Weakly corrosive high-conductivity glass powder and its use

Abstract

The application provides a weakly corrosive and high-conductivity glass powder, raw materials of which include: 30-50% of SiO2, 0.5-2% of Al2O3, 0.5-25% of CdO, 0.5-10% of MnO2, 0.5-6% of ZnO, 3-23% of CuO, 5-30% of Bi2O3, 0-5% of TeO2, 1-13% of rare earth metal oxide, 1-35% of MoO3 and / or WO3, synergistic effect of each component is used, so that the glass powder has lower activity and corrosivity to the passivation layer in the PERC battery, and a wider temperature window, when the silver paste is used in the back silver paste of the PERC solar cell, the silver paste has excellent adhesion tensile force and conductivity, and the conversion efficiency, stability and aging resistance of the battery are also improved.

Description

Technical Field

[0001] This invention relates to the field of crystalline silicon solar cell technology, C03C12 / 00, and particularly to a glass powder with weak corrosion and high conductivity and its applications. Background Technology

[0002] PERC cells are a type of solar cell technology that improves conversion efficiency by adding a dielectric passivation layer to the back of the cell. This passivation layer allows PERC cells to maximize the potential gradient across the PN junction in a standard cell structure, enabling electrons to flow more stably, reducing recombination, and resulting in higher conversion efficiency.

[0003] In the fabrication of crystalline silicon solar cells, silver paste is printed on the front and back sides of the silicon substrate. The front silver paste mainly serves to collect and guide photogenerated carriers, while the back silver paste mainly serves to bind the cells together in series or parallel. The requirements for conductivity are relatively low. However, if the back silver paste corrodes the back passivation layer of the PERC cell too deeply or has too low conductivity, it will have a significant impact on the cell efficiency. The key performance of the back silver paste is determined by the performance of the glass powder in it. Currently, most back-side silver paste products on the market still have the following problems: (1) The glass powder has too high activity, which causes deep corrosion to the silicon wafer, resulting in a low open-circuit voltage. When the activity of the glass powder is reduced, the conductivity of the silver paste cannot be taken into account, resulting in a high series resistance. Ultimately, this is reflected in the reduction of fill factor and efficiency. (2) After the silicon cell is sintered, there is interface cracking at the interface between the back aluminum paste and the silver paste, which leads to increased contact resistance, reduced battery efficiency, reduced back electrode welding performance and adhesion, etc. Therefore, optimizing the glass powder formulation system and composition for the back-side silver paste of PERC cells to improve efficiency is the current goal of silver paste development and research.

[0004] Chinese patent CN103771715B discloses a glass powder for back-side silver paste in solar cells and its preparation method. The technique uses a ratio of glass powder A (40-99%), glass powder B (0-60%), and inorganic additives (0-10%) to reduce the amount of glass powder and silver powder used, thereby increasing the electrode sintering window. However, the glass powder contains lead oxide, which has adverse effects on human health and the environment, and does not conform to future technological and policy development trends. Chinese patent CN103193391B discloses a lead-free glass powder for back-side silver paste in crystalline silicon solar cells and its preparation method. This technique optimizes the component ratio to match the expansion coefficients of the glass powder and the silicon wafer, enhancing the adhesion between the paste and the silicon substrate. However, the silica content in the glass powder is still relatively low, the structural stability of the glass powder cannot be guaranteed, and its solderability still needs improvement.

[0005] Therefore, it is necessary to develop glass powders with low corrosivity, high conductivity, stable structure, good silver paste adhesion, solderability, and aging resistance to match their application in PERC solar cells. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention first provides a glass powder with weak corrosion and high conductivity. The raw materials of the glass powder include, by total weight: 30-50% SiO2, 0.5-2% Al2O3, 0.5-25% CdO, 0.5-10% MnO2, 0.5-6% ZnO, 3-23% CuO, 5-30% Bi2O3, 0-5% TeO2, and 1-13% rare earth metal oxides.

[0007] This application optimizes the composition and weight ratio of glass powder to better balance key properties of the back electrode silver paste, such as corrosivity, conductivity, and aging tensile strength. In the glass powder of this application, the Si-O tetrahedra of SiO2 provide the overall structure of the glass, and Al2O3 improves the structural stability of the glass system, enhances its acid resistance, and effectively reduces the coefficient of thermal expansion. However, this strengthening effect is insufficient; therefore, Bi2O3 is added to incorporate a Bi-O tetrahedral network structure into the overall glass structure, increasing structural stability and widening the glass's temperature window. ZnO has a fluxing effect, increasing the high-temperature fluidity of the glass and further reducing the coefficient of thermal expansion. However, excessive addition can lead to crystallization during quenching, reducing the wettability of the glass to the silicon substrate interface. CdO and MnO2 can accelerate the clarification of the molten glass and promote glass melting. CuO exists in ionic form during the sintering of the PERC back electrode silver paste, enhancing the bonding between the glass and the silver powder in the silver paste and improving the back electrode welding tensile strength. TeO2 contains Te... 4+ With high polarizability, it can promote the melting and blending of silver powder and glass powder in silver paste. In the glass system, it participates in the establishment of the overall network structure as a triangular bipyramidal [TeO4]. However, if too much is added, it will transform from a triangular bipyramidal structure to an unstable triangular pyramid, reducing the structural stability of the glass system. By doping with rare earth metal elements, the glass can easily form crystals during the melting process, which increases the glass softening point and has the ability to restrain the migration of silver ions, thus minimizing the damage to the crystalline silicon layer and reducing carrier recombination loss, thereby improving the conversion efficiency of the battery.

[0008] Furthermore, in the raw materials of the glass powder, the weight of CdO and Bi2O3 accounts for 10-40% of the weight of the glass powder; and the weight of CuO and MnO2 accounts for 5-30% of the weight of the glass powder.

[0009] Preferably, the raw materials of the glass powder include, by total weight, 30-50% SiO2, 0.5-2% Al2O3, 4-20% CdO, 0.5-10% MnO2, 0.5-6% ZnO, 5-18% CuO, 5-30% Bi2O3, 0-5% TeO2, and 1-13% rare earth metal oxides.

[0010] Furthermore, the rare earth metal oxide is selected from at least one of La2O3, Eu2O3, CeO2, Y2O3, and Nb2O5.

[0011] In a preferred embodiment, the rare earth metal oxides are Y2O3 and Nb2O5; preferably, the weight percentage of Y2O3 in the glass powder is 0.5-5%, and the weight percentage of Nb2O5 in the glass powder is 1-8%.

[0012] Furthermore, the raw materials of the glass powder also include 1-35% MoO3 and / or WO3; MoO3 is widely used in supercapacitor anode materials due to its unique crystal structure and excellent optical and electrical properties. When applied to glass systems, it can exhibit high stability and conductivity. Using glass powder containing tungsten oxide can give the back silver paste good conductivity and reduce contact resistance; WO3 has significant surface effects, theoretical specific capacity and good electrochemical performance, which can improve the conductivity of the glass powder.

[0013] In a preferred embodiment, the glass powder further comprises 1-35% MoO3 and WO3; preferably, the weight percentage of MoO3 in the glass powder is 1-5%, and the weight percentage of WO3 in the glass powder is 4-30%. The incorporation of WO3 introduces [WO6] octahedra into the overall structure of the glass, enhancing the stability of the network structure. Simultaneously, W... 6+ With Te 4 + Ions can form WO-Te bonds, improving the compatibility and connectivity within the glass network structure and further enhancing the stability of the glass structure. However, excessive WO3 doping can lead to an excessively high glass transition temperature. MoO3 has a low melting point but reacts relatively inertly with other glass components, which can compensate for the disadvantage of excessive copper content causing aging and over-soldering, thus improving the battery's aging resistance.

[0014] Furthermore, the method for preparing the glass powder includes the following steps:

[0015] S1. The raw materials for preparing glass powder are mixed and then melted into molten glass at high temperature;

[0016] S2. The molten glass is poured into deionized water for quenching to produce glass material;

[0017] S3. After drying the glass material, use dry coarse grinding and wet fine grinding respectively to dry it into powder for later use.

[0018] Furthermore, the high-temperature melting temperature in S1 is 1400-1550℃, and the high-temperature melting holding time is 20-60 minutes.

[0019] Preferably, the high-temperature melting temperature in S1 is 1500-1550℃, and the high-temperature melting holding time is 30-50 minutes.

[0020] Furthermore, the glass powder in S1 can be placed in a ceramic crucible for melting, and the crucible includes, but is not limited to, any one of a quartz crucible, an alumina crucible, and a zirconia crucible.

[0021] Preferably, the ceramic crucible is an alumina crucible; alumina crucibles have superior thermal expansion and contraction properties and corrosion resistance.

[0022] Furthermore, in step S3, the D of the glass powder 50 The average particle size is 0.5-7 μm; more preferably 1.5-2.5 μm.

[0023] Furthermore, the glass powder has a glass transition temperature of 550-700℃ and a coefficient of thermal expansion of (1-5)×10⁻⁶. -6 / ℃.

[0024] Secondly, this application also provides the application of the aforementioned glass powder in the silver paste on the back side of PERC solar cells.

[0025] Furthermore, the raw materials for the back silver paste include: 50-64% silver powder, 0.5-2% glass powder, and organic phase to make up the balance to 100% by total weight.

[0026] In a preferred embodiment, the raw materials of the back silver paste include: 60-64% silver powder, 1-2% glass powder, and 34-40% organic phase by total weight.

[0027] Furthermore, the D of the silver powder 50 The average particle size is 0.5-5 μm, the tap density is 3-8 g / mL, and the specific surface area is 0.2-0.9 g / cm³. 2 .

[0028] In a preferred embodiment, the D of the silver powder 50 The average particle size is 1.5-2 μm, the tap density is 4-6.5 g / mL, and the specific surface area is 0.3-0.6 g / cm³. 2 .

[0029] Furthermore, the organic phase is selected from at least one of butyl carbitol, rosin resin, terpineol, turpentine oil, tributyl citrate, tributyl phosphate, ethylene glycol monobutyl ether, diethylene glycol butyl ether, polyvinyl alcohol, butyl carbitol acetate, ethyl cellulose, and butyl cellulose.

[0030] Furthermore, the organic phase is selected from rosin resin, terpineol, tributyl citrate, and ethyl cellulose.

[0031] Further, based on a total of 100 parts, the weight ratio of the rosin resin, terpineol, tributyl citrate and ethyl cellulose is (1-6):(40-65):(30-50):(0.5-3), preferably (2-5):(50-60):(38-48):(0.7-2.5).

[0032] Furthermore, the dry layer thickness of the silver paste on the back of the PERC solar cell is 10-20 μm.

[0033] Beneficial effects

[0034] 1. This application utilizes the synergistic effect of the components in the glass powder to make the glass powder exhibit lower activity and corrosion of the passivation layer, a wider temperature window, excellent adhesion and conductivity, and also improve the conversion efficiency, stability and aging resistance of the battery in the fabrication of PERC cells.

[0035] 2. The glass powder of this application has improved structural stability and aging resistance by optimizing the composition and increasing the proportion of silicon oxide. Its network structure effectively inhibits the migration of silver ions, avoids damage to the crystalline silicon layer and reduces carrier recombination loss, thereby improving the open circuit voltage and conversion efficiency of the battery.

[0036] 3. The glass powder of this application does not contain alkali metals and alkaline earth metals. Its back silver paste has good acid resistance, corrosion resistance and aging resistance properties, and can pass the test items such as PID, TC200, DH1000.

[0037] 4. The silver paste prepared by the glass powder of this application has high conductivity, good wettability to the aluminum paste interface layer of the battery, and low interface contact resistance, which can further improve the conversion efficiency of the battery; after aging test, the welding tensile strength of the silver paste layer is above 5N. Detailed Implementation

[0038] Example

[0039] Example 1

[0040] This embodiment provides a glass powder with weak corrosion and high conductivity. The raw materials of the glass powder include, by total weight: 31% SiO2, 2% Al2O3, 12% CdO, 4% MnO2, 5% ZnO, 15% CuO, 6% Bi2O3, 5% TeO2, 1% Y2O3, 7% Nb2O5, 2% MoO3, and 10% WO3.

[0041] The glass powder is prepared according to the following steps:

[0042] S1. Mix the raw materials for preparing glass powder according to the formula, place them in an alumina crucible, and melt them into glass liquid at 1530℃, and keep the temperature for 50 minutes.

[0043] S2. Pour the molten glass into deionized water at room temperature for quenching to produce glass material;

[0044] S3. After drying the glass material, it is thoroughly dried into powder using both dry coarse grinding and wet fine grinding methods at 80°C. In the wet fine grinding, anhydrous ethanol is used as the liquid dispersion medium, and the grinding balls are made of zirconium oxide with a diameter of 1 mm. The mass ratio of material to balls to liquid is 2:1:1. The D of the dried glass powder is... 50 The average particle size is 2 μm;

[0045] Secondly, this embodiment also provides an application of the glass powder in the back-side silver paste of a PERC solar cell. The raw materials of the back-side silver paste include: 60% silver powder, 1.5% glass powder, and organic phase to make up the balance to 100% by total weight; the silver powder has a particle size of 1.65 μm, a tap density of 5.2 g / mL, and a specific surface area of ​​0.4 g / cm³. 2 The organic phase is rosin resin, terpineol, tributyl citrate and ethyl cellulose, in a weight ratio of 3.5:53.8:41.1:1.6.

[0046] Examples 2-7

[0047] Consistent with Example 1, the raw material formula and preparation process information of the glass powder are shown in Table 1; the raw materials of the back silver paste are shown in Table 2.

[0048] Table 1

[0049]

[0050]

[0051] Table 2

[0052]

[0053] Comparative Examples 1-3

[0054] It is basically the same as Example 1, except that the raw material formula of the glass powder is different, as shown in Table 1.

[0055] Comparative Example 4

[0056] It is basically the same as Example 1, except that the specifications of the silver powder are different, as shown in Table 2.

[0057] Comparative Example 5

[0058] It is basically the same as Example 1, except that the organic phase of the back silver paste is different. The weight ratio of rosin resin, terpineol, tributyl citrate and ethyl cellulose in the organic phase is 3.5:59.4:35.7:1.4.

[0059] The purity of Y2O3 and Nb2O5 in the raw materials for preparing the glass powder is above 99.99%, and the purity of the remaining raw materials is above 99.9%. The silver powder was purchased from Ningbo Jingxin Electronic Materials Co., Ltd. The rosin resin was purchased from Shanghai Sanlian Industrial Co., Ltd., and the grade is 145#. The terpineol was purchased from Guangdong Baishun Chemical Technology Co., Ltd., and the grade is BS-07. The ethyl cellulose was purchased from Guangzhou Daojun Biotechnology Co., Ltd., and the grade is N-7.

[0060] Performance testing methods:

[0061] 1. Glass powder properties: The coefficient of thermal expansion and glass transition temperature of the glass powder in the above embodiments were tested using a thermal expansion meter and a differential scanning calorimeter, respectively. The results are shown in Table 3.

[0062] 2. Backside Silver Paste Performance: Silver pastes from Examples 1-7 and Comparative Examples 1-5 were printed onto the backside of PERC solar cells using a 325-mesh screen. The dry layer thickness of the silver paste was 15 μm. Aluminum paste and frontside silver paste were then printed using industry-standard methods. The aluminum paste used in the PERC solar cells was purchased from Guangzhou Ruxing Technology Co., Ltd., model RX63600A7, with a printing thickness of 38 μm. The frontside silver paste was purchased from Heraeus Precious Metals Technology (China) Co., Ltd., model SOL9651B, with a printing thickness of 10 μm. After printing all three pastes, a solar sintering furnace was used for sintering at 780℃ for 12 seconds. IV performance tests were then conducted using a solar simulator. The initial tensile strength and the tensile strength after aging of the welded backside silver paste were tested using a tensile testing machine (aging process: 150℃ for 1 hour). The results are shown in Table 4. Performance Test Results:

[0063] Table 3

[0064]

[0065] Table 4

[0066]

Claims

1. A glass powder with weak corrosion and high conductivity, characterized in that, The raw materials of the glass powder include, by total weight: 30-50% SiO2, 0.5-2% Al2O3, 4-20% CdO, 0.5-10% MnO2, 0.5-6% ZnO, 5-18% CuO, 5-30% Bi2O3, 0-5% TeO2, and 1-13% metal oxides; The metal oxides are Y₂O₃ and Nb₂O₅; The weight percentage of Y2O3 in the glass powder is 0.5-5%; The weight percentage of Nb2O5 in the glass powder is 1-8%.

2. The glass powder according to claim 1, characterized in that, The raw materials for the glass powder also include 1-35% MoO3 and / or WO3.

3. The glass powder according to claim 2, characterized in that, The weight percentage of MoO3 in the glass powder is 1-5%, and the weight percentage of WO3 in the glass powder is 4-30%.

4. The glass powder according to claim 3, characterized in that, The glass powder D 50 The average particle size is 0.5-7 μm, the glass transition temperature is 550-700℃, and the coefficient of thermal expansion is (1-5)×10. -6 / ℃.

5. The application of the weakly corrosive, highly conductive glass powder according to any one of claims 1-4 in the silver paste on the back side of PERC solar cells.

6. The application according to claim 5, characterized in that, The raw materials for the back silver paste include: 50-64% silver powder, 0.5-2% glass powder, and organic phase to make up the balance to 100% by total weight.

7. The application according to claim 6, characterized in that, The silver powder D 50 The average particle size is 0.5-5 μm, the tap density is 3-8 g / mL, and the specific surface area is 0.2-0.9 cm². 2 / g.

8. The application according to claim 7, characterized in that, The dry layer thickness of the silver paste on the back of the PERC solar cell is 10-20 μm.

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