Silver paste used for positive electrodes of solar batteries and grid lines, preparation method thereof and solar battery containing same

[0028] Example 1

[0029] The preparation of the silver paste for the front electrode of the solar cell and the grid line includes the following steps:

[0030] 1. Prepare highly dispersed ultrafine silver powder slurry by chemical liquid phase reduction method: prepare 20L of silver nitrate into a 0.15mol/L solution, adjust its pH to 7 with ammonia and nitric acid to form a silver ammonia solution, and then The reducing agent hydrazine hydrate is made into a 0.30mol/L solution of 20L, then 100g of the dispersant polyvinylpyrrolidone is added to the reducing agent solution, the pH value is adjusted to 8 with ammonia and nitric acid, and the silver ammonia solution is heated at 300 rpm Under electric stirring, add dropwise to the reducing agent and dispersant solution at a dropping rate of 2L/min. After the dropping is completed, react for another 10 minutes to obtain a highly dispersed ultrafine silver powder slurry;

[0031] 2. Solid-liquid separation of the ultrafine silver powder slurry to obtain wet silver powder: use a centrifuge to separate the solid and liquid, and the obtained solid is wet silver powder;

[0032] 3. Wash the wet silver powder: wash the solid with deionized water to make the resistivity of the washing liquid reach 1MΩ·cm, then centrifuge, and finally wash with 4L butyl carbitol for 3 times, and then centrifuge to obtain the wet state Silver powder

[0033] 4. Without drying, directly use the wet silver powder, glass powder, additives and organic carrier to prepare a positive silver paste as described below: First, 100 grams of wet silver powder is tested for solid content, and the test solid content is 95%. 100g wet silver powder and 5g glass powder (according to the application number: 200910304311.6, the weight percentage of the main components in the glass powder is: PbO 64.9%, B 2 O 3 3.5%, SiO 2 24.8%, ZnO 2.7%, TiO 0.7%, Al 2 O 3 3.4%), 1g additive (using BaO and CaO powder, the weight ratio of BaO and CaO powder is 1, the particle size range is 1-5 microns) and 13g of organic vehicle (using terpineol as the organic solvent to account for 70% of the total weight of the organic vehicle %, ethyl cellulose as a thickener accounts for 15% of the total weight of the organic carrier, stearate as a surfactant accounts for 10% of the total weight of the organic carrier, ethanol as a diluent accounts for 5% of the total weight of the organic carrier); Mix and stir, and grind with a three-roll mill for 3 to 5 times until the fineness of the slurry is below 8 μm to obtain the desired silver slurry.

[0034] After the silver paste is printed on the solar cell substrate and sintered, the front electrode and grid line of the solar cell are obtained. The electrode and grid line have no defects such as breakpoints, accumulation and disconnection, and the monocrystalline silicon solar cell sheet prepared can be Obtained excellent photoelectric conversion efficiency, which reached 17.324% after testing. Other electrical properties are shown in Table 1. From Table 1, the photoelectric conversion efficiency of Comparative Example 1 is 16.832%. Example 1 is about 0.5% higher than Comparative Example 1, and its performance is obvious Better than Comparative Example 1, in general, every 0.1% increase in photoelectric conversion efficiency is a great improvement. figure 1 It is a SEM comparison picture of the thick film of the prepared silver paste after printing and drying. The left picture is made by dry silver powder in Comparative Example 1, and the right picture is made by wet silver powder in Example 1. by figure 1 It can be seen from the left picture that the silver paste made of dry silver powder obviously has hard agglomerates (the white agglomerates in the picture), while there are no agglomerates in the right picture, and the particles are evenly distributed. After sintering, the test proves that the photoelectric conversion efficiency of the solar cell printed and fired in Example 1 using the wet silver powder without hard agglomerates is significantly higher than that of Comparative Example 1 with hard agglomerates.

[0035] Example 2

[0036] The preparation of the silver paste for the front electrode of the solar cell and the grid line includes the following steps:

[0037] 1. Prepare highly dispersed ultrafine silver powder slurry by chemical liquid phase reduction method: prepare 20L of silver nitrate into a 0.15mol/L solution, adjust its pH to 7 with ammonia and nitric acid to form a silver ammonia solution, and then The reducing agent formaldehyde is prepared into 20L of 0.30mol/L solution, and then 100g of dispersant polyvinyl alcohol is added to the reducing agent solution, the pH value is adjusted to 8 with ammonia and nitric acid, and the silver ammonia solution is driven at 300 revolutions per minute. Add dropwise to the reducing agent and dispersant solution under stirring at a dropping rate of 2L/min. After the dropping is completed, react for 10 minutes to obtain a highly dispersed ultrafine silver powder slurry;

[0038] 2. Solid-liquid separation of the ultrafine silver powder slurry to obtain wet silver powder: use a centrifuge to separate the solid and liquid, and the obtained solid is wet silver powder;

[0039] 3. Wash the wet silver powder: wash with deionized water to make the resistivity of the lotion reach 1MΩ·cm, then centrifuge, and finally wash 3 times with 4L butyl carbitol, and then centrifuge to obtain wet silver powder ;

[0040] 4. Without drying, directly use the wet silver powder, glass powder, additives and organic carrier to prepare a positive silver paste as described below: First, 100 grams of wet silver powder is tested for solid content, and the test solid content is 95%. 100g wet silver powder and 5g glass powder, 1g additive and 13g organic vehicle (the formula of glass powder, additive and organic vehicle are the same as in Example 1) are mixed and stirred, and the three-roll mill grinds 3 to 5 times until the slurry fineness is Below 8μm, the required silver paste is obtained.

[0041] After the silver paste is printed on the solar cell substrate and sintered, the front electrode and grid line of the solar cell are obtained. The electrode and grid line have no defects such as breakpoints, accumulation and disconnection, and the monocrystalline silicon solar cell sheet prepared can be Obtained excellent photoelectric conversion efficiency, reached 17.683% after testing, other electrical properties are shown in Table 1. The SEM image of the thick film of the prepared silver paste after printing and drying and figure 1 The picture on the right is similar, there are no agglomerates, and the particles are evenly distributed.

[0042] Example 3

[0043] The preparation of the silver paste for the front electrode of the solar cell and the grid line includes the following steps:

[0044] 1. Prepare highly dispersed ultrafine silver powder slurry by chemical liquid phase reduction method: prepare 20L of silver nitrate into a 0.15mol/L solution, adjust its pH to 7 with ammonia and nitric acid to form a silver ammonia solution, and then The reducing agent ascorbic acid is prepared into 20L of 0.30mol/L solution, and then 100g of dispersant gelatin is added to the reducing agent solution, and the pH value is adjusted to 8 with ammonia and nitric acid, and the silver ammonia solution is stirred at 300 revolutions per minute. Add dropwise to the reducing agent and dispersant solution at a dropping rate of 2L/min. After the dropping is completed, react for another 10 minutes to obtain a highly dispersed ultrafine silver powder slurry;

[0045] 2. Solid-liquid separation of the ultrafine silver powder slurry to obtain wet silver powder: use a centrifuge to separate the solid and liquid, and the obtained solid is wet silver powder;

[0046] 3. Wash the wet silver powder: wash with deionized water to make the resistivity of the lotion reach 1MΩ·cm, then centrifuge, and finally wash 3 times with 4L butyl carbitol, and then centrifuge to obtain wet silver powder , And then prepare the positive silver paste. First, test the solid content of 100g wet silver powder. The test solid content is 95%. 100g wet silver powder and 5g glass powder, 1g additive and 13g organic carrier (glass powder, additive and organic The carrier formula is the same as in Example 1) mixing and stirring, and grinding with a three-roll mill for 3 to 5 times until the slurry fineness is less than 8 μm to obtain the desired silver slurry.

[0047] After the silver paste is printed on the solar cell substrate and sintered, the front electrode and grid line of the solar cell are obtained. The electrode and grid line have no defects such as breakpoints, accumulation and disconnection, and the monocrystalline silicon solar cell sheet prepared can be Obtained excellent photoelectric conversion efficiency, which reached 17.801% after testing. See Table 1 for other electrical properties. The SEM image of the thick film of the prepared silver paste after printing and drying and figure 1 The picture on the right is similar, there are no agglomerates, and the particles are evenly distributed.