Heterojunction photovoltaic silver paste and preparation method and application thereof

Abstract

The invention discloses heterojunction photovoltaic silver paste and a preparation method and application thereof. The heterojunction photovoltaic silver paste comprises the following components in percentage by mass: 80-90% of conductive silver powder; 1-5% of resin; a solvent; 5%-10%; 0.5-3% of a curing agent; 0.5-2% of a dispersant; 0.5 to 2 percent of plasticizer; 0.2 to 2 percent of thixotropic agent; according to the heterojunction photovoltaic silver paste disclosed by the invention, the conductive silver powder such as the nano silver powder is added, so that a gap formed by stacking large-particle silver powder can be filled in a silver paste curing process, the contact area between silver particles is increased, and the contact surface between the silver paste and a TCO layer of a Si wafer can be greatly improved, thereby reducing ohmic contact and improving the production efficiency. Therefore, the current of the heterojunction photovoltaic cell is better collected, and better photoelectric conversion efficiency is provided.

Description

Technical Field

[0001] The invention relates to a heterojunction photovoltaic silver paste and a preparation method and application thereof, belonging to the technical field of batteries. Background Art

[0002] Heterojunction (HJT) solar cells are a hybrid type of solar cells made of crystalline silicon and amorphous silicon thin film. They combine the characteristics and advantages of crystalline silicon and thin film solar cells, and have the advantages of high efficiency, bifaciality, low attenuation and high temperature, strong weak light power generation capability, simple manufacturing process, low temperature process, thin Si wafer, etc., and their conversion efficiency has exceeded 26%. In the existing silicon high-efficiency cell technology, it has better taken into account the performance and cost factors, so it has been widely valued by photovoltaic research and industry, and will become the mainstream technology of the third-generation cell.

[0003] Traditional high-temperature silver paste can puncture silicon wafers at high temperatures through the combined effects of silver powder, aluminum powder and glass powder, thereby forming a very direct conductive line and a better ohmic contact. However, the process temperature of HJT solar cells is below 250°C, and low-temperature curing silver paste is required. Due to the low final curing temperature, it is far from the sintering conditions of silver powder, aluminum powder and glass powder. The current mainstream technology relies on the shrinkage of the resin to form very weak ohmic contact performance. This is also the reason why the ohmic contact of traditional low-temperature silver paste is poor.

[0004] Based on the defects of the current conductive silver paste used in HJT photovoltaic cells, it is necessary to improve it. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a heterojunction photovoltaic silver paste and a preparation method and application thereof. The technical problem to be solved is that by adding silver powder, the gaps between the stacked large-grain silver powder particles can be filled during the curing process of the silver paste, which not only increases the contact area between the silver particles, but also greatly increases the contact area between the silver paste and the TCO layer of the Si wafer, thereby reducing the ohmic contact, and further better collecting the current of the heterojunction photovoltaic cell, providing better photoelectric conversion efficiency.

[0006] The purpose of the present invention and the technical problem solved by the present invention are achieved by adopting the following technical measures. A heterojunction photovoltaic silver paste proposed by the present invention comprises the following components in terms of mass percentage:

[0007] Conductive silver powder 80-90%;

[0008] Resin 1-5%;

[0009] Solvent 5-10%;

[0010] Curing agent 0.5-3%;

[0011] Dispersant 0.5-2%;

[0012] Plasticizer 0.5-2%;

[0013] Thixotropic agent 0.5~2%.

[0014] The purpose of the present invention and the technical problems to be solved can be further achieved by adopting the following technical measures.

[0015] Preferably, in the aforementioned heterojunction photovoltaic silver paste, the conductive silver powder comprises three types: flaky silver powder, spherical silver powder and nano silver powder. The flaky silver powder has a D50 of 2-5 μm and a tap density of 5-6 g / mL; the spherical silver powder has a D50 of 0.5-1 μm and a tap density of 4.5-6 g / mL; and the nano silver powder has a D50 of 30-100 nm and a tap density of 2.5-4 g / mL.

[0016] Preferably, in the aforementioned heterojunction photovoltaic silver paste, the conductive silver powder is composed of, by mass percentage:

[0017] Flake silver powder: 10-15%;

[0018] Spherical silver powder: 75-85%;

[0019] Nano silver powder: 5%~10%.

[0020] Preferably, in the aforementioned heterojunction photovoltaic silver paste, the resin is selected from at least one of bisphenol A epoxy resin, phenoxy resin, bisphenol F epoxy resin, aliphatic epoxy resin, silicone-modified epoxy resin, polyether-modified epoxy resin, epoxidized rubber, polyester resin and thermosetting acrylic resin.

[0021] Preferably, in the aforementioned heterojunction photovoltaic silver paste, the solvent includes at least one of propylene carbonate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, butyl carbitol ether acetate, diethylene glycol ethyl ether acetate and butyl carbitol.

[0022] Preferably, in the aforementioned heterojunction photovoltaic silver paste, the curing agent is selected from at least one of blocked isocyanate curing agent, phthalate, silane coupling agent, dicyandiamide, modified dicyandiamide, imidazole, 2-ethyl-4-methylimidazole, acid anhydride, boron trifluoride monoethylamine and amino resin.

[0023] Preferably, in the aforementioned heterojunction photovoltaic silver paste, the dispersant is selected from at least one of polyvinyl pyrrolidone, sodium dodecyl sulfate, corn germ oil and soybean lecithin.

[0024] Preferably, in the aforementioned heterojunction photovoltaic silver paste, the plasticizer is polyethylene glycol 200.

[0025] Preferably, in the aforementioned heterojunction photovoltaic silver paste, the thixotropic agent is polyamide wax.

[0026] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions. A method for preparing a heterojunction photovoltaic silver paste proposed in the present invention comprises the following steps:

[0027] Step 1: Preparation of an organic carrier: 5-10 wt% of a solvent and 0.5-2 wt% of a dispersant are stirred at a rotation speed of 300-600 rpm to form a mixed solution, and the mixed solution is heated to 80-100° C.; then 1-5 wt% of a resin, 0.5-3 wt% of a curing agent, 0.5-2 wt% of a plasticizer and 0.5-2 wt% of a thixotropic agent are sequentially added to the obtained mixed solution, and the temperature of the mixed solution is maintained at 80-100° C. After 30-180 minutes, the resin is fully dissolved to obtain an organic carrier.

[0028] Step 2: Premixing of the conductive silver paste, adding the nano silver powder into the organic carrier, stirring to form a mixed carrier; adding the flaky silver powder and the spherical silver powder into the mixed carrier in turn for ball milling to obtain the premixed heterojunction photovoltaic silver paste;

[0029] Step 3: Grinding and sieving: Grind and disperse the premixed heterojunction photovoltaic silver paste for 3 to 5 times, and then sieve through a 500-mesh sieve to remove impurities and uneven large particles in the paste to obtain the heterojunction photovoltaic silver paste.

[0030] The purpose of the present invention and the technical problems to be solved can be further achieved by adopting the following technical measures.

[0031] Preferably, in the aforementioned method for preparing heterojunction photovoltaic silver paste, in step 1, the heating time is 30 to 180 minutes.

[0032] Preferably, in the aforementioned method for preparing heterojunction photovoltaic silver paste, in step 2, the stirring time is 30 to 180 min, and the rotation speed is 500 to 1000 rpm.

[0033] Preferably, in the aforementioned method for preparing heterojunction photovoltaic silver paste, in step 2, the ball milling parameters are set to 35-50 Hz, and the ball milling time is 0.5-3 h.

[0034] The purpose of the present invention and the solution of its technical problems can also be achieved by the following technical measures. A heterojunction solar cell proposed in the present invention includes a silver paste, wherein the silver paste is a heterojunction photovoltaic silver paste; the heterojunction photovoltaic silver paste includes the following components in terms of mass percentage:

[0035] Conductive silver powder 80-90%;

[0036] Resin 1-5%;

[0037] Solvent 5-10%;

[0038] Curing agent 0.5-3%;

[0039] Dispersant 0.5-2%;

[0040] Plasticizer 0.5-2%;

[0041] Thixotropic agent 0.5~2%.

[0042] Compared with the prior art, the heterojunction photovoltaic silver paste and its preparation method and application described in the present invention have the following beneficial effects:

[0043] The heterojunction photovoltaic silver paste described in the present invention can fill the gaps between the stacked large-grain silver powder particles during the curing process of the silver paste by adding silver powder, which not only increases the contact area between the silver particles, but also greatly increases the contact area between the silver paste and the TCO layer of the Si sheet, thereby reducing the ohmic contact, thereby better collecting the current of the heterojunction photovoltaic cell sheet and providing better photoelectric conversion efficiency.

[0044] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows. DETAILED DESCRIPTION

[0045] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of a heterojunction photovoltaic silver paste and its preparation method and its specific implementation method, structure, characteristics and effects of the application proposed by the present invention in combination with the preferred embodiment. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0046] Unless otherwise specified, the materials, reagents, etc. involved below are all commercially available products well known to those skilled in the art; unless otherwise specified, the methods described are all methods known in the art. Unless otherwise defined, the technical terms or scientific terms used should have the usual meanings understood by ordinary technicians in the field to which the present invention belongs. If no specific experimental steps or conditions are specified below, the operations or conditions of the conventional experimental steps described in the literature in the field can be followed.

[0047] Some embodiments of the present invention provide a heterojunction photovoltaic silver paste, which comprises the following components in terms of mass percentage:

[0048] Conductive silver powder 80-90%;

[0049] Resin 1-5%;

[0050] Solvent 5-10%;

[0051] Curing agent 0.5-3%;

[0052] Dispersant 0.5-2%;

[0053] Plasticizer 0.5-2%;

[0054] Thixotropic agent 0.5~2%.

[0055] In some embodiments, optionally, the conductive silver powder comprises three types: flaky silver powder, spherical silver powder, and nano silver powder, wherein the flaky silver powder has a D50 of 2-5 μm and a tap density of 5-6 g / mL, the spherical silver powder has a D50 of 0.5-1 μm and a tap density of 4.5-6 g / mL, and the nano silver powder has a D50 of 30-100 nm and a tap density of 2.5-4 g / mL. The quality of the silver powder directly affects the battery performance, especially the spherical silver powder as the matrix of the silver paste, and its dispersibility, tap density, particle size and distribution directly affect the density, uniformity and screen printing of the electrode thick film, thereby affecting its conductive properties. Flaky silver powder has a low specific surface area and a high effective contact area when stacked, which can reduce the gaps between the silver powder stacking in the silver paste and the gaps after the paste is printed and solidified to a certain extent, which greatly improves the increase of conductive channels and the improvement of photoelectron transmission efficiency, and plays a very important role in the silver paste. Nano-silver powder can further fill the gaps between the silver powder accumulation in the silver paste and the gaps after the paste is printed and solidified, thereby improving the conductive properties of the silver paste. It can be seen that there is a synergistic effect between flaky silver powder, spherical silver powder and nano-silver powder.

[0056] In some embodiments, optionally, the conductive silver powder has a composition, in terms of mass percentage, of:

[0057] Flake silver powder: 10-15%;

[0058] Spherical silver powder: 75-85%;

[0059] Nano silver powder: 5%~10%.

[0060] In some embodiments, optionally, the resin is selected from at least one of bisphenol A epoxy resin, phenoxy resin, bisphenol F epoxy resin, aliphatic epoxy resin, silicone-modified epoxy resin, polyether-modified epoxy resin, epoxidized rubber, polyester resin and thermosetting acrylic resin.

[0061] In some embodiments, optionally, the solvent includes at least one of propylene carbonate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, butyl carbitol ether acetate, diethylene glycol ethyl ether acetate and butyl carbitol.

[0062] In some embodiments, optionally, the curing agent is selected from at least one of a blocked isocyanate curing agent, a phthalate, a silane coupling agent, dicyandiamide, a modified dicyandiamide, an imidazole, 2-ethyl-4-methylimidazole, anhydride, boron trifluoride monoethylamine and an amino resin.

[0063] In some embodiments, optionally, the dispersant is selected from at least one of polyvinyl pyrrolidone, sodium lauryl sulfate, corn germ oil and soybean lecithin.

[0064] In some embodiments, optionally, the plasticizer is polyethylene glycol 200.

[0065] In some embodiments, optionally, the thixotropic agent is polyamide wax.

[0066] Some embodiments of the present invention also provide a method for preparing a heterojunction photovoltaic silver paste, comprising the following steps:

[0067] Step 1: Preparation of organic carrier

[0068] ① Weigh the corresponding solvent and dispersant according to the ratio and stir to form a mixed solution, heat the mixed solution to 80-100°C, the heating time is 30-180min, and the rotation speed is 300-600rpm;

[0069] ② Weigh the corresponding resin, curing agent, plasticizer and thixotropic agent according to the ratio, add them to the mixed solution in ①, maintain the temperature of the mixed solution at 80-100℃, the time used is 30-180min, the speed is 300-600rpm, wait for the resin to be fully dissolved, and obtain the organic carrier.

[0070] Step 2: Premixing of Conductive Silver Paste

[0071] ① Weigh the corresponding nano silver powder according to the ratio, add it to the organic carrier, and stir to form a mixed carrier. The stirring time is 30 to 180 minutes and the speed is 500 to 1000 rpm;

[0072] ② Weigh the corresponding flaky silver powder and spherical silver powder according to the ratio, add them to the mixed carrier, add them to the planetary ball mill, set the parameters to 35Hz~50Hz, and ball mill for 0.5h~3h to obtain the premixed heterojunction photovoltaic silver paste;

[0073] Step 3: Grinding and sieving

[0074] The premixed heterojunction photovoltaic silver paste is ground and dispersed for 3 to 5 times using a three-roll grinder, and then passed through a 500-mesh sieve to remove impurities and uneven large particles in the paste to obtain the finished heterojunction photovoltaic silver paste.

[0075] Some embodiments of the present invention further provide a heterojunction solar cell, comprising a silver paste, wherein the silver paste is the above-mentioned heterojunction photovoltaic silver paste.

[0076] The present invention is further described below in conjunction with specific embodiments.

[0077] Example 1

[0078] This embodiment provides a heterojunction photovoltaic silver paste, which is composed of the following components, as shown in Table 1, and the unit of each value is g.

[0079] Its preparation method is:

[0080] Step 1: Preparation of organic carrier

[0081] The corresponding solvent and dispersant are weighed and mixed according to the ratio to form a mixed solution, and the mixed solution is heated to 90°C for 90 minutes at a rotation speed of 450 rpm to obtain a first mixed solution; then the corresponding resin, curing agent, plasticizer, and thixotropic agent are weighed according to the ratio, added to the first mixed solution, and the temperature of the mixed solution is maintained at 90°C for 90 minutes at a rotation speed of 450 rpm until the resin is fully dissolved to obtain an organic carrier.

[0082] Step 2: Premixing of Conductive Silver Paste

[0083] Weigh the corresponding nano silver powder according to the ratio, add it to the organic carrier, stir to form a mixed carrier, the stirring time is 60 minutes, the rotation speed is 700 rpm, and then weigh the corresponding flaky silver powder and quasi-spherical silver powder according to the ratio, add them to the mixed carrier, add them to the planetary ball mill, set the parameters to 45 Hz, and ball mill for 1.5 hours to obtain the premixed heterojunction photovoltaic silver paste;

[0084] Step 3: Grinding and sieving

[0085] The premixed heterojunction photovoltaic silver paste was ground and dispersed four times using a three-roll grinder, and then passed through a 500-mesh sieve to remove impurities and uneven large particles in the paste to obtain the finished heterojunction photovoltaic silver paste.

[0086] Examples 2-6 were carried out in a similar manner to Example 1, except that the composition / amount was different, and the other conditions were the same as Example 1, see Table 1 for details.

[0087] Comparative Examples 1-6 were carried out in a similar manner to Example 1, except that the composition / amount was different, and the other conditions were the same as Example 1, see Table 1 for details.

[0088] The heterojunction photovoltaic silver paste prepared in Examples 1-6 can be used in the production of heterojunction solar cells.

[0089] Table 1 Composition of heterojunction photovoltaic silver paste of Examples 1-6 and Comparative Examples 1-6 (by mass percentage)

[0090]

[0091]

[0092] The heterojunction photovoltaic silver paste of Examples 1-6 and the silver paste of Comparative Examples 1-6 were applied to the surface of the heterojunction solar cells by screen printing, and then dried and cured at 200° C. for 30 minutes, and the resistivity and ohmic contact values ​​were tested.

[0093] Table 2 Performance test of heterojunction photovoltaic silver paste of Examples 1-6 and Comparative Examples 1-6

[0094]

[0095] From the data in Table 1 and Table 2, it can be seen that the resistivity of the heterojunction photovoltaic silver paste of Examples 1-6 of the present invention is 5.1-5.8 μΩ·cm, and the ohmic contact is 1.8-2.9 mΩ·cm 2 .

[0096] Compared with Example 2, the content of flaky silver powder in Comparative Example 1 exceeds 8wt%-13.5wt% (the scope of the present invention), and its corresponding resistivity increases, and the ohmic contact increases significantly. Compared with Example 3, the content of nano silver powder in Comparative Example 2 exceeds 4wt%-9wt% (the scope of the present invention), and its corresponding resistivity increases, and the ohmic contact increases significantly. Compared with Example 6, the content of resin in Comparative Example 3 exceeds 1wt%-5wt% (the scope of the present invention), and its corresponding resistivity increases, and the ohmic contact increases significantly. The content of flaky silver powder in Comparative Example 4 is 0, and the gaps between the silver powder accumulations in the silver paste are large, and the gaps are also large after the paste is printed and solidified. Compared with other embodiments, the conductive channels in the paste are reduced, which leads to an increase in its resistivity and an increase in ohmic contact. In Comparative Example 5, no nano silver powder was added. Compared with other embodiments, there were still more accumulation gaps between the silver powder in the slurry. After printing and curing, there were gaps between the silver powder particles and between the slurry and the surface of the battery cell, so its resistivity and ohmic contact were also significantly increased. In Comparative Example 6, neither flaky silver powder nor nano silver powder was added to the slurry. The accumulation gaps between the silver powder in the slurry were the largest, and the performance of the slurry printed on the electrode sheet was also the worst.

[0097] The above embodiments are only used to explain the content of the present invention, and are not intended to limit the present invention. Simple technical variations within the technical concept of the present invention should be considered to be covered by the content disclosed by the present invention and belong to the protection scope of the present invention.

[0098] In the specification of the present invention, a lot of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some embodiments, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this specification.

[0099] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0100] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0101] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A heterojunction photovoltaic silver paste, characterized in that: According to mass percentage, it includes the following components: Conductive silver powder 80-90%; Resin 1-5%; Solvent 5-10%; Curing agent 0.5-3%; Dispersant 0.5-2%; Plasticizer 0.5-2%; Thixotropic agent 0.5~2%.

2. The heterojunction photovoltaic silver paste according to claim 1, characterized in that: The conductive silver powder includes three types: flake silver powder, spherical silver powder and nano silver powder. The flake silver powder has a D50 of 2-5 μm and a tap density of 5-6 g / mL; the spherical silver powder has a D50 of 0.5-1 μm and a tap density of 4.5-6 g / mL; the nano silver powder has a D50 of 30-100 nm and a tap density of 2.5-4 g / mL.

3. The heterojunction photovoltaic silver paste according to claim 2, characterized in that: In terms of mass percentage, the conductive silver powder comprises: Flake silver powder: 10-15%; Spherical silver powder: 75-85%; Nano silver powder: 5%~10%.

4. The heterojunction photovoltaic silver paste according to claim 1, characterized in that: The resin is selected from at least one of bisphenol A epoxy resin, phenoxy resin, bisphenol F epoxy resin, aliphatic epoxy resin, silicone-modified epoxy resin, polyether-modified epoxy resin, epoxidized rubber, polyester resin and thermosetting acrylic resin.

5. The heterojunction photovoltaic silver paste according to claim 1, characterized in that: The solvent includes at least one of propylene carbonate, ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, butyl carbitol ether acetate, diethylene glycol ethyl ether acetate and butyl carbitol.

6. The heterojunction photovoltaic silver paste according to claim 1, characterized in that: The curing agent is selected from at least one of blocked isocyanate curing agent, phthalate, silane coupling agent, dicyandiamide, modified dicyandiamide, imidazole, 2-ethyl-4-methylimidazole, acid anhydride, boron trifluoride monoethylamine and amino resin.

7. The heterojunction photovoltaic silver paste according to claim 1, characterized in that: The dispersant is selected from at least one of polyvinyl pyrrolidone, sodium lauryl sulfate, corn germ oil and soybean lecithin; the plasticizer is polyethylene glycol 200; and the thixotropic agent is polyamide wax.

8. A method for preparing heterojunction photovoltaic silver paste, characterized in that: The following steps are involved: Step 1: Preparation of an organic carrier: 5-10 wt% of a solvent and 0.5-2 wt% of a dispersant are stirred at a rotation speed of 300-600 rpm to form a mixed solution, and the mixed solution is heated to 80-100° C.; then 1-5 wt% of a resin, 0.5-3 wt% of a curing agent, 0.5-2 wt% of a plasticizer and 0.5-2 wt% of a thixotropic agent are sequentially added to the obtained mixed solution, and the temperature of the mixed solution is maintained at 80-100° C. After 30-180 minutes, the resin is fully dissolved to obtain an organic carrier. Step 2: Premixing of the conductive silver paste, adding the nano silver powder into the organic carrier, stirring to form a mixed carrier; adding the flaky silver powder and the spherical silver powder into the mixed carrier in turn for ball milling to obtain the premixed heterojunction photovoltaic silver paste; Step 3: Grinding and sieving: Grind and disperse the premixed heterojunction photovoltaic silver paste for 3 to 5 times, and then sieve through a 500-mesh sieve to remove impurities and uneven large particles in the paste to obtain the heterojunction photovoltaic silver paste.

9. The method for preparing heterojunction photovoltaic silver paste according to claim 8, characterized in that: In step 1, the heating time is 30 to 180 min; in step 2, the stirring time is 30 to 180 min, and the rotation speed is 500 to 1000 rpm; the parameters of the ball mill are set to 35 to 50 Hz, and the ball milling time is 0.5 to 3 h.

10. A heterojunction solar cell, characterized in that: The invention comprises silver paste, wherein the silver paste adopts heterojunction photovoltaic silver paste; the heterojunction photovoltaic silver paste comprises the following components in terms of mass percentage: Conductive silver powder 80-90%; Resin 1-5%; Solvent 5-10%; Curing agent 0.5-3%; Dispersant 0.5-2%; Plasticizer 0.5-2%; Thixotropic agent 0.5~2%.

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