Silicon wafer back contact cell grooving additive and preparation method and use method thereof

Abstract

The invention relates to the technical field of crystal silicon wafer grooving, in particular to a crystal silicon wafer back contact battery grooving additive and a preparation method and a use method thereof. The invention provides a silicon wafer back contact battery grooving additive which comprises the following components in parts by weight: 1-2 parts of a surfactant, 0.5-1 part of a chelating agent, 3-5 parts of a cleaning agent, 5-10 parts of a corrosion accelerant and 80-100 parts of deionized water, the chelating agent is a chelating agent containing carboxyl, the cleaning agent is strong alkali and weak acid salt, and the corrosion accelerant is a corrosion accelerant containing hydroxyl. The crystal silicon wafer back contact cell grooving additive obtained through compounding can protect an oxidation film at a non-laser position of a crystal silicon wafer back contact cell, can rapidly corrode a molten oxidation film at the laser position and an inner layer, namely a tunneling oxidation layer and poly silicon protected by the molten oxidation film, and has the advantage of improving the production efficiency of a cell piece.

Description

Technical Field

[0001] The present invention relates to the technical field of crystalline silicon wafer groove cutting, and in particular to a crystalline silicon wafer back contact battery groove cutting additive and a preparation method and a use method thereof. Background Art

[0002] Back contact (BC) cells are a type of back contact solar cell that uses masks and laser technology to diffuse phosphorus and boron on the back surface of a crystalline silicon wafer, forming a cross-shaped p-region and n-region. At the same time, the positive and negative metal electrodes are also arranged in a cross-shaped manner on the back of the cell. Its theoretical efficiency limit is close to that of silicon. The crystalline silicon wafer BC cell groove additive is a chemical additive that can help the alkaline solution to etch and clean the molten oxide film in the laser patterned area on the back of the BC cell during the BC cell production process and protect the oxide film in the non-laser area from being corroded. Grooving is an important step in achieving the alternating existence of p-regions and n-regions on the back of the BC cell. The additive protects the oxide film in the non-laser area so that the polysilicon and tunnel oxide layer under the oxide film are not damaged. At the same time, it can also clean the laser molten oxide film and the tunnel oxide layer and polysilicon below it and etch to a certain depth, preventing leakage caused by phosphorus and boron diffusion to the same area in subsequent processes, thereby improving the efficiency of the cell.

[0003] However, there are many problems with the groove engraving additives on the market: First, the groove engraving time of traditional groove engraving additives is too long, generally more than 5 minutes. This is because the main factor affecting the groove engraving time is the corrosion rate of the molten oxide film. Traditional groove engraving additives cannot promote the corrosion of the molten oxide film, making the corrosion selectivity of the alkali solution to the molten oxide film and the oxide film that has not been hit by the laser small, which increases the time cost of the battery cell and significantly reduces the production efficiency. In addition, the low corrosion selectivity will also increase the risk of being pierced at the non-laser location. Second, the cleaning effect of traditional groove engraving additives on silicon wafers is limited. After groove engraving, there are black spots and agglomerated black cores on the tower base in the groove. The black spots and black cores on the surface of the tower base may pierce the subsequently deposited oxide layer and affect the passivation effect, resulting in aggravated carrier surface recombination, reducing the filling factor of the battery and thus reducing the battery efficiency. Third, the tower base of traditional groove engraving additives is large and flat after groove engraving, which reduces the adhesion ability of the subsequently deposited oxide layer and poly layer to the surface of the slot body, and there will be a risk of delamination, while a smaller tower base can form better contact with the subsequently deposited oxide layer.

[0004] However, the silicon wafer needs to be cleaned and polished before texturing, and needs to be polished again after diffusion, resulting in the tower base on the back of the BC battery being more than 20 μm. After the molten oxide film is completely cleaned, the tower base will grow to about 23 μm, which is not conducive to the subsequent deposited oxide layer contacting the surface of the tank. Therefore, it is still necessary to consider how to polish the large tower base in the laser groove after groove engraving into a small tower base to assist in improving the performance of BC batteries made of crystalline silicon wafers. Summary of the invention

[0005] The present invention provides a crystalline silicon wafer back contact battery groove engraving additive and a preparation method and a use method thereof. The compounded crystalline silicon wafer back contact battery groove engraving additive of the present invention can protect the oxide film at the non-laser position of the crystalline silicon wafer back contact battery while quickly corroding the molten oxide film at the laser position and the inner layer protected by the molten oxide film - the tunneling oxide layer and poly silicon, which has the advantage of improving the production efficiency of the battery cell. After the crystalline silicon wafer back contact battery groove engraving additive is used, there is no molten oxide film residue in the laser groove and there is no black core and dirt, which can reduce the risk of puncture of the subsequently deposited oxide layer; at the same time, the tower base in the laser groove is reduced from 20 μm to 3~5 μm, which can effectively enhance the adhesion of the subsequently deposited oxide layer.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: The present invention provides a crystalline silicon wafer back contact battery groove engraving additive, which comprises, by weight, 1 to 2 parts of a surfactant, 0.5 to 1 parts of a chelating agent, 3 to 5 parts of a cleaning agent, 5 to 10 parts of a corrosion accelerator, and 80 to 100 parts of deionized water; the chelating agent is a chelating agent containing a carboxyl group, the cleaning agent is a strong base weak acid salt, and the corrosion accelerator is a corrosion accelerator containing a hydroxyl group.

[0007] In the present invention, the surfactant can help form a protective film on the back contact cell surface of the crystalline silicon wafer, which has the function of forming another oxide film at the non-laser location, preventing the hydroxide ions in the alkaline polishing solution from attacking the defects on the silicon wafer, thereby protecting the poly silicon and the tunneling oxide layer at the non-laser location.

[0008] Chelating agents containing carboxyl groups, in which the oxygen atoms in the carboxyl groups can form stable five-membered or six-membered ring chelates with heavy metals on silicon wafers. In this way, the harm of free heavy metals can be greatly reduced, and the lower the concentration of free heavy metals, the higher the efficiency of the battery. It can mainly prevent the occurrence of the following three phenomena: First, free heavy metal ions catalyze the corrosion of the surface oxide film by alkaline polishing liquid, resulting in a decrease in the protective effect of the oxide film, and the destruction of the inner polysilicon and tunneling oxide layer. Second, heavy metal ions will form metal oxides on the surface of the silicon wafer through oxidation and adhere to the silicon wafer, reducing the performance of the silicon wafer. Third, the heavy metal ions remaining on the silicon wafer will capture minority carriers and reduce the minority carrier lifetime of the silicon wafer during power generation.

[0009] In strong base and weak acid salts, since they are salts formed by the combination of strong base and weak acid, a large amount of weak acid ions will precipitate when the salt dissolves in water, and the base in the alkaline polishing liquid is usually a strong base of sodium hydroxide. Therefore, the free weak acid ions can help catalyze the reaction between hydroxide ions and the molten oxide film after laser treatment, so that the molten oxide film can be quickly dissolved in the alkaline solution. As a strong base, the remaining cations have no promoting effect on the whole process but also no inhibitory effect. In addition, the adsorption effect of strong base and weak acid salt can clear the dirt on the surface of the molten oxide film, making it easier for hydroxide ions to combine with the defects on the surface of the molten oxide film and react.

[0010] The corrosion accelerator containing hydroxyl groups can change the anisotropic corrosion of the alkaline polishing solution on the silicon wafer and form a "nucleation point" on the surface of the silicon wafer, which accelerates the corrosion rate of the alkaline polishing solution on the (111) crystal surface of the silicon wafer. At the same time, it can help generate many small tower bases in the large tower base in the laser groove, thereby increasing the specific surface area of ​​silicon in the laser groove, and then increasing the adsorption force of the silicon surface to the subsequently deposited oxide film.

[0011] In summary, the present invention selects surfactants, chelating agents containing carboxyl groups, strong base weak acid salts, and corrosion accelerators containing hydroxyl groups, and compounding them in deionized water in a specific ratio to obtain a crystalline silicon wafer back contact battery groove additive, which can effectively improve the production efficiency of the battery. After the crystalline silicon wafer back contact battery groove additive is used to complete the grooving, there is no molten oxide film residue in the laser groove, and there is no black core and dirt, which can reduce the risk of subsequent deposited oxide layer being punctured; at the same time, the tower base in the laser groove is reduced from 20 μm to 3~5 μm, which can effectively enhance the adhesion of the subsequent deposited oxide layer.

[0012] Preferably, based on weight, the composition includes 1 to 2 parts of a surfactant, 0.5 to 1 parts of a chelating agent, 3 to 5 parts of a cleaning agent, 5 to 8 parts of a corrosion accelerator, and 85 to 95 parts of deionized water.

[0013] Preferably, the surfactant is selected from one of polyethylene glycol, sodium lauryl sulfate and alkyl glycoside.

[0014] Preferably, the surfactant is selected from at least two of polyethylene glycol, sodium lauryl sulfate and alkyl glycoside, and the mass ratio of polyethylene glycol, sodium lauryl sulfate and alkyl glycoside is (0-0.5):(0.5-1):1.

[0015] Preferably, the carboxyl-containing chelating agent is selected from one or more of disodium ethylenediaminetetraacetic acid, disodium nitrilotriacetic acid, and sodium gluconate.

[0016] Preferably, the carboxyl-containing chelating agent is disodium ethylenediaminetetraacetate and sodium gluconate, and the mass ratio of disodium ethylenediaminetetraacetate to sodium gluconate is 1:1.

[0017] Preferably, the strong base and weak acid salt is selected from one of sodium sulfite, sodium bicarbonate and sodium carbonate.

[0018] The emulsifying and dispersing effects of sodium carbonate can separate and encapsulate fat-soluble organic matter on the surface of the silicon wafer, reducing the black core caused by uneven corrosion rate on the surface of the silicon wafer during grooving.

[0019] Preferably, the strong base and weak acid salt are selected from at least two of sodium sulfite, sodium bicarbonate and sodium carbonate, and the mass ratio of the sodium sulfite, sodium bicarbonate and sodium carbonate is 1:(1-3):(0-2).

[0020] Preferably, the corrosion accelerator containing a hydroxyl group is selected from one of diethylene glycol monophenyl ether, Triton X-100 and isopropanol.

[0021] Preferably, the corrosion accelerator containing a hydroxyl group is selected from at least two of diethylene glycol monophenyl ether, Triton X-100, and isopropanol, and the mass ratio of diethylene glycol monophenyl ether, Triton X-100, and isopropanol is (0-5): (0-4):1.

[0022] The present invention also provides a method for preparing a crystalline silicon wafer back contact battery groove engraving additive, comprising: dissolving a surfactant, a carboxyl-containing chelating agent, a strong base weak acid salt, and a hydroxyl-containing corrosion accelerator in deionized water, and stirring to obtain a clear solution to obtain the crystalline silicon wafer back contact battery groove engraving additive.

[0023] The present invention also provides a method for using a crystalline silicon wafer back contact battery notching additive, comprising: adding the crystalline silicon wafer back contact battery notching additive and 45 wt% sodium hydroxide solution into water and mixing evenly, and then placing the crystalline silicon wafer back contact battery into the battery for notching at 60-80° C. for 3-4 min; wherein the volume ratio of the crystalline silicon wafer back contact battery notching additive, 45 wt% sodium hydroxide solution and water is (2-8): (35-40):1000.

[0024] Therefore, the present invention has the following beneficial effects: (1) The crystalline silicon wafer back contact battery groove engraving additive provided by the present invention can protect the oxide film at the non-laser position of the crystalline silicon wafer back contact battery while quickly corroding the molten oxide film at the laser position and the inner layer protected by the molten oxide film - the tunnel oxide layer and poly silicon, thereby having the advantage of improving the production efficiency of the battery cell.

[0025] (2) The crystalline silicon wafer back contact battery groove additive provided by the present invention can complete the groove cleaning within 5 minutes, and there is no molten oxide film residue in the laser groove after cleaning, and there is no black core and dirt, which can reduce the risk of puncture of the subsequently deposited oxide layer; at the same time, the tower base in the laser groove is reduced from 20 μm to 3~5 μm, which can effectively enhance the adhesion of the subsequently deposited oxide layer.

[0026] (3) The present invention uses a surfactant to help form a protective film on the back contact cell surface of the crystalline silicon wafer. Its function is equivalent to forming another oxide film in the non-laser area to prevent the hydroxide ions in the alkaline polishing solution from attacking the defects on the silicon wafer, thereby protecting the poly silicon and tunnel oxide layer in the non-laser area.

[0027] (4) The present invention uses a strong base and a weak acid salt as a cleaning agent. The freed weak acid ions can help catalyze the reaction between hydroxide ions and the molten oxide film after laser treatment, so that the molten oxide film can be quickly dissolved in the alkaline solution.

[0028] (5) The present invention uses a corrosion accelerator containing hydroxyl groups, which can change the anisotropic corrosion of the alkaline polishing liquid on the silicon wafer and form a "nucleation point" on the surface of the silicon wafer, so that the corrosion rate of the alkaline polishing liquid on the (111) crystal surface of the silicon wafer is accelerated. At the same time, it can help generate many small tower bases in the large tower base in the laser groove, thereby increasing the specific surface area of ​​silicon in the laser groove, and further increasing the adsorption force of the silicon surface to the subsequently deposited oxide film.

[0029] (6) The present invention uses a chelating agent containing a carboxyl group. The oxygen atom in the carboxyl group can form a stable five-membered ring or six-membered ring chelate with the heavy metals on the silicon wafer, which greatly reduces the harm of free heavy metals and improves battery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the metallographic microscope picture of Example 1; Figure 2 This is a metallographic microscope image of a conventional BC battery groove additive; Figure 3 is the Zeta diagram of Example 1; Figure 4 This is the Zeta diagram of the conventional BC battery groove additive; Figure 5 This is the Zeta scan diagram of Example 1. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0032] Unless otherwise specified, all raw materials in this section were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. and were of analytical grade.

[0033] [Example] Example 1 The following ingredients are mixed by weight: 1 part of alkyl polyglycoside, 0.5 part of disodium ethylenediaminetetraacetate, 3 parts of sodium carbonate, 5 parts of diethylene glycol monophenyl ether, and 90.5 parts of deionized water. After mixing, the mixed solution is stirred until all the ingredients are dissolved in the deionized water and the mixed solution becomes clear, thus obtaining a crystalline silicon wafer BC battery groove additive.

[0034] Example 2 The following ingredients are mixed by weight: 1 part of polyethylene glycol, 1 part of disodium nitrilotriacetate, 4 parts of sodium sulfite, 6 parts of Triton X-100, and 88 parts of deionized water. After mixing, the mixed solution is stirred until all the ingredients are dissolved in the deionized water and the mixed solution becomes clear, thus obtaining a crystalline silicon wafer BC battery groove additive.

[0035] Example 3 The following ingredients are mixed by weight: 1 part of sodium lauryl sulfate, 1 part of alkyl glycoside, 0.5 part of disodium ethylenediaminetetraacetate, 0.5 part of sodium gluconate, 3 parts of sodium bicarbonate, 1 part of sodium sulfite, 5 parts of diethylene glycol monophenyl ether, 1 part of isopropanol, and 87 parts of deionized water. After mixing, the mixed solution is stirred until all the ingredients are dissolved in the deionized water and the mixed solution becomes clear, thus obtaining a crystalline silicon wafer BC battery groove additive.

[0036] Example 4 The following ingredients are mixed by weight: 0.5 parts of polyethylene glycol, 0.5 parts of sodium lauryl sulfate, 1 part of alkyl glycoside, 1 part of disodium ethylenediaminetetraacetate, 1 part of sodium bicarbonate, 2 parts of sodium carbonate, 1 part of sodium sulfite, 4 parts of Triton X-100, 1 part of isopropanol, and 88 parts of deionized water. After mixing, the mixed solution is stirred until all the ingredients are dissolved in the deionized water and the mixed solution becomes clear, thus obtaining a crystalline silicon wafer BC battery groove additive.

[0037] Comparative Example 1 (chelating agent without carboxyl group) The following ingredients are mixed by weight: 1 part of alkyl polyglycoside, 0.5 part of sodium hexametaphosphate, 3 parts of sodium carbonate, 5 parts of diethylene glycol monophenyl ether, and 90.5 parts of deionized water. After mixing, the mixed solution is stirred until all the ingredients are dissolved in the deionized water and the mixed solution becomes clear, thus obtaining a crystalline silicon wafer BC battery groove additive.

[0038] Comparative Example 2 (Strong Acid and Strong Base Salt) The following ingredients are mixed by weight: 1 part of polyethylene glycol, 1 part of disodium nitrilotriacetate, 4 parts of sodium sulfate, 6 parts of Triton X-100, and 88 parts of deionized water. After mixing, the mixed solution is stirred until all the ingredients are dissolved in the deionized water and the mixed solution becomes clear, thus obtaining a crystalline silicon wafer BC battery groove additive.

[0039] Comparative Example 3 (without corrosion accelerator) The following ingredients are mixed by weight: 0.5 parts of polyethylene glycol, 0.5 parts of sodium lauryl sulfate, 1 part of alkyl glycoside, 1 part of disodium ethylenediaminetetraacetate, 1 part of sodium bicarbonate, 2 parts of sodium carbonate, 1 part of sodium sulfite, and 88 parts of deionized water. After mixing, the mixed solution is stirred until all the ingredients are dissolved in the deionized water and the mixed solution becomes clear, thus obtaining a crystalline silicon wafer BC battery groove additive.

[0040]

Performance test

[0041] The crystalline silicon wafer BC battery groove additives obtained in Examples 1 to 4 and Comparative Examples 1 to 3 and conventional BC battery groove additives (purchased from the market) were grooved in the manner of the above-mentioned "grooving experiment", wherein the groove time of the conventional BC battery groove additive was increased to 5 min. The results are recorded in Tables 1 and Figure 1~2 middle.

[0042] Table 1 Groove cutting results statistics Tower base area in groove after groove engraving / μm Appearance inside the tank Is there any hole in the oxide film? Example 1 3.10~4.26 clean No drilling Example 2 3.39~3.42 clean No drilling Example 3 3.13~4.64 clean No drilling Example 4 4.15~4.26 clean No drilling Comparative Example 1 9.88~11.06 clean No drilling Comparative Example 2 6.74~7.85 clean No drilling Comparative Example 3 24.23~25.59 There are black cores and aggregated stains No drilling Conventional BC battery groove additive 23.84~25.39 There are black cores and aggregated stains No drilling It can be seen from the above table that the four schemes of Examples 1 to 4 can all produce crystalline silicon wafer BC battery groove engraving additives with excellent performance, and their performance is far better than that of conventional BC battery groove engraving additives. Specifically, it has a smaller tower base area and a cleaner appearance inside the groove, and the tower base area is reduced from 23.84~25.39 μm to 3.10~4.26 μm. It is proved that when the crystalline silicon wafer BC battery groove engraving additive provided by the present invention is used for groove engraving, the tunneling oxide layer is in better contact with the groove body, and the cleaning effect is better. In addition, the crystalline silicon wafer BC battery groove engraving additive provided by the present invention does not drill holes after groove engraving, indicating that the crystalline silicon wafer BC battery groove engraving additive can enhance the selective corrosion of the alkali solution on the oxide film of the BC battery non-laser area and the molten oxide film at the laser area, widen the corrosion difference, and avoid the oxide film drilling affecting the battery efficiency.

[0043] Furthermore, the crystalline silicon wafer BC battery groove additive obtained in Example 1 and the conventional BC battery groove additive were subjected to zeta scanning, and the results are as follows: Figures 3-5 shown.

[0044] observe Figure 5 It can be seen that the groove depth of the crystalline silicon wafer BC battery groove additive is about 2 μm, and there is no mask residue at the laser and non-laser areas, and the boundary is clear.

Claims

1. A crystalline silicon wafer back contact battery groove additive, characterized in that: The invention comprises, by weight, 1 to 2 parts of a surfactant, 0.5 to 1 parts of a chelating agent, 3 to 5 parts of a cleaning agent, 5 to 10 parts of a corrosion accelerator, and 80 to 100 parts of deionized water; the chelating agent is a chelating agent containing a carboxyl group, the cleaning agent is a salt of a strong base and a weak acid, and the corrosion accelerator is a corrosion accelerator containing a hydroxyl group.

2. The crystalline silicon wafer back contact battery groove additive according to claim 1, characterized in that: The surfactant is selected from one of polyethylene glycol, sodium lauryl sulfate and alkyl glycoside.

3. The crystalline silicon wafer back contact battery groove additive according to claim 1, characterized in that: The surfactant is selected from at least two of polyethylene glycol, sodium lauryl sulfate, and alkyl glycoside, and the mass ratio of the polyethylene glycol, sodium lauryl sulfate, and alkyl glycoside is (0-0.5): (0.5-1):

1.

4. The crystalline silicon wafer back contact battery groove additive according to claim 1, characterized in that: The carboxyl-containing chelating agent is selected from one or more of disodium ethylenediaminetetraacetate, disodium nitrilotriacetate, and sodium gluconate.

5. The crystalline silicon wafer back contact battery groove additive according to claim 1, characterized in that: The strong base and weak acid salt is selected from one of sodium sulfite, sodium bicarbonate and sodium carbonate.

6. The crystalline silicon wafer back contact battery groove additive according to claim 1, characterized in that: The strong base and weak acid salt are selected from at least two of sodium sulfite, sodium bicarbonate and sodium carbonate, and the mass ratio of the sodium sulfite, sodium bicarbonate and sodium carbonate is 1: (1-3): (0-2).

7. The crystalline silicon wafer back contact battery groove additive according to claim 1, characterized in that: The corrosion accelerator containing hydroxyl group is selected from one of diethylene glycol monophenyl ether, Triton X-100 and isopropanol.

8. The crystalline silicon wafer back contact battery groove additive according to claim 1, characterized in that: The hydroxyl-containing corrosion accelerator is selected from at least two of diethylene glycol monophenyl ether, Triton X-100, and isopropanol, and the mass ratio of diethylene glycol monophenyl ether, Triton X-100, and isopropanol is (0-5): (0-4):

1.

9. The method for preparing a crystalline silicon wafer back contact cell groove additive according to any one of claims 1 to 8, characterized in that: include: After the surfactant, the chelating agent containing carboxyl, the strong base weak acid salt and the corrosion accelerator containing hydroxyl are dissolved in deionized water, the solution is stirred to obtain a clear solution, thereby obtaining a crystalline silicon wafer back contact battery groove engraving additive.

10. The method for using the crystalline silicon wafer back contact cell groove additive according to any one of claims 1 to 8, characterized in that: include: The crystalline silicon wafer back contact battery groove engraving additive and 45 wt% sodium hydroxide solution are added into water and mixed evenly, and then placed into a crystalline silicon wafer back contact battery for groove engraving at 60-80° C. for 3-4 min; wherein the volume ratio of the crystalline silicon wafer back contact battery groove engraving additive, 45 wt% sodium hydroxide solution and water is (2-8): (35-40):1000.

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