Texturing liquid and texturing method for monocrystalline PERC cells

Abstract

The present invention relates to a texturing liquid for a single crystal PERC cell and a texturing method thereof, and belongs to the technical field of solar cell manufacturing. The texturing liquid includes a first texturing liquid and a second texturing liquid; the first texturing liquid is composed of the following raw materials in weight percentage: 1%-2.5% of a KOH solution with a concentration of 45%, 0.3%-0.7% of a texturing additive, and the rest is deionized water; the texturing additive is composed of the following raw materials in weight percentage: deionized water, a texturing etchant, a complexing agent, molasses after clarification, a surfactant, and a defoaming agent; the second texturing liquid is composed of the following raw materials in weight percentage: 0.05%-0.1% of a KOH solution with a concentration of 45%, and the rest is deionized water. After texturing by the present invention, the conversion efficiency of the cell is improved, a small and uniform texturing surface is formed on the surface of the single crystal PERC cell, the reflectivity of the texturing surface is reduced, the use of chemicals is reduced, and costs are saved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell manufacturing, and in particular to a texturing liquid for a single crystal PERC cell and a texturing method thereof. Background Art

[0002] The photovoltaic industry is currently experiencing rapid growth. To reduce costs, silicon wafer manufacturers are beginning to trend towards thinner wafers. Some manufacturers are already using silicon wafers as thin as 140µm. Therefore, it is foreseeable that thin wafers will become the industry standard in the near future, with even thinner wafers likely to be used in photovoltaic cells. The cell manufacturing process includes multiple processes, including texturing, diffusion, SE, etching, oxidation, coating, laser processing, screen printing, and sintering. To minimize wafer weight throughout the entire manufacturing process, texturing, as the first step, presents technical challenges associated with wafer thinning. Texturing involves creating a "texture" on the silicon wafer surface through alkaline etching, increasing the wafer's absorption of sunlight and thereby improving cell efficiency. As we all know, higher cell efficiency leads to better power generation returns. This has prompted manufacturers to continuously optimize the wet texturing process to complement the alkaline etching process, minimizing texturing time while achieving lower etching depths and lower reflectivity, resulting in a superior surface "texture."

[0003] In the wet texturing process, since the texturing additives are limited by the reaction rate of the silicon wafer and the alkali, the growth rate of the velvet pyramids and the consumption of chemicals, the silicon wafer needs to reach a certain corrosion depth to achieve the complete growth of the pyramids or the optimization of the velvet. The more suitable velvet size that can be achieved by the existing texturing process is 1.5-3um. Even if some texturing processes can achieve rapid texturing in a shorter time, a certain amount of corrosion depth is required. Below this corrosion depth, the pyramids usually grow incompletely, resulting in the velvet size being too small (less than 1um) and the reflectivity being too high. Therefore, there is a need for a texturing process that can achieve rapid texturing under low damage layer conditions, with a suitable velvet size and low reflectivity, to contribute to the development of the industry.

[0004] In summary, how to develop a texturing process that can maintain the reflectivity of the textured surface and the conversion efficiency of the finished solar cell to reduce the thinning amount of texturing of single-crystal PERC solar cell silicon wafers and improve the texture removal rate is a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a texturing solution and texturing method for single crystal PERC cells. The technical solution is as follows:

[0006] In a first aspect, a texturing solution for a monocrystalline PERC cell is provided, wherein the texturing solution comprises a first texturing solution and a second texturing solution;

[0007] The first texturing solution is composed of the following raw materials in weight percentage: 1%-2.5% of a 45% KOH solution, 0.3%-0.7% of a texturing additive, and the remainder being deionized water;

[0008] The texturing additive is composed of the following raw materials: deionized water, a texturing etchant, a complexing agent, clarified molasses, a surfactant, and a defoaming agent; in the deionized water, the content of the texturing etchant is 3%-5%, the content of the complexing agent is 10%-22%, the content of the clarified molasses is 8%-15%, the content of the surfactant is 1%-8%, and the content of the defoaming agent is 0.8%-3%;

[0009] The second texturing solution is composed of the following raw materials in percentage by weight: 0.05%-0.1% of a 45% KOH solution, and the remainder is deionized water.

[0010] Optionally, the weight percentage of the KOH solution in the first texturing liquid is 1.36%, and the weight percentage of the texturing additive is 0.42%; the weight percentage of the KOH solution in the second texturing liquid is 0.07%.

[0011] Optionally, the molasses is beet molasses.

[0012] Optionally, the surfactant is a fluorosurfactant.

[0013] In a second aspect, a texturing method for a monocrystalline PERC cell is provided, comprising the following steps:

[0014] S1. Prepare a first texturing liquid and a second texturing liquid according to the following weight percentages: the first texturing liquid is composed of the following raw materials in weight percentages: 1%-2.5% of a 45% KOH solution, 0.3%-0.7% of a texturing additive, and the remainder being deionized water; the texturing additive is composed of the following raw materials: deionized water, a texturing etchant, a complexing agent, clarified molasses, a surfactant, and a defoaming agent; in the deionized water, the content of the texturing etchant is 3%-5%, the content of the complexing agent is 10%-22%, the content of the clarified molasses is 8%-15%, the content of the surfactant is 1%-8%, and the content of the defoaming agent is 0.8%-3%; the second texturing liquid is composed of the following raw materials in weight percentages: 0.05%-0.1% of a 45% KOH solution, and the remainder being deionized water;

[0015] S2, primary texturing: Place the monocrystalline PERC solar cell silicon wafer in the first texturing solution for reaction at a temperature of 80-82°C for 400-440 seconds, and control the texturing corrosion amount to 0.2-0.3g / pcs;

[0016] S3, secondary texturing: Place the monocrystalline PERC solar cell silicon wafer after the primary texturing in the second texturing solution for reaction at a temperature of 54-56°C for 100-110 seconds, and control the texturing corrosion amount to 0.01-0.02g / pcs;

[0017] S4, water washing;

[0018] S5, pickling;

[0019] S6, water washing;

[0020] S7, drying.

[0021] Optionally, during the pickling step S5: the monocrystalline PERC cell silicon wafer is immersed in a mixed aqueous solution of 12% by mass HF and 7% by mass HCl at a temperature of 15-30° C. for 170-190 seconds.

[0022] Optionally, during the water washing in S4 and S6, the monocrystalline PERC solar cell silicon wafer is immersed in flowing deionized water for 70-100 seconds.

[0023] Optionally, the thickness of the monocrystalline PERC cell silicon wafer is 140-160 μm.

[0024] All the above optional technical solutions can be combined arbitrarily, and the present invention does not provide detailed descriptions of the structures after each combination.

[0025] By means of the above solution, the beneficial effects of the present invention are as follows:

[0026] By setting the first texturing liquid and the second texturing liquid and dividing the texturing into primary texturing and secondary texturing, and on the basis of optimizing the texturing process (controlling the reaction temperature, time and texturing corrosion amount), the texturing process of the single crystal PERC cell silicon wafer is completed. On the basis of reducing the texturing corrosion amount and controlling the texturing corrosion amount to 0.2-0.3g / pcs, the production line compatibility and normal appearance of the cell are achieved, the conversion efficiency of the finished cell is improved, and a small and uniform velvet surface is formed on the surface of the single crystal PERC cell, which improves the velvet yield rate, reduces the reflectivity of the velvet surface, reduces the use of chemicals, and saves costs.

[0027] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the texturing method for the single crystal PERC battery provided by the present invention. DETAILED DESCRIPTION

[0029] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0030] Example 1

[0031] The texturing liquid for a monocrystalline PERC cell provided in an embodiment of the present invention includes a first texturing liquid and a second texturing liquid;

[0032] The first texturing solution is composed of the following raw materials in weight percentage: 1% of a 45% KOH solution, 0.3% of a texturing additive, and the remainder being deionized water; the texturing additive is composed of the following raw materials: deionized water, a texturing etchant, a complexing agent, clarified molasses, a surfactant, and a defoaming agent; in the deionized water, the content of the texturing etchant is 3%, the content of the complexing agent is 10%, the content of the clarified molasses is 8%, the content of the surfactant is 1%, and the content of the defoaming agent is 0.8%;

[0033] The second texturing solution is composed of the following raw materials in percentage by weight: 0.05% of a 45% KOH solution, and the remainder is deionized water.

[0034] Optionally, the molasses is beet molasses, and the surfactant is a fluorosurfactant. The main component of the complexing agent is sodium nitrilotriacetate (NTA), and the main component of the fluorosurfactant is perfluoropolyethylene ether.

[0035] The texturing method of the monocrystalline PERC cell provided in this embodiment includes the following steps when texturing the monocrystalline PERC cell:

[0036] S1, preparing a first texturing liquid and a second texturing liquid according to the above weight percentages.

[0037] S2, one-time texturing: Place the monocrystalline PERC cell silicon wafer in the first texturing solution for reaction at a temperature of 80-82°C for 400-440s, and control the texturing corrosion amount to 0.2-0.3g / pcs.

[0038] S3, secondary texturing: Place the monocrystalline PERC cell silicon wafer after the primary texturing in the second texturing solution for reaction. The reaction temperature is 54℃-56℃, the reaction time is 100-110s, and the texturing corrosion amount is controlled to 0.01-0.02g / pcs.

[0039] S4, water washing.

[0040] S5, pickling.

[0041] Specifically, during the pickling step S5: the monocrystalline PERC cell silicon wafer is immersed in a mixed aqueous solution of 12% by mass HF and 7% by mass HCl at a temperature of 15-30° C. for 170-190 seconds.

[0042] S6, water washing.

[0043] Specifically, during the water washing in S4 and S6, the monocrystalline PERC cell silicon wafer is immersed in flowing deionized water for 70-100 seconds.

[0044] S7, drying: The drying step is to dry in an oven at a temperature of 85°C-95°C for 450-480 seconds.

[0045] Example 2

[0046] The texturing liquid for a single crystal PERC cell provided in an embodiment of the present invention includes a first texturing liquid and a second texturing liquid;

[0047] The first texturing solution is composed of the following raw materials in weight percentage: 2.5% of a 45% KOH solution, 0.7% of a texturing additive, and the remainder being deionized water; the texturing additive is composed of the following raw materials: deionized water, a texturing etchant, a complexing agent, clarified molasses, a surfactant, and a defoaming agent; in the deionized water, the content of the texturing etchant is 5%, the content of the complexing agent is 22%, the content of the clarified molasses is 15%, the content of the surfactant is 8%, and the content of the defoaming agent is 3%;

[0048] The second texturing solution is composed of the following raw materials in percentage by weight: 0.1% of a KOH solution having a concentration of 45%, and the remainder being deionized water.

[0049] Optionally, the molasses is beet molasses, and the surfactant is a fluorosurfactant. The main component of the complexing agent is sodium nitrilotriacetate (NTA), and the main component of the fluorosurfactant is perfluoropolyethylene ether.

[0050] The texturing method of the monocrystalline PERC cell provided in this embodiment includes the following steps when texturing the monocrystalline PERC cell:

[0051] S1, preparing a first texturing liquid and a second texturing liquid according to the above weight percentages.

[0052] S2, one-time texturing: Place the monocrystalline PERC cell silicon wafer in the first texturing solution for reaction at a temperature of 80-82°C for 400-440s, and control the texturing corrosion amount to 0.2-0.3g / pcs.

[0053] S3, secondary texturing: Place the monocrystalline PERC cell silicon wafer after the primary texturing in the second texturing solution for reaction. The reaction temperature is 54℃-56℃, the reaction time is 100-110s, and the texturing corrosion amount is controlled to 0.01-0.02g / pcs.

[0054] S4, water washing.

[0055] S5, pickling.

[0056] Specifically, during the pickling step S5: the monocrystalline PERC cell silicon wafer is immersed in a mixed aqueous solution of 12% by mass HF and 7% by mass HCl at a temperature of 15-30° C. for 170-190 seconds.

[0057] S6, water washing.

[0058] Specifically, during the water washing in S4 and S6, the monocrystalline PERC cell silicon wafer is immersed in flowing deionized water for 70-100 seconds.

[0059] S7, drying: The drying step is to dry in an oven at a temperature of 85°C-95°C for 450-480 seconds.

[0060] Example 3

[0061] The texturing liquid for a monocrystalline PERC cell provided in an embodiment of the present invention includes a first texturing liquid and a second texturing liquid;

[0062] The first texturing solution is composed of the following raw materials in weight percentage: 1.75% of a 45% KOH solution, 0.5% of a texturing additive, and the remainder being deionized water; the texturing additive is composed of the following raw materials: deionized water, a texturing etchant, a complexing agent, clarified molasses, a surfactant, and a defoaming agent; the content of the texturing etchant in the deionized water is 4%, the content of the complexing agent is 15.5%, the content of the clarified molasses is 11.5%, the content of the surfactant is 4.5%, and the content of the defoaming agent is 1.9%;

[0063] The second texturing solution is composed of the following raw materials in percentage by weight: 0.075% of a KOH solution having a concentration of 45%, and the remainder being deionized water.

[0064] Optionally, the molasses is beet molasses, and the surfactant is a fluorosurfactant. The main component of the complexing agent is sodium nitrilotriacetate (NTA), and the main component of the fluorosurfactant is perfluoropolyethylene ether.

[0065] The texturing method of the monocrystalline PERC cell provided in this embodiment includes the following steps when texturing the monocrystalline PERC cell:

[0066] S1, preparing a first texturing liquid and a second texturing liquid according to the above weight percentages.

[0067] S2, one-time texturing: Place the monocrystalline PERC cell silicon wafer in the first texturing solution for reaction at a temperature of 80-82°C for 400-440s, and control the texturing corrosion amount to 0.2-0.3g / pcs.

[0068] S3, secondary texturing: Place the monocrystalline PERC cell silicon wafer after the primary texturing in the second texturing solution for reaction. The reaction temperature is 54℃-56℃, the reaction time is 100-110s, and the texturing corrosion amount is controlled to 0.01-0.02g / pcs.

[0069] S4, water washing.

[0070] S5, pickling.

[0071] Specifically, during the pickling step S5: the monocrystalline PERC cell silicon wafer is immersed in a mixed aqueous solution of 12% by mass HF and 7% by mass HCl at a temperature of 15-30° C. for 170-190 seconds.

[0072] S6, water washing.

[0073] Specifically, during the water washing in S4 and S6, the monocrystalline PERC cell silicon wafer is immersed in flowing deionized water for 70-100 seconds.

[0074] S7, drying: The drying step is to dry in an oven at a temperature of 85°C-95°C for 450-480 seconds.

[0075] Example 4

[0076] The texturing liquid for a single crystal PERC cell provided in an embodiment of the present invention includes a first texturing liquid and a second texturing liquid;

[0077] The first texturing solution is composed of the following raw materials in weight percentage: 1.36% of a 45% KOH solution, 0.42% of a texturing additive, and the remainder being deionized water; the texturing additive is composed of the following raw materials: deionized water, a texturing etchant, a complexing agent, clarified molasses, a surfactant, and a defoaming agent; the content of the texturing etchant in the deionized water is 4.2%, the content of the complexing agent is 18%, the content of the clarified molasses is 10%, the content of the surfactant is 6%, and the content of the defoaming agent is 2.2%;

[0078] The second texturing solution is composed of the following raw materials in percentage by weight: 0.07% of a KOH solution having a concentration of 45%, and the remainder being deionized water.

[0079] Optionally, the molasses is beet molasses, and the surfactant is a fluorosurfactant. The main component of the complexing agent is sodium nitrilotriacetate (NTA), and the main component of the fluorosurfactant is perfluoropolyethylene ether.

[0080] The texturing method of the monocrystalline PERC cell provided in this embodiment includes the following steps when texturing the monocrystalline PERC cell:

[0081] S1, preparing a first texturing liquid and a second texturing liquid according to the above weight percentages.

[0082] S2, one-time texturing: Place the monocrystalline PERC cell silicon wafer in the first texturing solution for reaction at a temperature of 80-82°C for 400-440s, and control the texturing corrosion amount to 0.2-0.3g / pcs.

[0083] S3, secondary texturing: Place the monocrystalline PERC cell silicon wafer after the primary texturing in the second texturing solution for reaction. The reaction temperature is 54℃-56℃, the reaction time is 100-110s, and the texturing corrosion amount is controlled to 0.01-0.02g / pcs.

[0084] S4, water washing.

[0085] S5, pickling.

[0086] Specifically, during the pickling step S5: the monocrystalline PERC cell silicon wafer is immersed in a mixed aqueous solution of 12% by mass HF and 7% by mass HCl at a temperature of 15-30° C. for 170-190 seconds.

[0087] S6, water washing.

[0088] Specifically, during the water washing in S4 and S6, the monocrystalline PERC cell silicon wafer is immersed in flowing deionized water for 70-100 seconds.

[0089] S7, drying: The drying step is to dry in an oven at a temperature of 85°C-95°C for 450-480 seconds.

[0090] In order to verify the performance of the single crystal PERC cell obtained by texturing in Example 4, this example also provides the following comparative example 1.

[0091] Comparative Example 1

[0092] A texturing method for a monocrystalline PERC cell comprises the following steps:

[0093] Preparation of velveting liquid:

[0094] The texturing additive comprises 1.82% KOH solution, 0.58% texturing additive, and the remainder deionized water. The texturing additive is composed of the following raw materials: deionized water, a texturing etchant, a complexing agent, clarified molasses, a surfactant, and a defoamer. The texturing etchant content in the deionized water is 3% to 5%, the complexing agent content in the solution is 10% to 22%, the clarified molasses content is 8% to 15%, the surfactant concentration is 1% to 8%, and the defoamer content is 0.8% to 3%.

[0095] (1) Place the monocrystalline PERC solar cell silicon wafer (thickness 140-160μm) with the same wafer source (Meike silicon wafer) and the same production line as Example 4 in the texturing solution of the above-mentioned comparative example 1 for texturing, and control the texturing corrosion amount to 0.3-0.4g / pcs; (2) After water washing, acid washing, water washing, and drying, the texturing process is completed. The texturing corrosion amount is 0.3-0.4mg / cm 2 The corrosion rate of Example 4 is 0.2-0.3 mg / cm 2 .

[0096] The comparison results of the electrical performance of the single crystal PERC cell after texturing in Example 4 and Comparative Example 1 are shown in Table 1.

[0097] Table 1

[0098] Electrical properties Eta Uoc Isc FF Rs Rsh IRev2 Example 1 23.223 0.6892 13.466 82.61 0.00068 192.93 0.133 Comparative Example 1 23.202 0.6897 13.453 82.55 0.00072 209.44 0.123 Gain (%) 0.020 -0.0005 0.013 0.05 -0.00004 -16.51 0.010

[0099] As shown in Table 1, Example 4 achieved an efficiency gain of 0.020% compared to Comparative Example 1, primarily due to an Isc gain of 13 mA. Other electrical properties were comparable. Comparing the textured surface produced in Example 4 with that produced in Comparative Example 1 revealed that the finished monocrystalline PERC cell produced in Example 4 had a superior textured surface and no abnormalities in the cell's appearance.

[0100] Example 5

[0101] The present invention also provides Example 5, in which the silicon wafer in Example 4 is replaced by a wafer sourced from (GCL silicon wafer), and other technical solutions are the same as those in Example 4; and a comparative example 2 is provided, in which, except that the wafer source is (GCL silicon wafer), other technical solutions are the same as those in Comparative Example 1;

[0102] The comparison results of the electrical performance of the single crystal PERC cells after texturing in Example 5 and Comparative Example 2 are shown in Table 2.

[0103] Table 2

[0104] Electrical properties Eta Uoc Isc FF Rs Rsh IRev2 Example 2 23.170 0.6880 13.409 82.92 0.00043 265.18 0.068 Comparative Example 2 23.139 0.6883 13.383 82.93 0.00042 291.61 0.057 Gain (%) 0.032 -0.0003 0.026 -0.01 0.00001 -26.43 0.011

[0105] As shown in Table 2, Example 5 has an efficiency gain of 0.032% compared with Comparative Example 2, which is mainly reflected in the 26mA increase in Isc. Other electrical properties are comparable.

[0106] In addition, after texturing using the texturing liquid and texturing method provided in the embodiments of the present invention, the obtained single-crystal PERC battery is compatible with the production line, has no abnormal appearance, has reduced texturing corrosion, and saves on chemical usage, as shown in the chemical consumption comparison table of Example 4 and Comparative Example 1 shown in Table 3 below.

[0107] Table 3

[0108]

[0109]

[0110] As shown in Table 3, Example 4 saves 0.172 ml of KOH solution per piece compared with Comparative Example 1, with a saving rate of 10.92%. The texturing additive saves 0.109 ml per piece, with a saving rate of 22.61%.

[0111] Preferably, the thickness of the monocrystalline PERC cell silicon wafer is 140-160 μm. In other words, the present invention is particularly suitable for texturing monocrystalline PERC cells with thin silicon substrates.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A texturing method for a single crystal PERC cell, characterized in that: The steps include: S1. Prepare a first texturing liquid and a second texturing liquid according to the following weight percentages: the first texturing liquid is composed of the following raw materials in weight percentages: 1%-2.5% of a 45% KOH solution, 0.3%-0.7% of a texturing additive, and the remainder being deionized water; the texturing additive is composed of the following raw materials: deionized water, a texturing etchant, a complexing agent, clarified molasses, a surfactant, and a defoaming agent; in the deionized water, the content of the texturing etchant is 3%-5%, the content of the complexing agent is 10%-22%, the content of the clarified molasses is 8%-15%, the content of the surfactant is 1%-8%, and the content of the defoaming agent is 0.8%-3%; the second texturing liquid is composed of the following raw materials in weight percentages: 0.05%-0.1% of a 45% KOH solution, and the remainder being deionized water; the complexing agent includes sodium nitrilotriacetate; the molasses is beet molasses; S2, primary texturing: Place the monocrystalline PERC solar cell silicon wafer in the first texturing solution for reaction at a temperature of 80-82°C for 400-440 seconds, and control the texturing corrosion amount to 0.2-0.3g / pcs; S3, secondary texturing: Place the monocrystalline PERC solar cell silicon wafer after the primary texturing in the second texturing solution for reaction at a temperature of 54-56°C for 100-110 seconds, and control the texturing corrosion amount to 0.01-0.02g / pcs; S4, water washing; S5, pickling; S6, water washing; S7, drying.

2. The texturing method for a single crystal PERC cell according to claim 1, characterized in that: During the pickling step of S5, the monocrystalline PERC cell silicon wafer is immersed in a mixed aqueous solution of 12% by mass HF and 7% by mass HCl at a temperature of 15-30° C. for 170-190 seconds.

3. The texturing method for a single crystal PERC cell according to claim 1 or 2, characterized in that: During the water washing in S4 and S6, the monocrystalline PERC solar cell silicon wafer is immersed in flowing deionized water for 70-100 seconds.

4. The texturing method for a single crystal PERC cell according to claim 1 or 2, characterized in that: The thickness of the monocrystalline PERC cell silicon wafer is 140-160 μm.

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