Micro-nano bubble assisted alkali texturing method and system

Abstract

The invention belongs to the technical field of solar energy manufacturing, and particularly relates to a micro-nano bubble assisted alkali texturing method and system, and the method comprises the following steps: S1, taking an original silicon wafer, carrying out the pre-cleaning and water washing treatment, preparing an alkali texturing liquid medicine, and heating the liquid medicine to 65-90 DEG C; s2, starting a micro-nano bubble generator, mixing an air source with the alkali texturing liquid medicine in the micro-nano bubble generator to prepare micro-nano bubble water, and continuously introducing the micro-nano bubble water into the bottom of the alkali texturing tank through a pipeline; s3, immersing the original silicon wafer treated in the step S1 into an alkali texturing groove, and fully corroding to finish texturing; and S4, taking out the textured silicon wafer, and sequentially carrying out alkali washing, acid washing, water washing and drying.

Description

Technical Field

[0001] This invention belongs to the field of solar energy manufacturing technology, specifically relating to a method and system for alkaline texturing assisted by micro-nano bubbles. Background Technology

[0002] Solar photovoltaic (PV) power generation is one of the fastest-growing and most promising renewable energy industries. Silicon wafers are the core component in PV technology, and the production process from silicon wafers to solar cells requires multiple steps. Texturing is a crucial step in the cell manufacturing process.

[0003] Traditional alkaline texturing involves using anisotropic alkaline etching solutions to create a textured surface on a silicon wafer through controlled chemical reactions. This textured surface effectively reduces the reflectivity of sunlight, thereby increasing the battery's absorption of light energy and improving its short-circuit current and final conversion efficiency.

[0004] However, traditional alkaline texturing has several problems: hydrogen (H2) bubbles, a byproduct of the reaction, easily adhere to the silicon wafer surface, forming a gas film that hinders the corrosion reaction, leading to uneven texture or appearance, especially when creating low-reflectivity textured structures. Conventional methods such as bubbling and pump circulation are difficult to effectively and uniformly remove the attached hydrogen bubbles and may damage the silicon wafer. With increasing production capacity demands, texturing tanks are becoming larger and the tooth spacing of the basket carriers is becoming smaller, creating concentration and temperature gradients in the solution within the tank, which affects the uniformity of texturing. These problems result in large dispersion in the size distribution of the textured structure within the solar cell and a wide range of reflectivity fluctuations, ultimately leading to a decrease in the average conversion efficiency (Eta) and a deterioration in the uniformity of efficiency distribution, resulting in yield losses.

[0005] Therefore, overcoming the unevenness of the pile surface in the existing alkali pile forming process is a technical problem that urgently needs to be solved in this field.

[0006] It should be noted that the information disclosed in this background section is only for understanding the background technology of the present application concept, and therefore, the above description is not considered to constitute prior art information. Summary of the Invention

[0007] This disclosure provides at least one method and system for alkali texturing assisted by micro / nano bubbles.

[0008] In a first aspect, this disclosure provides a method for alkaline texturing assisted by micro-nano bubbles, comprising the following steps: S1, taking a raw silicon wafer for pre-cleaning and water washing, preparing an alkaline texturing solution and heating it to 65-90°C; S2, starting a micro-nano bubble generator, mixing the gas source and the alkaline texturing solution in the micro-nano bubble generator to prepare micro-nano bubble water, which is then continuously introduced into the bottom of the alkaline texturing tank through a pipeline; S3, immersing the raw silicon wafer treated in S1 into the alkaline texturing tank for thorough etching to complete texturing; S4, removing the texturized silicon wafer and sequentially performing post-alkaline washing, acid washing, water washing, and drying; wherein, the rising speed of the micro-nano bubbles is not higher than 0.5 cm / min, and the internal pressure of the micro-nano bubbles is not lower than 0.3 atmospheres.

[0009] In one optional embodiment, the micro-nano bubble generator produces micro-nano bubbles with a diameter range of 50 nm to 100 μm, and the concentration of the micro-nano bubbles is 10^5 to 10^8 bubbles / ml.

[0010] In one optional embodiment, the gas source includes any one or more of the following mixed gases: air, nitrogen, oxygen, and ozone, and the gas flow rate is 0.1 to 5 L / min.

[0011] In one optional embodiment, the concentration of the alkaline flossing solution is 0.1–5 wt%.

[0012] In one optional embodiment, the corrosion time in S3 is 1 to 40 minutes.

[0013] In one optional embodiment, the heating temperature of the alkaline flossing solution in S1 is preferably 70-85°C.

[0014] In one optional embodiment, the diameter of the micro-nano bubbles is preferably 100 nm to 50 μm, and the concentration is preferably 10^7 bubbles / ml.

[0015] In one optional embodiment, the gas flow rate is preferably 0.5 to 1.5 L / min.

[0016] Secondly, this disclosure also provides a micro-nano bubble-assisted alkali texturing system, comprising: a micro-nano bubble generator and an alkali texturing tank connected by pipelines; the micro-nano bubble generator has inlets for alkali texturing liquid and gas source.

[0017] In one alternative implementation, the gas source has its flow rate regulated by a gas control unit.

[0018] The beneficial effects of this invention are that the micro-nano bubble-assisted alkaline texturing method and system utilize the high mass transfer efficiency and ultra-slow rise rate of micro-nano bubbles to form higher dissolved oxygen content and higher specific surface area. In the alkaline texturing reaction, the reaction solution can be more evenly dispersed, and the gas-liquid-solid interface between the solution and the silicon wafer can form better contact, thereby obtaining a more uniform textured surface structure and appearance after texturing. In addition, during the alkaline texturing process, the reaction between silicon and alkaline solution releases hydrogen gas. Through the synergistic effect of micro-nano bubbles with the microstructure on the silicon wafer surface, a superhydrophobic interface and surface negative charge repulsion can be formed, promoting the rapid detachment of hydrogen bubbles from the surface, reducing interference with the corrosion reaction, and further improving the uniformity of the textured surface.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0022] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0023] In this document, as used herein, expressions such as “at least one of…” modify the entire list of elements when following a list of elements, rather than individual elements in the list. For example, the expression “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0024] The terminology used herein is for the purpose of describing specific exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may also be intended to include plural forms unless otherwise clearly stated herein. The terms “comprising,” “including,” and “having” are inclusive and thus specify the presence of features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the specific order discussed or shown, unless specifically identified as such. Additional or alternative steps may be employed.

[0025] The following describes some embodiments of the present invention in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] This disclosure provides a method for alkaline texturing assisted by micro-nano bubbles, comprising the following steps: S1, taking a raw silicon wafer for pre-cleaning and water washing, preparing an alkaline texturing solution and heating it to 65-90°C; S2, starting a micro-nano bubble generator, mixing the gas source and the alkaline texturing solution in the micro-nano bubble generator to prepare micro-nano bubble water, which is then continuously introduced into the bottom of the alkaline texturing tank through a pipeline; S3, immersing the raw silicon wafer treated in S1 into the alkaline texturing tank for thorough etching to complete texturing; S4, removing the texturized silicon wafer and sequentially performing post-alkaline washing, acid washing, water washing, and drying; wherein, the rising speed of the micro-nano bubbles is not higher than 0.5 cm / min, and the internal pressure of the micro-nano bubbles is not lower than 0.3 atmospheres.

[0027] Specifically, micro- and nano-bubbles act as dynamic media in the texturing solution. Their high specific surface area and surface energy enhance gas-liquid mass transfer efficiency and promote the reaction between the alkaline etching solution (NaOH or KOH) and the silicon wafer surface. The micro-jet scouring effect generated by bubble collapse strengthens anisotropic etching characteristics and accelerates the formation of pyramid structures. The slow rising characteristics of micro- and nano-bubbles allow them to remain suspended in the texturing solution for a long time, providing ample time for the diffusion and detachment of hydrogen bubbles. Simultaneously, the self-pressurization effect of micro- and nano-bubbles drives the continuous dissolution of gas into the water, accelerating the contraction and detachment of hydrogen bubbles.

[0028] Specifically, micro- and nano-bubbles are uniformly dispersed in the texturing solution and move slowly with circulation. This characteristic avoids the uneven corrosion problem caused by local differences in solution concentration in traditional processes, ensuring the consistency of the texturing structure between silicon wafers and within single-crystal silicon wafers.

[0029] Specifically, during the alkaline texturing process, the reaction between silicon and alkali releases hydrogen gas. In traditional processes, large hydrogen bubbles tend to adhere to the silicon wafer surface, forming shielding areas and leading to uneven corrosion. Micro- and nano-bubbles, through synergistic interaction with the microstructure of the silicon wafer surface, can form a superhydrophobic interface and a repulsive effect from the negative charge on the surface. The surface of the micro- and nano-bubbles adsorbs OH groups... - The ions, carrying a negative charge, form a stable electric double layer structure. This dense arrangement at the gas-liquid interface significantly reduces surface tension, weakening the adhesion between hydrogen bubbles and the silicon wafer interface. According to the Yang-Laplace equation, the reduction in surface tension directly decreases the critical buoyancy required for bubble detachment, making it easier for hydrogen bubbles to desorb from the silicon wafer surface, reducing interference with the corrosion reaction, and improving the uniformity of the textured surface.

[0030] Specifically, micro- and nanobubbles possess an enormous specific surface area; a 10μm bubble has a specific surface area 100 times that of a 1mm bubble. This vast specific surface area provides an ample interface for gas-liquid mass transfer, significantly enhancing the mass transfer efficiency of oxygen and hydrogen at the gas-liquid interface. When micro- and nanobubbles approach a silicon wafer, oxygen within the bubbles escapes and reacts with the silicon in an oxidation reaction. Simultaneously, the hydrogen produced during this reaction is absorbed or reacted by the oxygen within the micro- and nanobubbles, accelerating the forward reaction. This selective acceleration creates a rougher, textured surface on the silicon wafer, further reducing the reflectivity of the textured surface to light.

[0031] In some embodiments, specifically, the diameter of the micro-nano bubbles generated by the micro-nano bubble generator ranges from 50 nm to 100 μm, and the concentration of the micro-nano bubbles is 10^5 to 10^8 bubbles / ml.

[0032] In some embodiments, specifically, the gas source includes any one or more of the following mixed gases: air, nitrogen, oxygen, and ozone, and the gas flow rate is 0.1 to 5 L / min.

[0033] In some embodiments, specifically, the concentration of the alkaline flossing solution is 0.1–5 wt%.

[0034] In some embodiments, specifically, the corrosion time in S3 is 1 to 40 minutes.

[0035] In some embodiments, specifically, the heating temperature of the alkaline flossing solution in S1 is preferably 70-85°C.

[0036] In some embodiments, specifically, the diameter of the micro-nano bubbles is preferably 100 nm to 50 μm, and the concentration is preferably 10^7 bubbles / ml.

[0037] In some embodiments, specifically, the gas flow rate is preferably 0.5 to 1.5 L / min.

[0038] This disclosure also provides a system for alkali texturing assisted by micro-nano bubble, comprising: a micro-nano bubble generator and an alkali texturing tank connected by pipelines; the micro-nano bubble generator has inlets for alkali texturing liquid and gas source.

[0039] In some embodiments, specifically, the gas source has its flow rate regulated by a gas control unit.

[0040] Example 1:

[0041] Conditions: N2 gas was used, with an average bubble diameter of 100 nm, a concentration of 1.5 x 10^7 bubbles / mL, and a flow rate of 0.5 L / min. The NaOH concentration was 2%, the temperature was 80 °C, and the time was 25 minutes.

[0042] According to the formula for specific surface area, S / V = 3 / r (where r is the bubble radius), the specific surface area of ​​a bubble is inversely proportional to its radius. Theoretically, a 100nm (0.1μm) bubble has 10,000 times the specific surface area of ​​a 1mm bubble of the same volume.

[0043] Results: The surface texture was uniform, the appearance was normal, the average reflectivity was 9.8%, the photoelectric conversion efficiency of the solar cells was 0.048% higher than that of the control group, and the short-circuit current (Isc) was 0.031A higher than that of the control group.

[0044] Comparative Example 1:

[0045] Conditions: Same texturing solution and parameters, but without introducing micro / nano bubbles.

[0046] Results: The size of the velvet surface is slightly uneven, with an average reflectance of 11.2%.

[0047] Specifically, the results of Example 1 and Comparative Example 1 are shown in Table 1.

[0048] Table 1

[0049] Eta Uoc Isc Rser FF Rsh IRev2 quantity Example 1 26.762％ 0.7388 14.110 0.0021 85.93 1514 0.038 1820 Comparative Example 1 26.714％ 0.7388 14.079 0.0021 85.96 1462 0.025 2661 Difference 0.048％ 0.00 0.031 0.00 -0.03 52 0.013

[0050] Specifically, in the table, Eta refers to conversion efficiency, Uoc refers to open-circuit voltage (V), Isc refers to short-circuit current (A), Rser refers to contact resistance (Ω), FF refers to fill factor, Rsh refers to parallel resistance (Ω), and Irev2 refers to leakage current (A). If they appear again in the following text, they have the same meaning as they do here.

[0051] Example 2:

[0052] Conditions: N2 gas was used, with an average bubble diameter of 1 μm, a concentration of 1.3 x 10^7 bubbles / mL, and a flow rate of 1.0 L / min. The NaOH concentration was 2%, the temperature was 80 °C, and the time was 25 minutes.

[0053] Specifically, the specific surface area of ​​micro / nano bubbles with a particle size of 1 μm is approximately 6000 m². 2 / m 3 .

[0054] Results: The surface was uniform with no white spots, the average reflectivity was 10.3%, the photoelectric conversion efficiency of the solar cell was 0.032% higher than that of the control group, and the short-circuit current (Isc) was 0.014A higher than that of the control group.

[0055] Comparative Example 2:

[0056] Conditions: Same texturing solution and parameters, but without introducing micro / nano bubbles.

[0057] Results: The size of the velvet surface is slightly uneven, with an average reflectance of 11%.

[0058] Specifically, the results of Example 2 and Comparative Example 2 are shown in Table 2.

[0059] Table 2

[0060] Eta Uoc Isc Rser FF Rsh IRev2 quantity Example 2 26.776％ 0.7386 14.122 0.002 85.88 861 0.041 2017 Comparative Example 2 26.744％ 0.7385 14.108 0.002 85.86 807 0.048 2092 Difference 0.032％ 0.00 0.014 0.00 0.02 54 -0.007

[0061] Example 3:

[0062] Conditions: N2 gas was used, with an average bubble diameter of 50 μm, a concentration of 4.2 x 10^6 bubbles / mL, and a flow rate of 1.0 L / min. The NaOH concentration was 2%, the temperature was 80 °C, and the time was 25 minutes.

[0063] Results: The surface was uniform with no white spots, the average reflectivity was 10.5%, the photoelectric conversion efficiency of the solar cell was 0.022% higher than that of the control group, and the short-circuit current (Isc) was 0.01A higher than that of the control group.

[0064] Comparative Example 3:

[0065] Conditions: Same texturing solution and parameters, but without introducing micro / nano bubbles.

[0066] Results: The size of the velvet surface is slightly uneven, with an average reflectance of 11%.

[0067] Specifically, the results of Example 3 and Comparative Example 3 are shown in Table 3.

[0068] Table 3

[0069] Eta Uoc Isc Rser FF Rsh IRev2 quantity Example 3 26.773％ 0.7385 14.094 0.0019 86.090 1776 0.043 2055 Comparative Example 3 26.751％ 0.7387 14.084 0.0019 86.040 1697 0.034 1955 Difference 0.022％ 0.00 0.01 0.00 0.05 79 0.009

[0070] In summary, this micro / nano bubble-assisted alkaline texturing method and system utilizes the high mass transfer efficiency and ultra-slow rise rate of micro / nano bubbles to generate higher dissolved oxygen content and higher specific surface area. In the alkaline texturing reaction, this allows the reaction solution to be more uniformly dispersed, and at the same time, it forms better contact between the solution and the gas-liquid-solid interface of the silicon wafer, thereby obtaining a more uniform textured surface structure and appearance after texturing. In addition, during the alkaline texturing process, the reaction between silicon and alkaline solution releases hydrogen gas. Through synergistic interaction with the microstructure on the silicon wafer surface, micro / nano bubbles can form a superhydrophobic interface and a surface negative charge repulsion effect, promoting the rapid detachment of hydrogen microbubbles from the surface, reducing interference with the corrosion reaction, and further improving the uniformity of the textured surface.

[0071] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for alkali texturing assisted by micro / nano bubbles, characterized in that, Includes the following steps: S1, take the original silicon wafer for pre-cleaning and water washing, prepare alkaline texturing solution and heat to 65-90℃; S2, start the micro-nano bubble generator, mix the gas source and the alkaline texturing solution in the micro-nano bubble generator, prepare micro-nano bubble water, and then continuously introduce it into the bottom of the alkaline texturing tank through the pipeline; S3, the original silicon wafer processed in S1 is immersed in the alkaline texturing bath for full etching to complete the texturing process; S4. The texturized silicon wafer is taken out and subjected to post-alkali washing, acid washing, water washing and drying in sequence. The rising speed of the micro-nano bubbles is no higher than 0.5 cm / min, and the internal pressure of the micro-nano bubbles is no lower than 0.3 atmospheres.

2. The method for alkali texturing assisted by micro / nano bubbles as described in claim 1, characterized in that, The micro-nano bubble generator produces micro-nano bubbles with diameters ranging from 50 nm to 100 μm, and the concentration of the micro-nano bubbles is 10^5 to 10^8 bubbles / ml.

3. The method for alkali texturing assisted by micro / nano bubbles as described in claim 1, characterized in that, The gas source includes any one or more of the following gases: air, nitrogen, oxygen, and ozone, and the gas flow rate is 0.1 to 5 L / min.

4. The method for alkali texturing assisted by micro / nano bubbles as described in claim 1, characterized in that, The concentration of the alkaline floss solution is 0.1–5 wt%.

5. The method for alkali texturing assisted by micro / nano bubbles as described in claim 1, characterized in that, The corrosion time in S3 is 1 to 40 minutes.

6. The method for alkali texturing assisted by micro / nano bubbles as described in claim 1, characterized in that, The preferred heating temperature for the alkaline flossing solution in S1 is 70–85°C.

7. The method for alkali texturing assisted by micro / nano bubbles as described in claim 2, characterized in that, The diameter of the micro-nano bubbles is preferably 100 nm to 50 μm, and the concentration is preferably 10^7 bubbles / ml.

8. The method for alkali texturing assisted by micro / nano bubbles as described in claim 3, characterized in that, The preferred gas flow rate is 0.5 to 1.5 L / min.

9. A system for alkali texturing assisted by micro / nano bubble, characterized in that, include: A micro-nano bubble generator and an alkali texturing tank are connected by pipelines; The micro-nano bubble generator has inlets for both alkaline flossing solution and gas source.

10. The micro / nano bubble-assisted alkali texturing system as described in claim 9, characterized in that, The gas source has its flow rate regulated by a gas control unit.