阅读说明：本技术 一种低温烧结银浆及其制备方法 (Low-temperature sintered silver paste and preparation method thereof ) 是由 毛平 于 2021-01-08 设计创作，主要内容包括：本发明提供一种低温烧结银浆及其制备方法,属于太阳能电池技术领域。其中,本发明的低温烧结银浆包括：80wt%-90 wt%的银粉,5wt%-15wt%的有机载体,2wt%-10wt%的低软化点玻璃粉,以及,0.01wt%-0.9wt%的铝合金粉添加剂,所述铝合金粉添加剂包括铝硅合金粉添加剂、铝硼合金粉添加剂、铝硅硼合金粉添加剂中的至少一者。本发明通过在低温烧结银浆中加入铝合金粉添加剂作为烧结促进剂,有效的增加了银浆的烧结活性,使得银浆跟太阳能电池硅片之间形成较好欧姆接触,有效降低了烧结温度,其烧结温度范围为700℃-720℃,解决了目前烧结温度过高的问题,从而减少高温烧结给太阳能电池片的损坏,进一步提高光电转化效率。(The invention provides a low-temperature sintered silver paste and a preparation method thereof, and belongs to the technical field of solar cells. The low-temperature sintering silver paste comprises the following components: 80-90 wt% of silver powder, 5-15 wt% of organic carrier, 2-10 wt% of low-softening-point glass powder and 0.01-0.9 wt% of aluminum alloy powder additive, wherein the aluminum alloy powder additive comprises at least one of aluminum-silicon alloy powder additive, aluminum-boron alloy powder additive and aluminum-silicon-boron alloy powder additive. According to the invention, the aluminum alloy powder additive is added into the low-temperature sintering silver paste as the sintering accelerant, so that the sintering activity of the silver paste is effectively increased, better ohmic contact is formed between the silver paste and the solar cell silicon wafer, the sintering temperature is effectively reduced, the sintering temperature range is 700-720 ℃, and the problem of overhigh sintering temperature at present is solved, so that the damage of high-temperature sintering to the solar cell is reduced, and the photoelectric conversion efficiency is further improved.)

1. The low-temperature sintering silver paste is characterized by comprising the following components:

80wt% -90wt% of silver powder;

5-15 wt% of an organic vehicle;

2-10 wt% of low softening point glass powder; and the number of the first and second groups,

0.01-0.9 wt% of aluminum alloy powder additive; wherein the content of the first and second substances,

the median particle size range of the aluminum alloy powder additive is 0.6-4 mu m;

the aluminum alloy powder additive comprises at least one of an aluminum-silicon alloy powder additive, an aluminum-boron alloy powder additive and an aluminum-silicon-boron alloy powder additive; wherein the content of the first and second substances,

the content range of silicon in the aluminum-silicon alloy powder additive is 0.1 to 0.9 weight percent, and the tap density range is 1g/cm³-2g/cm³Median particle diameter D₅₀In the range of 1.6 μm to 4 μm; and/or the presence of a gas in the gas,

the content range of boron in the aluminum-boron alloy powder additive is 0.1 to 0.9 weight percent, and the tap density range is 1.2g/cm³-1.5g/cm³The loose packed density range is 0.65g/cm³-0.75 g/cm³(ii) a And/or the presence of a gas in the gas,

the content range of boron in the aluminum-silicon-boron alloy powder additive is 0.1 to 0.5 weight percent, the content range of silicon is 0.1 to 0.5 weight percent, and the tap density range is 1.2g/cm³-3.0g/cm³The loose packed density range is 0.65g/cm³-1.00 g/cm³。

2. The low-temperature sintered silver paste of claim 1, wherein the content of oxygen in the silver powder is in a range of 0wt% to 5 wt%.

3. The low temperature sintering silver paste of claim 1, wherein the silver paste further comprises an aluminum copper alloy or an aluminum zinc manganese alloy.

4. The low temperature sintering silver paste of any one of claims 1 to 3, wherein the organic vehicle comprises a resin, an organic solvent, and an organic additive; wherein the mass ratio range of the resin, the organic solvent and the organic additive is as follows: (70-85): (10-20): (5-10).

5. The low-temperature sintering silver paste of claim 4, wherein the resin comprises at least one of ethyl cellulose, acrylic resin, rosin and its derivatives, and phenolic resin; and/or the presence of a gas in the gas,

the molecular weight range of the resin is 1000-50000; and/or the presence of a gas in the gas,

the organic solvent comprises at least one of alcohol ester dodeca, terpineol, tributyl citrate and butyl carbitol acetate; and/or the presence of a gas in the gas,

the organic additive comprises at least one of a leveling agent, a thixotropic agent, a defoaming agent, a drier, a dispersing agent and a viscosity reducer.

6. The low-temperature sintered silver paste according to any one of claims 1 to 3, wherein the low-softening-point glass frit has a softening temperature in the range of 280 ℃ to 400 ℃ and a median particle size in the range of 0.1 μm to 10 μm; and/or the presence of a gas in the gas,

the low softening point glass frit includes at least one of a Pb-based glass frit and a Pb-Te-Bi-based glass frit.

7. The preparation method of the low-temperature sintering silver paste is characterized in that the low-temperature sintering silver paste of any one of claims 1 to 6 is adopted, and the preparation method comprises the following steps:

weighing the components according to the proportion, and preparing the organic carrier and the low-softening-point glass powder into glass slurry;

placing the glass slurry in a multi-roller machine for multi-roller grinding treatment for multiple times;

and adding a mixture of silver powder and an aluminum alloy powder additive into the ground glass paste, and centrifuging to obtain the low-temperature sintered silver paste.

8. The method of claim 7, wherein the preparing the organic vehicle and the low softening point glass frit to form a glass paste comprises:

adding an organic carrier and the low-softening-point glass powder into a centrifugal tube, uniformly mixing, and placing the centrifugal tube into a centrifugal machine for centrifugal treatment for 1-3 times to prepare the glass slurry; wherein the rotating speed range of the centrifugal machine is 800rmp-1200rmp, and the centrifugal time range is 3min-7 min.

9. The method according to claim 8, wherein the subjecting the glass paste to a multi-roll grinding process for a plurality of times in a multi-roll machine comprises:

putting the glass slurry into a three-roller machine to carry out three-roller grinding treatment;

wherein the roller spacing range of the three-roller machine is 5-40 μm, the rotating speed range of the three-roller machine is 100-200 rmp, and the distance between each roller decreases with the increase of the grinding times,

and the distance between the first roller and the second roller is larger than the distance between the second roller and the third roller during each grinding treatment.

10. The preparation method according to claim 9, wherein the low-temperature sintered silver paste obtained after the centrifugation treatment comprises:

and centrifuging for 2-4 times under the condition that the centrifugal rotating speed range is 500-600 rmp to obtain the low-temperature sintered silver paste.

Technical Field

The invention belongs to the technical field of solar cells, and particularly relates to low-temperature sintered silver paste and a preparation method thereof.

Background

The solar cell technology is highly concerned about cleanness, environmental protection and inexhaustibility, but further popularization of the solar cell is restricted due to the price of monocrystalline and polycrystalline silicon wafers leading the solar cell industry, complex process flow of cell production and the like. The cost can be effectively reduced by improving the photoelectric conversion efficiency of the solar cell. Theoretical studies show that for every increase of the photoelectric conversion efficiency of a solar cell by a percentage, the corresponding power generation cost is reduced by 7%.

The efficiency of the solar cell is influenced by various factors, namely, the photoelectric conversion efficiency difference caused by the P-N junction, and the structure and the performance of different layer materials in the solar cell module. Wherein the preparation of the front electrode has great influence on the series-parallel resistance and the filling factor of the battery. At present, the screen printing process is generally adopted by the traditional solar cell industry to prepare the front electrode. The silk-screen printing process flow is simple, is relatively suitable for large-scale industrial production, and has a plurality of defects at the same time, for example, the sintering temperature of the slurry is generally controlled to be 800-850 ℃ and is accompanied with higher temperature rising and cooling rates, and the metal impurities of the silicon wafer are influenced by the overhigh temperature amplitude, so that the service life of the battery piece is influenced. Meanwhile, the higher sintering temperature also affects the passivation performance of the surface, and causes the silicon wafer to warp and the like. The research and development of the high-efficiency low-cost solar cell front electrode material and the reduction of the cell sintering temperature form a key technical point in the production of the solar cell.

One of the prior arts, chinese patent CN103000255B discloses a solar cell front silver paste suitable for low temperature sintering, which mainly uses a mixture of submicron silver powder and micron silver powder as a conductor of silver paste, on one hand, the sintering activity of the silver powder system can be enhanced, and the peak temperature of paste sintering is reduced; on the other hand, the submicron silver powder can effectively fill gaps among the micron silver powder in the slurry, so that the compactness of a silver film formed by sintering the silver paste is greatly improved, the sintering shrinkage rate is reduced, and the comprehensive performance of the sintered electrode is improved. But this method has limited effect on lowering the sintering temperature of the slurry.

One of the prior art, chinese patent application CN106887269A discloses a solar cell front silver paste suitable for low temperature sintering and a preparation method thereof, and the application adopts a direct current arc plasma evaporation and condensation method to prepare nano silver powder to prepare low temperature sintered silver paste. However, the nano silver powder in the method is expensive, the preparation method is complex, and the method is not suitable for industrial large-scale production.

Therefore, there is a need to provide a new low temperature sintering silver paste to lower the sintering temperature of the silver paste.

Disclosure of Invention

The invention aims to at least solve one of the technical problems in the prior art and provides a low-temperature sintered silver paste and a preparation method thereof.

In one aspect of the present invention, a low temperature sintering silver paste is provided, including:

80wt% -90wt% of silver powder;

5-15 wt% of an organic vehicle;

2-10 wt% of low softening point glass powder; and the number of the first and second groups,

0.01-0.9 wt% of aluminum alloy powder additive; wherein the content of the first and second substances,

the median particle size range of the aluminum alloy powder additive is 0.6-4 mu m;

the aluminum alloy powder additive comprises at least one of an aluminum-silicon alloy powder additive, an aluminum-boron alloy powder additive and an aluminum-silicon-boron alloy powder additive; wherein the content of the first and second substances,

the content range of silicon in the aluminum-silicon alloy powder additive is 0.1 to 0.9 weight percent, and the tap density range is 1g/cm³-2g/cm³Median particle diameter D₅₀In the range of 1.6 μm to 4 μm; and/or the presence of a gas in the gas,

the content range of boron in the aluminum-boron alloy powder additive is 0.1 to 0.9 weight percent, and the tap density range is 1.2g/cm³-1.5g/cm³The loose packed density range is 0.65g/cm³-0.75 g/cm³。

The content range of boron in the aluminum-silicon-boron alloy powder additive is 0.1 to 0.5 weight percent, the content range of silicon is 0.1 to 0.5 weight percent, and the tap density range is 1.2g/cm³-3.0g/cm³The loose packed density range is 0.65g/cm³-1.00 g/cm³。

Optionally, the content of oxygen in the silver powder ranges from 0wt% to 5 wt%.

Optionally, the silver paste further includes an aluminum copper alloy or an aluminum zinc manganese alloy.

Optionally, the organic vehicle comprises a resin, an organic solvent, and an organic additive; wherein the mass ratio range of the resin, the organic solvent and the organic additive is as follows: (70-85): (10-20): (5-10).

Optionally, the resin comprises at least one of ethyl cellulose, acrylic resin, rosin and its derivatives, and phenolic resin; and/or the presence of a gas in the gas,

the molecular weight range of the resin is 1000-50000; and/or the presence of a gas in the gas,

the organic solvent comprises at least one of alcohol ester dodeca, terpineol, tributyl citrate and butyl carbitol acetate; and/or the presence of a gas in the gas,

the organic additive comprises at least one of a leveling agent, a thixotropic agent, a defoaming agent, a drier, a dispersing agent and a viscosity reducer.

Optionally, the softening temperature range of the low-softening-point glass powder is 280-400 ℃, and the median particle size range is 0.1-10 μm; and/or the presence of a gas in the gas,

the low softening point glass frit includes at least one of a Pb-based glass frit and a Pb-Te-Bi-based glass frit.

In another aspect of the present invention, there is provided a method for preparing a low-temperature sintered silver paste, where the method includes:

weighing the components according to the proportion, and preparing the organic carrier and the low-softening-point glass powder into glass slurry;

placing the glass slurry in a multi-roller machine for multi-roller grinding treatment for multiple times;

and adding a mixture of silver powder and an aluminum alloy powder additive into the ground glass paste, and centrifuging to obtain the low-temperature sintered silver paste.

Optionally, the preparing the organic vehicle and the low softening point glass frit to form a glass paste includes:

adding an organic carrier and the low-softening-point glass powder into a centrifugal tube, uniformly mixing, and placing the centrifugal tube into a centrifugal machine for centrifugal treatment for 1-3 times to prepare the glass slurry; wherein the content of the first and second substances,

the rotating speed range of the centrifugal machine is 800rmp-1200rmp, and the centrifugal time range is 3min-7 min.

Optionally, the glass slurry is placed in a multi-roll machine for multiple multi-roll grinding treatments, including:

putting the glass slurry into a three-roller machine to carry out three-roller grinding treatment; wherein the content of the first and second substances,

the roller spacing range of the three-roller machine is 5-40 μm, the rotating speed range of the three-roller machine is 100-200 rmp, the distance between the rollers decreases with the increase of the grinding times, and the distance between the first roller and the second roller is larger than the distance between the second roller and the third roller during each grinding treatment.

Optionally, the low-temperature sintered silver paste obtained after the centrifugation treatment includes:

and centrifuging for 2-4 times under the condition that the centrifugal rotating speed range is 500-600 rmp to obtain the low-temperature sintered silver paste.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the low-temperature sintering silver paste formula system provided by the invention, at least one of an appropriate aluminum-silicon alloy powder additive, an aluminum-boron alloy powder additive and an aluminum-silicon-boron alloy powder additive is added as a sintering accelerant, so that the sintering temperature is reduced to 700-720 ℃, the damage of high-temperature sintering to a solar cell piece is reduced on the premise of ensuring the electrical efficiency of the solar cell, and the yield of solar cell production is improved.

2. According to the invention, by selecting proper silver powder (for example, mixed silver powder of flake silver powder and spherical silver powder), the low-temperature sintered silver paste can form better contact with the surface of the solar cell silicon wafer, and the sintered gap is effectively filled, so that the surface of the sintered silver paste is smoother and more compact.

Drawings

Fig. 1 is a flow chart of a method for preparing a low-temperature sintered silver paste according to an embodiment of the invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

In one aspect of the present invention, a low temperature sintering silver paste is provided, including: 80wt% -90wt% of silver powder; 5-15 wt% of an organic vehicle; 2-10 wt% of low softening point glass powder; and 0.01-0.9 wt% of aluminum alloy powder additive. Wherein the median particle size range of the aluminum alloy powder additive is 0.6-4 μm; the aluminum alloy powder additive comprises at least one of an aluminum-silicon alloy powder additive, an aluminum-boron alloy powder additive and an aluminum-silicon-boron alloy powder additive; wherein the content range of silicon in the aluminum-silicon alloy powder additive is 0.1-0.9 wt%, and the tap density range is 1g/cm³-2g/cm³Median particle diameter D₅₀In the range of 1.6 μm to 4 μm; the content range of boron in the aluminum-boron alloy powder additive is 0.1 to 0.9 weight percent, and the tap density range is 1.2g/cm³-1.5g/cm³The loose packed density range is 0.65g/cm³-0.75 g/cm³(ii) a The additive of the aluminum-silicon-boron alloy powder contains 0.1 to 0.5 weight percent of boron, 0.1 to 0.5 weight percent of silicon and 1.2g/cm of tap density³-3.0g/cm³The loose packed density range is 0.65g/cm³-1.00 g/cm³。

According to the embodiment, the aluminum alloy powder additive is added into the silver paste to serve as the sintering accelerant, so that the sintering temperature is effectively reduced, the sintering temperature range is 700-720 ℃, and the problem that the existing sintering temperature is too high is solved, so that the damage of high-temperature sintering to the solar cell is reduced, and the yield of solar cell production is improved. In addition, the aluminum alloy powder additive is added into the low-temperature sintering silver paste to serve as the sintering accelerant, so that the sintering activity of the silver paste is effectively increased, good ohmic contact is formed between the silver paste and the solar cell silicon wafer, and the photoelectric conversion efficiency is further improved.

It should be noted that, since the melting point of pure aluminum is 660 ℃, the melting point of pure silicon is 1410 ℃, the melting point of pure boron is 2180 ℃ and the melting point of aluminum alloy is lower than the melting point of any one of the constituent metals, the melting points of aluminum-boron alloy and aluminum-silicon alloy are lower than 660 ℃. Therefore, based on multiple experiments of the inventor, in the embodiment, at least one of an aluminum-boron alloy, an aluminum-silicon alloy or an aluminum-silicon-boron alloy powder additive is added into the silver paste, so that the sintering temperature can be reduced while the adhesive force of the paste on the silicon substrate is effectively ensured, the influence of high temperature on the silicon wafer is avoided, the sintering temperature is reduced to 700-720 ℃ from the original 800-850 ℃, the influence of high-temperature sintering on the silicon wafer is effectively reduced, and the damage to the silicon wafer is reduced.

Specifically, in some embodiments, an aluminum-silicon alloy powder additive may be selected, wherein the silicon content ranges from 0.1wt% to 0.9wt%, and when the silicon content in the aluminum-silicon alloy powder is lower than 0.1wt%, the effect of reducing the sintering temperature of the silver paste is not significant, so that the sintering temperature is above 720 ℃. When the content of silicon in the aluminum-silicon alloy powder is higher than 0.9wt%, the electrical property of the prepared silver paste is influenced, so that the photoelectric conversion efficiency is reduced, and simultaneously, when the tap density range of the selected aluminum-silicon alloy powder is 1g/cm³-2g/cm³Median particle diameter D₅₀When the range is 1.6-4 μm, the photoelectric conversion efficiency of the prepared silver paste can reach more than 21%.

Further, in other embodiments, an aluminum boron alloy powder additive may be further selected, wherein the boron content ranges from 0.1wt% to 0.9wt%, and when the boron content in the aluminum boron alloy powder is less than 0.1wt%, the effect of reducing the sintering temperature is not obvious, so that the sintering temperature is above 720 ℃. When the content of boron in the aluminum-boron alloy powder is higher than 0.9wt%, the electrical property of the prepared silver paste is influenced, the photoelectric conversion efficiency is reduced, and simultaneously, when the tap density range of the selected aluminum-boron alloy powder is 1.2g/cm³-1.5g/cm³The loose packed density range is 0.65g/cm³-0.75 g/cm³In the process, the photoelectric conversion efficiency of the prepared silver paste can reach more than 21%.

Furthermore, in other embodiments, an Al-Si-B alloy powder additive may be used, wherein the content of B in the alloy is in the range of 0.1wt% to 0.5wt%, and the content of Si in the alloy is in the range of 0.1wt% to 0.5wt%, and similarly, the photoelectric conversion efficiency of the prepared silver paste is influenced by too high and too low boron and silicon contents, and meanwhile, when the tap density range of the selected aluminum-silicon-boron alloy powder additive is 1.2g/cm³-3.0g/cm³The loose packed density range is 0.65g/cm³-1.00 g/cm³ _，The photoelectric conversion efficiency of the prepared silver paste can reach more than 21%. The aluminum-silicon-boron alloy powder additive selected in the embodiment has a low melting point, so that the slurry can be ensured to be at a lower sintering temperature, and the doping concentration of the solar cell can be increased by the diffusion of boron in the alloy in the sintering process, so that the photoelectric conversion efficiency of the solar cell is improved on the premise of reducing the damage of a silicon substrate.

It should be understood that in other embodiments, any two or three of the al-si alloy powder additive, the al-bo alloy powder additive, and the al-si-bo alloy powder additive may also be selected.

It should be noted that in some embodiments, it is preferable that the median particle size of the aluminum alloy powder additive is in the range of 0.6 μm to 4 μm for the purpose of low temperature sintering, because when the median particle size of the aluminum alloy powder additive is greater than 4 μm, sintering is performed at a higher temperature, and thus, the purpose of low temperature sintering cannot be achieved, and when the median particle size of the aluminum alloy powder additive is less than 0.6 μm, surface recombination occurs in the aluminum alloy powder additive during sintering, thereby damaging the surface of the substrate.

Further, in other embodiments, other additives may be added to the silver paste, such as: the aluminum-copper alloy or the aluminum-zinc-manganese alloy has the advantages that the crystal grains of the aluminum-copper alloy are large, the aluminum-copper alloy is added as an additive of the silver paste, the circulation path of current can be reduced, the flow rate of the current is enabled to be fast, the line resistance of the silver paste is reduced, and the photoelectric conversion efficiency of the solar cell is improved. In addition, the potential difference between Zn and Mn in the aluminum-zinc-manganese alloy is small, the generated electrochemical reaction is small, the aluminum-zinc-manganese alloy is corrosion-resistant, the reliability of a conductive electrode can be effectively improved by adding the alloy into silver paste, and the service life of a solar cell is prolonged.

Specifically, as for another component of silver powder in this embodiment, the inventors of the present invention have conducted an elaborate study on sintered silver powder formed by various silver powders, and as a result, it has been found that the flake silver powder is beneficial to increasing ohmic contact between the silver powder and the surface of the solar cell, but the flake silver powder alone can make the surface of the sintered silver powder unsmooth, and therefore, the silver powder of this embodiment is a mixed silver powder of the flake silver powder and the spherical silver powder, and thus, the flake silver powder and the spherical silver powder are mixed for use, so that the surface of the sintered silver powder is more compact and smooth, and the cost can be effectively reduced compared with the currently used nano silver powder.

Further, in some embodiments, the mass ratio range of the plate-like silver powder and the spherical silver powder is set to 1: (1-3), the content of oxygen in the silver powder is in the range of 0wt% to 5wt%, and when the content of oxygen in the silver powder is higher than 5wt%, the silver powder is blackened, so that the prepared silver paste is not sintered sufficiently, and the photoelectric conversion efficiency of the solar cell is affected.

It should be noted that, in the present example, specific sizes of the plate-like silver powder and the spherical silver powder are not particularly limited, and it is preferable that the plate-like silver powder has a length ranging from 0.8 μm to 12 μm and a width ranging from 150nm to 250nm, and that the spherical silver powder has a median particle diameter ranging from 0.05 μm to 10 μm and a tap density ranging from 4g/cm³-6g/cm³。

Specifically, the other component of the organic vehicle in the low-temperature sintering silver paste of the embodiment includes a resin, an organic solvent and an organic additive. Wherein the mass ratio range of the resin, the organic solvent and the organic additive is as follows: (70-85): (10-20): (5-10) within which a person skilled in the art can arbitrarily select.

It should be noted that the present embodiment is not limited to the type of the resin, for example, in some embodiments, the resin may include at least one of ethyl cellulose, acrylic resin, rosin and its derivatives, and phenolic resin, and it is possible for those skilled in the art to select the resin according to actual needs. Secondly, the molecular weight of the resin is one of the important indicators for selecting the resin, and also needs to be selected specifically according to the actual situation, for example, in other embodiments, the preferred molecular weight range of the resin is 1000-50000.

It should be further noted that the present embodiment also does not specifically limit the types of the organic solvent and the organic additive, for example, in some embodiments, the organic solvent includes at least one of alcohol ester dodeca, terpineol, tributyl citrate, and butyl carbitol acetate. And the organic additive includes at least one of a leveling agent, a thixotropic agent, an antifoaming agent, a drier, a dispersing agent and a viscosity reducer, and it is needless to say that the organic additive may be appropriately selected and added by those skilled in the art according to the condition of the slurry to be actually prepared, since the condition of the slurry may be affected by the ambient temperature.

Specifically, the softening temperature range of the other component of the low-softening-point glass powder in the low-temperature sintering silver paste of the embodiment is 280 ℃ to 400 ℃, and the median particle size range is 0.1 μm to 10 μm. In addition, the low softening point glass frit of the present embodiment may include at least one of a Pb-based glass frit and a Pb — Te — Bi-based glass frit, and is not particularly limited thereto. Thus, the low softening point glass powder ensures that the low-temperature sintering temperature can be sintered at a lower temperature and can ensure better ohmic contact.

The comprehensive properties of the low-temperature sintered silver paste, such as sintering temperature, light conversion efficiency and the like, will be further described below by combining several specific examples and comparative examples:

example 1

The low-temperature sintered silver paste of the embodiment is formed by selecting 83.6wt% of silver powder, 10wt% of organic carrier, 6wt% of low-softening-point glass powder and 0.4wt% of aluminum-silicon alloy powder, and the comprehensive properties of the low-temperature sintered silver paste are shown in table 1, so that the low-temperature sintered silver paste obtained in the embodiment has the sintering temperature of 700 ℃, the surface of the sintered silver paste is smooth through a profilometer, the generated holes are few, and the contact resistivity is 0.5m omega cm^-2The adhesive force is 4.3N, and the photoelectric conversion efficiency range is 21.35%.

Example 2

The selection of 90wt% silver powder, 7.1wt% organic vehicle, 2wt% low softening point glass frit, and 0.9wt% aluminum boron alloy powder additive resulted in the low temperature sintered silver paste of this example, which has the combination of properties shown in table 1,the sintering temperature of the low-temperature sintered silver paste obtained in the embodiment is 720 ℃, the surface of the sintered silver paste is observed to be smooth through a profiler, the generated holes are few, and the contact resistivity is 0.5m omega cm^-2The adhesive force is 4.1N, and the photoelectric conversion efficiency range is 21.25%.

Example 3

The silver powder with the mass fraction of 80wt%, the organic carrier with the mass fraction of 9.99wt%, the glass powder with the low softening point with the mass fraction of 10wt% and the aluminum-silicon-boron alloy powder with the mass fraction of 0.01wt% are selected to form the low-temperature sintered silver paste of the embodiment, the comprehensive performance of the low-temperature sintered silver paste is shown in table 1, and the low-temperature sintered silver paste obtained in the embodiment has the sintering temperature of 715 ℃, the surface of the sintered silver paste is smooth through the observation of a profilometer, the generated holes are few, and the contact resistivity is 0.5m omega cm^-2The adhesive force is 4.2N, and the photoelectric conversion efficiency range is 21.45%.

Example 4

The low-temperature sintering silver paste of the embodiment is formed by selecting the silver powder with the mass fraction of 86wt%, the organic carrier with the mass fraction of 11wt%, the low-softening-point glass powder with the mass fraction of 8wt%, the aluminum-silicon alloy powder additive with the mass fraction of 0.5wt% and the aluminum-boron alloy powder additive with the mass fraction of 0.4wt%, and the comprehensive properties of the low-temperature sintering silver paste are shown in table 1^-2The adhesive force is 4.5N, and the photoelectric conversion efficiency range is 21.25%.

Example 5

The low-temperature sintered silver paste of the embodiment is formed by selecting 83.4wt% of silver powder, 8wt% of organic carrier, 8wt% of low-softening-point glass powder, 0.5wt% of aluminum-silicon-boron alloy powder additive and 0.1wt% of aluminum-copper alloy or aluminum-zinc-manganese alloy, and the comprehensive properties of the low-temperature sintered silver paste are shown in table 1, so that the sintering temperature of the low-temperature sintered silver paste obtained in the embodiment is 720 ℃, the surface of the sintered silver paste is smooth through observation of a profilometer, the generated cavities are few, and the contact resistivity is 0.6m omega cm^-2The adhesive force is 4.3N, and the photoelectric conversion efficiency range is 21.45%.

Comparative example 1

To illustrate the low temperature sintering of the present inventionThe silver paste has better comprehensive performance, the embodiment is further illustrated as a comparative example, specifically, in the embodiment, the aluminum alloy powder additive is not added, the adding amount of the silver powder is 84wt%, the rest formula system is the same as the embodiment 1, and the sintered silver paste of the comparative example is prepared, the comprehensive performance of which is shown in table 1, it can be seen that the sintering temperature of the low-temperature sintered silver paste obtained in the embodiment is 750 ℃, the roughness of the surface of the sintered silver paste is observed by a profilometer, the generated cavities are more, and the contact resistivity is 1.2m Ω · cm^-2The adhesive force is 0.7N, and the photoelectric conversion efficiency range is 20.68%.

Comparative example 2

In order to illustrate that the low-temperature sintered silver paste of the present invention has better comprehensive properties, this example further illustrates as a comparative example, specifically, the content of the aluminum alloy powder additive added in this example is 1wt%, the addition amount of the silver powder is 83wt%, and the rest formula system is the same as that in example 1, and the sintered silver paste of this comparative example is prepared, and the comprehensive properties of the sintered silver paste are shown in table 1, it can be seen that, the sintering temperature of the low-temperature sintered silver paste obtained in this example is 850 ℃, the roughness of the surface of the sintered silver paste is observed by a profiler, many voids are generated, and the contact resistivity is 1.3m Ω · cm^-2The adhesive force is 3.5N, and the photoelectric conversion efficiency range is 20.89%.

TABLE 1 Overall Performance results for each example and each comparative example

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To sum up, as shown in table 1, the sintering temperature range of the low-temperature sintered silver paste of the present invention is 700 ℃ to 720 ℃, the sintering temperature is effectively reduced by adding a suitable aluminum alloy powder additive as a sintering accelerant, and the surface of the sintered silver paste is smooth and less in voids observed by a profilometer, and the contact resistivity range of the low-temperature sintered silver paste is 0.5m Ω · cm^-2-0.6mΩ·cm^-2The range of adhesive force is 4.1N-4.5N, and the range of photoelectric conversion efficiency is 21.25% -21.45%. Therefore, the low-temperature sintering silver paste disclosed by the invention has the advantages that the sintering temperature is reduced, and the photoelectric conversion efficiency is higher.

As shown in fig. 1, another aspect of the present invention provides a method for preparing a low-temperature sintered silver paste S100, which specifically includes the following steps S110 to S130:

step S110, weighing the components according to the proportion, and preparing the organic carrier and the low-softening-point glass powder into glass slurry.

Specifically, the weight of each component is weighed according to a preset proportion, the organic carrier and the low-softening-point glass powder are respectively added into a centrifugal tube to be uniformly mixed, and then the centrifugal tube is placed into a centrifugal machine to be centrifugally treated for 1-3 times to prepare the glass slurry. Wherein the rotating speed range of the centrifugal machine is 800rmp-1200rmp, and the centrifugal time range is 3min-7 min. That is, in this embodiment, the organic vehicle and the low-softening-point glass powder are first centrifuged by a centrifuge to prepare a glass slurry, so that the system is dispersed more uniformly.

And step S120, placing the glass slurry in a multi-roller machine for multi-roller grinding treatment for multiple times.

It should be noted that, in the present embodiment, the multi-roll machine is not specifically limited, for example, a three-roll machine, an eight-roll machine, etc. may be adopted, and those skilled in the art may select the multi-roll machine according to actual needs.

Specifically, in this step, the glass paste is placed in a three-roll machine to be subjected to three-roll grinding treatment, that is, the glass paste is subjected to submerging treatment by using three rollers of the three-roll machine, wherein the range of the roller spacing of the three-roll machine can be set to be 5 μm to 40 μm, the range of the rotation speed of the three-roll machine is set to be 100rmp to 200rmp, and the distance between the rollers decreases with the increase of the grinding times, and the distance between the first roller and the second roller is greater than the distance between the second roller and the third roller at each grinding treatment, which is beneficial to making the obtained glass paste more uniform by grinding.

It should be noted that, in the grinding process, the distance between the rollers in the three-roller machine is not particularly limited, and for example, in the first three-roller grinding, the distance between the first roller and the second roller is 40 μm, the distance between the second roller and the third roller is 30 μm, in the second three-roller grinding, the distance between the first roller and the second roller is 30 μm, the distance between the second roller and the third roller is 20 μm, in the third roller grinding, the distance between the first roller and the second roller is 10 μm, and the distance between the second roller and the third roller is 5 μm, so that the obtained glass slurry is more uniform by three times of grinding. Of course, the glass paste may be ground more times by a three-roll mill, and this is not particularly limited.

And S130, adding a mixture of silver powder and an aluminum alloy powder additive into the ground glass paste, and performing centrifugal treatment to obtain the low-temperature sintered silver paste.

Specifically, the mixture of the silver powder and the aluminum alloy powder additive weighed before is added into the glass paste ground in the step S120, and the mixture is centrifuged for 2 times under the condition that the centrifugal rotating speed range is 500rmp-600rmp, so that the low-temperature sintered silver paste is obtained.

The low-temperature sintered silver paste described above can be formed by the preparation method of this embodiment, specifically, the organic vehicle and the low-softening-point glass powder of each embodiment are respectively prepared into glass paste according to the weight of each component of the embodiments 1 to 5 described above, the glass paste is placed in a three-roll machine to be subjected to multi-roll grinding treatment for multiple times, the mixture of silver powder and aluminum alloy powder additive is added into the ground glass paste, and the low-temperature sintered silver paste of each embodiment is obtained after centrifugation treatment. And the viscosity range of the low-temperature sintering silver paste at the rotating speed of 10rmp is 270 Pa.s/25-390 Pa.s/25 ℃.

Compared with the prior art, the low-temperature sintered silver paste and the preparation method thereof provided by the invention have the following beneficial effects: firstly, 0.01-0.9 wt% of aluminum alloy powder additive is added into the low-temperature sintering silver paste as a sintering accelerant, and glass powder with a low softening point is used in a matched mode, so that the silver paste can be sintered at the temperature of 700-720 ℃, damage to solar cells caused by high-temperature sintering is reduced, and the yield of solar cell production is improved. Secondly, at least one of an aluminum-silicon alloy powder additive, an aluminum-boron alloy powder additive and an aluminum-silicon-boron alloy powder additive can be selected as the aluminum alloy powder additive, wherein the addition of the silicon element effectively increases the sintering activity of the silver paste, and the addition of the boron element enables the silver paste to form good ohmic contact with a solar cell silicon wafer, so that the photoelectric conversion efficiency is further improved. Thirdly, the silver powder used for low-temperature sintering of the silver paste is mixed metal powder of flake silver powder and spherical silver powder, the flake silver powder can be in better contact with the surface of a solar cell silicon wafer, and the spherical silver powder can effectively fill a sintering gap, so that the surface of the sintered silver paste is smoother and more compact. Fourthly, the silver paste also comprises additives such as aluminum copper alloy or aluminum zinc manganese alloy and the like, so that the photoelectric conversion efficiency of the solar cell can be effectively increased.

It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.