Low-temperature photovoltaic silver paste and preparation method and application thereof

Abstract

The invention relates to low-temperature photovoltaic silver paste and a preparation method and application thereof, and belongs to the technical field of photovoltaic conductive materials. The silver paste comprises the following components in parts by mass: 80-90 parts of conductive silver powder and 0.5-3 parts of low-melting-point metal powder; wherein the D50 of the low-melting-point metal powder ranges from 50 nm to 300 nm, the tap density of the low-melting-point metal powder ranges from 3 g / mL to 4.5 g / mL, and the melting point of the low-melting-point metal powder is not higher than 300 DEG C; the low-melting-point metal powder is adopted as a component, the low-melting-point metal powder can form welding spots among silver particles in the silver paste curing process, the particle size of the low-melting-point metal powder is controlled to be within a small range, and by means of the attribute of the small particles, the melting assisting effect can be achieved, and the conductivity of the paste is improved; and the contact surface between the silver paste and the TCO layer of the Si wafer can be greatly improved, so that the resistivity and the ohmic contact are improved.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic conductive materials, and in particular to a low-temperature photovoltaic silver paste and a preparation method and application thereof. Background Art

[0002] Photovoltaic cells are the core raw materials for photovoltaic power generation and play a core role in photoelectric conversion. Silver paste is an important conductive material in cells. The quality of silver paste directly affects the current collection efficiency. The resistivity and ohmic contact quality are the key factors in evaluating whether a silver paste is compatible with photovoltaic cells.

[0003] The emergence of high-efficiency silicon heterojunction photovoltaic cells (HJT) has improved the power generation efficiency of photovoltaic panels. It has better balanced performance and cost factors in existing silicon high-efficiency cell technology, so it has received widespread attention from photovoltaic research and industry, and will become the mainstream technology of the third-generation cells. However, the process temperature of HJT solar cells is below 250℃, and low-temperature curing silver paste is required. Summary of the invention

[0004] At present, low-temperature curing silver paste has the following problems: (1) The resistivity of heterojunction silver paste under low-temperature curing is much higher than that of high-temperature paste, and even more than twice as high, which affects the efficiency of current conduction in the silver paste line; (2) Compared with high-temperature silver paste, the ohmic contact resistance of low-temperature heterojunction silver paste is relatively large. The silver powders in high-temperature silver paste are connected to each other by surface melting. The glass phase melts the silver powder and etches the silicon plate to a certain extent, forming a reliable bond and ohmic contact with the Si wafer. However, due to the low curing temperature of low-temperature silver paste, it mainly relies on the shrinkage of the resin to form a very weak ohmic contact performance.

[0005] The present application provides a low-temperature photovoltaic silver paste and a preparation method and application thereof, which can improve the resistivity and ohmic contact of photovoltaic cells made of the low-temperature photovoltaic silver paste.

[0006] In the first aspect, the present application provides a low-temperature photovoltaic silver paste, the components of the silver paste comprising, by mass: 80 to 90 parts of conductive silver powder and 0.5 to 3 parts of low-melting-point metal powder; wherein the D50 of the low-melting-point metal powder is 50nm to 300nm, the tap density of the low-melting-point metal powder is 3g / mL to 4.5g / mL, and the melting point of the low-melting-point metal powder is not higher than 300°C.

[0007] As an optional embodiment, the low melting point metal powder includes at least one of mercury, gallium, indium, tin, bismuth, amalgam, gallium alloy, indium alloy, tin alloy, bismuth alloy, lead alloy, cadmium alloy and dysprosium alloy.

[0008] As an optional implementation, the conductive silver powder includes flaky silver powder, nano silver powder and spherical silver powder.

[0009] As an optional embodiment, the D50 of the flaky silver powder is 2 μm to 5 μm, and the tap density of the flaky silver powder is 5 g / mL to 6 g / mL; and / or

[0010] The D50 of the nano silver powder is 50 nm to 300 nm, and the tap density of the nano silver powder is 3 g / mL to 4.5 g / mL; and / or

[0011] The D50 of the quasi-spherical silver powder is 0.5 μm to 1 μm, and the tap density of the quasi-spherical silver powder is 4.5 g / mL to 6 g / mL.

[0012] As an optional implementation manner, in the conductive silver powder, the mass proportion of the flaky silver powder is 10% to 15%; and / or

[0013] In the conductive silver powder, the mass proportion of the nano silver powder is 0.5% to 5%; and / or

[0014] In the conductive silver powder, the mass proportion of the spherical silver powder is 80% to 90%.

[0015] As an optional embodiment, the components of the silver paste further include, by mass, 1 to 5 parts of resin, 5 to 10 parts of solvent, 0.5 to 3 parts of curing agent, 0.5 to 2 parts of dispersant, 0.5 to 2 parts of plasticizer and 0.2 to 2 parts of thixotropic agent.

[0016] As an optional embodiment, the resin includes bisphenol A epoxy resin; and / or

[0017] The epoxy equivalent of the bisphenol A epoxy resin is 6000 g / equivalent to 9000 g / equivalent; and / or

[0018] The solvent comprises 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; and / or

[0019] The curing agent includes at least one of a blocked isocyanate curing agent, a phthalate, a silane coupling agent, dicyandiamide, a modified dicyandiamide, an imidazole, a modified imidazole, an acid anhydride, boron trifluoride monoethylamine and an amino resin; and / or

[0020] The dispersant comprises at least one of polyvinyl pyrrolidone, sodium lauryl sulfate, corn germ oil and soybean lecithin; and / or

[0021] The plasticizer comprises polyethylene glycol 200; and / or

[0022] The thixotropic agent includes polyamide wax.

[0023] In a second aspect, the present application provides a method for preparing a low-temperature photovoltaic silver paste, the method comprising:

[0024] mixing the solvent and the dispersant to obtain a mixed solution;

[0025] The mixed material, resin, curing agent, plasticizer and thixotropic agent are mixed to obtain an organic carrier;

[0026] The low melting point metal powder and the organic carrier are mixed to obtain a mixed carrier; the D50 of the low melting point metal powder is 50nm to 300nm, the tap density of the low melting point metal powder is 3g / mL to 4.5g / mL, and the melting point of the low melting point metal powder is not higher than 300°C

[0027] The conductive silver powder and the mixed carrier are mixed, and then ball-milled to obtain a primary silver paste;

[0028] The primary silver paste is ground and then sieved to obtain a low-temperature photovoltaic silver paste, wherein the silver paste comprises, by weight, 80 to 90 parts of conductive silver powder and 0.5 to 3 parts of low-melting-point metal powder.

[0029] As an optional embodiment, the temperature of the mixed solution is 60° C. to 90° C.; and / or

[0030] The frequency of the ball milling is 35 Hz to 50 Hz, and the time of the ball milling is 0.5 h to 3 h; and / or

[0031] The sieve used in the sieving process is a 500-mesh sieve.

[0032] In a second aspect, the present application provides an application of the low-temperature photovoltaic silver paste of the first aspect or the low-temperature photovoltaic silver paste prepared by the method provided in the second aspect in a photovoltaic cell.

[0033] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0034] The low-temperature photovoltaic silver paste provided in the embodiment of the present application adopts low-melting-point metal powder as an ingredient. The low-melting-point metal powder can form solder joints between silver particles during the solidification process of the silver paste, and the particle size of the low-melting-point metal powder is controlled within a smaller range. By utilizing the properties of its small particles, it can not only play a melting role and improve the conductivity of the paste, but also greatly increase the contact area between the silver paste and the TCO layer of the Si wafer, thereby improving the resistivity and ohmic contact, thereby better collecting the current of the photovoltaic cell and providing better photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0037] Figure 1 A flowchart of the method provided in the embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0039] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0040] At present, the process temperature of HJT solar cells is below 250℃, and low-temperature curing silver paste is required. However, low-temperature curing silver paste has the following problems: (1) The resistivity of heterojunction silver paste under low-temperature curing is much higher than that of high-temperature paste, even more than twice as high, which affects the conduction efficiency of current in the silver paste line; (2) Compared with high-temperature silver paste, the ohmic contact resistance of low-temperature heterojunction silver paste is relatively large. The silver powder of high-temperature silver paste is connected to each other by surface melting. The glass phase melts the silver powder to a certain extent and etches the silicon plate to form a reliable bond and ohmic contact with the Si wafer. However, due to the low curing temperature of low-temperature silver paste, it mainly relies on the shrinkage of the resin to form a very weak ohmic contact performance.

[0041] To this end, the present application intends to provide a low-temperature photovoltaic silver paste, which uses low-melting-point metal powder as an ingredient, which can form solder joints between silver particles during the solidification process of the silver paste, and control the particle size of the low-melting-point metal powder within a smaller range. By utilizing the properties of its small particles, it can not only play a melting role and improve the conductivity of the paste, but also greatly increase the contact area between the silver paste and the TCO layer of the Si wafer, thereby improving the resistivity and ohmic contact.

[0042] An embodiment of the present application provides a low-temperature photovoltaic silver paste, wherein the components of the silver paste include, by mass: 80 to 90 parts of conductive silver powder and 0.5 to 3 parts of low-melting-point metal powder; wherein the D50 of the low-melting-point metal powder is 50 nm to 300 nm, the tap density of the low-melting-point metal powder is 3 g / mL to 4.5 g / mL, and the melting point of the low-melting-point metal powder is not higher than 300°C.

[0043] The low-temperature photovoltaic silver paste uses low-melting-point metal powder as an ingredient. The low-melting-point metal powder can form solder joints between silver particles during the solidification process of the silver paste, and the particle size of the low-melting-point metal powder is controlled within a smaller range. By utilizing the properties of its small particles, it can not only play a melting role and improve the conductivity of the paste, but also greatly increase the contact area between the silver paste and the TCO layer of the Si wafer, thereby improving the resistivity and ohmic contact, and then better collecting the current of the photovoltaic cell, providing better photoelectric conversion efficiency.

[0044] Exemplarily, the mass fraction of the conductive silver powder can be 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, etc., which can also be any value in the range of 80 to 90 parts. The mass fraction of the low melting point metal powder can be 0.5 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, etc., which can also be any value in the range of 0.5 to 3 parts. The D50 of the low melting point metal powder can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, etc., which can also be any value in the range of 50nm to 300nm. The tap density of the low melting point metal powder can be 3g / mL, 3.2g / mL, 3.4g / mL, 3.6g / mL, 3.8g / mL, 4g / mL, 4.2g / mL, 4.4g / mL, 4.5g / mL, etc., and it can also be any value in the range of 3g / mL to 4.5g / mL. The melting point of the low melting point metal powder can be 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, etc., and it can also be any value in the range of not more than 300°C.

[0045] Furthermore, the low melting point metal powder includes at least one of mercury, gallium, indium, tin, bismuth, amalgam, gallium alloy, indium alloy, tin alloy, bismuth alloy, lead alloy, cadmium alloy and dysprosium alloy.

[0046] In some embodiments, the conductive silver powder includes flake silver powder, nano silver powder and spherical silver powder.

[0047] Using spherical silver powder as the main conductive component, combined with flaky silver powder and nano silver powder, can reduce the pores after the silver paste is solidified. The specific reasons are as follows: due to its low specific surface area and high effective contact area when stacked, flaky silver powder can reduce the gaps between the silver powder accumulation 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. 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.

[0048] Further, in the conductive silver powder, the mass proportion of the flaky silver powder is 10% to 15%; the mass proportion of the nano silver powder is 0.5% to 5%; and the mass proportion of the quasi-spherical silver powder is 80% to 90%. Exemplarily, the mass proportion of the flaky silver powder can be 10%, 11%, 12%, 13%, 14%, 15%, etc., and it can also be any value within the range of 10% to 15%. The mass proportion of the nano silver powder can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., and it can also be any value within the range of 0.5% to 5%. The mass proportion of the quasi-spherical silver powder can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, etc., and it can also be any value within the range of 80% to 90%.

[0049] Further, the D50 of the flaky silver powder is 2μm to 5μm, and the tap density of the flaky silver powder is 5g / mL to 6g / mL; the D50 of the nano silver powder is 50nm to 300nm, and the tap density of the nano silver powder is 3g / mL to 4.5g / mL; the D50 of the quasi-spherical silver powder is 0.5μm to 1μm, and the tap density of the quasi-spherical silver powder is 4.5g / mL to 6g / mL. Exemplarily, the D50 of the flaky silver powder can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, etc., and it can also be any value within the range of 2μm to 5μm. The tap density of the flaky silver powder can be 5g / mL, 5.1g / mL, 5.2g / mL, 5.3g / mL, 5.4g / mL, 5.5g / mL, 5.6g / mL, 5.7g / mL, 5.8g / mL, 5.9g / mL, 6g / mL, etc., and it can also be any value in the range of 5g / mL to 6g / mL. The D50 of the nano silver powder can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, etc., and it can also be any value in the range of 50nm to 300nm. The tap density of the nano silver powder can be 3g / mL, 3.2g / mL, 3.4g / mL, 3.6g / mL, 3.8g / mL, 4g / mL, 4.2g / mL, 4.4g / mL, 4.5g / mL, etc., and it can also be any value in the range of 3g / mL to 4.5g / mL. The D50 of the quasi-spherical silver powder can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc., and it can also be any value in the range of 0.5 μm to 1 μm. The tap density of the flaky silver powder can be 4.5 g / mL, 4.6 g / mL, 4.7 g / mL, 4.8 g / mL, 4.9 g / mL, 5 g / mL, 5.1 g / mL, 5.2 g / mL, 5.3 g / mL, 5.4 g / mL, 5.5 g / mL, 5.6 g / mL, 5.7 g / mL, 5.8 g / mL, 5.9 g / mL, 6 g / mL, etc., and it can also be any value in the range of 4.5 g / mL to 6 g / mL.

[0050] In some embodiments, the components of the silver paste further include, by mass, 1 to 5 parts of resin, 5 to 10 parts of solvent, 0.5 to 3 parts of curing agent, 0.5 to 2 parts of dispersant, 0.5 to 2 parts of plasticizer and 0.2 to 2 parts of thixotropic agent.

[0051] Furthermore, the resin includes bisphenol A epoxy resin; the epoxy equivalent of the bisphenol A epoxy resin is 6000g / equivalent to 9000g / equivalent; 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; the curing agent includes at least one of a blocked isocyanate curing agent, a phthalate, a silane coupling agent, dicyandiamide, modified dicyandiamide, imidazole, modified imidazole, anhydride, boron trifluoride monoethylamine and an amino resin; the dispersant includes at least one of polyvinyl pyrrolidone, sodium dodecyl sulfate, corn germ oil and soybean lecithin; the plasticizer includes polyethylene glycol 200; and the thixotropic agent includes polyamide wax.

[0052] Based on a general inventive concept, an embodiment of the present application also provides a method for preparing a low-temperature photovoltaic silver paste.

[0053] This method is used for the preparation of the above-mentioned low-temperature photovoltaic silver paste. The specific content of the low-temperature photovoltaic silver paste can refer to the above-mentioned embodiment. Since this method adopts part or all of the technical solutions of the above-mentioned embodiment, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here one by one.

[0054] Figure 1 A flow chart of the method provided in the embodiment of the present application is as follows: Figure 1 As shown, in some embodiments, the method includes:

[0055] S1. mixing the solvent and the dispersant to obtain a mixed solution;

[0056] In some embodiments, the mixed solution is heated to 60-90° C. for 30-180 min. The heating process is accompanied by stirring at a speed of 300-600 rpm.

[0057] S2. The mixture is mixed with a resin, a curing agent, a plasticizer and a thixotropic agent to obtain an organic carrier;

[0058] The temperature of the mixed liquid is maintained at 60-90° C., the mixing time is 30-180 min, and the mixing process is accompanied by stirring at a speed of 300-600 rpm to allow the resin to be fully dissolved.

[0059] S3. Mixing a low-melting-point metal powder and the organic carrier to obtain a mixed carrier; the D50 of the low-melting-point metal powder is 50nm to 300nm, the tap density of the low-melting-point metal powder is 3g / mL to 4.5g / mL, and the melting point of the low-melting-point metal powder is not higher than 300°C.

[0060] The mixing process is accompanied by stirring, the stirring time is 30 to 180 minutes, and the stirring speed is 300 to 600 rpm.

[0061] S4. The conductive silver powder and the mixed carrier are mixed, and then ball-milled to obtain a primary silver paste;

[0062] The ball milling can be performed by a planetary ball mill with a stirring frequency of 35 to 50 Hz and a ball milling time of 0.5 to 3 h.

[0063] S5. Grind the primary silver paste, and then sieve it to obtain a low-temperature photovoltaic silver paste, wherein the components of the silver paste include, by mass: 80 to 90 parts of conductive silver powder and 0.5 to 3 parts of low-melting-point metal powder.

[0064] The grinding can be performed by a three-roller grinder, and the grinding times can be 3 to 5 times. The sieve used for the sieving process is a 500-mesh sieve to remove impurities and uneven large particles in the slurry.

[0065] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0066] Examples and Comparative Examples

[0067] A low-temperature photovoltaic silver paste, the preparation process of which is as follows:

[0068] Step 1: Preparation of organic carrier

[0069] The corresponding solvent and dispersant were weighed according to the ratio to form a mixed solution, and the mixed solution was heated to 75°C for 105 min at a rotation speed of 450 rpm to obtain a first mixed solution; then the corresponding resin, curing agent, plasticizer, and thixotropic agent were weighed according to the ratio, added to the first mixed solution, and the temperature of the mixed solution was maintained at 75°C for 105 min at a rotation speed of 450 rpm until the resin was fully dissolved to obtain an organic carrier.

[0070] Step 2: Premixing of Conductive Silver Paste

[0071] Weigh the corresponding low-melting-point metal powder according to the ratio, add it to the organic carrier, stir to form a mixed carrier, stir for 105 min, rotate at 450 rpm, then weigh the corresponding conductive silver powder according to the ratio, add it to the mixed carrier, add it to the planetary ball mill, set the parameter to 42 Hz, and ball mill for 2 h to obtain a primary silver paste;

[0072] Step 3: Grinding and sieving

[0073] The primary silver paste is ground and dispersed 3 to 5 times with a three-roll grinder, and then passed through a 500-mesh sieve to remove impurities and uneven large particles in the paste to obtain a finished low-temperature photovoltaic silver paste.

[0074] The parameter control of each embodiment and comparative example is shown in the following table:

[0075]

[0076]

[0077]

[0078] The low-temperature photovoltaic silver paste of each embodiment and comparative example was screen-printed on the surface of the heterojunction solar cell, and then dried and cured at 200° C. for 30 minutes, and the resistivity and ohmic contact values ​​were tested. The results are shown in the following table:

[0079] Resistivity (μΩ·cm) Ohmic contact (mΩ·cm2) Comparative Example 1 7.2 4.6 Example 1 6.1 3.3 Example 2 5.1 1.7 Example 3 5.5 3.2 Example 4 5.9 2.7 Example 5 6.2 3.3 Comparative Example 2 11.3 5.3 Example 6 6.7 5.4 Example 7 5.8 3.4 Example 8 6.2 3.2 Example 9 8.9 5.5

[0080] It can be seen from the above table that the resistivity and ohmic contact of the low-temperature photovoltaic silver paste prepared by the method provided in the embodiment of the present application after curing are good.

[0081] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0082] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc, or abc, where a, b and c can be single or multiple.

[0083] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A low-temperature photovoltaic silver paste, characterized in that: The components of the silver paste include, by mass, 80 to 90 parts of conductive silver powder and 0.5 to 3 parts of low-melting-point metal powder; wherein the D50 of the low-melting-point metal powder is 50 nm to 300 nm, the tap density of the low-melting-point metal powder is 3 g / mL to 4.5 g / mL, and the melting point of the low-melting-point metal powder is not higher than 300°C.

2. The low-temperature photovoltaic silver paste according to claim 1, characterized in that: The low melting point metal powder includes at least one of mercury, gallium, indium, tin, bismuth, amalgam, gallium alloy, indium alloy, tin alloy, bismuth alloy, lead alloy, cadmium alloy and dysprosium alloy.

3. The low-temperature photovoltaic silver paste according to claim 1, characterized in that: The conductive silver powder includes flaky silver powder, nano silver powder and spherical silver powder.

4. The low-temperature photovoltaic silver paste according to claim 3, characterized in that: The D50 of the flaky silver powder is 2 μm to 5 μm, and the tap density of the flaky silver powder is 5 g / mL to 6 g / mL; and / or The D50 of the nano silver powder is 50 nm to 300 nm, and the tap density of the nano silver powder is 3 g / mL to 4.5 g / mL; and / or The D50 of the quasi-spherical silver powder is 0.5 μm to 1 μm, and the tap density of the quasi-spherical silver powder is 4.5 g / mL to 6 g / mL.

5. The low-temperature photovoltaic silver paste according to claim 3, characterized in that: In the conductive silver powder, the mass proportion of the flaky silver powder is 10% to 15%; and / or In the conductive silver powder, the mass proportion of the nano silver powder is 0.5% to 5%; and / or In the conductive silver powder, the mass proportion of the spherical silver powder is 80% to 90%.

6. The low-temperature photovoltaic silver paste according to claim 1, characterized in that: The silver paste also includes, by weight, 1 to 5 parts of resin, 5 to 10 parts of solvent, 0.5 to 3 parts of curing agent, 0.5 to 2 parts of dispersant, 0.5 to 2 parts of plasticizer and 0.2 to 2 parts of thixotropic agent.

7. The low-temperature photovoltaic silver paste according to claim 6, characterized in that: The resin comprises bisphenol A epoxy resin; and / or The epoxy equivalent of the bisphenol A epoxy resin is 6000 g / equivalent to 9000 g / equivalent; and / or The solvent comprises 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; and / or The curing agent includes at least one of a blocked isocyanate curing agent, a phthalate, a silane coupling agent, dicyandiamide, a modified dicyandiamide, an imidazole, a modified imidazole, an acid anhydride, boron trifluoride monoethylamine and an amino resin; and / or The dispersant comprises at least one of polyvinyl pyrrolidone, sodium lauryl sulfate, corn germ oil and soybean lecithin; and / or The plasticizer comprises polyethylene glycol 200; and / or The thixotropic agent includes polyamide wax.

8. A method for preparing low-temperature photovoltaic silver paste, characterized in that: The method comprises: mixing the solvent and the dispersant to obtain a mixed solution; The mixed material, resin, curing agent, plasticizer and thixotropic agent are mixed to obtain an organic carrier; The low melting point metal powder and the organic carrier are mixed to obtain a mixed carrier; the D50 of the low melting point metal powder is 50nm to 300nm, the tap density of the low melting point metal powder is 3g / mL to 4.5g / mL, and the melting point of the low melting point metal powder is not higher than 300°C The conductive silver powder and the mixed carrier are mixed, and then ball-milled to obtain a primary silver paste; The primary silver paste is ground and then sieved to obtain a low-temperature photovoltaic silver paste, wherein the silver paste comprises, by weight, 80 to 90 parts of conductive silver powder and 0.5 to 3 parts of low-melting-point metal powder.

9. The method for preparing low-temperature photovoltaic silver paste according to claim 8, characterized in that: The temperature of the mixed solution is 60°C to 90°C; and / or The frequency of the ball milling is 35 Hz to 50 Hz, and the time of the ball milling is 0.5 h to 3 h; and / or The sieve used in the sieving process is a 500-mesh sieve.

10. Use of the low-temperature photovoltaic silver paste according to any one of claims 1 to 7 or the low-temperature photovoltaic silver paste prepared by the method according to any one of claims 8 to 9 in photovoltaic cells.

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