Texturing Additives for Preparing Bamboo-like Textured Monocrystalline Silicon and Their Application Process

Abstract

This invention discloses a texturing additive for preparing monocrystalline silicon with a bamboo shoot-like textured surface and its application process. The mass percentage of each component in the texturing additive is as follows: polyvinyl alcohol 0.01-0.2%, polymeric dispersant 0.03-0.25%, texture modifier 0.005-0.025%, reaction promoter 0.4-1.5%, and the balance being water. Using the texturing additive of this invention, monocrystalline silicon wafers can be texturized once or twice. When applied to the monocrystalline silicon texturing process, the additive of this invention can obtain a "bamboo shoot-like" textured surface structure. This textured surface structure has a stronger absorption effect on sunlight than the traditional pyramid textured surface structure, resulting in a significant improvement in the current performance of the solar cells. Furthermore, the additive of this invention is applicable not only to primary and secondary texturing processes, but also to secondary texturing processes where the same type of additive is used in both texturing tanks, greatly improving production line compatibility and reducing production line supply costs.

Description

Technical Field

[0001] This invention belongs to the field of surface texturing technology for monocrystalline silicon solar cells, specifically relating to texturing additives for preparing monocrystalline silicon with a bamboo shoot-like textured surface and their application process. Background Technology

[0002] As a key photovoltaic assembly device, the core technology of solar cells lies in the fabrication of textured structures with strong light-trapping effects. These structures can better absorb sunlight, generate higher short-circuit currents, and thus effectively improve the photoelectric conversion efficiency of the cells. Numerous research reports on the microstructure of monocrystalline silicon surfaces have emerged. Wet etching for constructing textured structures mainly employs two systems: alkaline and acidic. Alkaline systems produce textured surfaces with a conventional pyramidal structure, while acidic systems produce conventional pyramidal, "wormhole," and inverted pyramidal shapes. There is limited room for further reduction in the reflectivity of conventional pyramidal textured surfaces. While inverted pyramidal textured surfaces can achieve lower reflectivity, the process conditions required for constructing this structure are quite demanding, making mass production currently impossible. Chinese patent CN202110796329 discloses a two-step texturing additive for preparing multi-layered pyramidal monocrystalline silicon textured surfaces and its application. However, its application process involves only two texturing steps, and the additive requires an A+B composite additive to construct the target textured surface, making the operation complex. Therefore, further research is needed on the textured surface morphology of monocrystalline silicon to obtain a textured surface morphology that can enhance the absorption of sunlight, thereby obtaining a lower solar reflectance value and improving the photoelectric conversion efficiency of the solar cell. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an additive for preparing a "bamboo shoot-shaped" textured monocrystalline silicon and its application process. This texturing additive can be applied to single-stage or multi-stage texturing processes of monocrystalline silicon to produce a distinct "bamboo shoot-shaped" textured surface, thereby achieving a lower solar reflectivity.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a texturing additive for preparing monocrystalline silicon with a bamboo shoot-like textured surface, wherein the mass percentage of each component is: polyvinyl alcohol 0.01-0.2%, polymeric dispersant 0.03-0.25%, textured surface modifier 0.005-0.025%, reaction promoter 0.4-1.5%, and the balance is water.

[0005] As a preferred embodiment of the above technical solution, the polyvinyl alcohol is selected from any one or more combinations of polyvinyl alcohol 1788, polyvinyl alcohol 1799, polyvinyl alcohol 2088, and modified polyvinyl alcohol.

[0006] As a preferred embodiment of the above technical solution, the polymeric dispersant is selected from one or any combination of polysodium methacrylate, polymaleic anhydride, and polymethacrylate-polymethacrylate block copolymer.

[0007] As a preferred embodiment of the above technical solution, the suede finishing agent is one or any combination of polysaccharide polymers, xylan, modified starch, and polyvinyl alcohol.

[0008] As a preferred embodiment of the above technical solution, the reaction promoter is one or any combination of flavonoid glycosides, sterols, and arbutin.

[0009] As a preferred embodiment of the above technical solution, the mass percentage of each component is as follows: polyvinyl alcohol 0.05-0.15%, polymeric dispersant 0.05-0.2%, suede finishing agent 0.01-0.02%, reaction accelerator 0.5-1.2%, and the balance being water.

[0010] The texturing additive is used in the process of texturing monocrystalline silicon wafers in one or two steps.

[0011] The specific steps of a single-stage fleece fabrication process include:

[0012] 1) Preparation of additives: Add 0.05-0.15% polyvinyl alcohol, 0.05-0.2% polymeric dispersant, 0.01-0.02% texturing agent, and 0.5-1.2% reaction promoter by mass percentage to the remaining water, mix evenly to prepare a single crystal silicon texturing additive.

[0013] 2) Preparation of texturing solution: Add the monocrystalline silicon primary texturing additive prepared in step 1) to the alkaline solution and mix evenly to prepare the texturing solution; the mass ratio of monocrystalline silicon primary texturing additive to alkaline solution is 0.3-0.8:100; the alkaline solution is a 1.0-2.0 wt% aqueous solution of sodium hydroxide or potassium hydroxide.

[0014] 3) Immerse the monocrystalline silicon wafer in the texturing solution obtained in step 2) for a first texturing process;

[0015] The specific steps of secondary flocking include:

[0016] 1) Preparation of additives: Add 0.05-0.15% polyvinyl alcohol, 0.05-0.2% polymeric dispersant, 0.01-0.02% texturing agent, and 0.5-1.2% reaction promoter by mass percentage to the remaining water, mix evenly to prepare a monocrystalline silicon secondary texturing additive.

[0017] 2) Preparation of texturing solution for one-step texturing tank: Add part of the monocrystalline silicon secondary texturing additive prepared in step 1) to the alkaline solution and mix evenly to prepare a one-step texturing solution; the mass ratio of additive to alkaline solution is 0.3-0.8:100; the alkaline solution is a 1.0-2.0 wt% aqueous solution of sodium hydroxide or potassium hydroxide.

[0018] 3) Preparation of the two-step texturing solution: Add part of the monocrystalline silicon secondary texturing additive prepared in step 1) to the alkaline solution and mix evenly to prepare the two-step texturing solution; the mass ratio of additive to alkaline solution is 0.1-0.4:100; the alkaline solution is a 0.3-1.0 wt% aqueous solution of sodium hydroxide or potassium hydroxide.

[0019] 4) Immerse the monocrystalline silicon wafer in the texturing solution prepared in step 2) for one-step texturing, then transfer it to a water tank for cleaning, and then immerse it in the texturing solution prepared in step 3) for two-step texturing.

[0020] As a preferred embodiment of the above technical solution, the flocking temperature in the single flocking process is 80-85℃ and the flocking time is 300-500s.

[0021] As a preferred embodiment of the above technical solution, in the secondary fleecing process, the fleecing temperature of the first fleecing step is 80-85℃ and the fleecing time of the first fleecing step is 300-500s; the fleecing temperature of the second fleecing step is 65-80℃ and the fleecing time of the second fleecing step is 100-200s.

[0022] The working principle of the additive in this invention is as follows: The additive contains a silanol nonionic surfactant, also known as a wetting agent. Its low molecular weight and multi-hydrophobic, umbrella-shaped symmetrical structure accelerate the wetting of the silicon surface by the feed solution. Simultaneously, the reduced interfacial tension allows the generated bubbles to detach quickly. The nucleating agent is uniformly adsorbed on the silicon surface, providing heterogeneous nucleation centers as the starting point for pyramid structure formation. The reaction promoter synergistically works with the wetting agent and nucleating agent to rapidly form an initial pyramidal textured surface. The textured surface modifier selectively adsorbs onto the formed pyramids, further enhancing the anisotropy of the textured surface, thereby producing a "bamboo shoot" structure through micro-corrosion on the initial pyramidal surface. In the primary texturing process, the additive of this invention can control the silicon-alkali reaction to achieve a "bamboo shoot" structure through rapid initial followed by slow corrosion. Alternatively, in the secondary texturing process, the "bamboo shoot" structure can be achieved by adjusting the feed solution ratio.

[0023] The beneficial effects of this invention are as follows: When the additive of this invention is applied to the texturing process of monocrystalline silicon, a "bamboo shoot" textured surface structure can be obtained. This textured surface structure has a stronger absorption effect on sunlight than the traditional pyramid textured surface structure, resulting in a significant improvement in the current performance of the solar cells. Furthermore, the additive of this invention is applicable not only to primary and secondary texturing processes, but also to the use of the same type of additive in both texturing tanks in the secondary texturing process, greatly improving production line compatibility and reducing production line liquid supply costs. Attached Figure Description

[0024] Figure 1 The image shows a scanning electron microscope (SEM) view of the "bamboo shoot" pyramid structure obtained by one-step texturing of single-crystal silicon in Example 1.

[0025] Figure 2 The image shows a scanning electron microscope (SEM) view of the "bamboo shoot" pyramid structure obtained by two-step texturing of single-crystal silicon in Example 2.

[0026] Figure 3 This is a scanning electron microscope (SEM) image of the pyramid structure obtained by one-step texturing of single-crystal silicon in Comparative Example 1.

[0027] Figure 4 This is a scanning electron microscope (SEM) image of the pyramid structure obtained by two-step texturing of single-crystal silicon in Comparative Example 2.

[0028] Figure 5 This is a schematic diagram of the "bamboo shoot-shaped" pyramid velvet structure of the present invention;

[0029] Figure 6 This is a schematic diagram of the pyramid-shaped velvet surface structure in Comparative Example 1 or 2. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] Example 1

[0033] A texturing additive for monocrystalline silicon and a one-step texturing process, comprising the following steps:

[0034] (1) Preparation of additives: Add 0.08% polyvinyl alcohol, 0.06% polymeric dispersant, 0.02% texturing agent and 1.0% reaction promoter by mass percentage to the remaining water, mix evenly to prepare a single crystal silicon texturing additive.

[0035] (2) Preparation of texturing solution: Add the additive prepared in step (1) to the alkaline solution and mix evenly to prepare the texturing solution; the mass ratio of additive to alkaline solution is 0.6:100; the alkaline solution is a 1.2wt% sodium hydroxide aqueous solution;

[0036] (3) Immerse the single crystal silicon wafer in the texturing solution obtained in step (2) for a first texturing process. The texturing temperature for the first texturing process is 82°C and the texturing time for the first texturing process is 400s.

[0037] Example 2

[0038] A texturing additive for preparing a "bamboo shoot-shaped" textured surface structure in monocrystalline silicon and a secondary texturing process, comprising the following steps:

[0039] (1) Preparation of additives: Add 0.08% polyvinyl alcohol, 0.06% polymeric dispersant, 0.02% texturing agent and 1.0% reaction promoter by mass percentage to the remaining water, mix evenly to prepare a single crystal silicon texturing additive.

[0040] (2) Preparation of the texturing solution for the one-step texturing tank: Add the additive prepared in step (1) to the alkaline solution and mix evenly to prepare the texturing solution; the mass ratio of the additive to the alkaline solution is 0.5:100; the alkaline solution is a 1.2wt% sodium hydroxide aqueous solution;

[0041] (3) Preparation of the two-step texturing tank texturing solution: Add the additive prepared in step (1) to the alkaline solution and mix evenly to prepare the texturing solution; the mass ratio of the additive to the alkaline solution is 0.2:100; the alkaline solution is a 0.5wt% sodium hydroxide aqueous solution;

[0042] (4) The monocrystalline silicon wafer is immersed in the texturing solution obtained in step (2) for one-step texturing, and then transferred to a water tank for cleaning. It is then immersed in the texturing solution obtained in step (3) for two-step texturing. The texturing temperature of the one-step texturing tank is 82°C and the texturing time of one step is 300s. The texturing temperature of the two-step texturing tank is 75°C and the texturing time of the two-step texturing tank is 120s.

[0043] Comparative Example 1

[0044] A texturing additive for monocrystalline silicon and a one-step texturing process, comprising the following steps:

[0045] (1) Preparation of additives: The “K02(T30D)” monocrystalline silicon texturing additive produced by Jiaxing Xiaochen Photovoltaic Technology Co., Ltd. is used directly.

[0046] (2) Preparation of texturing solution: Add the additive from step (1) to the alkaline solution and mix evenly to prepare the texturing solution; the mass ratio of additive to alkaline solution is 0.6:100; the alkaline solution is a 1.2wt% sodium hydroxide aqueous solution;

[0047] (3) Immerse the single crystal silicon wafer in the texturing solution obtained in step (2) for a first texturing process. The texturing temperature for the first texturing process is 82°C and the texturing time for the first texturing process is 400s.

[0048] Comparative Example 2

[0049] A texturing additive for monocrystalline silicon and a secondary texturing process, comprising the following steps:

[0050] (1) Preparation of additives: The “K02(T30D)” monocrystalline silicon texturing additive produced by Jiaxing Xiaochen Photovoltaic Technology Co., Ltd. is used directly.

[0051] (2) Preparation of the texturing solution for the one-step texturing tank: Add the additive prepared in step (1) to the alkaline solution and mix evenly to prepare the texturing solution; the mass ratio of the additive to the alkaline solution is 0.5:100; the alkaline solution is a 1.2wt% sodium hydroxide aqueous solution;

[0052] (3) Preparation of the two-step texturing tank texturing solution: Add the additive prepared in step (1) to the alkaline solution and mix evenly to prepare the texturing solution; the mass ratio of the additive to the alkaline solution is 0.2:100; the alkaline solution is a 0.5wt% sodium hydroxide aqueous solution;

[0053] (4) The monocrystalline silicon wafer is immersed in the texturing solution obtained in step (2) for one-step texturing, and then transferred to a water tank for cleaning. It is then immersed in the texturing solution obtained in step (3) for two-step texturing. The texturing temperature of the one-step texturing tank is 82°C and the texturing time of one step is 300s. The texturing temperature of the two-step texturing tank is 75°C and the texturing time of the two-step texturing tank is 120s.

[0054] The texturized monocrystalline silicon wafers of Examples 1 and 2 and Comparative Examples 1 and 2 were analyzed by scanning electron microscopy (SEM). The SEM images are shown below. Figure 1-4 As shown. (See attached instruction manual) Figure 1-4 A comparison shows that the monocrystalline silicon wafers obtained using the texturing additives and their application process described in this application have a distinct pyramidal textured surface structure, such as... Figure 5 As shown. The surface of the single-crystal silicon wafer produced using the applicant's earlier texturing additives only exhibits a simple pyramidal texturing structure, such as... Figure 6As shown, it does not have a "bamboo shoot" structure.

[0055] After texturing the monocrystalline silicon wafers of Examples 1 and 2 and Comparative Examples 1 and 2, and then processing them into solar cells using the same subsequent processing techniques, their photoelectric conversion performance was tested. The specific results are shown in Table 1. The test results were obtained using the formula:

[0056]

[0057] In the formula, Eta represents the photoelectric conversion efficiency, Uoc represents the open-circuit voltage, Isc represents the short-circuit current, FF represents the fill factor, and P in This represents the incident power density of sunlight. In Table 2, Rs represents the series resistance, Rsh represents the parallel resistance, and IRev2 represents the reverse current.

[0058] Table 1

[0059]

[0060] As can be seen from the table above, the single-crystal silicon wafers obtained by using the texturing additive and its application process of this application have significantly improved photoelectric conversion efficiency. At the same time, the electrical performance advantage is mainly reflected in the current. This is because the "bamboo shoot" textured surface structure increases the refraction frequency of the light beam, and the generation of more photogenerated current-carrying electrons increases the short-circuit current of the solar cell.

[0061] It is worth mentioning that the scanning electron microscope and other technical features involved in this patent application should be regarded as prior art. The specific structure, working principle, and possible control methods and spatial arrangement of these technical features can be adopted using conventional choices in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0062] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experimentation on the basis of the prior art should be within the scope of protection defined by the claims.

Claims

1. A texturing additive for preparing monocrystalline silicon with a bamboo shoot-like textured surface, characterized in that, The mass percentage of each component is as follows: polyvinyl alcohol 0.01-0.2%, polymeric dispersant 0.03-0.25%, suede modifier 0.005-0.025%, reaction accelerator 0.4-1.5%, and the balance is water. The polyvinyl alcohol is selected from any one or more combinations of polyvinyl alcohol 1788, polyvinyl alcohol 1799, polyvinyl alcohol 2088, and modified polyvinyl alcohol. The polymeric dispersant is selected from one or more combinations of sodium polymethacrylate, polymaleic anhydride, and polymethacrylate-polymethacrylate block copolymer. The suede modifier is selected from one or more combinations of polysaccharide polymers, xylan, modified starch, and polyvinyl alcohol. The reaction accelerator is selected from one or more combinations of flavonoid glycosides, sterols, and arbutin.

2. The texturing additive for preparing monocrystalline silicon with a bamboo shoot-like textured surface as described in claim 1, characterized in that, The mass percentage of each component is as follows: polyvinyl alcohol 0.05-0.15%, polymeric dispersant 0.05-0.2%, suede finishing agent 0.01-0.02%, reaction accelerator 0.5-1.2%, and the balance is water.

3. The application process of the flocking additive as described in claim 2, characterized in that, Single-crystal silicon wafers can undergo one or two texturing processes. The specific steps of a single-stage fleece fabrication process include: 1) Preparation of additives: Add 0.05-0.15% polyvinyl alcohol, 0.05-0.2% polymeric dispersant, 0.01-0.02% texturing agent, and 0.5-1.2% reaction promoter by mass percentage to the remaining water, mix evenly to prepare a single-crystal silicon texturing additive. 2) Preparation of texturing solution: Add the monocrystalline silicon primary texturing additive prepared in step 1) to the alkaline solution and mix evenly to prepare the texturing solution; the mass ratio of monocrystalline silicon primary texturing additive to alkaline solution is 0.3-0.8:100; the alkaline solution is a 1.0-2.0 wt% sodium hydroxide or potassium hydroxide aqueous solution; 3) Immerse the monocrystalline silicon wafer in the texturing solution obtained in step 2) for a first texturing process; The specific steps of secondary flocking include: 1) Preparation of additives: Add 0.05-0.15% polyvinyl alcohol, 0.05-0.2% polymeric dispersant, 0.01-0.02% texturing agent, and 0.5-1.2% reaction promoter by mass percentage to the remaining water, mix evenly to prepare a monocrystalline silicon secondary texturing additive. 2) Preparation of texturing solution for one-step texturing tank: Add part of the monocrystalline silicon secondary texturing additive prepared in step 1) to the alkaline solution and mix evenly to prepare a one-step texturing solution; the mass ratio of additive to alkaline solution is 0.3-0.8:100; the alkaline solution is a 1.0-2.0 wt% sodium hydroxide or potassium hydroxide aqueous solution; 3) Preparation of the two-step texturing solution: Add part of the monocrystalline silicon secondary texturing additive prepared in step 1) to the alkaline solution and mix evenly to prepare the two-step texturing solution; the mass ratio of additive to alkaline solution is 0.1-0.4:100; the alkaline solution is a 0.3-1.0wt% sodium hydroxide or potassium hydroxide aqueous solution; 4) Immerse the monocrystalline silicon wafer in the texturing solution prepared in step 2) for one-step texturing, then transfer it to a water tank for cleaning, and then immerse it in the texturing solution prepared in step 3) for two-step texturing.

4. The application process of the flocking additive as described in claim 3, characterized in that, The flocking temperature during the first flocking process is 80-85℃, and the flocking time is 300-500s.

5. The application process of the flocking additive as described in claim 4, characterized in that, In the secondary fleece fabrication process, the fleece fabrication temperature of the first fleece fabrication step is 80-85℃, and the fleece fabrication time of the first fleece fabrication step is 300-500s; the fleece fabrication temperature of the second fleece fabrication step is 65-80℃, and the fleece fabrication time of the second fleece fabrication step is 100-200s.

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