Conductive silver paste for BC battery, preparation method and BC battery

Abstract

The invention relates to the technical field of electronic materials, in particular to conductive silver paste for a BC battery, and the conductive silver paste comprises the following components in percentage by weight: 88-93 wt% of silver powder, 3-5 wt% of glass powder, 1-3 wt% of organic resin, 6-10 wt% of solvent and 0-1 wt% of other auxiliaries, the sum of the components is 100 wt%, and the glass powder comprises gallium sesquioxide. The conductive silver paste can be used for a BC battery so as to completely or partially solve the problem of large contact resistance of a P region of the BC battery, and meanwhile, the reliability is guaranteed.

Description

Technical Field

[0001] This application relates to the field of electronic materials technology, particularly to the field of solar cell technology, and especially to a conductive silver paste for BC cells, a preparation method thereof, and the BC cell itself. Background Technology

[0002] A solar cell is a semiconductor device that converts sunlight into electrical energy through the photovoltaic effect. Its basic working principle is that under sunlight, electrons in the semiconductor material are excited by photon energy, generating electron-hole pairs, which then separate and move under the influence of a built-in electric field, forming an electric current.

[0003] Bipolar Junction Cells (BCs) are a novel high-efficiency solar cell structure. They achieve electron and hole separation and collection by fabricating interdigitated P-regions and N-regions on the back of the cell, and then mounting ohmic contact grid electrodes on these regions. The absence of grid lines on the front allows for higher short-circuit current. The wide metal electrodes on the back reduce series resistance, resulting in a higher fill factor. However, the contact resistance of the metallized P-regions is significantly higher than that of the N-regions. Therefore, reducing the contact resistance of the P-region subgrid paste is a crucial issue for improving photoelectric conversion efficiency.

[0004] Therefore, it is necessary to develop a conductive silver paste material for BC batteries that can, to some extent, solve the problem of high contact resistance in the P-region. Summary of the Invention

[0005] The inventors of acetic acid discovered that adding an appropriate amount of gallium trioxide to glass powder, along with a suitable amount of glass, can reduce contact resistance and improve efficiency. Based on this, the purpose of this application is to provide a silver paste and its preparation method that can be used in the P-region of a BC battery to reduce the contact resistance of the P-region and thus improve photoelectric conversion efficiency, thereby completely or partially solving the problem of high contact resistance in the P-region of BC batteries.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, this application provides a conductive silver paste for BC batteries, wherein the conductive silver paste comprises the following components by weight percentage: 88-93 wt% silver powder, 3-5 wt% glass powder, 1-3 wt% organic resin, 6-10 wt% solvent, and 0-1 wt% other additives, the sum of the above components being 100 wt%, wherein the glass powder comprises gallium trioxide.

[0007] In the above technical solution, the conductive silver paste mainly comprises silver powder as the conductive phase and low-melting-point glass powder as the binder phase. The organic resin, solvent, and other additives provide the conductive silver paste with flow properties, viscosity, thixotropy, and other modifiable properties. The glass powder contains lead oxide, which can further reduce the softening point and high-temperature melting viscosity of the glass, making it more suitable for the actual application scenarios of BC silver paste. Additionally, the glass powder contains gallium, and free Ga... 3+ Ions can diffuse into the poly layer along with the glass, increasing the doping concentration and reducing the contact resistance.

[0008] In conjunction with the first aspect, in one possible implementation, the glass powder is a lead-bismuth-tellurium glass powder, the softening point of which is controlled at 500-650℃. The lead-bismuth-tellurium glass powder comprises a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system comprises 30-40wt% PbO, 30-40wt% Bi2O3, and 20-30wt% TeO2; the second component system comprises 0-10wt% SiO2 and / or 0-3wt% Al2O3 and / or 0-2wt% Li2CO3 and / or 0-2wt% Na2CO3 and / or 0-2wt% Rb2CO3; and the third component system comprises gallium trioxide.

[0009] In the above technical solution, the lead oxide includes PbO, which is a flux mainly used to lower the melting temperature, significantly reducing the softening point of conductive silver paste; adjusting viscosity to achieve moderate fluidity of the molten glass; enhancing wettability by improving the wettability of the glass to silicon and silver; and providing reactivity to participate in the etching reaction of the silicon nitride layer. In other words, glass containing PbO has a low softening temperature and high fluidity, allowing it to flow smoothly between silver powder particles and reach the contact interface. Furthermore, the high PbO content further reduces the softening point and high-temperature melting viscosity of the glass, making it more suitable for the actual application scenarios of BC silver paste. The alkali metal ion compounds include lithium, sodium, rubidium, and cesium ion compounds. Trace amounts of these alkali metal ion compounds are used to adjust the softening temperature and etching rate of the glass. The third component system, gallium trioxide, can provide free Ga... 3+ Ions can diffuse into the poly layer along with the glass, increasing the doping concentration and reducing the contact resistance.

[0010] In conjunction with the first aspect, in one possible implementation, the gallium trioxide content is 0 ≤ y ≤ 4 wt%.

[0011] In conjunction with the first aspect, in one possible implementation, the gallium trioxide content is 2 ≤ y ≤ 3 wt%.

[0012] In conjunction with the first aspect, in one possible implementation, the gallium trioxide content is 2.5 wt%.

[0013] In the above technical solution, the glass powder system is more suitable for BC batteries. While opening the current channel, it constructs a robust conductive electrode bridge, thereby achieving higher battery conversion efficiency and long-term reliability.

[0014] In conjunction with the first aspect, in one possible implementation, the silver powder is spherical with a particle size D50 of 1.4–2.1 μm and a specific surface area of ​​0.25–0.5 m². 2 / g, tap density is 5.5-6.5g / ml, organic coating amount ≤0.7%.

[0015] In the above technical solution, the large pores between medium and large-sized silver powder particles provide ample flow channels for the glass; the low organic coating content gives the silver powder high sintering activity and effectively reduces the grid line resistance of the silver paste.

[0016] In conjunction with the first aspect, in one possible implementation, the organic resin includes one or more of SEPS resin, acrylic resin, PVB resin, and CAB resin, wherein the mass ratio of SEPS resin: acrylic resin: PVB resin: CAB resin is (3~5):2:1:1.

[0017] In conjunction with the first aspect, in one possible implementation, the solvent comprises one or more of diethylene glycol dibutyl ether, dimethyl phthalate, dodecyl alcohol ester, and diethylene glycol butyl ether acetate, wherein the mass ratio of diethylene glycol dibutyl ether: dimethyl phthalate: dodecyl alcohol ester: diethylene glycol butyl ether acetate is 1:2:1.5:(1~3).

[0018] In conjunction with the first aspect, in one possible implementation, the other additives include one or more of castor oil thixotropic agents and silicone leveling agents, wherein the mass ratio of castor oil thixotropic agent to silicone leveling agent is 5:1.

[0019] In the above technical solution, the SEPS resin imparts good ink permeability to the silver paste, avoiding problems such as incomplete or broken grid lines; the acrylic resin has strong plasticity, giving the silver paste an excellent aspect ratio; the PVB and CAB resins provide sufficient viscosity to the paste, making the silver paste printing more uniform. Optionally, the diethylene glycol dibutyl ether, with its weak polarity and low viscosity, is used to quickly reduce the viscosity of the paste; dimethyl phthalate, with its viscosity-enhancing effect, acts as a plasticizer, which is beneficial for narrowing the line width of the silver paste printing grid; dodecyl alcohol ester and diethylene glycol butyl ether acetate have moderate polarity and are compatible with most resins, serving as stable diluents. Optionally, the castor oil is used to adjust the rheological properties of the paste, which is beneficial for the stability and storage of the paste; silicone oil has the function of lubrication and promoting the differential phase of the organic system, narrowing the grid width while ensuring smooth printing.

[0020] Secondly, this application provides a method for preparing conductive silver paste for BC batteries, comprising the following steps: mixing the silver powder, the glass powder, the organic resin, the solvent, and the other additives, and placing them into a disperser; dispersing the mixture at a speed of 500-2000 rpm for 1 hour, and then grinding and dispersing it on a three-roll mill until the fineness is ≤7 μm, thereby obtaining a conductive paste with a viscosity of 50-70 Pa·S, wherein the viscosity of the paste is measured using a Brookfield DV2T viscometer at 25°C and a speed of 50 rpm.

[0021] Thirdly, this application provides a BC battery, which is prepared by printing and sintering the aforementioned conductive silver paste for BC batteries.

[0022] The first aspect of this application provides a silver paste that can be used in the P-region of a BC battery to reduce the contact resistance of the P-region and thereby improve the photoelectric conversion efficiency. This paste reduces the contact resistance of the P-region of the BC battery, either wholly or partially. The high PbO content lowers the softening point and high-temperature melting viscosity of the glass, making the glass more suitable for the actual application scenarios of BC silver paste. The glass powder contains gallium, including free Ga... 3+ Ions can diffuse into the poly layer along with the glass, increasing the doping concentration and reducing the contact resistance.

[0023] The second aspect of this application provides a method for preparing silver paste, which can be used in BC batteries to solve, in whole or in part, the problem of contact resistance in the P region of BC batteries.

[0024] A third aspect of this application provides a BC battery, wherein the P-region contact resistance of the BC battery is low, while ensuring reliability. Detailed Implementation

[0025] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description, in conjunction with embodiments, is provided. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0026] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0027] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items.

[0028] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0029] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0030] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as µg, mg, g, or kg.

[0031] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0032] The term "range" disclosed herein takes the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges that can be defined in this way are inclusive and composable; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is understood that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0033] Both the P and N regions of a BC battery achieve electron collection through passivated contacts. Generally, the N region primarily collects electrons and is mostly composed of deposited phosphorus-doped polycrystalline silicon. The doping process is relatively easy, and the doping concentration is high. The thickness is relatively thin, generally <100nm. The n-type silicon wafer structure is n+ Poly-Si / SiOx / c-Si, and its contact resistance ρ after metallization can reach below 0.5mΩ·cm². The p-region is used to provide holes and is usually deposited as boron-doped polysilicon. The doping process is generally boron diffusion or ion implantation. The maximum solid solubility of boron in silicon is much lower than that of phosphorus, which physically limits the effective carrier concentration that the p+ polysilicon layer can achieve. Boron atoms are small and diffuse quickly in silicon dioxide, making the process control of the passivation layer (SiOx) very sensitive. This can easily lead to a decrease in passivation quality or uneven doping. Therefore, the doping process is difficult and the doping concentration is low. The thickness is thick, usually >150nm. The p-type silicon wafer structure is p+Poly-Si / SiOx / c-Si. The low doping concentration means that there are fewer carriers that can participate in tunneling near the interface of the polysilicon layer, which directly weakens the tunneling probability. The thick polysilicon layer means that although it is beneficial to passivation, it will increase the lateral resistance of carrier transport to the metal electrode. The combined effect of low doping and large thickness makes the contact resistance ρ after metallization several mΩ·cm² or even higher, which is much higher than that of the N region.

[0034] The core difference lies in the manufacturing processes of the P-region and N-region, which necessitates the use of silver pastes with different properties for the two regions. In particular, it requires the development of P-type pastes specifically adapted to p+ Poly-Si. In other words, improving the photoelectric conversion efficiency of BC cells hinges on reducing the contact resistance of the P-region.

[0035] In related technologies, silver paste includes silver powder, glass powder, organic resin, solvent and other trace components. The main component, silver powder, acts as a conductive phase after sintering, while the glass powder, which acts as a binder phase, determines whether the silver paste can form excellent ohmic contact with the solar cell and affects the long-term reliability of the electrode.

[0036] This application provides a conductive silver paste, its preparation method, and a battery for reducing the contact resistance in the P-region of a BC battery, in order to better reduce the contact resistance in the P-region and improve the reliability of the BC battery. The conductive silver paste for BC batteries in this application involves adding gallium to the composition of glass powder, resulting in free Ga... 3+ Ions can diffuse into the poly layer along with the glass, increasing the doping concentration and reducing the contact resistance. This reduces the softening temperature of the glass powder and, at the same time, reduces the contact resistance of the P region of the BC cell, thereby improving the cell efficiency.

[0037] The first aspect of this application provides a conductive silver paste for BC batteries, comprising: The conductive silver paste comprises, by weight percentage, the following components: 88-93 wt% silver powder, 3-5 wt% glass powder, 1-3 wt% organic resin, 6-10 wt% solvent, and 0-1 wt% other additives, with the sum of the above components being 100 wt%. The conductive silver paste includes silver powder as the main conductive phase, low-melting-point glass powder as the binder phase, and the organic resin, solvent, and other additives provide the conductive silver paste with flow properties, viscosity, thixotropy, and other modifiable properties.

[0038] The glass powder is a lead-bismuth-tellurium glass powder, the softening point of which is controlled at 500-650℃. The lead-bismuth-tellurium glass powder comprises a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system comprises 30-40wt% PbO, 30-40wt% Bi2O3, and 20-30wt% TeO2; the second component system comprises 0-10wt% SiO2 and / or 0-3wt% Al2O3 and / or 0-2wt% Li2CO3 and / or 0-2wt% Na2CO3 and / or 0-2wt% Rb2CO3; and the third component system comprises gallium trioxide.

[0039] The glass powder comprises lead oxides and / or alkali metal ion compounds. The lead oxides include PbO, which is a fluxing agent primarily used to lower the melting temperature, significantly reducing the softening point of conductive silver paste; adjusting viscosity to achieve moderate fluidity of the molten glass; enhancing wettability by improving the wetting of silicon and silver; and providing reactivity to participate in the etching reaction of the silicon nitride layer. In other words, glass containing PbO has a low softening temperature and high fluidity, allowing it to flow smoothly between silver powder particles and reach the contact interface. Furthermore, the high PbO content further reduces the softening point and high-temperature melting viscosity of the glass, making it more suitable for the actual application scenarios of BC silver paste. In this application, the PbO content in the glass powder is 30-40 wt%.

[0040] Bi₂O₃ possesses strong corrosive properties, and its ionic characteristics facilitate the dissolution and transport of silver. It can quickly break through the passivation film at the contact site, forming contact points with the poly layer, and can also adjust the coefficient of thermal expansion. SiO₂, as a network structure, promotes the uniform integration of the glass components, preventing crystallization and inhomogeneity, and providing structural stability, mechanical strength, and chemical durability. WO₃ reduces the surface tension of the glass after high-temperature melting, making it easier to wet the silver powder surface and contact interface. TeO₂, being an ultra-low melting point oxide, is used for specific ultra-low temperature sintering requirements. Al₂O₃ improves the chemical stability of the glass system, enhances its resistance to hydrolysis and corrosion, and can also increase viscosity, making the molten glass more viscous and controlling its flow and diffusion range. Its main function is to prevent excessive flow of the glass during sintering, maintain the grid morphology, and improve weather resistance.

[0041] Optionally, alkali metal ion compounds can be used to rapidly reduce the softening temperature of glass powder and improve the fluidity of glass when used in small quantities.

[0042] Optionally, the glass powder contains gallium, including free Ga. 3+ Ions can diffuse into the poly layer along with the glass, increasing the doping concentration and reducing the contact resistance.

[0043] In some possible embodiments, the gallium trioxide content is 0 ≤ y ≤ 4 wt%. In some possible embodiments, the gallium trioxide content is 2 ≤ y ≤ 3 wt%. In some possible embodiments, the gallium trioxide content is 2.5 wt%.

[0044] Optionally, the silver powder is spherical with a particle size D50 of 1.4–2.1 μm and a specific surface area of ​​0.25–0.5 m². 2 / g, tap density is 5.5-6.5g / ml, and organic coating content is ≤0.7%. Among them, the large porosity between medium and large-sized silver powder particles provides ample flow channels for glass; the low organic coating content gives the silver powder high sintering activity and effectively reduces the grid line resistance of silver paste.

[0045] Optionally, the glass powder may contain lead oxide and / or alkali metal ion compounds. The lead oxide in the glass powder can further reduce the softening point and high-temperature melting viscosity of the glass, making it more suitable for the actual application scenarios of BC silver paste.

[0046] Optionally, the glass powder contains alkali metal ion compounds. The alkali metal ions act as a mesh-breaking agent in the glass, providing the glass powder with a lower softening temperature and excellent flowability. The alkali metal ions selected in this application include Rb+ and Li+. Rb+ is mixed with Li+ used in conventional glass, and the amount of PbO used in the glass is increased.

[0047] According to a second aspect of this application, a method for preparing conductive silver paste for BC batteries is provided, the method comprising the following steps: S01: Prepare the slurry by weighing 88-93 wt% silver powder, 3-5 wt% glass powder, 1-3 wt% organic resin, 6-10 wt% solvent, and 0-1 wt% other additives, with the sum of the above components being 100 wt%. Mix the silver powder, glass powder, organic resin, solvent, and other additives, and place them into a disperser. S02: Disperse using a disperser at a speed of 500-2000 rpm for 1 hour; S03: Grind and disperse the conductive slurry on a three-roll mill until the fineness is ≤7μm, and the viscosity of the slurry is 50-70Pa·S. The viscosity of the slurry is measured by a Brookfield DV2T viscometer at 25℃ and 10r / min. Optionally, the roller spacing of the three-roll mill is set to 10-120μm and the grinding speed is 100-200r / min to obtain the conductive slurry. According to a third aspect of this application, a BC battery is provided, wherein the BC battery is prepared by printing and sintering the aforementioned conductive silver paste for BC batteries.

[0048] Specifically, the following steps are included: S10: Front surface and bulk passivation treatment, using N-type silicon wafers, a pyramid-shaped textured surface is formed on the front side through chemical etching to reduce reflection; on the textured surface structure on the front side, an extremely thin, high-quality intrinsic amorphous silicon or aluminum oxide layer is grown through techniques such as atomic layer deposition to achieve excellent chemical passivation; covered with a silicon nitride anti-reflection film. S20: Backside patterning and selective doping: P-type and N-type regions are precisely fabricated on the back of the battery. S30: Backside passivation layer deposition. A high-quality aluminum oxide / silicon nitride stacked passivation film is deposited on the entire backside, including the newly formed P+ and N+ regions, to reduce backside recombination. Using a laser again, micron-sized contact holes are precisely drilled on the passivation layer directly above the P+ and N+ regions on the backside, exposing the heavily doped silicon regions underneath. Using a high-precision screen printing machine, silver paste is printed once or twice to fill the contact holes in the P and N regions, forming the backside gate lines and pads, so that the paste can form good ohmic contact with both P-type and N-type silicon.

[0049] S40: Post-sintering testing, including sintering at high temperature to allow the glass material in the silver paste to form an ohmic contact with the silicon, while simultaneously solidifying the electrode; then testing the battery's electrical performance parameters.

[0050] To achieve better experimental comparison, the slurry in the embodiments and comparative examples of this application was weighed according to the following weight percentages: 88 wt% silver powder, 3.9 wt% glass powder, 2 wt% organic resin, 6 wt% solvent, and 0.1 wt% other additives, with the sum of the above components being 100 wt%. The silver powder used had a particle size D50 of 1.9 μm and a specific surface area of ​​0.5 m². 2 The sample has a tap density of 5.9 g / ml and an organic coating weight of 0.5%. The organic resin comprises a mixture of SEPS resin, acrylic resin, PVB resin, and CAB resin, with a mass ratio of SEPS resin:acrylic resin:PVB resin:CAB resin of (3~5):2:1:1. The solvent comprises a mixture of diethylene glycol dibutyl ether, dimethyl phthalate, dodecyl alcohol ester, and diethylene glycol butyl ether acetate, wherein the mass ratio of diethylene glycol dibutyl ether:dimethyl phthalate:dodecyl alcohol ester:diethylene glycol butyl ether acetate is 1:2:1.5:(1~3). Other additives include a mixture of castor oil thixotropic agent and silicone leveling agent, with a mass ratio of castor oil thixotropic agent:silicone leveling agent of 5:1.

[0051] The differences are explained below with reference to specific embodiments. Table 1 below shows the content of each component of the glass powder in each embodiment and comparative example. Unless otherwise specified, the silver powder used is spherical with a particle size D50 of 1.4–2.1 μm and a specific surface area of ​​0.25–0.5 m². 2 / g, tap density is 5.5-6.5g / ml, organic coating amount ≤0.7%.

[0052] Table 1

[0053] Example 1 A conductive silver paste for BC batteries is prepared by the following steps: (1) Prepare the slurry by weighing 88wt% silver powder, 3.9wt% glass powder, 2wt% organic resin, 6wt% solvent, and 0.1wt% other additives, with the total weight of the above components being 100wt%. The glass powder is a lead-bismuth-tellurium glass powder, i.e., a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system includes 4.5wt% PbO3, 29wt% Bi2O3, and 28wt% TeO2; the second component system includes 4.5wt% SiO2, 2wt% Al2O3, 0.5wt% Li2CO3, and 0.5wt% Rb2CO3; and the third component system includes 1wt% Ga2O3. Mix the silver powder, glass powder, organic resin, solvent, and other additives, and place them in a disperser. (2) Disperse using a disperser at a speed of 500-2000 rpm for 1 hour; (3) Grind and disperse the conductive slurry on a three-roll mill until the fineness is ≤7μm, and the viscosity of the conductive slurry is 50-70Pa·S, wherein the viscosity of the slurry is measured by a Brookfield DV2T viscometer at 25℃ and 10r / min. (4) The conductive silver paste prepared above is printed and sintered to prepare a photovoltaic cell for paste contact resistance test and photoelectric conversion efficiency test.

[0054] Compared with Comparative Example 1, this shows that adding 1 wt% Ga2O3 can reduce the contact resistance of the P region of the BC battery.

[0055] Example 2 A conductive silver paste for BC batteries is prepared by the following steps: (1) Prepare the slurry by weighing 88wt% silver powder, 3.9wt% glass powder, 2wt% organic resin, 6wt% solvent, and 0.1wt% other additives, with the total weight of the above components being 100wt%. The glass powder is a lead-bismuth-tellurium glass powder, i.e., a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system includes 3.5wt% PbO3, 29wt% Bi2O3, and 28wt% TeO2; the second component system includes 4.5wt% SiO2, 2wt% Al2O3, 0.5wt% Li2CO3, and 0.5wt% Rb2CO3; and the third component system includes 2wt% Ga2O3. Mix the silver powder, glass powder, organic resin, solvent, and other additives, and place them in a disperser. (2) Disperse using a disperser at a speed of 500-2000 rpm for 1 hour; (3) Grind and disperse the conductive slurry on a three-roll mill until the fineness is ≤7μm, and the viscosity of the conductive slurry is 50-70Pa·S, wherein the viscosity of the slurry is measured by a Brookfield DV2T viscometer at 25℃ and 10r / min. (4) The conductive silver paste prepared above is printed and sintered to prepare a photovoltaic cell for paste contact resistance test and photoelectric conversion efficiency test.

[0056] Compared with Example 1, this demonstrates that increasing the amount of Ga2O3 added can better reduce the contact resistance of the P region in the BC battery.

[0057] Example 3 A conductive silver paste for BC batteries is prepared by the following steps: (1) Prepare the slurry by weighing 88wt% silver powder, 3.9wt% glass powder, 2wt% organic resin, 6wt% solvent, and 0.1wt% other additives, with the total weight of the components being 100wt%. The glass powder is a lead-bismuth-tellurium glass powder, i.e., a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system includes 3wt% PbO3, 29wt% Bi2O3, and 28wt% TeO2; the second component system includes 4.5wt% SiO2, 2wt% Al2O3, 0.5wt% Li2CO3, and 0.5wt% Rb2CO3; and the third component system includes 2.5wt% Ga2O3. Mix the silver powder, glass powder, organic resin, solvent, and other additives, and place them in a disperser. (2) Disperse using a disperser at a speed of 500-2000 rpm for 1 hour; (3) Grind and disperse the conductive slurry on a three-roll mill until the fineness is ≤7μm, and the viscosity of the conductive slurry is 50-70Pa·S, wherein the viscosity of the slurry is measured by a Brookfield DV2T viscometer at 25℃ and 10r / min. (4) The conductive silver paste prepared above is printed and sintered to prepare a photovoltaic cell for paste contact resistance test and photoelectric conversion efficiency test.

[0058] Compared with Examples 1 and 2, it is shown that by increasing the amount of Ga2O3 added, the contact resistance of the P region of the BC battery can be reduced more effectively.

[0059] Example 4 A conductive silver paste for BC batteries is prepared by the following steps: (1) Prepare the slurry by weighing 88wt% silver powder, 3.9wt% glass powder, 2wt% organic resin, 6wt% solvent, and 0.1wt% other additives, with the total weight of the components being 100wt%. The glass powder is a lead-bismuth-tellurium glass powder, i.e., a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system includes 2.5wt% PbO3, 29wt% Bi2O3, and 28wt% TeO2; the second component system includes 4.5wt% SiO2, 2wt% Al2O3, 0.5wt% Li2CO3, and 0.5wt% Rb2CO3; and the third component system includes 3wt% Ga2O3. Mix the silver powder, glass powder, organic resin, solvent, and other additives, and place them in a disperser. (2) Disperse using a disperser at a speed of 500-2000 rpm for 1 hour; (3) Grind and disperse the conductive slurry on a three-roll mill until the fineness is ≤7μm, and the viscosity of the conductive slurry is 50-70Pa·S, wherein the viscosity of the slurry is measured by a Brookfield DV2T viscometer at 25℃ and 10r / min. (4) The conductive silver paste prepared above is printed and sintered to prepare a photovoltaic cell for paste contact resistance test and photoelectric conversion efficiency test.

[0060] Compared with Examples 1 / 2 / 3 and Comparative Example 1, it is further demonstrated that by increasing the amount of Ga2O3 added, the contact resistance of the P region of the BC battery can be reduced to a certain extent.

[0061] Example 5 A conductive silver paste for BC batteries is prepared by the following steps: (1) Prepare the slurry by weighing 88wt% silver powder, 3.9wt% glass powder, 2wt% organic resin, 6wt% solvent, and 0.1wt% other additives, with the total weight of the components being 100wt%. The glass powder is a lead-bismuth-tellurium glass powder, i.e., a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system includes 1.5wt% PbO3, 29wt% Bi2O3, and 28wt% TeO2; the second component system includes 4.5wt% SiO2, 2wt% Al2O3, 0.5wt% Li2CO3, and 0.5wt% Rb2CO3; and the third component system includes 4wt% Ga2O3. Mix the silver powder, glass powder, organic resin, solvent, and other additives, and place them in a disperser. (2) Disperse using a disperser at a speed of 500-2000 rpm for 1 hour; (3) Grind and disperse the conductive slurry on a three-roll mill until the fineness is ≤7μm, and the viscosity of the conductive slurry is 50-70Pa·S, wherein the viscosity of the slurry is measured by a Brookfield DV2T viscometer at 25℃ and 10r / min. (4) The conductive silver paste prepared above is printed and sintered to prepare a photovoltaic cell for paste contact resistance test and photoelectric conversion efficiency test.

[0062] Compared to Examples 1 / 2 / 3 / 4 and Comparative Example 1, this further illustrates that increasing the amount of Ga2O3 added can better reduce the contact resistance of the P region in the BC battery to some extent. However, with the increase in the amount added, the glass system may become unstable. The inhomogeneity of the glass system can lead to instability between batches of the final product.

[0063] Comparative Example 1 A conductive silver paste for BC batteries is prepared by the following steps: (1) Prepare the slurry by weighing 88wt% silver powder, 3.9wt% glass powder, 2wt% organic resin, 6wt% solvent, and 0.1wt% other additives, with the total weight of the above components being 100wt%. The glass powder is a lead-bismuth-tellurium glass powder, i.e., a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system includes 5.5wt% PbO3, 29wt% Bi2O3, and 28wt% TeO2; the second component system includes 4.5wt% SiO2, 2wt% Al2O3, 0.5wt% Li2CO3, and 0.5wt% Rb2CO3; and the third component system includes 0wt% Ga2O3. Mix the silver powder, glass powder, organic resin, solvent, and other additives, and place them in a disperser. (2) Disperse using a disperser at a speed of 500-2000 rpm for 1 hour; (3) Grind and disperse the conductive slurry on a three-roll mill until the fineness is ≤7μm, and the viscosity of the conductive slurry is 50-70Pa·S, wherein the viscosity of the slurry is measured by a Brookfield DV2T viscometer at 25℃ and 10r / min. (4) The conductive silver paste prepared above is printed and sintered to prepare a photovoltaic cell for paste contact resistance test and photoelectric conversion efficiency test.

[0064] Compared to the examples, this comparative example contains 30 wt% Ga2O and has a larger contact resistance in the P region of its BC battery.

[0065] Comparative Example 2 A conductive silver paste for BC batteries is prepared by the following steps: (1) Prepare the slurry by weighing 88wt% silver powder, 3.9wt% glass powder, 2wt% organic resin, 6wt% solvent, and 0.1wt% other additives, with the total weight of the components being 100wt%. The glass powder is a lead-bismuth-tellurium glass powder, i.e., a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system includes 3wt% PbO3, 29wt% Bi2O3, and 28wt% TeO2; the second component system includes 4.5wt% SiO2, 2wt% Al2O3, 0.5wt% Li2CO3, and 0.5wt% Rb2CO3; and the third component system includes 5wt% Ga2O3. Mix the silver powder, glass powder, organic resin, solvent, and other additives, and place them in a disperser. (2) Disperse using a disperser at a speed of 500-2000 rpm for 1 hour; (3) Grind and disperse the conductive slurry on a three-roll mill until the fineness is ≤7μm, and the viscosity of the conductive slurry is 50-70Pa·S, wherein the viscosity of the slurry is measured by a Brookfield DV2T viscometer at 25℃ and 10r / min. (4) The conductive silver paste prepared above is printed and sintered to prepare a photovoltaic cell for paste contact resistance test and photoelectric conversion efficiency test.

[0066] Compared to the examples, this comparative example can reduce the contact resistance of the P region of the BC battery to a certain extent by increasing the amount of Ga2O3 added. However, as the amount added increases, it may lead to inhomogeneity of the glass system.

[0067] Comparative Example 3 A conductive silver paste for BC batteries is prepared by the following steps: (1) Prepare the slurry by weighing 88wt% silver powder, 3.9wt% glass powder, 2wt% organic resin, 6wt% solvent, and 0.1wt% other additives, with the total weight of the components being 100wt%. The glass powder is a lead-bismuth-tellurium glass powder, i.e., a PbO-Bi2O3-TeO2 system. By weight percentage, the first component system includes 4.5wt% PbO3, 33wt% Bi2O3, and 24wt% TeO2; the second component system includes 4.5wt% SiO2, 2wt% Al2O3, 0.5wt% Li2CO3, and 0.5wt% Rb2CO3; and the third component system includes 1wt% Ga2O3. Mix the silver powder, glass powder, organic resin, solvent, and other additives, and place them in a disperser. The silver powder used has a D50 of 1.36μm, a D90 of 4.25μm, and an organic coating of 0.53%. (2) Disperse using a disperser at a speed of 500-2000 rpm for 1 hour; (3) Grind and disperse the conductive slurry on a three-roll mill until the fineness is ≤7μm, and the viscosity of the conductive slurry is 50-70Pa·S, wherein the viscosity of the slurry is measured by a Brookfield DV2T viscometer at 25℃ and 10r / min. (4) The conductive silver paste prepared above is printed and sintered to prepare a photovoltaic cell for paste contact resistance test and photoelectric conversion efficiency test.

[0068] The only difference between Comparative Example 3 and Example 1 is the use of different silver powder. Smaller silver powder affects the effectiveness of Ga2O3 and glass, resulting in a larger contact resistance in the P region of the BC battery.

[0069] Performance testing: The conductive silver pastes prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to paste contact resistance and photoelectric conversion efficiency tests. The test results are shown in Table 2 below.

[0070] Table 2

[0071] As can be seen from the data in Table 2 above, the glass powder of the conductive silver paste based on the embodiments of this application contains gallium, and the free Ga... 3+ Ions can diffuse into the poly layer along with the glass, increasing the doping concentration and reducing the contact resistance. By adding gallium to the glass powder, the contact resistance in the P-region of the BC cell is reduced, thereby improving the cell's efficiency. Furthermore, this application experimentally investigated the availability of free Ga... 3+ The range of gallium oxide addition is 0≤y≤4wt%, and can be 2≤y≤3wt%, with an optional gallium oxide content of 2.5wt%.

[0072] The conductive silver paste of this application can be used in BC batteries to reduce the contact resistance of the P region of the BC battery in whole or in part, while ensuring reliability.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A conductive silver paste for BC battery, characterized in that, The conductive silver paste comprises the following components in percentage by weight: silver powder 88-93wt%, glass powder 3-5wt%, organic resin 1-3wt%, solvent 6-10wt%, and other additives 0-1wt%, the sum of the above components being 100wt%, wherein the composition of the glass powder comprises gallium sesquioxide.

2. The conductive silver paste for BC battery of claim 1, wherein, The glass powder is a lead bismuth tellurium glass powder, the softening point of the lead bismuth tellurium glass powder is controlled at 500-650℃, the lead bismuth tellurium glass powder comprises a PbO-Bi2O3-TeO2 system, the first component system comprises PbO 30-40wt%, Bi2O3 30-40wt%, and TeO2 20-30wt%; the second component system comprises SiO2 0-10wt% and / or Al2O3 0-3wt% and / or Li2CO3 0-2wt% and / or Na2CO3 0-2wt% and / or Rb2CO3 0-2wt%, and the third component system is gallium sesquioxide.

3. The conductive silver paste for BC battery as claimed in claim 2, wherein, The content of the gallium sesquioxide is 0≤y≤4wt%.

4. The conductive silver paste for BC battery of claim 3, wherein, The content of the gallium sesquioxide is 2≤y≤3wt%.

5. The conductive silver paste for BC battery of claim 1, wherein, The silver powder is spherical, the particle size D50 is 1.4-2.1 μm, the specific surface area is 0.25-0.5 m 2 / g, the tap density is 5.5-6.5 g / ml, and the organic coating amount is ≤0.7%.

6. The conductive silver paste for BC battery of claim 1, wherein, The organic resin comprises a mixture of one or more of SEPS resin, acrylic resin, PVB resin, and CAB resin, wherein the mass ratio of SEPS resin:acrylic resin:PVB resin:CAB resin is (3-5):2:1:

1.

7. The conductive silver paste for BC batteries of claim 1, wherein, The solvent comprises a mixture of one or more of diethylene glycol dibutyl ether, dimethyl phthalate, alcohol ester twelve, and diethylene glycol butyl ether acetate, wherein the mass ratio of diethylene glycol dibutyl ether:dimethyl phthalate:alcohol ester twelve:diethylene glycol butyl ether acetate is 1:2:1.5:(1-3).

8. The conductive silver paste for BC battery of claim 1, wherein, The other additives comprise a mixture of one or more of castor oil thixotropic agent and silicone leveling agent, and the mass ratio of castor oil thixotropic agent:silicone leveling agent is 5:

1.

9. A method for preparing the conductive silver paste for BC battery to produce the conductive silver paste for BC battery according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: The silver powder, the glass powder, the organic resin, the solvent, and the other additives are mixed and placed in a disperser; the disperser is used to disperse for 1h at a rotation speed of 500-2000rpm, and then the mixture is ground on a three-roll mill to a fineness of ≤7um, so as to obtain the conductive silver paste with a viscosity of 50-70Pa·S.

10. A BC battery characterized by, The BC battery is prepared by printing and sintering the conductive silver paste according to any one of claims 1-8 or prepared by the method of claim 9.

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