Photovoltaic solar cell monocrystalline silicon alkaline polishing etching additive and application thereof

Abstract

The invention provides an alkaline polishing and etching additive for monocrystalline silicon of a photovoltaic solar cell and application of the alkaline polishing and etching additive. The alkaline polishing and etching additive comprises the following components: chitosan, inorganic base, quercetin, resveratrol, tannic acid, inositol hexaphosphate and water. The alkaline polishing etching additive can effectively improve the etching uniformity, a layer of compact hydrophobic film is formed on the surface of the etched and polished silicon wafer, secondary pollution is avoided, the pickling process is not needed, and the yield and efficiency of solar cells can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic material preparation, and relates to an additive for alkaline polishing and etching of single crystal silicon for photovoltaic solar cells and its application. Background Art

[0002] Through the continuous improvement of the global technical team in the emerging industry of photovoltaic solar energy, the power generation power and application fields of photovoltaic solar cells are developing rapidly. Currently, the efficiency of photovoltaic solar cells has reached new highs, and continuous cost reduction and optimization are also indispensable. Now the industry is becoming more and more refined, and some sections that urgently need to be optimized are extremely obvious, especially the section that requires pickling after alkaline polishing.

[0003] The alkaline polishing process in the production of photovoltaic solar cells is generally: pre-cleaning - water washing - alkaline polishing - water washing - post-cleaning - water washing - pickling - water washing - slow lifting - drying. In the pickling stage, the chemicals in the tank are: hydrofluoric acid + hydrochloric acid + water, and the volume ratio is: 5:5:90. The functions of pickling are: 1. Using the chelating ability of hydrochloric acid to remove some metal impurities (such as copper, nickel, zinc, etc.) remaining on the surface of the silicon wafer; 2. Hydrofluoric acid can quickly ionize hydrogen ions and fluoride ions in water. The hydrogen ions can quickly occupy the dangling bonds on the surface of the silicon wafer to form a hydrophobic layer, blocking the secondary adsorption of subsequent sections and dust in the air, thereby being beneficial to improving the yield in the photovoltaic cell production workshop. However, at the same time, some problems are brought. Hydrofluoric acid will corrode the oxide layer, resulting in an increase in leakage current, directly affecting the photoelectric conversion efficiency.

[0004] Solving the problem that pickling must be used after alkaline polishing has become extremely important. At present, some commercially available alkaline polishing additives focus on the morphology and reflectivity after polishing, avoiding damage to the front oxide layer. Since a dense hydrophobic film will not be formed on the back after alkaline polishing, the pickling section must be used. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an additive for alkaline polishing and etching of single crystal silicon for photovoltaic solar cells and its application. The alkaline polishing and etching additive of the present invention can form a dense hydrophobic film on the back after alkaline polishing, eliminating the need to use the pickling process. At the same time, the uniformity of alkaline polishing and etching is improved, which helps to improve the yield and efficiency of the photovoltaic production workshop.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides an additive for alkaline polishing and etching of single crystal silicon for photovoltaic solar cells, and the alkaline polishing and etching additive comprises the following components: chitosan, sodium hydroxide, quercetin, resveratrol, tannic acid, cyclohexanehexol hexaphosphate, and water.

[0008] In the present invention, chitosan has strong adsorption capacity for silicon and can effectively bind to the hydrogen-oxygen bonds on the silicon surface; inorganic bases can regulate the stability of the alkaline polishing solution system. Since the polysaccharide concentration in the system is relatively high and it is prone to mildew, inorganic bases can prevent this phenomenon; quercetin is a natural small-molecule polysaccharide that can reduce the surface tension and enable the hydrogen gas generated by the reaction to quickly leave the interface; resveratrol has a certain effect of cleaning the organic matter on the silicon wafer surface; tannic acid can regulate the corrosion rate during the corrosion process and prevent over-etching; cyclohexanehexol hexaphosphate can be combined with resveratrol to strengthen the cleaning of the organic matter on the silicon wafer surface, and at the same time take into account the effect of reducing the surface tension to some extent. It is also a good chelating agent and can form coordination precipitates with some metal ions such as calcium, zinc, and magnesium.

[0009] Preferably, based on 100% by mass percentage, the monocrystalline silicon alkaline polishing and etching additive for photovoltaic solar cells comprises the following components:

[0010] Chitosan 0.4 - 0.9%, inorganic base 0.1 - 0.3%, quercetin 0.3 - 0.6%, resveratrol 0.2 - 0.4%, tannic acid 0.01 - 0.3%, cyclohexanehexol hexaphosphate 0.4 - 1%, and the balance is water.

[0011] In the monocrystalline silicon alkaline polishing and etching additive for photovoltaic solar cells of the present invention, the content of chitosan is 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.7%, 0.8% or 0.9%; the content of sodium hydroxide is 0.1%, 0.15%, 0.18%, 0.2%, 0.25%, 0.28% or 0.3%; the content of quercetin is 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55% or 0.6%; the content of resveratrol is 0.2%, 0.25%, 0.3%, 0.35% or 0.4%; the content of tannic acid is 0.01%, 0.05%, 0.1%, 0.15%, 0.18%, 0.2%, 0.25% or 0.3%; the content of cyclohexanehexol hexaphosphate is 0.4%, 0.5%, 0.6%, 0.8% or 1%.

[0012] Preferably, the weight-average molecular weight of the chitosan is 100,000 - 300,000, such as 100,000, 120,000, 150,000, 180,000, 200,000, 230,000, 250,000, 280,000 or 300,000.

[0013] Preferably, the inorganic base is sodium hydroxide or potassium hydroxide.

[0014] Preferably, the water is deionized water.

[0015] In the present invention, the preparation method of the alkaline polishing and etching additive for single-crystalline silicon of a photovoltaic solar cell is to mix the components, and then the alkaline polishing and etching additive for single-crystalline silicon of the photovoltaic solar cell is obtained.

[0016] Preferably, the mixing is carried out at 25-30 °C (such as 25 °C, 26 °C, 27 °C, 28 °C, 29 °C or 30 °C), and the mixing time is 3-4 hours (such as 3 hours, 3.2 hours, 3.5 hours, 3.8 hours or 4 hours).

[0017] On the other hand, the present invention provides an alkaline polishing and etching solution for single-crystalline silicon of a photovoltaic solar cell, and the alkaline polishing and etching solution includes a basic etching solution and the alkaline polishing and etching additive for single-crystalline silicon of the photovoltaic solar cell as described above.

[0018] Preferably, the mass ratio of the alkaline polishing and etching additive for single-crystalline silicon of the photovoltaic solar cell to the basic etching solution is (0.5-2):100, such as 0.5:100, 0.8:100, 1:100, 1.3:100, 1.5:100, 1.8:100 or 2:100.

[0019] Preferably, the basic etching solution is an alkali solution, and the mass percentage concentration of the alkali solution is 42%-48%, such as 42%, 43%, 44%, 45%, 46%, 47% or 48%.

[0020] Preferably, the alkali solution is an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide.

[0021] In the present invention, the alkaline polishing and etching solution for single-crystalline silicon of the photovoltaic solar cell is obtained by mixing the alkaline polishing and etching additive for single-crystalline silicon of the photovoltaic solar cell with the basic etching solution.

[0022] Preferably, the mixing is carried out at 55-62 °C, such as 55 °C, 58 °C, 60 °C or 62 °C.

[0023] On the other hand, the present invention provides an alkali-etched silicon wafer, and the alkali-etched silicon wafer is obtained by etching a single-crystalline silicon wafer with the alkaline polishing and etching solution for single-crystalline silicon of the photovoltaic solar cell as described above.

[0024] Preferably, during the etching, the temperature of the alkaline polishing and etching solution for single-crystalline silicon of the photovoltaic solar cell is controlled at 55-62 °C, such as 55 °C, 58 °C, 60 °C or 62 °C, and the etching time is 200-240 s, such as 200 s, 210 s, 220 s, 230 s or 240 s.

[0025] During the alkali etching process, silicon first reacts with hydroxide ions in the solution to form silicate and hydrogen gas. The silicate dissolves in water and leaves the etching interface. The reaction repeats continuously. The by-product hydrogen gas becomes a significant obstacle to the reaction. It requires an extremely low surface tension to enable the rapid detachment of hydrogen gas from the interface. This necessitates the intervention of some surfactants. Introducing some polyols and organic acids into the system can make the reaction proceed more smoothly. Organic acids help prevent the destruction of the positive oxide layer. Chitosan in the system is a high-molecular polysaccharide with strong dispersing ability in the solution. It adsorbs on the surface of the silicon wafer after etching, thereby forming a dense hydrophobic layer that can prevent the adsorption of some impurities, which is very helpful for improving the yield and efficiency.

[0026] On the other hand, the present invention provides a photovoltaic solar cell, and the photovoltaic solar cell includes the alkali-etched silicon wafer as described above.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) Adding the additive of the present invention to the polishing etching solution can make the reaction proceed more smoothly. At the same time, it blocks the etching of hydroxide ions on the front side, preventing short circuits in the battery chips. The generated tower-like structure is uniform and there is no residue on the surface, which can achieve a higher reflectivity, helping to reduce the light escape ability and greatly improving the photoelectric conversion efficiency.

[0029] (2) The etching solution containing the etching additive of the present invention can be used for back polishing etching of silicon wafers, effectively forming a hydrophobic film on the back side after etching, which can effectively reduce dirt. At the same time, the corrosion of the oxide layer by hydrofluoric acid in the subsequent pickling can be avoided, reducing the production cost of photovoltaic manufacturing and improving the photoelectric conversion efficiency. Specific Embodiments

[0030] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0031] The sources of raw materials used in the following examples are as follows:

[0032] Chitosan, manufacturer: Macklin, specification: deacetylation degree ≥ 95%, Mw 100000 - 300000;

[0033] Quercetin, manufacturer: Titan, specification: purity ≥ 99.50%;

[0034] Resveratrol, manufacturer: Macklin, specification: ≥ 99.00%;

[0035] Tannic acid, manufacturer: Macklin, specification: AR grade ≥ 98.00%;

[0036] Cyclohexanehexol hexaphosphate, manufacturer: Macklin, specification: 50% aqueous solution of AR grade.

[0037] Example 1

[0038] This example provides an alkaline polishing and etching additive for monocrystalline silicon of a photovoltaic solar cell, which comprises the following components:

[0039] Mix 0.4 g of chitosan, 0.1 g of sodium hydroxide, 0.3 g of quercetin, 0.2 g of resveratrol, 0.01 g of tannic acid, 0.4 g of cyclohexanehexol hexaphosphate and 98.59 g of deionized water, and mix and stir for 4 hours to obtain the alkaline polishing and etching additive;

[0040] Weigh 5 g of the above-mentioned alkaline polishing and etching additive and 1000 g of a base solution (an aqueous solution of potassium hydroxide with a mass concentration of 42%), control the temperature at 62 °C, mix evenly to obtain an alkaline polishing and etching solution, put the monocrystalline silicon wafer to be etched into it and react for 200 s to obtain a silicon wafer with the back polished.

[0041] Example 2

[0042] This example provides an alkaline polishing and etching additive for monocrystalline silicon of a photovoltaic solar cell, which comprises the following components:

[0043] Mix 0.6 g of chitosan, 0.2 g of sodium hydroxide, 0.4 g of quercetin, 0.3 g of resveratrol, 0.05 g of tannic acid, 0.6 g of cyclohexanehexol hexaphosphate and 97.85 g of deionized water, and mix and stir for 4 hours to obtain the alkaline polishing and etching additive;

[0044] Weigh 8 g of the above-mentioned alkaline polishing and etching additive and 1000 g of a base solution (an aqueous solution of potassium hydroxide with a mass percentage concentration of 42%), control the temperature at 62 °C, mix evenly to obtain an alkaline polishing and etching solution, put the monocrystalline silicon wafer to be etched into it, and react for 200 s to obtain a silicon wafer with the back polished.

[0045] Example 3

[0046] This example provides an alkaline polishing and etching additive for monocrystalline silicon of a photovoltaic solar cell, which comprises the following components:

[0047] Mix 0.8 g of chitosan, 0.3 g of sodium hydroxide, 0.6 g of quercetin, 0.3 g of resveratrol, 0.2 g of tannic acid, 1.0 g of cyclohexanehexol hexaphosphate and 96.8 g of deionized water, and mix and stir for 4 hours to obtain the alkaline polishing and etching additive.

[0048] Weigh 12 g of the alkaline polishing and etching additive as described above, 1000 g of the base solution (an aqueous potassium hydroxide solution with a mass concentration of 42%), control the temperature at 62 °C, mix evenly to obtain an alkaline polishing and etching solution, put in the single-crystalline silicon wafer to be etched, react for 200 s, and obtain a silicon wafer with the back polished.

[0049] Example 4

[0050] This example provides a single-crystalline silicon alkaline polishing and etching additive for photovoltaic solar cells, which comprises the following components:

[0051] Mix 0.8 g of chitosan, 0.2 g of sodium hydroxide, 0.4 g of quercetin, 0.2 g of resveratrol, 0.1 g of tannic acid, 0.7 g of cyclohexanehexol hexaphosphate and 97.6 g of deionized water, mix and stir for 4 hours to obtain an alkaline polishing and etching additive;

[0052] Weigh 14 g of the alkaline polishing and etching additive as described above, 1000 g of the base solution (an aqueous potassium hydroxide solution with a mass concentration of 45%), control the temperature at 62 °C, mix evenly to obtain an alkaline polishing and etching solution, put in the single-crystalline silicon wafer to be etched, react for 200 s, and obtain a silicon wafer with the back polished.

[0053] Example 5

[0054] This example provides a single-crystalline silicon alkaline polishing and etching additive for photovoltaic solar cells, which comprises the following components:

[0055] Mix 0.5 g of chitosan, 0.2 g of sodium hydroxide, 0.6 g of quercetin, 0.4 g of resveratrol, 0.2 g of tannic acid, 0.5 g of cyclohexanehexol hexaphosphate and 97.6 g of deionized water, mix and stir for 4 hours to obtain an alkaline polishing and etching additive;

[0056] Weigh 15 g of the alkaline polishing and etching additive as described above, 1000 g of the base solution (an aqueous potassium hydroxide solution with a mass concentration of 48%), control the temperature at 62 °C, mix evenly to obtain an alkaline polishing and etching solution, put in the single-crystalline silicon wafer to be etched, react for 200 s, and obtain a silicon wafer with the back polished.

[0057] Example 6

[0058] This example provides a single-crystalline silicon alkaline polishing and etching additive for photovoltaic solar cells, which comprises the following components:

[0059] Mix 0.9 g of chitosan, 0.2 g of sodium hydroxide, 0.5 g of quercetin, 0.3 g of resveratrol, 0.3 g of tannic acid, 0.5 g of cyclohexanehexol hexaphosphate and 97.3 g of deionized water, mix and stir for 4 hours to obtain an alkaline polishing and etching additive;

[0060] Weigh 20 g of the above-mentioned alkaline polishing and etching additive and 1000 g of the base solution (aqueous potassium hydroxide solution with a mass concentration of 42%). Control the temperature at 55 °C, mix evenly to obtain the alkaline polishing and etching solution. Put the single-crystalline silicon wafer to be etched into it and react for 200 s to obtain the silicon wafer with the back polished.

[0061] Comparative Example 1

[0062] The difference from Example 1 is only that chitosan is replaced with glycosaminoglycan (FineTest, model EU2626, molecular weight: 5000 - 6400).

[0063] Comparative Example 2

[0064] The difference from Example 1 is only that the photovoltaic solar cell single-crystalline silicon alkaline polishing and etching additive does not include quercetin, and the amount of deionized water used is 98.89 g.

[0065] Comparative Example 3

[0066] The difference from Example 1 is only that the photovoltaic solar cell single-crystalline silicon alkaline polishing and etching additive does not include resveratrol, and the amount of deionized water used is 98.79 g.

[0067] Comparative Example 4

[0068] The difference from Example 1 is only that the photovoltaic solar cell single-crystalline silicon alkaline polishing and etching additive does not include tannic acid, and the amount of deionized water used is 98.6 g.

[0069] Comparative Example 5

[0070] The difference from Example 1 is only that the photovoltaic solar cell single-crystalline silicon alkaline polishing and etching additive does not include inositol hexaphosphate, and the amount of deionized water used is 98.99 g.

[0071] Apply the alkaline polishing and etching additive of the present invention to the alkaline polishing and etching of single-crystalline silicon. The obtained polishing effects are shown in Table 1 below (where ISC: short-circuit current, UOC: open-circuit voltage, FF: fill factor, Eta: photoelectric conversion efficiency).

[0072] Table 1

[0073]

[0074]

[0075] The applicant declares that the present invention uses the above embodiments to illustrate the alkaline polishing and etching additive for monocrystalline silicon of photovoltaic solar cells and its application, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. An alkaline polishing and etching additive for single-crystalline silicon of a photovoltaic solar cell, characterized in that, The alkaline polishing and etching additive comprises the following components: chitosan, inorganic base, quercetin, resveratrol, tannic acid, cyclohexanehexol hexaphosphate and water.

2. The alkaline polishing and etching additive for monocrystalline silicon of a photovoltaic solar cell according to claim 1, wherein The alkaline polishing and etching additive for monocrystalline silicon of a photovoltaic solar cell, calculated by mass percentage as 100%, comprises the following components: chitosan 0.4 - 0.9%, inorganic base 0.1 - 0.3%, quercetin 0.3 - 0.6%, resveratrol 0.2 - 0.4%, tannic acid 0.01 - 0.3%, cyclohexanehexol hexaphosphate 0.4 - 1%, and the balance is water.

3. The alkaline polishing and etching additive for single crystal silicon of a photovoltaic solar cell according to claim 1 or 2, characterized in that, The weight-average molecular weight of the chitosan is 100,000 - 300,000; Preferably, the inorganic base is sodium hydroxide or potassium hydroxide; Preferably, the water is deionized water.

4. A monocrystalline silicon alkaline polishing and etching solution for a photovoltaic solar cell, characterized in that, The alkaline polishing and etching solution comprises a basic etching solution and the alkaline polishing and etching additive for monocrystalline silicon of a photovoltaic solar cell according to any one of claims 1 - 3.

5. The alkaline polishing and etching solution for single crystal silicon of a photovoltaic solar cell according to claim 4, characterized in that, The mass ratio of the alkaline polishing and etching additive for monocrystalline silicon of a photovoltaic solar cell to the basic etching solution is (0.5 - 2):

100.

6. The alkaline polishing and etching solution for monocrystalline silicon of a photovoltaic solar cell according to claim 4, wherein, The basic etching solution is an alkaline solution, and the mass percentage concentration of the alkaline solution is 42% - 48%; Preferably, the alkaline solution is an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide.

7. The alkaline polishing and etching solution for single-crystalline silicon of a photovoltaic solar cell according to any one of claims 4-6, characterized in that The alkaline polishing and etching solution for monocrystalline silicon of a photovoltaic solar cell is obtained by mixing the alkaline polishing and etching additive for monocrystalline silicon of a photovoltaic solar cell with the basic etching solution; Preferably, the mixing is carried out at 55 - 62 °C.

8. An alkali-etched silicon wafer, characterized in that, The alkali-etched silicon wafer is obtained by etching a monocrystalline silicon wafer with the alkaline polishing and etching solution for monocrystalline silicon of a photovoltaic solar cell according to any one of claims 4 - 7.

9. The alkali-etched silicon wafer according to claim 8, wherein, During the etching, the temperature of the alkaline polishing and etching solution for monocrystalline silicon of a photovoltaic solar cell is controlled at 55 - 62 °C, and the etching time is 200 - 240 s.

10. A photovoltaic solar cell, characterized in that, The photovoltaic solar cell comprises the alkali-etched silicon wafer according to claim 8 or 9.

Images