A grid line paste for bifacial PERC cells and a preparation method thereof

Abstract

The present invention discloses a gridline slurry for a bifacial PERC cell and a preparation method thereof, belonging to the field of battery electrode slurries. The present invention reduces the resistance of the slurry by using a mixture of aluminum-boron alloy powder and aluminum powder as the aluminum-boron conductive phase, which can reduce the series resistance of the cell and improve the front conversion efficiency of the cell. By limiting the content of boron and oxygen elements in the aluminum-boron alloy powder, the resistance of the slurry is significantly reduced, and aluminum beads are less likely to appear after sintering. By using specific glass powder in combination with the aluminum-boron alloy powder, the line resistance and contact resistance of the back field slurry can be effectively reduced, thereby improving the slurry filling and improving the conversion efficiency. Compared with traditional aluminum paste, the gridline slurry of the present invention can reduce the line resistance by 5-30%, and can improve the conversion efficiency of the cell by 0.05-0.2%.

Description

Technical Field

[0001] The present invention relates to the field of battery electrode slurry, and in particular to a grid line slurry for a bifacial PERC battery and a preparation method thereof. Background Art

[0002] Crystalline silicon solar bifacial passivated emitter and rear (PERC) cell technology builds on conventional PERC cells by adding a backside light-receiving design. SiNx and Al2O3 passivation layers are formed on the backside of the cell, followed by local laser etching of the passivation layer. On the backside, the aluminum paste is printed in a grid pattern, increasing the absorption of reflected light by the backside of the cell. PERC bifacial cells can achieve superposition of front- and backside photoelectric conversion, thereby improving photoelectric conversion efficiency. Because the aluminum paste for bifacial PERC cells is printed only in the laser-opened film area and in a grid pattern, the well-defined, locally deep backside field (BSF) layer and ohmic contact, along with the low bulk resistance of the aluminum layer, contribute to the efficiency improvement of bifacial PERC cells.

[0003] Bifacial PERC cells have similar conductive phase components to traditional PERC cells, primarily containing aluminum powder, an inorganic binder, an organic binder, and other additives. The aluminum powder has a particle size of 1-10μm and an activity greater than 99.0%. However, compared to traditional PERC cells, bifacial PERC cells require the slurry to be printed on grid lines instead of the entire surface. This significantly reduces the printing area, resulting in a significant increase in grid line resistance relative to the resistance of the entire aluminum layer. This change increases the series resistance of the cell, affecting the overall front-side conversion efficiency of the cell. Therefore, existing slurries using aluminum powder as the conductive phase, due to the higher resistance of the aluminum powder, affect the series resistance of the cell, reducing the conversion efficiency of the cell.

[0004] Therefore, developing a conductive phase that can reduce the resistance of aluminum paste, thereby reducing the series resistance of the battery cell and improving the front conversion efficiency of the battery cell is a current research hotspot. Summary of the Invention

[0005] The object of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a grid line paste for bifacial PERC cells and a preparation method thereof, which can reduce the series resistance of the cell and improve the front conversion efficiency of the cell.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a grid line paste for bifacial PERC solar cells, comprising the following components in weight percentage: 70-80% aluminum-boron conductive phase, 1-3% glass powder, and 18-28% organic binder; the aluminum-boron conductive phase comprises aluminum-boron alloy powder and aluminum powder; the boron content of the aluminum-boron alloy powder is 0.05-1%, and the oxygen content is 0.1%-0.2%; the glass powder contains PbO2, SiO2 and B2O3.

[0007] The present invention adopts a mixture of aluminum-boron alloy powder and aluminum powder as the aluminum-boron conductive phase. Compared with aluminum powder alone as the conductive phase, the resistance of the conductive phase can be reduced, the series resistance of the battery cell can be reduced, and the front conversion efficiency of the battery cell can be improved.

[0008] The inventors discovered that the boron and aluminum contents in the aluminum-boron alloy powder significantly affect the performance of the battery cell. When the boron content is within the range of the present invention, the resistance of the battery cell can be significantly reduced. When the oxygen content is lower than 0.1%, aluminum beads are more likely to form after the slurry is sintered. When the oxygen content is higher than 0.2%, the resistance of the slurry after sintering is too high, affecting the electrical performance of the battery cell.

[0009] The inventors further discovered that by using the above-mentioned specific glass powder in combination with aluminum-boron alloy powder, the line resistance and contact resistance of the back field paste can be effectively reduced, thereby improving the paste filling and improving the conversion efficiency of the battery.

[0010] Preferably, the glass powder contains the following components in weight percentage: PbO2 70-90%, SiO2 5-10%, and B2O3 5-20%. The inventors have found through experiments that by using glass powder with this weight percentage in combination with aluminum-boron alloy powder, the line resistance and contact resistance of the back field slurry can be more effectively reduced, the slurry filling can be greatly improved, and the conversion efficiency of the battery can be improved.

[0011] Preferably, the aluminum-boron conductive phase comprises the following components in weight percentage: 20-99% aluminum-boron alloy powder and 1-80% aluminum powder. The inventors have found through experiments that the aluminum-boron conductive phase prepared using the above-mentioned specific weight percentage of aluminum-boron alloy powder can reduce the resistance of the slurry by 5-30% compared with the traditional slurry with aluminum powder as the conductive phase.

[0012] Preferably, the aluminum content in the aluminum-boron alloy powder is 98.5-99.6%.

[0013] Preferably, the median diameter D of the aluminum-boron alloy powder is 50 The median diameter D of aluminum boron alloy powder is 1μm-10μm. 50 >10μm, the slurry will cause printing screen plugging problems, the median diameter D of the aluminum boron alloy powder 50 <1μm will lead to a significant increase in cost.

[0014] Preferably, the aluminum content in the aluminum powder is 99.2-99.7%, the oxygen content is 0.1-0.2%, and the median diameter D of the aluminum powder is 50 1μm-10μm.

[0015] Preferably, the glass powder has a particle size of 0.5 μm-1.2 μm.

[0016] Preferably, the organic binder comprises the following components in weight percentage: 20-35% terpineol, 20-35% butyl carbitol, 10-25% butyl carbitol acetate, and 5-25% ethyl cellulose.

[0017] Preferably, the glass powder is prepared by mixing the raw materials uniformly and then melting them, and then quenching the melted material with water and ball milling to obtain the glass powder.

[0018] The present invention also provides a method for preparing the grid line slurry for the bifacial PERC cell, comprising the following steps: uniformly mixing the raw materials, and then performing dispersion rolling to obtain the grid line slurry for the bifacial PERC cell.

[0019] The beneficial effects of the present invention are as follows: the present invention provides a grid line paste for a bifacial PERC cell, which reduces the resistance of the paste by adopting a mixture of aluminum-boron alloy powder and aluminum powder as the aluminum-boron conductive phase, can reduce the series resistance of the cell, and improve the front conversion efficiency of the cell; by limiting the content of boron and oxygen elements in the aluminum-boron alloy powder, the resistance of the paste is significantly reduced, and aluminum beads are less likely to appear after sintering; by adopting specific glass powder in combination with the aluminum-boron alloy powder, the line resistance and contact resistance of the back field paste can be effectively reduced, thereby improving the paste filling and improving the conversion efficiency of the cell; compared with traditional aluminum paste, the grid line paste of the present invention can reduce the line resistance by 5-30%, and can improve the conversion efficiency of the cell by 0.05-0.2%. DETAILED DESCRIPTION

[0020] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0021] Example 1

[0022] An embodiment of the grid line paste for bifacial PERC cells according to the present invention, wherein the glass powder in this embodiment comprises the following components in weight percentage: PbO2 70%, SiO2 10%, and B2O3 20%; the aluminum-boron conductive phase comprises the following components in weight percentage: aluminum-boron alloy powder 20%, and aluminum powder 80%; wherein the aluminum-boron alloy powder has a boron content of 0.05%, an aluminum content of 99.4%, and an oxygen content of 0.2%, and the median diameter D of the aluminum-boron alloy powder is 0.05%. 50 The aluminum content of the aluminum powder is 99.3%, the oxygen content is 0.2%, and the median diameter D of the aluminum powder is 1 μm. 50The thickness of the organic binder is 10 μm; the organic binder comprises the following components in weight percentage: 35% terpineol, 35% butyl carbitol, 25% butyl carbitol acetate, and 5% ethyl cellulose; the grid line paste for the bifacial PERC battery described in this embodiment comprises the following components in weight percentage: 77% aluminum boron conductive phase, 2% glass powder, and 21% organic binder.

[0023] In Example 1, the preparation method of the glass powder is as follows: the ingredients are prepared according to the above-mentioned glass powder formula (weight percentage), (1) various raw materials are mixed and stirred evenly, and the mixed materials are placed in a crucible and smelted in a high-temperature muffle furnace at a smelting temperature of 1200°C and a smelting time of 90 minutes; (2) the smelted melt is water quenched, and the quenched glass slag is ball-milled to a particle size of 0.5μm-1.2μm, thereby obtaining the glass powder.

[0024] The preparation method of the grid line slurry for the bifacial PERC cell is as follows: ingredients are prepared according to the above formula (weight percentage), the components are mixed and stirred evenly, and dispersion rolling is performed using a three-roll mill to obtain the grid line slurry.

[0025] Example 2

[0026] The only difference between this embodiment and embodiment 1 is that the median diameter D of the aluminum-boron alloy powder is 50 The median diameter D of the aluminum powder is 5 μm; 50 8μm.

[0027] Example 3

[0028] The only difference between this embodiment and embodiment 1 is that the content of boron in the aluminum-boron alloy powder is 0.1%, the content of aluminum is 99.4%, and the median diameter D of the aluminum-boron alloy powder is 0.1%. 50 9μm.

[0029] Example 4

[0030] The only difference between this embodiment and embodiment 1 is that the aluminum-boron conductive phase comprises the following components in weight percentage: aluminum-boron alloy powder 80%, aluminum powder 20%; the content of boron element in the aluminum-boron alloy powder is 0.2%, and the median diameter D of the aluminum-boron alloy powder is 0.2%. 50 The aluminum content of the aluminum powder is 99.3%, the oxygen content is 0.2%, and the median diameter D of the aluminum powder is 7μm. 50 7μm.

[0031] Example 5

[0032] The difference between this embodiment and embodiment 1 is that the glass powder contains the following components in weight percentage: PbO2 80%, SiO2 10%, B2O3 10%, and the median diameter D of the aluminum-boron alloy powder is 50The median diameter D of the aluminum powder is 7 μm; 50 7μm.

[0033] Example 6

[0034] The only difference between this embodiment and embodiment 1 is that the glass powder contains the following components in weight percentage: PbO2 90%, SiO2 5%, B2O3 5%; the median diameter D of the aluminum powder is 50 1μm.

[0035] Example 7

[0036] The only difference between this embodiment and embodiment 1 is that the glass powder contains the following components in weight percentage: PbO2 80%, SiO2 10%, and B2O3 10%; the aluminum-boron conductive phase contains the following components in weight percentage: aluminum-boron alloy powder 80%, aluminum powder 20%; wherein the content of boron in the aluminum-boron alloy powder is 0.1%, and the median diameter D of the aluminum-boron alloy powder is 0.1%. 50 The median diameter D of the aluminum powder is 7 μm; 50 7μm.

[0037] Example 8

[0038] The difference between this embodiment and embodiment 1 is that the glass powder contains the following components in weight percentage: PbO2 80%, SiO2 10%, B2O3 10%; the aluminum-boron conductive phase contains the following components in weight percentage: aluminum-boron alloy powder 60%, aluminum powder 40%; wherein the content of boron in the aluminum-boron alloy powder is 0.1%, and the median diameter D of the aluminum-boron alloy powder is 0.1%. 50 10μm.

[0039] Example 9

[0040] The only difference between this embodiment and embodiment 1 is that in the aluminum-boron conductive phase, the content of boron element in the aluminum-boron alloy powder is 1%, and the content of oxygen element is 0.1%. The grid line paste for the bifacial PERC cell contains the following components in weight percentage: 70% aluminum-boron conductive phase, 3% glass powder, and 27% organic binder.

[0041] Example 10

[0042] The only difference between this embodiment and embodiment 1 is that the grid line paste for the bifacial PERC cell comprises the following components in weight percentage: 80% aluminum-boron conductive phase, 2% glass powder, and 18% organic binder.

[0043] Example 11

[0044] The only difference between this embodiment and embodiment 1 is that the grid line paste for the bifacial PERC cell comprises the following components in weight percentage: 71% aluminum-boron conductive phase, 1% glass powder, and 28% organic binder.

[0045] Comparative Example 1

[0046] The only difference between this comparative example and Example 1 is that the conductive phase contains only aluminum powder, and the glass powder contains the following components in weight percentages: PbO2 50%, SiO2 15%, and B2O3 35%.

[0047] Comparative Example 2

[0048] The only difference between this comparative example and Example 1 is that the conductive phase contains only aluminum powder without glass powder.

[0049] Comparative Example 3

[0050] The only difference between this comparative example and Example 1 is that the glass powder contains the following components in weight percentage: PbO2 40%, SiO2 15%, and B2O3 45%.

[0051] Comparative Example 4

[0052] The only difference between this comparative example and Example 1 is that in the aluminum-boron conductive phase, the content of boron element in the aluminum-boron alloy powder is 0.03%, and the content of oxygen element is 0.05%.

[0053] Comparative Example 5

[0054] The only difference between this comparative example and Example 1 is that in the aluminum-boron conductive phase, the content of boron element in the aluminum-boron alloy powder is 2%, and the content of oxygen element is 0.5%.

[0055] Effect Examples

[0056] The gate line pastes of the above-mentioned Examples 1-11 and Comparative Examples 1-5 were printed on the surface of the battery cells respectively, and the conversion efficiency of the battery was tested using an IV tester, and the open circuit voltage and open circuit current of the battery were tested using an IV tester.

[0057] Table 1

[0058] Eta (%) Uoc(V) Isc(A) FF Rsh Rs(mΩ) Example 1 22.362 0.6873 18.102 79.35 490 1.95 Example 2 22.413 0.6875 18.102 79.42 498 1.93 Example 3 22.424 0.6887 18.093 79.51 520 1.86 Example 4 22.468 0.6883 18.098 79.53 458 1.83 Example 5 22.418 0.6881 18.096 79.48 456 1.86 Example 6 22.424 0.6883 18.098 79.46 498 1.88 Example 7 22.51 0.6892 18.105 79.64 522 1.78 Example 8 22.422 0.6871 18.11 79.46 546 1.91 Example 9 22.421 0.6876 18.105 79.42 520 1.91 Example 10 22.425 0.6877 18.099 79.45 522 1.89 Example 11 22.429 0.6874 18.108 79.46 527 1.89 Comparative Example 1 22.314 0.6871 18.091 79.25 520 1.99 Comparative Example 2 22.305 0.6869 18.105 79.18 589 2.01 Comparative Example 3 22.337 0.6873 18.095 79.29 517 2.0 Comparative Example 4 22.326 0.6873 18.093 79.26 530 2.0 Comparative Example 5 22.276 0.6875 18.089 79.08 489 2.17

[0059] As can be seen from Table 1, compared with Comparative Example 1 in which boron powder is not added to the conductive phase, Examples 1-11 of the present invention have a conversion efficiency Eta increased by 0.05-0.2%, and Rs reduced by 5-30%; Comparative Example 2 has a higher contact resistance of the slurry, a higher Rs, and a lower conversion efficiency Eta due to the lack of addition of glass powder; Comparative Example 3 has a higher Rs of the battery due to the weight proportions of the components of the glass powder exceeding the scope of the present invention; Comparative Example 4 has a higher Rs of the battery due to the contents of boron and oxygen elements not reaching the specified range of the present invention, and aluminum beads are present on the surface of the slurry obtained in Comparative Example 4; Comparative Example 5 has an excessively large resistance Rs due to the contents of boron and oxygen elements exceeding the specified range of the present invention, which has a greater impact on the electrical properties of the battery cell.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A grid line paste for bifacial PERC cells, characterized in that: The invention comprises the following components in weight percentage: 70-80% aluminum-boron conductive phase, 1-3% glass powder, and 18-28% organic binder; the aluminum-boron conductive phase comprises aluminum-boron alloy powder and aluminum powder; the boron content in the aluminum-boron alloy powder is 0.05-1%, and the oxygen content is 0.1%-0.2%; the glass powder comprises the following components in weight percentage: 70-90% PbO2, 5-10% SiO2, and 5-20% B2O3; the aluminum-boron conductive phase comprises the following components in weight percentage: 20-99% aluminum-boron alloy powder and 1-80% aluminum powder.

2. The grid line paste for bifacial PERC solar cells according to claim 1, wherein: The median diameter D of the aluminum boron alloy powder 50 1μm-10μm.

3. The busbar paste for bifacial PERC solar cells according to claim 1, wherein: The aluminum content in the aluminum powder is 99.2-99.7%, and the oxygen content is 0.1-0.2%.

4. The grid line paste for bifacial PERC solar cells according to claim 1, wherein: The median diameter D of the aluminum powder 50 1μm-10μm.

5. The grid line paste for bifacial PERC solar cells according to claim 1, wherein: The particle size of the glass powder is 0.5 μm-1.2 μm.

6. The busbar paste for bifacial PERC solar cells according to claim 1, wherein: The organic adhesive comprises the following components in percentage by weight: 20-35% of terpineol, 20-35% of butyl carbitol, 10-25% of butyl carbitol acetate, and 5-25% of ethyl cellulose.

7. The busbar paste for bifacial PERC solar cells according to claim 1, wherein: The glass powder preparation method comprises the following steps: uniformly mixing various raw materials and then smelting the raw materials; then water quenching and ball milling the smelted materials to obtain the glass powder.

8. The method for preparing a grid line paste for a bifacial PERC cell according to any one of claims 1 to 7, wherein: The method comprises the following steps: uniformly mixing the raw materials, and then performing dispersion rolling to obtain the grid line slurry for the bifacial PERC battery.