaction tank are prone to detachment. Conventional texturing cannot interrupt the reaction process, resulting in the need to use at least two reaction tanks to achieve the final texturing purpose. Although two-step texturing can improve efficiency, it requires an increase in production costs, and some manufacturers also need to modify the texturing machine to achieve it. By changing the additives, the present invention makes conventional texturing change from two-step texturing to one-step texturing without changing the texturing effect, and a silicon wafer with a stepped pyramid microstructure is prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 It is the surface pyramid morphology of the silicon wafer obtained in the first reaction tank in Example 1.

[0023] Figure 2 It is the surface pyramid morphology of the silicon wafer obtained in the second reaction tank in Example 1.

[0024] Figure 3 It is the surface pyramid morphology of the silicon wafer obtained in Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] Next, the technical solutions of the present invention will be described in conjunction with the embodiments. However, the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified. The % in the following embodiments is the mass percentage unless otherwise specified. The ratios in the following embodiments are mass ratios unless otherwise specified.

[0026] Example 1

[0027] This example provides a conventional texturing process.

[0028] Exemplarily, the specific process of the conventional texturing process is as follows:

[0029] Step 1: Place the single-crystal silicon wafer in a cleaning solution for cleaning; the cleaning solution contains 32% sodium hydroxide, 1.3% hydrogen peroxide, and the balance water; the cleaning temperature is 65°C, and the cleaning time is 2 minutes.

[0030] Step 2: Use the texturing solution to texture the cleaned silicon wafer to form a pyramid structure. The texturing solution is a mixture of 0.22 wt% sodium hydroxide solution and an additive (Xi'an Lanqiao New Energy Technology Co., Ltd., model LQ61-1) in a volume ratio of 400:1. The texturing temperature is 80 °C and the texturing time is 200 s, thus obtaining a silicon wafer with a pyramid structure formed on its surface through the conventional texturing process.

[0031] As Figure 1 shown, the surface of the formed pyramid is smooth and flat, without microstructures formed. At this time, the reflectivity is 11.0%.

[0032] Step 3: Put the single-crystalline silicon wafer processed in Step 2 into the cleaning solution for cleaning. The cleaning temperature is 65 °C and the cleaning time is 2 minutes.

[0033] Step 4: Add 0.22 wt% sodium hydroxide solution and an additive for reducing the reflectivity with microstructures to deionized water. The sodium hydroxide solution and the additive (additive for reducing the reflectivity with microstructures, Xi'an Lanqiao New Energy Technology Co., Ltd., model LQ61-2) are mixed in a volume ratio of 200:1 to form a reaction solution, and after dissolution, stir evenly.

[0034] Step 5: Place the single-crystalline silicon wafer obtained in Step 3 into the reaction solution in Step 4 for microstructural preparation. The temperature is 78 °C and the time is 120 s, thus obtaining a single-crystalline silicon wafer with a terraced pyramid single-crystalline silicon textured surface as Figure 2 shown.

[0035] The conventional low-reflectivity silicon wafer texturing production needs to be divided into two steps. The silicon wafer enters the first reaction tank for reaction for 200 - 400 s. After the reaction ends, the silicon wafer is put into the second reaction tank for reaction for 50 - 150 s, which has problems of multiple processes and long time.

[0036] Example 2

[0037] This example provides a one-step texturing process using a specific additive.

[0038] Step 1: Put the single-crystalline silicon wafer into the cleaning solution for cleaning; the cleaning solution contains 32% sodium hydroxide, 1.3% hydrogen peroxide, and the balance water; the cleaning temperature is 65 °C and the cleaning time is 2 minutes.

[0039] Step 2: Prepare an additive composed of 0.3% polydimethyldiallylammonium chloride, 0.1% polyaspartic acid, 0.1% sodium dodecylbenzenesulfonate, and the balance deionized water.

[0040] Step 3: Use the reaction solution to texture the cleaned silicon wafer to form a pyramid structure. The texturing temperature is 60 °C and the texturing time is 60 s; the reaction solution is a 1% sodium hydroxide solution and the volume ratio of the additive is 100:0.1.

[0041] Example 3

[0042] This example provides a one-step texturing process using specific additives.

[0043] Step 1: Place the monocrystalline silicon wafer in a cleaning solution for cleaning; the cleaning solution contains 32% sodium hydroxide, 1.3% hydrogen peroxide, and the balance water; the cleaning temperature is 65°C, and the cleaning time is 2 minutes.

[0044] Step 2: Prepare an additive composed of 0.3% polydimethyldiallylammonium chloride, 0.2% polyacrylamide, 0.1% polyaspartic acid, 0.2% sodium mercaptobenzothiazole, 0.1% sodium dodecylbenzenesulfonate, 0.3% sodium lignosulfonate, and the balance deionized water.

[0045] Step 3: Use the reaction solution to texture the cleaned silicon wafer to form a pyramid structure, the texturing temperature is 70°C, and the texturing time is 300 s; the reaction solution is a solution of 1% sodium hydroxide + 1% potassium hydroxide, and the volume ratio of the reaction solution to the additive is 100:1.

[0046] Example 4

[0047] This example provides a one-step texturing process using specific additives.

[0048] Step 1: Place the monocrystalline silicon wafer in a cleaning solution for cleaning; the cleaning solution contains 32% sodium hydroxide, 1.3% hydrogen peroxide, and the balance water; the cleaning temperature is 65°C, and the cleaning time is 2 minutes.

[0049] Step 2: Prepare an additive composed of 0.5% polyethylene glycol (molecular weight: 12000), 0.5% arabic gum (molecular weight: 220000), 0.5% sodium mercaptobenzothiazole, 0.5% catechol, 0.3% sodium dodecylbenzenesulfonate, 0.7% alkyl polyglycoside, and the balance deionized water.

[0050] Step 3: Use the reaction solution to texture the cleaned silicon wafer to form a pyramid structure, the texturing temperature is 90°C, and the texturing time is 420 s; the reaction solution is a 3% potassium hydroxide solution, and the volume ratio of the reaction solution to the additive is 100:5.

[0051] The parameters of the silicon wafers obtained in each example are shown in Table 1.

[0052] Table 1: Parameters of the silicon wafers obtained in each example

[0053]

[0054] As can be seen from Table 1, the present invention preferably realizes the texturing of silicon wafers through a reaction in one reaction tank, and under the premise of not changing the texturing effect, it changes the conventional two-step texturing into one-step texturing, and silicon wafers with terraced pyramid microstructures are prepared.

[0055] As described above, the basic principles, main features and advantages of the present invention are preferably described. The above embodiments and the description are only descriptions of the preferred embodiments of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the present invention.

Claims

1. A method for one-step texturing of a silicon wafer, comprising: The silicon wafer is pre-cleaned, and then texturing is performed after cleaning, wherein the texturing is a one-step texturing, including: placing the silicon wafer in a reaction solution for reaction, wherein the reaction temperature is 60-90° C., and the reaction time is 60s-420s; The reaction solution is obtained by mixing an alkaline solution with a concentration of 1-3 wt% and an additive; In terms of mass percentage, the additive is composed of: 0.3-1.0% of a template, 0.1-1.0% of a corrosion inhibitor, 0.1-1.0% of a surfactant, and the balance of deionized water; The template agent is at least one of high molecular polymers with a molecular weight of not less than 10000Da, and the surfactant is at least one of anionic surfactants and alkyl polyether surfactants; The high molecular weight polymer with a molecular weight of not less than 10000Da is selected from polydimethyldiallyl ammonium chloride, polyacrylamide, polyethylene glycol, and gum arabic; The corrosion inhibitor is selected from polyaspartic acid, sodium mercaptobenzothiazole, and catechol; The anionic surfactant is selected from sodium dodecylbenzene sulfonate and sodium lignin sulfonate; The alkyl polyether surfactant is selected from alkyl glycosides and polyethylene glycol ethers; The resistivity of the deionized water is greater than 18 MΩ.

2. The method according to claim 1, characterized in that The volume ratio of the alkaline solution to the additive is 100:0.1-5.

3. The method according to claim 1, characterized in that The alkali in the alkali solution is sodium hydroxide and / or potassium hydroxide.

4. The application of additives in one-step texturing of silicon wafers is characterized in that: In terms of mass percentage, the additive is composed of: 0.3-1.0% of a template, 0.1-1.0% of a corrosion inhibitor, 0.1-1.0% of a surfactant, and the balance of deionized water; The template agent is at least one of high molecular polymers with a molecular weight of not less than 10000Da, and the surfactant is at least one of anionic surfactants and alkyl polyether surfactants; The high molecular weight polymer with a molecular weight of not less than 10000Da is selected from polydimethyldiallyl ammonium chloride, polyacrylamide, polyethylene glycol, and gum arabic; The corrosion inhibitor is selected from polyaspartic acid, sodium mercaptobenzothiazole, and catechol; The anionic surfactant is selected from sodium dodecylbenzene sulfonate and sodium lignin sulfonate; The alkyl polyether surfactant is selected from alkyl glycosides and polyethylene glycol ethers; The resistivity of the deionized water is greater than 18 MΩ.

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