Winding plating removing additive and winding plating removing method

Abstract

The invention relates to the technical field of solar cells, in particular to a dewound plating additive and a dewound plating method, and the dewound plating additive comprises the following components in percentage by mass: 0.5-1.0% of a surfactant, 1.0-2.0% of a defoaming agent, 0.05-0.1% of a directional reverse accelerator, 0.1-0.05% of a directional corrosion inhibitor, 1.0-1.5% of a dispersing agent, 2-3% of inorganic salt and the balance of deionized water. Directional reverse-promoting and corrosion-inhibiting components are adopted, so that the problems of incomplete winding plating removal and back surface damage are effectively solved, the polycrystalline silicon layers on the front surface and the side surface can be accelerated to be removed under an alkaline condition, the polycrystalline silicon layers are effectively adsorbed on a PSG layer to prevent back surface reaction, the problem of edge electric leakage of a Topcon battery is solved, meanwhile, no abnormal appearance is ensured, and the service life of the Topcon battery is prolonged. And the conversion efficiency is equal or improved.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, in particular to a de-wrap plating additive and a de-wrap plating method. Background Art

[0002] Currently, Topcon cells have gradually replaced PERC cells and become the mainstream process with their higher photoelectric conversion rate and high equipment adaptability. Topcon cells, whether single-insert or dual-insert LPCVD or PECVD, will deposit an amorphous silicon layer on the back. In this process, plating will inevitably occur on the front and sides, and polysilicon will be formed through phosphorus diffusion. If the polysilicon on the front and sides is not removed, it will cause excessive reverse current, edge leakage and abnormal appearance in the future, thus affecting efficiency.

[0003] At present, the conventional process for de-coating of Topcon batteries is to use alkaline solution for double-sided cleaning, and use the different corrosion rates of the coated polysilicon and the PSG (phosphorus silicon glass) on the back under alkali to achieve the effect of de-coating and back protection. Although the corrosion rate of alkaline solution on polysilicon is nearly three times that of PSG, in actual use, due to the long de-coating reaction time, there will be no etching on the back but incomplete de-coating or complete de-coating but corrosion on the back. The reaction difference between the two is difficult to control, which will lead to severe corrosion on the back, thus affecting the battery efficiency and yield.

[0004] In order to effectively solve the above-mentioned problems, the two reaction zones can be clearly separated, and the etching of the back PSG can be effectively limited to protect the back side during de-plating. The present invention provides a high-efficiency additive that takes into account both de-plating and back side protection and its application process, which can ensure that the removal of the front and side polysilicon layers is accelerated under alkaline conditions, and is effectively adsorbed on the PSG layer to prevent its back side reaction. Summary of the invention

[0005] The purpose of the present invention is to provide a de-wrap additive and a de-wrap method to solve the above technical problems.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: A de-wrap additive, the components of which, by mass percentage, include: 0.5-1.0% surfactant, 1.0-2.0% deaerator, 0.5-1‰ of directional reaction promoter, 0.1-0.5‰ directional corrosion inhibitor, 1.0-1.5% dispersant, 2-3% inorganic salt, the balance is deionized water.

[0007] Furthermore, the surfactant is selected from one or more combinations of sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether sulfate, polysorbate-20, succinic acid monoglyceride, and dodecyl betaine.

[0008] Furthermore, the defoaming agent is selected from one or more combinations of polyethylene glycol, polypropylene glycol, Span 85, propylene oxide, and ethylene oxide.

[0009] Furthermore, the directional reaction promoter is selected from amphoteric siloxane substances that are easily adsorbed on the surface of polycrystalline silicon, and the molecular weight is controlled below 1000, specifically one or more combinations of polyether modified heptamethylsiloxane, amino modified diethoxysiloxane, hydroxyl-terminated dimethylsiloxane, and epoxy-modified polyether siloxane.

[0010] One end of the amphoteric siloxane contains a large number of Si-O bonds, which are hydrolyzed under alkaline conditions to form Si-OH bonds, and are easily combined with polysilicon through chemical bonds; the other end contains active groups that can form more reaction points on the surface of polysilicon, and the better unfolding of the Si-O-Si chain segment accelerates the OH - Reacts to silicon oxide, thereby achieving the effect of directionally accelerating corrosion.

[0011] Furthermore, the directional corrosion inhibitor is a high molecular polymer that can effectively adsorb to phosphosilicate glass, specifically one or more combinations of copolyvidone, polyvinyl pyrrolidone, modified phenolic resin, lignin sulfonate, and modified petroleum ether.

[0012] High molecular weight polymers, especially those with a molecular weight of more than 2w, have longer molecular chains and are difficult to spread due to the presence of hydrophobic bonds. They are easy to agglomerate in water and are more easily adsorbed on the surface containing PSG because of their smaller bond energy, which can effectively slow down OH - The corrosion of phosphosilicate glass can effectively protect the back of the silicon wafer.

[0013] Furthermore, the dispersant is selected from one or more combinations of sodium tripolyphosphate, sodium hexametaphosphate, dibutylnaphthalene sulfonate, diisopropylnaphthalene sulfonate, alkyl phosphate, and bisalkylphenol polyoxyethylene ether phosphate.

[0014] Furthermore, the inorganic salt is selected from one or more combinations of sodium bicarbonate, sodium chloride, sodium carbonate, ammonium chloride, potassium iodide, and sodium citrate.

[0015] A de-winding plating method, wherein the de-winding plating additive is added into a de-winding plating alkali tank.

[0016] Furthermore, the method comprises the following steps: S1 firstly prepares the de-coating additive according to the above mass percentage; S2 places the unwound silicon wafer in a 15-25% hydrofluoric acid solution for "water floating" to remove the PSG and oxide layer on the front and side surfaces; S3: placing the silicon wafer after the treatment in step S2 in an alkaline pretreatment solution for pretreatment to remove surface residues and HF, and then placing it in a pure water tank for cleaning; S4: placing the silicon wafer treated in step S3 into a de-winding alkali plating tank, wherein the tank contains 0.5%-1% additives and 1-2% 45% NaOH solution; S5: After the de-plating is completed in step S4, the silicon wafer is washed again with water and then placed in an alkaline pretreatment solution for cleaning. The silicon wafer after alkaline cleaning is washed again with water and then placed in an acid solution for cleaning; the silicon wafer after acid cleaning is washed again with water and finally dried.

[0017] Furthermore, in step S3, the alkaline pretreatment solution is a mixed solution of 1-1.5% 45% NaOH and 4-5% H2O2, the treatment temperature is 50-60°C, and the treatment time is 60-80s; The reaction temperature in step S4 is 66-70°C and the reaction time is 360-420s; The pretreatment solution in step S5 is a mixed solution of 1-1.5% 45% NaOH and 4-5% H2O2, the treatment temperature is 50-60°C, and the treatment time is 60-80s; The acidic solution in step S5 is an aqueous solution of HF, and the HF concentration is 5%.

[0018] Beneficial Effects The present invention adopts directional reaction-promoting and corrosion-inhibiting components to effectively solve the problems of incomplete de-plating and back damage, and can ensure the accelerated removal of the polysilicon layer on the front and side under alkaline conditions, and effectively adsorb on the PSG layer to prevent its back reaction, solve the leakage problem of the Topcon battery edge, and ensure that the appearance is normal, and the conversion efficiency is maintained or improved, as follows: 1. The plating is completely removed, and the side tower base is maintained above 20~26um, which solves the leakage problem; 2. Effectively limit the reaction rate of PSG on the back side, and the back side is not damaged during the reaction time; 3. The efficiency of the battery cell is increased by 0.01~0.05%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a morphological image of the back side of the silicon wafer after alkali etching to remove the de-plating in Example 1; Figure 2 This is a side morphology image of the silicon wafer after alkali etching to remove the de-plating in Example 1; Figure 3 This is a morphological image of the back side of the silicon wafer after alkali etching to remove the de-plating in Example 2; Figure 4 This is a side morphology image of the silicon wafer after alkali etching to remove the de-plating in Example 2; Figure 5 This is a morphology image of the back side of the silicon wafer after alkali etching to remove the de-plating in Example 3; Figure 6 This is a side morphology image of the silicon wafer after alkali etching to remove the de-plating in Example 3; Figure 7 This is a morphology image of the back side of the silicon wafer after alkaline etching to remove the de-plating in the comparative example of Example 3; Figure 8 This is a side morphology image of the silicon wafer after alkaline etching and de-coating in the comparative example of Example 3; Fig. 9 This is a morphology image of the back side of the silicon wafer after alkali etching to remove the de-plating in Example 4; Fig.10 This is a side morphology image of the silicon wafer after alkali etching to remove the de-plating in Example 4; Fig.11 This is a morphology image of the back side of the silicon wafer after alkaline etching to remove the de-plating in the comparative example of Example 4; Fig.12 This is a side morphology image of the silicon wafer after alkaline etching and de-plating in the comparative example of Example 4. DETAILED DESCRIPTION

[0020] The present invention will now be described in further detail in conjunction with specific embodiments. The following embodiments may enable those skilled in the art to more fully understand the present invention, but these embodiments are not intended to limit the scope of protection of the present invention. "One embodiment" or "embodiment" referred to herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. "In one embodiment" appearing in different places in this specification does not refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0021] All raw materials in the present invention are commonly available on the market.

[0022] Embodiment 1: A de-wrap additive comprises the following components calculated by mass percentage: 0.5% of polyether-modified heptamethylsiloxane, 0.1% of polyvinyl pyrrolidone K90, 1% of polysorbate-20, 2% of polypropylene glycol, 1% of sodium tripolyphosphate, 2% of sodium carbonate, and the balance is pure water.

[0023] A process for applying a de-wrap additive, the steps comprising: Firstly, the required de-wrap additive is prepared according to the above mass percentage; The prepared silicon wafer is a solar cell with front-side winding plating after double-sided texturing, front-side boron diffusion, back-side polishing, and back-side deposition of tunnel oxide layer and phosphorus diffusion doping annealing. The above processes are all prior art and will not be repeated in this application; Then, the silicon wafer obtained in the above steps is placed in a 15% hydrofluoric acid solution for "water floating" treatment; The silicon wafer is then placed in an alkaline pretreatment solution for pretreatment, wherein the alkaline pretreatment solution is a 1% mixed solution of 45% NaOH and 4% H2O2, the treatment temperature is 60°C, the treatment time is 60s, and then placed in a pure water tank for cleaning; Then, the silicon wafer was placed in a 1L de-winding plating alkali bath, which contained 0.5% additives, 1% 45% NaOH solution, a reaction temperature of 70°C, and a reaction time of 420s. After the de-plating, the silicon wafer is washed again with water and then placed in an alkaline pretreatment solution for cleaning. The pretreatment solution is a 1% mixed solution of 45% NaOH and 4% H2O2. The treatment temperature is 50°C and the treatment time is 60s. After alkaline cleaning, the silicon wafer is washed again with water and then placed in an acid solution for cleaning. The acid solution is an aqueous solution of HF with an HF concentration of 5%. After pickling, the silicon wafers are washed again with water and finally dried.

[0024] from Figure 1 and Figure 2 It can be seen that the side tower base is about 25um, the plating is thorough, and there is no obvious corrosion on the back, indicating that the polysilicon layer is protected.

[0025] Embodiment 2: A de-wrap additive comprises the following components calculated by mass percentage: 0.8% hydroxyl-terminated dimethylsiloxane, 0.2% modified phenolic resin (molecular weight greater than 2w), 0.5% sodium dodecylbenzene sulfonate, 1% polypropylene glycol, 1.5% sodium dibutylnaphthalene sulfonate, 3% sodium bicarbonate, and the balance is pure water.

[0026] A process for applying a de-wrap additive, the steps comprising: Firstly, the required de-wrap additive is prepared according to the above mass percentage; The prepared silicon wafer is a solar cell with front-side wrap-around plating after double-sided texturing, front-side boron diffusion, back-side polishing, and back-side deposition of tunnel oxide layer and phosphorus diffusion doping annealing; Then, the silicon wafer obtained in the above steps is placed in a 15% hydrofluoric acid solution for "water floating" treatment; The silicon wafer is then placed in an alkaline pretreatment solution for pretreatment, wherein the alkaline pretreatment solution is a 1% mixed solution of 45% NaOH and 4% H2O2, the treatment temperature is 50°C, the treatment time is 60s, and then placed in a pure water tank for cleaning; Then, the silicon wafer was placed in a 1L de-winding plating alkali bath, which contained 1% additives, 0.8% 45% NaOH solution, a reaction temperature of 65°C, and a reaction time of 360s. After the de-plating, the silicon wafer is washed again with water and then placed in an alkaline pretreatment solution for cleaning. The pretreatment solution is a 1% mixed solution of 45% NaOH and 4% H2O2. The treatment temperature is 50°C and the treatment time is 60s. After alkaline cleaning, the silicon wafer is washed again with water and then placed in an acid solution for cleaning. The acid solution is an aqueous solution of HF with an HF concentration of 5%. After pickling, the silicon wafers are washed again with water and finally dried.

[0027] from Figure 3 and Figure 4 It can be seen that the side tower base is above 20um, indicating that the de-plating is thorough and there is no obvious corrosion on the back, indicating that the polysilicon layer is protected.

[0028] Embodiment 3: A de-wrap additive comprises the following components calculated by mass percentage: 0.8% amino-modified diethoxysiloxane, 0.2% modified phenolic resin (molecular weight greater than 2w), 0.5% dodecyl betaine, 1% polyethylene glycol, 1.5% sodium dibutylnaphthalene sulfonate, 3% sodium bicarbonate, and the balance is pure water.

[0029] A process for applying a de-wrap additive, the steps comprising: Firstly, the required de-wrap additive is prepared according to the above mass percentage; The prepared silicon wafer is a solar cell with front-side wrap-around plating after double-sided texturing, front-side boron diffusion, back-side polishing, and back-side deposition of tunnel oxide layer and phosphorus diffusion doping annealing; Then, the silicon wafer obtained in the above steps is placed in a 15% hydrofluoric acid solution for "water floating" treatment; The silicon wafer is then placed in an alkaline pretreatment solution for pretreatment, wherein the alkaline pretreatment solution is a 1% mixed solution of 45% NaOH and 4% H2O2, the treatment temperature is 60°C, the treatment time is 60s, and then placed in a pure water tank for cleaning; Then place the silicon wafer in a 10L de-winding plating alkali tank containing 1% additive and 0.8% 45% NaOH solution. The reaction temperature is 69°C and the reaction time is 420s. After the de-plating, the silicon wafer is washed again with water and then placed in an alkaline pretreatment solution for cleaning. The pretreatment solution is a 1% mixed solution of 45% NaOH and 4% H2O2. The treatment temperature is 50°C and the treatment time is 60s. After alkaline cleaning, the silicon wafer is washed again with water and then placed in an acid solution for cleaning. The acid solution is an aqueous solution of HF with an HF concentration of 5%. After pickling, the silicon wafers are washed again with water and finally dried.

[0030] This embodiment adopts a laboratory small batch testing method, with a total of 5 batches of 400 pieces each, and the results are detailed in the attached figure.

[0031] The experimental group is the de-wrap plating additive of the present invention, the comparative group is the modified phenolic resin without directional corrosion inhibitor, and the other components are the same as the experimental group. Figure 5 , Figure 6 , Figure 7 , Figure 8 As shown in Table 1, under the same reaction conditions, the back corrosion is significantly lighter than that of the control group, the de-plating is more thorough, and the efficiency is also improved by 0.006%.

[0032] Embodiment 4: A de-wrap additive comprises the following components calculated by mass percentage: 0.8% amino-modified diethoxysiloxane, 0.2% modified phenolic resin (molecular weight greater than 2w), 0.5% dodecyl betaine, 1% polyethylene glycol, 1.5% sodium dibutylnaphthalene sulfonate, 3% sodium bicarbonate, and the balance is pure water.

[0033] A process for applying a de-wrap additive, the steps comprising: Firstly, the required de-wrap additive is prepared according to the above mass percentage; The prepared silicon wafer is a solar cell with front-side wrap-around plating after double-sided texturing, front-side boron diffusion, back-side polishing, and back-side deposition of tunnel oxide layer and phosphorus diffusion doping annealing; Then, the silicon wafer obtained in the above steps is placed in a 15% hydrofluoric acid solution for "water floating" treatment; The silicon wafer is then placed in an alkaline pretreatment solution for pretreatment, wherein the alkaline pretreatment solution is a 1% mixed solution of 45% NaOH and 4% H2O2, the treatment temperature is 50°C, the treatment time is 60s, and then placed in a pure water tank for cleaning; Then place the silicon wafer in a 10L de-winding plating alkali tank containing 1% additive and 0.8% 45% NaOH solution. The reaction temperature is 69°C and the reaction time is 420s. After the de-plating, the silicon wafer is washed again with water and then placed in an alkaline pretreatment solution for cleaning. The pretreatment solution is a 1% mixed solution of 45% NaOH and 4% H2O2. The treatment temperature is 50°C and the treatment time is 60s. After alkaline cleaning, the silicon wafer is washed again with water and then placed in an acid solution for cleaning. The acid solution is an aqueous solution of HF with an HF concentration of 5%. After pickling, the silicon wafers are washed again with water and finally dried.

[0034] This embodiment adopts a large-scale testing method in a production line, with a total of 200 batches of 400 pieces each, and the results are illustrated in detail with the attached figure.

[0035] Table 2 The experimental group is the de-wrap additive of the present invention, and the control group is composed of 1% sodium carboxymethyl starch, 0.5% sodium dodecyl sulfate, 2% ethylenediaminetetraacetic acid, and 0.1% β-cyclodextrin. Fig. 9 , Fig.10 , Fig.11 , Fig.12 As can be seen from Table 2, the back corrosion of the late-stage reaction pieces selected in large quantities is obviously lighter than that of the control group, and the efficiency is also improved by 0.027%.

[0036] With the above embodiments of the present invention as inspiration, through the above description, relevant personnel in this field can make various changes and modifications without departing from the technical idea of ​​the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention. The technical scope of the present invention is not limited to the content of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A de-wrap additive, characterized in that its components, by mass percentage, include: 0.5-1.0% surfactant, 1.0-2.0% deaerator, 0.5-1‰ of directional reaction promoter, 0.1-0.5‰ directional corrosion inhibitor, 1.0-1.5% dispersant, 2-3% inorganic salt, the rest are deionized water.

2. The de-wrap additive according to claim 1, characterized in that: The surfactant is selected from one or more combinations of sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether sulfate, polysorbate-20, succinic acid monoglyceride, and dodecyl betaine.

3. The de-wrap additive according to claim 1, characterized in that: The defoaming agent is selected from one or more combinations of polyethylene glycol, polypropylene glycol, Span 85, propylene oxide, and ethylene oxide.

4. The de-wrap additive according to claim 1, characterized in that: The directional reaction promoter is selected from amphoteric siloxane substances that are easily adsorbed on the surface of polycrystalline silicon, and the molecular weight is controlled below 1000, specifically one or more combinations of polyether modified heptamethylsiloxane, amino modified diethoxysiloxane, hydroxyl-terminated dimethylsiloxane, and epoxy modified polyether siloxane.

5. The de-wrap additive according to claim 1, characterized in that: The directional corrosion inhibitor is a high molecular polymer that can effectively adsorb to phosphosilicate glass, specifically one or more combinations of copolyvidone, polyvinyl pyrrolidone, modified phenolic resin, lignin sulfonate, and modified petroleum ether.

6. The de-wrap additive according to claim 1, characterized in that: The dispersant is selected from one or more combinations of sodium tripolyphosphate, sodium hexametaphosphate, dibutylnaphthalene sulfonate, diisopropylnaphthalene sulfonate, alkyl phosphate, and bisalkylphenol polyoxyethylene ether phosphate.

7. The de-wrap additive according to claim 1, characterized in that: The inorganic salt is selected from one or more combinations of sodium bicarbonate, sodium chloride, sodium carbonate, ammonium chloride, potassium iodide and sodium citrate.

8. A de-coating method, characterized in that: The method comprises adding the de-winding plating additive according to any one of claims 1 to 6 into the de-winding plating alkali tank.

9. A de-coating method according to claim 8, characterized in that: The method comprises the following steps: S1 firstly prepares the de-coating additive according to the above mass percentage; S2: Place the unwound silicon wafer in a 15-25% hydrofluoric acid solution for "water floating" to remove the PSG and oxide layer on the front and side surfaces; S3: placing the silicon wafer after the treatment in step S2 in an alkaline pretreatment solution for pretreatment to remove surface residues and HF, and then placing it in a pure water tank for cleaning; S4: placing the silicon wafer treated in step S3 into a de-winding alkali plating tank, wherein the tank contains 0.5%-1% additives and 1-2% 45% NaOH solution; S5: After the de-plating is completed in step S4, the silicon wafer is washed again with water and then placed in an alkaline pretreatment solution for cleaning. The silicon wafer after alkaline cleaning is washed again with water and then placed in an acid solution for cleaning; the silicon wafer after acid cleaning is washed again with water and finally dried.

10. A de-wrap method according to claim 8, characterized in that: In step S3, the alkaline pretreatment solution is a mixed solution of 1-1.5% 45% NaOH and 4-5% H2O2, the treatment temperature is 50-60°C, and the treatment time is 60-80s; The reaction temperature in step S4 is 66-70°C and the reaction time is 360-420s; The pretreatment solution in step S5 is a mixed solution of 1-1.5% 45% NaOH and 4-5% H2O2, the treatment temperature is 50-60°C, and the treatment time is 60-80s; The acidic solution in step S5 is an aqueous solution of HF, and the HF concentration is 5%.

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