An aluminum electrode, its preparation process and application

Abstract

The application relates to the technical field of metal electrodes, and discloses an aluminum electrode and a preparation process and application thereof. The preparation process of the aluminum electrode comprises the following steps: printing aluminum paste, wherein the aluminum paste comprises aluminum powder, a metal compound, an organic phase, an inorganic glass phase and conductive carbon nanomaterial, the inorganic glass phase comprises rare earth oxides; sintering the aluminum paste: placing the aluminum paste in a pre-sintering section at 150-350 DEG C, so that the organic phase is volatilized and decomposed; placing the aluminum paste in a middle sintering section at 350-600 DEG C, so that the inorganic glass phase is softened into a glass body, and a silicon-oxygen protective thin layer is formed on the doped polysilicon after etching and anti-reflection passivation; placing the aluminum paste in a post-sintering section at 600-700 DEG C, so that a metal-based composite carbon nanomaterial layer is formed on the silicon-oxygen protective thin layer, the aluminum powder is gradually dissolved, and the aluminum layer is formed on the metal-based composite carbon nanomaterial layer after cooling. The aluminum paste is not in contact with the doped polysilicon in the sintering process, and the obtained aluminum electrode can greatly reduce the interface metal composite and contact resistance.

Description

Technical Field

[0001] This invention relates to the field of metal electrode technology, specifically to an aluminum electrode, its fabrication process, and its application in solar cells. Background Technology

[0002] In the metallization process of solar cells, existing aluminum paste is usually printed onto the surface of the anti-reflection passivation layer of the solar cell to form an electrode pattern. Then, it is sintered at conventional high temperatures (such as 800-1200℃) to burn through the anti-reflection passivation layer and form an aluminum electrode that contacts doped polycrystalline silicon.

[0003] Among them, the existing aluminum paste, such as the aluminum paste for the back electrode of silicon solar cells and its preparation method disclosed in CN102779567B, can effectively reduce the warping caused by the mismatch of thermal expansion coefficients between the aluminum back field and the silicon wafer after sintering, and the aluminum back field surface is smooth without obvious defects such as aluminum beads or aluminum clumps. However, in the conventional metallization sintering process, this aluminum paste can react with the doped polycrystalline silicon (especially heavily doped polycrystalline silicon) of the solar cell, and react with the n, n+, and n++ silicon of the solar cell to form an anti-doped layer. This will not only greatly reduce the interfacial metal recombination of the solar cell, but also lead to a large back contact resistance of the solar cell, making it impossible to form a good ohmic contact, which will greatly reduce the photoelectric conversion efficiency of the solar cell. Summary of the Invention

[0004] One of the objectives of this invention is to overcome the shortcomings of the prior art and provide a process for preparing an aluminum electrode so that the aluminum paste does not react with doped polycrystalline silicon during its sintering process, thereby greatly reducing interfacial metal recombination and contact resistance of the resulting aluminum electrode.

[0005] The second objective of this invention is to overcome the shortcomings of the prior art and provide an aluminum electrode prepared using the above-described preparation process.

[0006] The third objective of this invention is to overcome the shortcomings of the prior art and provide an application of aluminum electrodes, namely, to apply aluminum electrodes to solar cells.

[0007] Based on this, the present invention discloses a process for preparing an aluminum electrode, comprising the following process steps:

[0008] Step S1: Print aluminum paste onto the surface of the battery cell; wherein the aluminum paste comprises the following raw materials by weight percentage: 65-85% aluminum powder, 1.5-8% metal compound, 4-15% organic phase, 7-18% inorganic glass phase and 0.05-0.1% conductive carbon nanomaterials, wherein the inorganic glass phase comprises rare earth oxides in the aluminum paste at a weight percentage of 0.01-1%;

[0009] Step S2, sintering aluminum paste:

[0010] Step S21: Place the printed aluminum paste in the pre-sintering section at 150-350℃ to dry the aluminum paste, allowing the organic phase to volatilize and decompose.

[0011] Step S22: The aluminum paste is then placed in the intermediate sintering section at 350-600℃ to soften the inorganic glass phase and form a glass body. After that, it flows to the anti-reflection passivation layer outside the solar cell to etch and remove the anti-reflection passivation layer, so as to form a silicon-oxygen protective thin layer of doped polycrystalline silicon attached to the solar cell.

[0012] In step S23, the aluminum paste is placed in the post-sintering section at 600-700℃, so that the metal compound and the conductive carbon nanomaterial cross-link to form a metal-based composite carbon nanomaterial layer attached to the silicon oxide protective thin layer. Then, the aluminum powder is gradually melted, and the aluminum paste is placed in the cooling section to cool down to room temperature, so that the melted aluminum powder forms an aluminum layer attached to the metal-based composite carbon nanomaterial layer, thus obtaining the aluminum electrode.

[0013] Preferably, in step S1, the conductive carbon nanomaterial is carbon nanotube and / or graphene; the metal compound is at least one of tin oxide, indium oxide and antimony oxide.

[0014] Preferably, in step S1, the rare earth oxide is at least one of cerium oxide, lanthanum oxide, erbium oxide, yttrium oxide, and samarium oxide; the inorganic glass phase further includes at least one of bismuth oxide, boron oxide, silicon dioxide, calcium oxide, aluminum oxide, zinc oxide, and lead oxide.

[0015] Preferably, in step S1, the organic phase is at least one selected from terpineol, acetone, isopropanol, tetrabutyl titanate, ethanol, ethyl acetate, dichloroethane, and polypropylene.

[0016] Preferably, before step S1, the method further includes the following step of preparing aluminum paste: first, the aluminum powder, metal compound and conductive carbon nanomaterials of the specified amount are mixed evenly, then the inorganic glass phase and organic phase of the specified amount are added, and the mixture is ground to obtain an aluminum paste with a viscosity of 15000-25000 mpa.s / 25℃, a paste fineness of 12-20 μm and a sheet resistance of 6-15 mΩ / sq.

[0017] Preferably, step S22 specifically includes: placing aluminum paste in a temperature range of 350-500°C to soften the inorganic glass phase and form the glass body, which then flows downwards to coat the metal compound and conductive carbon nanomaterials; and then placing the aluminum paste in a temperature range of 500-600°C to etch and remove the glass body flowing to the anti-reflection passivation layer, thereby forming the silicon oxide protective thin layer.

[0018] Preferably, before the cooling section, step S23 specifically includes: first placing the aluminum paste in a temperature range of 600-650°C to allow the metal compound to crosslink with the conductive carbon nanomaterial to form the metal-based composite carbon nanomaterial layer, and then placing the aluminum paste in a temperature range of 650-700°C to allow the aluminum powder to gradually melt.

[0019] Preferably, in step S1, the aluminum powder is prepared according to a particle size of D. 50 =5um, D 90 Aluminum powder with a gradation ratio of 8µm.

[0020] More preferably, in step S23, after forming the metal-based composite carbon nanomaterial layer, the specific preparation process of the aluminum layer is as follows: aluminum paste is placed in a temperature range of 650-700℃, so that aluminum powder is gradually melted. The melted aluminum powder and glass flow downward together to cool in the cooling section to form an aluminum precipitation layer attached to the metal-based composite carbon nanomaterial layer and an aluminum coating layer with aluminum encapsulated by the glass. The remaining aluminum powder grows to form a volume aluminum layer attached to the aluminum coating layer, thus obtaining the aluminum layer.

[0021] The present invention also discloses an aluminum electrode, wherein the aluminum electrode is formed sequentially on a doped polycrystalline silicon of a solar cell by the aluminum electrode preparation process described above. The process consists of a silicon oxide protective thin layer, a metal-based composite carbon nanomaterial layer, and an aluminum layer.

[0022] Preferably, the thickness of the silicon-oxygen protective layer is 0.5-5 nm, and the thickness of the metal-based composite carbon nanomaterial layer is 0.5-10 nm.

[0023] Preferably, the aluminum layer comprises an aluminum precipitate layer, an aluminum cladding layer, and a volumetric aluminum layer that are sequentially self-grown on the surface of the metal-based composite carbon nanomaterial layer.

[0024] The present invention also discloses an application of an aluminum electrode, namely, the application of the aluminum electrode described above in the present invention in a solar cell.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] In the preparation process of the aluminum electrode of the present invention, the rare earth oxides added to the specially formulated aluminum paste can lower the softening temperature of the inorganic glass phase in the specific sintering process of the present invention, so that the inorganic glass phase softens at a temperature below 400°C to form a flowing glass body, and can inhibit the reaction between other inorganic glass phases in the glass body and the doped polycrystalline silicon. Therefore, the glass body only covers the surface of the doped polycrystalline silicon, and sintering forms a silicon oxide protective thin layer attached to the doped polycrystalline silicon, which plays a role in protecting the doped polycrystalline silicon, isolating the aluminum powder from the doped polycrystalline silicon, so as to prevent the aluminum powder from reacting with the doped polycrystalline silicon, thus greatly reducing the interfacial metal recombination, and the silicon oxide protective thin layer does not affect the current transmission, and can form a good ohmic contact; moreover, in the specific sintering process of the present invention, the conductive carbon nanomaterials and metal compounds with low resistivity in the specially formulated aluminum paste can also form a metal-based composite carbon nanomaterial layer between the aluminum layer and the silicon oxide protective thin layer, so as to further enhance the conductivity of the aluminum electrode and greatly reduce the contact resistivity.

[0027] In summary, this invention employs a specially formulated aluminum paste and a specific sintering process. In this sintering process, by utilizing the different softening or melting temperatures of different raw materials in the aluminum paste, the fluidity of the softened materials, the different reactions between raw materials and between raw materials and the anti-reflection passivation layer at different temperatures, the density of raw materials and reactants, and the characteristics of raw materials and reactants, a new aluminum electrode can be self-grown (which includes a silicon oxide protective thin layer, a metal-based composite carbon nanomaterial layer, and an aluminum layer sequentially self-grown on doped polycrystalline silicon). When this aluminum electrode is applied to solar cells, it can significantly reduce interfacial metal recombination and contact resistivity, thus effectively improving the photoelectric conversion efficiency of the cell. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of aluminum paste before sintering in the preparation process of an aluminum electrode according to this embodiment.

[0029] Figure 2 This is a schematic diagram of the structure of the aluminum electrode after sintering of aluminum paste in the aluminum electrode preparation process of this embodiment. Detailed Implementation

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] The preparation process of an aluminum electrode according to this embodiment includes the following process steps:

[0033] Step 1, Prepare aluminum paste:

[0034] Aluminum paste, by mass percentage, comprises the following raw materials: 65-85% aluminum powder, 1.5-8% metal compounds, 4-15% organic phase, 7-18% inorganic glass phase, and 0.05-0.1% conductive carbon nanomaterials.

[0035] The aluminum powder is not simply uniformly sized aluminum powder particles, but rather particles with a particle size of D. 50 =5um, D 90 The aluminum powder with a particle size of 8µm is formed. This can effectively control the melting rate and reaction mode of aluminum powder with different particle sizes during subsequent high-temperature sintering. During the subsequent sintering process, the smaller aluminum powder particles melt first and then grow on the larger aluminum powder particles, so that the bulk aluminum accumulates to form a dense and smooth volume aluminum layer, ensuring its excellent electrical conductivity.

[0036] The metal compound is at least one of tin oxide, indium oxide, and antimony oxide; of course, in addition to existing in the aluminum paste in the form of oxides, metallic tin, indium, and antimony can also exist in the aluminum paste in the form of other compounds.

[0037] The organic phase is an organic solvent and / or organic additive, including but not limited to at least one of terpineol, acetone, isopropanol, tetrabutyl titanate, ethanol, ethyl acetate, dichloroethane and polypropylene.

[0038] The inorganic glass phase comprises 0.01-1% by weight of rare earth oxides in the aluminum paste, with the remainder being other inorganic glass phases; the other inorganic glass phases are at least one of bismuth oxide, boron oxide, silicon dioxide, calcium oxide, aluminum oxide, zinc oxide and lead oxide; the rare earth oxides are at least one of cerium oxide, lanthanum oxide, erbium oxide, yttrium oxide and samarium oxide.

[0039] Among them, the conductive carbon nanomaterials are nano-sized carbon nanotubes and / or graphene.

[0040] The specific steps for preparing aluminum paste are as follows:

[0041] Step 11: According to the above-mentioned raw material formula for aluminum paste, weigh the prescribed amounts of aluminum powder, metal compound, and conductive carbon nanomaterials, and mix them evenly to obtain a mixture. The mixing method includes, but is not limited to, manual stirring or grinding with a grinding equipment (such as grinding with a planetary ball mill for 2 hours) to ensure that the aluminum powder, metal compound, and conductive carbon nanomaterials are fully and evenly mixed.

[0042] Step 12: According to the above raw material formula for aluminum paste, weigh the inorganic glass phase and organic phase in the prescribed amounts, pour the weighed inorganic glass phase and organic phase into the mixture in step 11, continue mixing, and then put the mixed material into a grinding device such as a three-roll mill for grinding until an aluminum paste with a viscosity of 15000-25000 mpa.s / 25℃, a paste fineness of 12-20 μm, and a sheet resistance of 6-15 mΩ / sq is obtained.

[0043] Step 2, Aluminum paste printing: The aluminum paste is transferred from the screen to the solar cell under the force of a squeegee, forming an electrode pattern on the surface of the anti-reflection passivation layer (such as silicon nitride) of the solar cell (see...). Figure 1 The preferred printing method for aluminum paste is screen printing.

[0044] Step 3, Sintering aluminum paste:

[0045] Step 31: Place the printed aluminum paste (i.e., electrode pattern) in a pre-sintering section at 150-350℃ to dry the aluminum paste, allowing the organic phase in the aluminum paste to volatilize and decompose.

[0046] Step 32: The aluminum paste is then placed in the intermediate sintering section at 350-600℃, so that the inorganic glass phase in the aluminum paste softens and forms a glass body. After that, it flows to the surface of the anti-reflection passivation layer outside the solar cell to etch and remove the anti-reflection passivation layer, thereby forming a silicon oxide protective thin layer attached to the doped polycrystalline silicon inside the solar cell.

[0047] Specifically, in step 32, the aluminum paste is first placed in a temperature range of 350-500°C to soften the inorganic glass phase in the aluminum paste and form a flowing glass body. At this time, the glass body flows and coats the outer surface of the metal compound and conductive carbon nanomaterial, allowing the metal compound and conductive carbon nanomaterial to flow downward with the glass body. Then, the aluminum paste is placed in a temperature range of 500-600°C to allow part of the glass body to flow to the surface of the anti-reflection passivation layer outside the solar cell to etch and remove the anti-reflection passivation layer, and then continues to flow to form a silicon oxide protective thin layer of doped polycrystalline silicon attached to the solar cell.

[0048] Step 33: The aluminum paste is then placed in a post-sintering section at 600-700℃, allowing the metal compounds in the aluminum paste to crosslink with the conductive carbon nanomaterials to form a metal-based composite carbon nanomaterial layer attached to the surface of the silicon oxide protective thin layer. Next, the aluminum powder in the aluminum paste is gradually melted. The aluminum paste is then placed in a cooling section to reach room temperature, allowing the molten aluminum powder to form an aluminum layer attached to the surface of the metal-based composite carbon nanomaterial layer, thus obtaining the aluminum electrode (see...). Figure 2 ).

[0049] Specifically, in step 33, before the cooling section, the aluminum paste is first placed in a temperature range of 600-650℃ to allow the metal compounds in the aluminum paste to cross-link with the conductive carbon nanomaterials to form a metal-based composite carbon nanomaterial layer attached to the surface of the silicon oxide protective thin layer; then, the aluminum paste is placed in a temperature range of 650-700℃, since the aluminum powder in the aluminum paste is arranged according to a particle size of D 50 =5um, D 90 The aluminum powder with a gradation ratio of 8µm forms aluminum powder of different particle sizes. Therefore, in this temperature range, the smaller aluminum powder particles will melt first. The melted aluminum powder and the glass body flow downward together, and then in the cooling section, they can cool and form an aluminum precipitation layer attached to the surface of the metal-based composite carbon nanomaterial layer and an aluminum coating layer with glass body covering the aluminum attached to the surface of the aluminum precipitation layer. Moreover, the remaining aluminum powder grows on the larger aluminum powder particles, and then attaches and accumulates on the surface of the aluminum coating layer to form a smooth and dense volume aluminum layer, which is the aluminum layer.

[0050] In practice, the sintering process of aluminum paste is preferably carried out in a sintering furnace, which is divided into several sections: a pre-sintering section, a middle sintering section, a post-sintering section, and a cooling section. Each section has a different temperature range (referred to as a temperature zone). The temperature zone of the pre-sintering section is 150-350℃, the temperature zone of the middle sintering section is 350-600℃, and the temperature zone of the post-sintering section is 600-700℃. Meanwhile, the solar cells printed with aluminum paste are conveyed by a conveyor belt at a specific speed (e.g., ...). The aluminum paste-printed solar cells enter the sintering furnace from the inlet of the front sintering section (9000-10000 mm / min), pass through the middle and rear sintering sections in sequence, and are then discharged from the outlet of the cooling section. The furnace temperature of the front, middle, and rear sintering sections gradually increases from the inlet to the outlet of each section. However, the solar cells with printed aluminum paste enter the cooling section and rapidly decrease to room temperature at a rate of 100-200℃ / s.

[0051] In the process of sintering aluminum paste, the organic phase of the aluminum paste volatilizes and decomposes (such as combustion) at a temperature of 150°C. When the temperature reaches 350°C, all the organic phases in the aluminum paste can be completely volatilized and decomposed.

[0052] The aluminum paste is continuously heated. (The applicant's research found that the softening temperature of the inorganic glass phase without rare earth oxides is >400℃. After adding rare earth oxides, the softening temperature of the inorganic glass phase will be further reduced, and it can soften and form a flowing glass body between 380-400℃.) Therefore, when the temperature exceeds 380℃, the inorganic glass phase in the aluminum paste begins to soften and form a glass body. The glass body flows and begins to coat the outer surface of the aluminum powder, causing them to begin to aggregate on the surface. As the temperature continues to rise to 400-500℃, the metal compounds and conductive carbon nanomaterials begin to undergo cross-linking reactions to form a composite structure. Since the aluminum powder needs to be 660℃ to melt, the aluminum powder is still a solid particle at this time and does not flow easily. Moreover, since the density of the composite structure is greater than that of the aluminum powder, as the glass body continues to flow downward, the metal compounds (i.e., at least one of tin oxide, indium oxide, and antimony oxide) and conductive carbon nanomaterials can be coated by the glass body and sink to the surface of the battery cell with the glass body.

[0053] When the temperature reaches 500-600℃, the glass phase and the anti-reflection passivation layer on the surface of the solar cell begin to corrode, rapidly opening the anti-reflection passivation layer. This allows the glass phase to directly contact the doped polycrystalline silicon within the solar cell. Because rare earth oxides can inhibit the reaction between other inorganic glass phase oxides in the glass phase and the doped polycrystalline silicon (this is because rare earth oxides can soften the glass phase below 400℃ to form a glass phase, thus allowing the glass phase to flow to the surface of the anti-reflection passivation layer earlier, thereby preventing the oxidation of the glass phase, which is more likely to react with the doped polycrystalline silicon, from reacting with the oxides), the reaction is disrupted. Materials (such as lead oxide) react prematurely with the anti-reflection passivation layer and are consumed. Therefore, when the anti-reflection passivation layer is opened, the remaining oxides in the glass will not react with the doped polycrystalline silicon. That is, rare earth oxides can inhibit the reaction of oxides of other inorganic glass phases in the glass with the doped polycrystalline silicon. Therefore, the glass only covers the surface of the doped polycrystalline silicon, that is, it forms a silicon-oxygen protective thin layer attached to the doped polycrystalline silicon, which plays a role in protecting the doped polycrystalline silicon and isolating aluminum powder from the doped polycrystalline silicon to prevent the aluminum powder from reacting with the doped polycrystalline silicon.

[0054] The temperature is further increased to 600-650℃, and the composite structure formed by the metal compound and the conductive carbon nanomaterial further cross-links to form a metal-based composite carbon nanomaterial layer that aggregates and adheres to the surface of the silicon oxide protective thin layer. The thickness of the metal-based composite carbon nanomaterial layer is preferably 0.5-10 nm, such as 0.5 nm, 1 nm, 3 nm, 5 nm, 8 nm or 10 nm. The temperature is further increased to 650-700℃, at which point the aluminum powder particles aggregated on the top of the glass body begin to melt. The melting rate of the smaller aluminum powder particles is greater than that of the larger aluminum powder particles. Due to the concentration gradient difference and the drive of energy minimization, the small aluminum powder particles gradually melt, while the large aluminum powder particles begin to grow, and the surface becomes smooth and dense and slowly deposits on the surface of the metal-based composite carbon nanomaterial layer.

[0055] Finally, in the cooling section, the molten aluminum powder forms an aluminum layer attached to the surface of the metal-based composite carbon nanomaterial layer. The top of this aluminum layer is still a volumetric aluminum layer formed by a large amount of dense and smooth bulk aluminum. Below it is an aluminum cladding layer containing aluminum encapsulated in a glass phase. Further down is an aluminum precipitation layer that is rapidly cooled and precipitated. Continuing downwards, there are the metal-based composite carbon nanomaterial layer and the silicon oxide protective thin layer in sequence.

[0056] Therefore, the aluminum electrode prepared using the aluminum electrode fabrication process described above in this embodiment is shown in the figure. Figure 2 The aluminum layer consists of a silicon oxide protective thin layer, a metal-based composite carbon nanomaterial layer, and an aluminum layer that are sequentially self-grown on the doped polycrystalline silicon of the solar cell; wherein the aluminum layer includes an aluminum precipitation layer, an aluminum coating layer, and a volumetric aluminum layer that are sequentially self-grown on the surface of the metal-based composite carbon nanomaterial layer.

[0057] The aluminum electrode is formed by self-growth of aluminum paste with the aforementioned specific raw material formulation during the aforementioned specific sintering process, without the need for additional deposition. The thickness of the silicon oxide protective layer is 0.5-5 nm, such as 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, or 5 nm. In this way, the self-grown silicon oxide protective layer in the aluminum electrode can both protect the doped polycrystalline silicon, effectively preventing contact reactions between aluminum and doped polycrystalline silicon and reducing interfacial metal recombination, and not affect current transmission, forming a good ohmic contact. This allows current to smoothly pass from the doped polycrystalline silicon through the silicon oxide protective layer and be conducted to the aluminum layer by the metal-based composite carbon nanomaterial layer.

[0058] Furthermore, the conductive carbon nanomaterials such as graphene and carbon nanotubes in the aluminum paste have a resistivity of 1×10⁻⁶. -8 Its resistivity is Ω·m, which is much higher than that of aluminum (aluminum has a resistivity of 2.85 × 10⁻⁶ Ω·m). -8 Therefore, the metal-based composite carbon nanomaterial layer formed by the cross-linking of conductive carbon nanomaterials and metal compounds during sintering can enhance the conductivity of aluminum electrodes and reduce the contact resistivity. Tests revealed that the resistance of conventional aluminum paste wire is relatively high, at 2.0 × 10⁻⁶ Ω·m. -5 The aluminum-electrode prepared in this embodiment exhibits a significantly reduced overall line resistance of 7 × 10 Ω·cm due to the presence of a metal-based composite carbon nanomaterial layer. -6 Ω·cm to 8.5×10 -6 Within the range of Ω·cm.

[0059] This embodiment describes an application of an aluminum electrode; see [link to previous section]. Figure 2The aluminum electrode is applied to solar cells to further reduce interfacial metal recombination and contact resistivity, thereby improving the photoelectric conversion efficiency of the cell. This aluminum electrode is particularly suitable for use in passivated contact solar cells, significantly reducing interfacial metal recombination between the aluminum electrode and the passivation contact structure on the back of the solar cell (which includes a stacked tunneling oxide layer and doped polycrystalline silicon), and further reducing the contact resistivity of the passivated contact solar cell.

[0060] Examples 2-6

[0061] Examples 2-6 describe an aluminum electrode, its preparation process, and its application, all following the same principle as Example 1. The differences between Examples 2-6 and Example 1 are shown in Table 1 below:

[0062] Table 1

[0063]

[0064]

[0065] Performance testing

[0066] 1. The aluminum pastes prepared in Examples 2-6 were subjected to viscosity, fineness, and sheet resistance tests. The test results are shown in Table 2 below:

[0067] Table 2

[0068]

[0069] 2. The aluminum electrodes prepared in Examples 2-6 and conventional aluminum paste wires were subjected to line resistance, interfacial contact resistivity, and interfacial metal composite tests; the test results are shown in Table 3 below:

[0070] Table 3

[0071]

[0072] As shown in Table 3, compared with conventional aluminum paste wire, the aluminum electrode prepared by the process of this invention exhibits significantly lower line resistance, interfacial contact resistivity, and interfacial metal recombination. It is evident that during the aluminum paste sintering process of this invention, a silicon oxide protective thin layer can be self-grown on the doped polycrystalline silicon. Therefore, the aluminum paste will not undergo a contact reaction with the doped polycrystalline silicon, reducing interfacial metal recombination and forming a good ohmic contact. Furthermore, during the aluminum paste sintering process, a metal-based composite carbon nanomaterial layer can be formed on the surface of the silicon oxide protective thin layer to further enhance the conductivity of the aluminum electrode. Therefore, the aluminum electrode prepared by the process of this invention has lower line resistance, interfacial contact resistivity, and interfacial metal recombination.

[0073] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0074] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A process for preparing an aluminum electrode, characterized in that, The process includes the following steps: Step S1: Print aluminum paste onto the surface of the battery cell; wherein the aluminum paste comprises the following raw materials by weight percentage: 65-85% aluminum powder, 1.5-8% metal compound, 4-15% organic phase, 7-18% inorganic glass phase and 0.05-0.1% conductive carbon nanomaterials, wherein the inorganic glass phase comprises rare earth oxides in the aluminum paste at a weight percentage of 0.01-1%; Step S2, sintering aluminum paste: Step S21: Place the printed aluminum paste in the pre-sintering section at 150-350℃ to dry the aluminum paste, allowing the organic phase to volatilize and decompose. Step S22: The aluminum paste is then placed in the intermediate sintering section at 350-600℃ to soften the inorganic glass phase and form a glass body. After that, it flows to the anti-reflection passivation layer outside the solar cell to etch and remove the anti-reflection passivation layer, so as to form a silicon-oxygen protective thin layer of doped polycrystalline silicon attached to the solar cell. In step S23, the aluminum paste is placed in the post-sintering section at 600-700℃, so that the metal compound and the conductive carbon nanomaterial cross-link to form a metal-based composite carbon nanomaterial layer attached to the silicon oxide protective thin layer. Then, the aluminum powder is gradually melted, and the aluminum paste is placed in the cooling section to cool down to room temperature, so that the melted aluminum powder forms an aluminum layer attached to the metal-based composite carbon nanomaterial layer, thus obtaining the aluminum electrode.

2. The process for preparing an aluminum electrode according to claim 1, characterized in that, In step S1, the conductive carbon nanomaterial is carbon nanotube and / or graphene. The metal compound is at least one of tin oxide, indium oxide, and antimony oxide.

3. The process for preparing an aluminum electrode according to claim 1, characterized in that, In step S1, the rare earth oxide is at least one of cerium oxide, lanthanum oxide, erbium oxide, yttrium oxide, and samarium oxide; The inorganic glass phase further includes at least one of bismuth oxide, boron oxide, silicon dioxide, calcium oxide, aluminum oxide, zinc oxide, and lead oxide.

4. The process for preparing an aluminum electrode according to claim 1, characterized in that, In step S1, the organic phase is at least one of terpineol, acetone, isopropanol, tetrabutyl titanate, ethanol, ethyl acetate, dichloroethane, and polypropylene.

5. The process for preparing an aluminum electrode according to claim 1, characterized in that, Before step S1, the following steps are included to prepare aluminum paste: first, the aluminum powder, metal compound and conductive carbon nanomaterials of the formula amount are mixed evenly, then the inorganic glass phase and organic phase of the formula amount are added, and the mixture is ground to obtain an aluminum paste with a viscosity of 15000-25000 mpa.s / 25℃, a paste fineness of 12-20 μm and a sheet resistance of 6-15 mΩ / sq.

6. The process for preparing an aluminum electrode according to claim 1, characterized in that, Step S22 specifically includes: placing aluminum paste in a temperature range of 350-500°C to soften the inorganic glass phase and form the glass body, which then flows downwards to coat the metal compound and conductive carbon nanomaterials; and then placing the aluminum paste in a temperature range of 500-600°C to etch and remove the glass body flowing to the anti-reflection passivation layer, thereby forming the silicon oxide protective thin layer.

7. The process for preparing an aluminum electrode according to claim 1, characterized in that, Before the cooling section, step S23 specifically includes: first placing the aluminum paste in a temperature range of 600-650℃ to crosslink the metal compound with the conductive carbon nanomaterial to form the metal-based composite carbon nanomaterial layer, and then placing the aluminum paste in a temperature range of 650-700℃ to gradually melt the aluminum powder.

8. The process for preparing an aluminum electrode according to claim 1, characterized in that, In step S1, the aluminum powder is prepared according to a particle size of D. 50 =5um, D 90 Aluminum powder with a gradation ratio of 8µm.

9. The process for preparing an aluminum electrode according to claim 8, characterized in that, In step S23, after the metal-based composite carbon nanomaterial layer is formed, the specific preparation process of the aluminum layer is as follows: aluminum paste is placed in a temperature range of 650-700℃, so that aluminum powder is gradually melted. The melted aluminum powder and glass flow downward together to cool in the cooling section to form an aluminum precipitation layer attached to the metal-based composite carbon nanomaterial layer and an aluminum coating layer covered by the glass. The remaining aluminum powder grows to form a volume aluminum layer attached to the aluminum coating layer, thus obtaining the aluminum layer.

10. An aluminum electrode, characterized in that, The aluminum electrode is formed sequentially on the doped polycrystalline silicon of the solar cell using the aluminum electrode fabrication process described in any one of claims 1-9, consisting of a silicon oxide protective thin layer, a metal-based composite carbon nanomaterial layer, and an aluminum layer.

11. An aluminum electrode according to claim 10, characterized in that, The thickness of the silicon-oxygen protective layer is 0.5-5 nm, and the thickness of the metal-based composite carbon nanomaterial layer is 0.5-10 nm.

12. An aluminum electrode according to claim 10, characterized in that, The aluminum layer comprises an aluminum precipitate layer, an aluminum coating layer, and a volumetric aluminum layer that are sequentially self-grown on the surface of the metal-based composite carbon nanomaterial layer.

13. The application of an aluminum electrode according to any one of claims 10-12, characterized in that, The aluminum electrode is used in a solar cell.

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