Monocrystalline silicon alkali polishing additive for inverted pyramid structure tower footing and application thereof

Abstract

The invention discloses a monocrystalline silicon alkali polishing additive with an inverted pyramid structure tower footing and application of the monocrystalline silicon alkali polishing additive. The monocrystalline silicon alkali polishing additive comprises, by mass, 1-2 parts of glue, 0.5-2 parts of sodium lignin sulfonate, 1-3 parts of quaternary ammonium salt, 0.1-0.3 part of sodium benzoate, 2-3 parts of DL-proline, 2-5 parts of other auxiliaries and the balance deionized water. By adding the additive disclosed by the invention into a polishing solution for alkali polishing of monocrystalline silicon, the reaction rate of a [111] / [100] surface can be changed, the reaction rate of a [110] surface can be increased, an inverted pyramid structure which is uniformly distributed and complete in structure can be formed on the back surface of the monocrystalline silicon, the roughness of the back surface of the monocrystalline silicon can be increased, on one hand, back slurry contact and slurry tension improvement are facilitated, and FF can be improved; and on the other hand, the double-sided rate of the photovoltaic module is improved, thereby improving the electrical performance of the battery piece.

Description

Technical Field

[0001] The invention relates to the technical field of crystalline silicon wafer alkali polishing, and more particularly to a single crystal silicon alkali polishing additive for an inverted pyramid structure tower base and application thereof. Background Art

[0002] Monocrystalline silicon back-polishing additives are chemical additives added to the polishing slurry during the manufacturing process of monocrystalline silicon solar cells to protect the front surface texture and PN junction of the monocrystalline silicon from damage and improve the back-polishing effect. Back-polishing makes the back of the monocrystalline silicon more flat, which not only enhances the reflection of transmitted light and reduces light transmittance, but also allows for good contact between the slurry and the silicon wafer surface, improving the passivation effect, thereby reducing contact resistance and increasing FF.

[0003] The bifaciality of a photovoltaic module reflects the power generation capacity of the module's backside. The key difference between bifacial photovoltaic modules and traditional modules is that they can generate electricity not only from incident light on the front side but also from light reflected from the back side, thereby improving overall power generation efficiency. Currently, the monocrystalline silicon backside polishing additives on the market only achieve backside polishing; no additives have been marketed that can effectively increase the bifaciality of photovoltaic modules. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a single crystal silicon alkaline polishing additive for an inverted pyramid structure tower base and its application, to provide a single crystal silicon alkaline polishing additive for an inverted pyramid structure tower base and its application, which can change the reaction rate of the

[111] /

[100] surface, increase the reaction speed of the

[110] surface, form a uniformly distributed and structurally complete inverted pyramid structure on the back of the single crystal silicon, increase the roughness of the back of the single crystal silicon, on the one hand, be beneficial to the back slurry contact, increase the slurry tension, and also improve FF, on the other hand, improve the bifaciality of the photovoltaic module, thereby improving the electrical performance of the cell.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The invention provides a single crystal silicon alkali polishing additive for an inverted pyramid structure tower base. The polishing additive comprises the following components: 1-2 parts by mass of a glue, 0.5-2 parts by mass of sodium lignin sulfonate, 1-3 parts by mass of a quaternary ammonium salt, 0.1-0.3 parts by mass of sodium benzoate, 2-3 parts by mass of DL-proline, 2-5 parts by mass of other additives, and the balance being deionized water.

[0006] Preferably, the gum is at least one of xanthan gum, gum arabic and konjac gum.

[0007] Preferably, the quaternary ammonium salt is at least one of tert-butylammonium chloride, allyltrimethylammonium chloride, and tetraethylammonium chloride.

[0008] Preferably, the other additives include wetting agents, scale inhibitors, and dispersants.

[0009] Preferably, the mass ratio of the wetting agent, the scale inhibitor and the dispersant is 1:(0.5-3):(1-2).

[0010] Preferably, the wetting agent is at least one of polyethylene glycol 200, polyethylene glycol 400, β-hydroxyethyl urea, and Tween 60.

[0011] Preferably, the scale inhibitor is at least one of hydroxyethylidene diphosphonic acid, sodium ethylenediamine tetramethylene phosphonate, and sodium polyphosphate.

[0012] Preferably, the dispersant is at least one of polyacrylamide and polyvinyl alcohol.

[0013] The present invention also provides a polishing liquid containing an alkali polishing additive for a monocrystalline silicon inverted pyramid structure tower base, which contains an alkali solution and the above-mentioned additive, and the mass ratio of the additive to the alkali solution is 0.5-2:100; the alkali solution is an aqueous solution of an alkali component, and the alkali component includes potassium hydroxide and / or sodium hydroxide.

[0014] The present invention also provides a method for using the single crystal silicon alkali polishing additive for an inverted pyramid structure tower base, and the single crystal silicon is polished using the polishing liquid.

[0015] Preferably, the method for using the single crystal silicon alkali polishing additive for the inverted pyramid structure tower base comprises the following steps: 1) Prepare additives: add 1-2 parts by mass of gum, 0.5-2 parts by mass of sodium lignin sulfonate, 1-3 parts by mass of quaternary ammonium salt, 0.1-0.3 parts by mass of sodium benzoate, 2-3 parts by mass of DL-proline, and 2-5 parts by mass of other additives to deionized water and mix well to prepare the additives; 2) preparing the polishing solution: adding the additive prepared in step 1) to the alkaline solution and mixing well to prepare the polishing solution; 3) Polishing the single crystal silicon using the polishing liquid prepared in step 2).

[0016] Preferably, the polishing temperature in step 3) is controlled at 65-85° C., and the polishing time is controlled at 200-300 s.

[0017] Due to the application of the above technical solution, the present invention has the following beneficial effects: 1) The main role of sodium lignin sulfonate in the alkali polishing process is to prevent the floating of single crystal silicon and the formation of raindrops and air columns; DL-proline helps to improve the black core situation on the back of single crystal silicon after alkali polishing and prevent the formation of black core; sodium benzoate mainly plays a role in sterilization and stabilization of the system.

[0018] 2) Among other additives, the role of the wetting agent in the alkaline polishing process is to help wet the surface of the single crystal silicon and achieve full contact with the alkali, thereby preventing the local polishing rate of the single crystal silicon from being too fast during the alkaline polishing process; the role of the scale inhibitor in the alkaline polishing process is to prevent the sodium silicate, a by-product of alkali polishing, from affecting the polishing effect; the role of the dispersant is to improve the stability of the additive solution and prevent problems such as stratification.

[0019] 3) The adsorption and film-forming properties of the glue can reduce the reaction rate of the

[111] / 100] surface when adsorbed on the silicon wafer surface. At the same time, the catalytic properties of the quaternary ammonium salt can accelerate the reaction rate of the base on the

[110] surface. It can form an evenly distributed and structurally complete inverted pyramid structure on the back of the single crystal silicon, thereby increasing the specific surface area of ​​the back side. The inverted pyramid structure is controllable, which has a positive effect on the conversion efficiency of solar cells.

[0020] 4) The single crystal silicon alkali polishing additive for the inverted pyramid structure base provided by the present invention can realize an inverted pyramid structure on the back side at low alkali concentration and / or low weight loss. On the one hand, it can reduce the fragmentation rate under the general trend of thinning and reduce the manufacturing cost of solar cells; on the other hand, it can reduce the back side reflectivity and improve the bifacial performance of solar cells.

[0021] 5) The method for using the single crystal silicon alkali polishing additive for the inverted pyramid structure tower base provided by the present invention is easy to operate and easy to control, requires simple equipment, has little impact on the environment during use, has low labor intensity, is suitable for continuous large-scale production, and has high promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of the back side of the single crystal silicon after the alkali polishing treatment of Example 1; Figure 2 This is a ZETA image of the back side of single crystal silicon after the alkali polishing treatment according to Example 1. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0024] The present invention provides a method for using a single crystal silicon alkali polishing additive for an inverted pyramid structure tower base, comprising the following steps: 1) Preparation of additives: 1-2 parts by mass of gum, 0.5-2 parts by mass of sodium lignin sulfonate, 1-3 parts by mass of quaternary ammonium salt, 0.1-0.3 parts by mass of sodium benzoate, 2-3 parts by mass of DL-proline, and 2-5 parts by mass of other additives are added to deionized water and mixed evenly to form additives; the gum is at least one of xanthan gum, gum arabic, and konjac gum; the quaternary ammonium salt is at least one of tert-butylammonium chloride, allyltrimethylammonium chloride, and tetraethylammonium chloride; the other additives include a wetting agent, a scale inhibitor, and a dispersant; the mass ratio of the wetting agent, scale inhibitor, and dispersant is 1:(0.5-3):(1-2); the wetting agent is at least one of polyethylene glycol 200, polyethylene glycol 400, β-hydroxyethyl urea, and Tween 60; the scale inhibitor is at least one of hydroxyethylidene diphosphonic acid, sodium ethylenediaminetetramethylenephosphonate, and sodium polyphosphate.

[0025] 2) preparing a polishing solution: adding the additive prepared in step 1) to an alkaline solution and mixing them uniformly to prepare a polishing solution; the polishing solution comprises an alkaline solution and the above-mentioned additives, with the mass ratio of the additives to the alkaline solution being 0.5-2:100; the alkaline solution is an aqueous solution of an alkaline component, and the alkaline component includes potassium hydroxide and / or sodium hydroxide.

[0026] 3) The single crystal silicon is polished using the polishing liquid prepared in step 2), with the polishing temperature controlled at 65-85° C. and the polishing time controlled at 200-300 seconds.

[0027] According to the material ratios and preparation conditions shown in Table 1, single crystal silicon alkali polishing additives for inverted pyramid structure tower bases were prepared according to the above method, which are recorded as Examples 1-4.

[0028] Table 1 Comparative Example 1 The present invention provides a single crystal silicon alkali polishing additive for an inverted pyramid structure tower base and application thereof, which is similar to Example 1, except that tert-butylammonium chloride is not added.

[0029] Comparative Example 2 The present invention provides a single crystal silicon alkali polishing additive for an inverted pyramid structure tower base and application thereof, which is similar to Example 1, except that tetraethylammonium chloride is not added.

[0030] The backside polishing effect of the single crystal silicon alkali polishing additive for the inverted pyramid structure tower base prepared in Examples 1-4 and Comparative Examples 1-2 was tested respectively: The polishing experiment was as follows: 28 mL of a 45 wt% NaOH solution was added to 1.4 L of water, followed by 4 mL of a single-crystal silicon alkaline polishing additive for the inverted pyramid structure base. The mixture was thoroughly mixed. A crystalline silicon wafer (P-type textured wafer) was then placed in the polishing chamber and polished at 75°C for 240 seconds. After polishing, the reflectivity, corrosion rate, and average size of the inverted pyramid structures were measured, and the appearance of the wafer was observed.

[0031] Table 2 The experimental results in Table 2 show that the reflectivity of the experimental silicon wafers was greater than 45%, with no appearance issues, normal corrosion rates, and uniform distribution of inverted pyramid structures. Furthermore, a comparison of the polishing performance of the additives prepared in Examples 1 and 2 revealed that the simultaneous addition of tert-butylammonium chloride and tetraethylammonium chloride significantly improved these properties.

[0032] Example 1: A low-alkali polishing experiment was conducted as follows: 18 mL and 12 mL of a 45 wt% NaOH solution were added to 1.4 L of water. A single-crystal silicon alkaline polishing additive (4 mL) for the inverted pyramid structure base was added and thoroughly mixed. A crystalline silicon wafer (P-type textured wafer) was then placed and polished at 75°C for 240 seconds. After polishing, the reflectivity, corrosion rate, and average size of the inverted pyramid structure were measured, and the appearance of the wafer was observed.

[0033] Table 3 The experimental results in Table 3 show that the reflectivity of the experimental silicon wafers was greater than 45%, with no appearance issues. The inverted pyramid structures were evenly distributed, achieving excellent polishing results even at low alkali concentrations and / or low weight loss. Furthermore, experiments revealed that the polishing performance (reflectivity, corrosion rate, and average size of the inverted pyramids) of the single-crystal silicon alkaline polishing additives for the inverted pyramid bases prepared in Examples 1-4 of the present invention, after aging at 0°C and 50°C for 10 days, was essentially consistent with that at room temperature, with no raindrops, black cores, or floating wafers observed.

[0034] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A single crystal silicon alkali polishing additive for an inverted pyramid structure tower base, characterized in that: The contents of the components are as follows: 1-2 parts by weight of gum, 0.5-2 parts by weight of sodium lignin sulfonate, 1-3 parts by weight of quaternary ammonium salt, 0.1-0.3 parts by weight of sodium benzoate, 2-3 parts by weight of DL-proline, 2-5 parts by weight of other additives, and the balance is deionized water.

2. The single crystal silicon alkali polishing additive for an inverted pyramid structure tower base according to claim 1, characterized in that: The gum is at least one of xanthan gum, gum arabic and konjac gum.

3. The single crystal silicon alkali polishing additive for an inverted pyramid structure tower base according to claim 1, characterized in that: The quaternary ammonium salt is at least one of tert-butylammonium chloride, tetraethylammonium chloride and allyltrimethylammonium chloride.

4. The single crystal silicon alkali polishing additive for an inverted pyramid structure tower base according to claim 1, characterized in that: The other additives include wetting agents, scale inhibitors and dispersants.

5. The single crystal silicon alkali polishing additive for an inverted pyramid structure tower base according to claim 4, characterized in that: The mass ratio of the wetting agent, the scale and corrosion inhibitor, and the dispersant is 1:(0.5-3):(1-2).

6. The single crystal silicon alkali polishing additive for an inverted pyramid structure tower base according to claim 5, characterized in that: The wetting agent is at least one of polyethylene glycol 200, polyethylene glycol 400, β-hydroxyethyl urea and Tween 60.

7. The single crystal silicon alkali polishing additive for an inverted pyramid structure tower base according to claim 5, characterized in that: The scale inhibitor is at least one of hydroxyethylidene diphosphonic acid, sodium ethylenediamine tetramethylene phosphonate, and sodium polyphosphate; and the dispersant is at least one of polyacrylamide and polyvinyl alcohol.

8. The method for using the single crystal silicon alkali polishing additive for an inverted pyramid structure tower base according to claim 1, characterized in that: The steps include: 1) Prepare additives: add 1-2 parts by mass of gum, 0.5-2 parts by mass of sodium lignin sulfonate, 1-3 parts by mass of quaternary ammonium salt, 0.1-0.3 parts by mass of sodium benzoate, 2-3 parts by mass of DL-proline, and 2-5 parts by mass of other additives into deionized water, and mix well to prepare additives; 2) preparing the polishing liquid: adding the additive prepared in step 1) to the alkali solution and mixing them evenly to prepare the polishing liquid; 3) Polishing the single crystal silicon using the polishing liquid prepared in step 2).

9. The method for using the single crystal silicon alkali polishing additive for an inverted pyramid structure tower base according to claim 8, characterized in that: In the step 2), the mass ratio of the additive to the alkali solution is 0.5-2:100; the alkali solution is an aqueous solution of an alkali component, and the alkali component includes potassium hydroxide and / or sodium hydroxide.

10. The method for using the single crystal silicon alkali polishing additive for an inverted pyramid structure tower base according to claim 8, characterized in that: The prepared polishing liquid is used to polish the single crystal silicon, and the polishing temperature is controlled at 65-85° C. and the time is controlled at 200-300 seconds.

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