Conductive paste and preparation method thereof, solar cell and preparation method thereof, and photovoltaic module

Abstract

The invention relates to conductive paste and a preparation method thereof, a solar cell and a preparation method thereof, and a photovoltaic module. The conductive paste comprises 82%-88% of metal powder, 1%-5% of glass powder, 8%-15% of an organic carrier, 0.5%-3% of a wave-absorbing material and 0.1%-1% of a polymer pore-forming agent, and the wave-absorbing material can absorb laser and release heat. During laser-assisted sintering treatment, the wave-absorbing material can efficiently absorb laser energy and instantly release heat, so that the surrounding polymer pore-forming agent is quickly gasified. After the polymer pore-forming agent is gasified, a cavity structure is formed in the conductive slurry, a multi-reflection cavity of light is formed, laser which is subsequently transmitted in is reflected for multiple times in the cavity, a light path is prolonged, and the absorption rate of laser energy is greatly improved. Due to the high absorptivity of the laser, the laser power required by good ohmic contact is formed, the energy consumption is reduced, and the damage to the surface of the battery is reduced.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to conductive pastes and their preparation methods, solar cells and their preparation methods, and photovoltaic modules. Background Technology

[0002] The grid lines on solar cells can be formed by coating with a conductive paste (such as silver paste) and then sintering. Sintering processes include heated sintering and laser-assisted sintering (LECO). The core principle of LECO is the synergistic effect of laser-induced localized carrier injection and instantaneous high temperature, which optimizes the metal-silicon contact and thus improves cell efficiency.

[0003] However, laser-assisted sintering processes suffer from the problem of low absorption rate of laser energy by conductive pastes. Metal particles (such as silver particles) in traditional conductive pastes have limited absorption rates for commonly used infrared lasers (wavelengths such as 1064nm), resulting in significant energy reflection or transmission and energy waste. To meet process requirements, higher laser power is needed, which not only increases energy consumption but also easily damages the battery surface, such as the passivation layer, due to excessively high localized energy, leading to a decrease in open-circuit voltage (Voc). Summary of the Invention

[0004] Therefore, it is necessary to provide a conductive paste and its preparation method, a solar cell and its preparation method, and a photovoltaic module to solve the problem of low laser energy absorption rate of traditional conductive paste stacks.

[0005] The first aspect of this application provides a conductive paste, as follows:

[0006] A conductive paste includes metal powder, glass powder, organic carrier, microwave absorbing material, and polymer pore-forming agent. The microwave absorbing material is capable of absorbing laser light and releasing heat. The mass fraction of the metal powder is 82%~88%, the mass fraction of the glass powder is 1%~5%, the mass fraction of the organic carrier is 8%~15%, the mass fraction of the microwave absorbing material is 0.5%~3%, and the mass fraction of the polymer pore-forming agent is 0.1%~1%.

[0007] In some embodiments, the polymeric pore-forming agent has a particulate structure with a D50 particle size of 1 μm to 5 μm.

[0008] In some embodiments, the thermal decomposition temperature of the polymeric pore-forming agent is 200°C to 500°C.

[0009] In some embodiments, the polymeric pore-forming agent is made of one or more of polymethyl methacrylate, polystyrene, polylactic acid, polyvinyl butyral, and expanded microspheres, wherein the expanded microspheres comprise a thermoplastic polymer shell and volatile alkanes disposed within the thermoplastic polymer shell.

[0010] In some embodiments, the absorbing material includes one or more of tellurium, antimony, and tungsten trioxide.

[0011] In some embodiments, the microwave absorbing material is a granular structure with a D50 particle size of 1μm to 5μm, and the surface of the microwave absorbing material is provided with a coating layer. The coating layer material includes one or more of surfactants, silane coupling agents, polymer dispersants, and organic acids.

[0012] In some embodiments, the surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, alkylphenol polyoxyethylene ether phosphate, hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether.

[0013] In some embodiments, the silane coupling agent includes one or more of aminopropylalkoxysilane, glycidyl etheroxypropylalkoxysilane, mercaptopropylalkoxysilane, vinylalkoxysilane, and methacryloxypropylalkoxysilane.

[0014] In some embodiments, the polymer dispersant includes one or more of polyvinylpyrrolidone and polyvinyl alcohol.

[0015] In some embodiments, the organic acid includes one or more of oleic acid, stearic acid, palmitic acid, and linoleic acid.

[0016] In some embodiments, the metal powder includes one or more of silver powder, aluminum powder, copper powder, nickel powder, silver-coated copper powder, and silver-coated nickel powder.

[0017] A second aspect of this application provides a method for preparing the above-mentioned conductive paste, the scheme of which is as follows:

[0018] A method for preparing a conductive paste includes the following steps:

[0019] The organic carrier and the glass powder are stirred and mixed to obtain a first mixture;

[0020] The first mixture is rolled and mixed with the metal powder to obtain a second mixture;

[0021] The second mixture is rolled and mixed with the microwave absorbing material to obtain a third mixture;

[0022] The third mixture is rolled and mixed with the polymer pore-forming agent to obtain the fourth mixture.

[0023] A third aspect of this application provides a method for preparing a solar cell, the scheme of which is as follows:

[0024] A method for preparing a solar cell includes the following steps:

[0025] Provide battery body;

[0026] The conductive paste is coated onto the battery body, wherein the conductive paste is the aforementioned conductive paste or a conductive paste prepared by the aforementioned preparation method;

[0027] The conductive paste is subjected to laser-assisted sintering to form a first sintered product.

[0028] In some embodiments, the laser used in the laser-assisted sintering process has a wavelength of 1000nm~1300nm and a power of 170W~230W.

[0029] In some embodiments, the preparation method further includes the following steps:

[0030] The first sintered product is subjected to heating and sintering treatment to form a second sintered product.

[0031] In some embodiments, the temperature of the heating sintering process is 500°C to 600°C.

[0032] The fourth aspect of this application provides a solar cell, the solution of which is as follows:

[0033] A solar cell is prepared by the preparation method described in any of the above embodiments.

[0034] The fourth aspect of this application provides a photovoltaic module, the solution of which is as follows:

[0035] A photovoltaic module includes a first encapsulation component, a second encapsulation component, and a solar cell, wherein the solar cell is disposed between the first encapsulation component and the second encapsulation component.

[0036] Compared with traditional methods, the above-mentioned conductive paste and preparation method, solar cell and preparation method, and photovoltaic module have the following advantages:

[0037] The aforementioned conductive paste and its preparation method add specific amounts of microwave absorbing material and polymer pore-forming agent to the base material. During laser-assisted sintering, the microwave absorbing material efficiently absorbs laser energy and instantly releases heat, causing the surrounding polymer pore-forming agent to rapidly vaporize. After vaporization, the polymer pore-forming agent forms a cavity structure within the conductive paste, constituting a multi-reflection cavity for light. This causes subsequent laser light to undergo multiple reflections within the cavity, extending the optical path and significantly improving the absorption rate of laser energy. The high laser absorption rate reduces the laser power required to form a good ohmic contact, lowers production energy consumption, and reduces damage to the battery surface, such as the passivation layer, caused by excessively high local energy, thus contributing to improved open-circuit voltage.

[0038] The above-described solar cell and its preparation method use the above-described conductive paste to prepare electrodes, and the above-described photovoltaic module includes the above-described solar cell, thus achieving corresponding beneficial effects. Attached Figure Description

[0039] Figure 1 This is a schematic flowchart of a method for preparing a conductive paste according to one embodiment;

[0040] Figure 2 This is a schematic flowchart illustrating a method for fabricating a solar cell according to one embodiment.

[0041] Figure 3 This is a schematic diagram of the structure of a solar cell according to one embodiment.

[0042] Explanation of reference numerals in the attached figures:

[0043] 100. Solar cell; 110. Cell body; 111. Silicon wafer; 112. Emitter; 113. Front passivation layer; 114. Tunneling layer; 115. Doped polycrystalline silicon layer; 116. Back passivation layer; 120. Front electrode; 130. Back electrode. Detailed Implementation

[0044] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein; these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0045] In the accompanying drawings, the thicknesses of layers, films, regions, substrates, etc., are exaggerated for clarity. Throughout the specification, the same reference numerals refer to the same elements. It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it may be directly on the other element or there may be intervening elements. Conversely, when an element is referred to as being "directly on" another element, there are no intervening elements.

[0046] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number or order of the indicated technical features.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0048] The first aspect of this application provides a conductive paste.

[0049] One embodiment of the conductive paste comprises the following components in the indicated mass fractions:

[0050] The composition consists of 82%~88% metal powder, 1%~5% glass powder, 8%~15% organic carrier, 0.1%~1% polymer pore-forming agent, and 0.5%~3% microwave absorbing material.

[0051] The absorbing material absorbs the laser light and releases heat, causing the surrounding polymer pore-forming agent to rapidly vaporize. After vaporization, the polymer pore-forming agent forms a cavity structure within the conductive slurry, creating a multi-reflection cavity for the light. This causes subsequent laser light to undergo multiple reflections within the cavity, extending the optical path and significantly increasing the laser energy absorption rate. The high laser absorption rate reduces the laser power required to form a good ohmic contact, lowers production energy consumption, and minimizes damage to the battery surface, such as the passivation layer, caused by excessively high local energy, thus contributing to improved open-circuit voltage.

[0052] Furthermore, due to the uneven distribution of traditional conductive pastes on the textured surface and inconsistent laser energy absorption, the uniformity of contact points formed after laser activation is poor, and local areas may experience over-burning or under-burning, limiting the improvement of fill factor (FF) and conversion efficiency. The aforementioned conductive paste, however, rapidly vaporizes the polymer pore-forming agent. The instantaneous expansion of the gas generates microscopic high pressure within the paste, which drives molten metal particles to impact the surface of the solar cell at high speed. This significantly improves the physical contact and embedding depth between the metal and silicon material, forming more and more uniform ohmic contact points, thereby improving the fill factor (FF) and conversion efficiency.

[0053] Metal powder is the main component of conductive paste and is used to form conductive paths. The mass fraction of metal powder in conductive paste is 82% to 88%, for example, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, etc.

[0054] As an example, the metal powder includes, but is not limited to, one or more of silver powder, aluminum powder, copper powder, nickel powder, silver-coated copper powder, and silver-coated nickel powder. In some examples, the metal powder is silver powder.

[0055] Glass powder is used to form the binder phase. The mass fraction of glass powder in the conductive paste is 1% to 5%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. Glass powder within the above range can provide the necessary bonding and slight etching effect during low-temperature sintering to form ohmic contacts. Too high a glass powder content will excessively erode the battery surface and increase resistance, while too low a content will result in insufficient bonding strength.

[0056] As an example, glass powder includes, but is not limited to, one or more of bismuthate glass powder, phosphate glass powder, lead silicate glass powder, borosilicate glass powder, zinc borate glass powder, vanadate glass powder, and tellurate glass powder.

[0057] The organic carrier is a continuous phase that supports solid components such as metal powder and glass powder, and provides the required rheological properties and printability of the paste. The mass fraction of the organic carrier in the conductive paste is 8% to 15%, for example, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc. Organic carriers within this range impart suitable viscosity and thixotropy to the conductive paste, resulting in clear, leak-free lines in screen printing.

[0058] In some examples, the organic carrier includes one or more of a solvent, a thickener, and a film-forming agent. Solvents include, but are not limited to, one or more of terpineol, butyl carbitol, and diethylene glycol monobutyl ether. Thickeners include, but are not limited to, one or more of ethyl cellulose, hydroxypropyl cellulose, polyethylene glycol, polyvinyl butyral, rosin resin, hydrogenated castor oil, fumed silica, and organobentonite. Film-forming agents include, but are not limited to, one or more of hydroxypropyl methylcellulose, polyvinyl acetate, acrylic resin, and polyurethane resin.

[0059] Microwave-absorbing materials are used to absorb laser light and release heat during laser-assisted sintering. The mass fraction of the microwave-absorbing material in the conductive slurry is 0.5% to 3%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc. Microwave-absorbing materials within this range can absorb the laser light and release sufficient heat to allow the polymer pore-forming agent to fully vaporize in a short time. Excessive microwave-absorbing material content may lead to a decrease in the conductivity of the electrode layer.

[0060] As an example, absorbing materials include, but are not limited to, one or more of tellurium (Te), antimony (Sb), and tungsten trioxide (WO3). These materials exhibit extremely high absorption efficiency for commonly used industrial laser wavelengths such as 1064 nm.

[0061] In some examples, the absorbing material has a granular structure. This granular structure facilitates uniform dispersion within the conductive slurry, forming uniform absorbing centers, and allows for more thorough mixing with the polymer pore-forming agent. It also promotes rapid vaporization of the polymer pore-forming agent when the absorbing material releases heat.

[0062] In some examples, the D50 particle size (median particle size) of the absorbing material is 1 μm to 5 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any range between two of the above values. The D50 particle size of the absorbing material is measured using laser diffraction particle size analysis, specifically using a laser particle size analyzer (equipment model such as Malvern Mastersizer 3000), according to the ISO 13320 standard. A small amount of absorbing material sample is dispersed in a suitable medium (such as anhydrous ethanol), and after ultrasonic treatment to ensure sufficient dispersion, the sample is injected for measurement.

[0063] In some examples, a coating layer is provided on the surface of the absorbing material. The coating layer material includes one or more of surfactants, silane coupling agents, polymer dispersants, and organic acids. By providing this coating layer on the surface of the absorbing material, the particle agglomeration phenomenon of the absorbing material can be reduced. Agglomerated particles may clog the mesh and may also cause damage to the electrode layer structure due to thermal stress concentration during laser irradiation. Simultaneously, the coating layer can improve the compatibility of the absorbing material with other components such as organic carriers, avoiding problems such as sedimentation of conductive paste and uneven absorption performance.

[0064] As examples, surfactants include, but are not limited to, one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, alkylphenol polyoxyethylene ether phosphate, hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether. Silane coupling agents include, but are not limited to, one or more of aminopropylalkoxysilane, glycidyl etheroxypropylalkoxysilane, mercaptopropylalkoxysilane, vinylalkoxysilane, and methacryloxypropylalkoxysilane. Polymer dispersants include, but are not limited to, one or more of polyvinylpyrrolidone and polyvinyl alcohol. Organic acids include, but are not limited to, one or more of oleic acid, stearic acid, palmitic acid, and linoleic acid.

[0065] Polymer pore-forming agents are used to rapidly vaporize when heated by the microwave absorbing material, thereby forming a cavity structure inside the conductive paste. The mass fraction of the polymer pore-forming agent in the conductive paste is 0.1% to 1%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0066] In some examples, the polymeric pore-forming agent has a particulate structure. This particulate structure facilitates uniform dispersion in the conductive slurry and promotes the formation of uniformly distributed voids in the electrode layer after vaporization.

[0067] The D50 particle size of the polymer pore-forming agent is 1μm to 5μm, for example, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or any range between two of the above values. The D50 particle size of the polymer pore-forming agent is tested using laser diffraction particle size analysis, specifically using a laser particle size analyzer (equipment model such as Malvern Mastersizer 3000), according to the ISO 13320 standard. A small amount of polymer pore-forming agent sample is dispersed in a suitable medium (such as anhydrous ethanol), and after ultrasonic treatment to ensure sufficient dispersion, the sample is injected for measurement.

[0068] The thermal decomposition temperature of the polymer pore-forming agent is preferably higher than the drying temperature of the conductive slurry but lower than the temperature during laser-assisted sintering, so as to vaporize at an appropriate time. In some examples, the thermal decomposition temperature of the polymer pore-forming agent is 200℃~500℃, for example, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, etc.

[0069] As an example, the materials of polymeric pore-forming agents include one or more of polymethyl methacrylate, polystyrene, polylactic acid, polyvinyl butyral, and expanded microspheres.

[0070] The expanded microspheres comprise a thermoplastic polymer shell and volatile alkanes disposed within the thermoplastic polymer shell. As examples, the thermoplastic polymer shell material includes, but is not limited to, one or more of polymethyl methacrylate, acrylonitrile-vinylidene chloride copolymer, acrylonitrile-acrylate copolymer, vinyl chloride / vinylidene chloride copolymer, styrene-based copolymers, and polyurethane. Volatile alkanes include, but are not limited to, one or more of butane, cyclobutane, pentane, cyclopentane, hexane, and cyclohexane.

[0071] A second aspect of this application provides a method for preparing a conductive paste according to any of the above examples.

[0072] like Figure 1 As shown, a method for preparing a conductive paste according to an embodiment includes the following steps:

[0073] Step S11: The organic carrier and glass powder are stirred and mixed to obtain the first mixture;

[0074] Step S12: The first mixture is rolled and mixed with metal powder to obtain the second mixture;

[0075] Step S13: The second mixture is rolled and mixed with the microwave absorbing material to obtain the third mixture;

[0076] Step S14: The third mixture is rolled and mixed with the polymer pore-forming agent to obtain the fourth mixture.

[0077] In steps S2 to S4, the rolling mixing can be performed using a three-roll mill. In step S12, the first mixture is added to the feeding zone of the three-roll mill, metal powder is slowly added, and rolling is performed to form a uniform metal slurry matrix. The roll gap is, for example, 50μm-100μm. In step S13, microwave absorbing material is added and rolled to ensure that the microwave absorbing material is uniformly dispersed in the slurry system. The roll gap is, for example, 30μm-60μm. In step S14, a polymer pore-forming agent is added and rolled. The roll gap is, for example, 10μm-20μm. This step achieves uniform distribution of microspheres while minimizing compression and shear damage to the microspheres, maintaining their intact spherical structure. The fineness of the slurry is detected by a scraper fineness gauge. When a predetermined standard is reached (e.g., fineness below 10μm) and the color is uniform, it indicates uniform dispersion, and the slurry can be discharged.

[0078] Compared to traditional high-speed shear mixing, the shear force generated by the different rotation speeds of the three rollers effectively breaks up powder agglomerates, achieving nanoscale dispersion while avoiding mechanical damage to the polymer pore-forming agent. Furthermore, it ensures that high-solids-content, high-viscosity slurries achieve extremely high uniformity and fineness, improving the uniformity of subsequent laser absorption.

[0079] A third aspect of this application provides a method for preparing a solar cell.

[0080] like Figure 2 As shown, a method for preparing a solar cell includes the following steps:

[0081] Step S21: Provide the battery body.

[0082] Step S22: Coat the battery body with a conductive paste. The conductive paste includes: 82%~88% metal powder, 1%~5% glass powder, 8%~15% organic carrier, 0.1%~1% polymer pore-forming agent, and 0.5%~3% microwave absorbing material. The microwave absorbing material can absorb laser light and release heat.

[0083] Step S23: Laser-assisted sintering is performed on the conductive paste to form the first sintered product.

[0084] The aforementioned solar cells can be either single-junction cells or tandem cells.

[0085] Alternatively, the single-junction cell can be, for example, but not limited to, passivated emitter back contact cell (PERC cell), passivated emitter back contact cell (TOPCon cell), heterojunction cell (HJT cell), back contact cell (BC cell), perovskite cell, etc.

[0086] As an example, such as Figure 3 As shown, the solar cell is a TOPCon cell. In step S21, the cell body 110 includes, for example, a silicon wafer 111; an emitter 112 and a front passivation layer 113 disposed on a first side of the silicon wafer 111; a tunneling layer 114, a doped polycrystalline silicon layer 115 and a back passivation layer 116 disposed on a second side of the silicon wafer 111.

[0087] In step S22, the conductive paste can be applied to the front side (light-receiving surface) of the solar cell, the back side (backlight-receiving surface), or both. For example, in the above example, the conductive paste can be applied to the front passivation layer 113, the back passivation layer 116, or both. The conductive paste applied to the front passivation layer 113 is sintered to form the front electrode 120. The conductive paste applied to the back passivation layer 116 is sintered to form the back electrode 130.

[0088] The tandem solar cell includes a bottom cell and a top cell disposed on the bottom cell. Optionally, the bottom cell can be, for example, but not limited to, a PERC cell, a TOPCon cell, an HJT cell, a BC cell, etc. Optionally, the top cell can be, for example, but not limited to, a perovskite cell, a III-V compound cell (III-V compounds such as GaInP, AlGaAs, etc.), a cadmium telluride (CdTe) cell, a copper indium gallium selenide (CIGS) cell, an organic solar cell, etc.

[0089] In step S22, the conductive paste is the conductive paste of any of the above examples or the conductive paste prepared by any of the above examples.

[0090] In some examples, in step S22, the conductive paste is applied by screen printing. The conductive paste can be applied directly using traditional screen printing equipment without requiring any modification to the equipment hardware.

[0091] In some examples, in step S23, the wavelength of the laser used in the laser-assisted sintering process is 1000nm~1300nm, for example, 1000nm, 1050nm, 1100nm, 1150nm, 1200nm, 1250nm, 1300nm, etc.

[0092] In some examples, the laser power used in step S23 for laser-assisted sintering is 170W to 230W, for example, 170W, 180W, 190W, 200W, 210W, 220W, 230W, etc. Because the aforementioned conductive paste can significantly improve the absorption rate of laser energy, paste sintering can be achieved at a reduced laser power. The aforementioned laser power range is significantly lower than the laser power used in conventional conductive pastes (approximately 350W), thereby reducing laser damage to the solar cell surface. Simultaneously, laser energy consumption is significantly reduced, and the laser power required to form a good ohmic contact can be reduced by 30% to 50%.

[0093] In some examples, in step S23, the laser scanning speed of the laser-assisted sintering process is 55 m / s to 67 m / s, for example, 56 m / s, 58 m / s, 60 m / s, 62 m / s, 64 m / s, 66 m / s, etc.

[0094] In some examples, the fabrication method of solar cells also includes the following steps:

[0095] Step S24: The first sintered product is heated and sintered to form the second sintered product.

[0096] In the above example, further heating and sintering can more thoroughly remove residual organic carriers in the electrode layer, make the contact between metal particles more stable, and improve the conductivity of the electrode layer.

[0097] In some examples, the heating and sintering temperature in step S24 is 500℃~600℃, for example, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, etc. The above heating and sintering temperatures are lower than the traditional electrode sintering temperature (700℃~800℃), which helps to reduce energy consumption.

[0098] In some examples, the heating and sintering process in step S24 takes 80 to 120 seconds, for example, 80, 85, 90, 95, 100, 105, 110, 115, or 120 seconds. This heating and sintering process takes less time than traditional electrode sintering, which helps reduce energy consumption.

[0099] A fourth aspect of this application provides a solar cell.

[0100] A solar cell of one embodiment is prepared by the preparation method of any of the above examples.

[0101] The fifth aspect of this application provides a photovoltaic module.

[0102] One embodiment of the photovoltaic module includes a first encapsulation component, a second encapsulation component, and the aforementioned solar cell. The solar cell is disposed between the first encapsulation component and the second encapsulation component.

[0103] In some examples, the first encapsulation component includes an encapsulation panel and a first encapsulating film disposed between the encapsulation panel and the battery cell. The material of the encapsulation panel is, for example, but not limited to, glass, organic polymers, etc. The first encapsulating film is, for example, but not limited to, EVA (ethylene-vinyl acetate copolymer) film, POE (polyolefin elastomer) film, etc.

[0104] In some examples, the second encapsulation component includes an encapsulation backplane and a second encapsulating film disposed between the encapsulation backplane and the battery cell. The material of the encapsulation backplane is, for example, but not limited to, glass, organic polymers, etc. The second encapsulating film is, for example, but not limited to, EVA film, POE film, etc.

[0105] The following specific embodiments further illustrate the present invention. These specific embodiments are provided to better understand the present invention, but are not intended to limit the scope of the invention and do not constitute a limitation on its content or protection.

[0106] Example 1

[0107] This embodiment provides a conductive paste and its preparation method.

[0108] The conductive paste comprises the following components by mass fraction:

[0109] The composition consists of 88% silver powder, 1% bismuthate glass powder, 8% organic carrier, 1% polymer pore-forming agent, and 2% microwave absorbing material. The organic carrier is a mixture of terpineol and ethyl cellulose in a 1:1 mass ratio. The polymer pore-forming agent is polymethyl methacrylate particles. The microwave absorbing material is oleic acid-coated tellurium powder.

[0110] The preparation method of conductive paste includes the following steps:

[0111] Step 1: Mix the organic carrier and glass powder in a mixing container at low speed to initially wet and disperse the glass powder, thus obtaining the first mixture.

[0112] Step 2: Add the first mixture to the feeding zone of the three-roll mill, set the roll gap to 80μm, slowly add metal powder, and roll to obtain the second mixture.

[0113] Step 3: Continue adding microwave absorbing material, set the roller gap to 40μm, and roll to obtain the third mixture.

[0114] Step 4: Continue adding polymer pore-forming agent, set the roller gap to 20μm, and roll the slurry. Use a scraper fineness gauge to check the fineness of the slurry. Discharge the slurry when the fineness is less than 10μm and the color is uniform.

[0115] Example 2

[0116] This embodiment provides a conductive paste and its preparation method.

[0117] The conductive paste comprises the following components by mass fraction:

[0118] The composition includes 85% silver powder, 3% bismuthate glass powder, 10% organic carrier, 0.5% polymer pore-forming agent, and 1.5% microwave absorbing material. The organic carrier is a mixture of terpineol and ethyl cellulose in a 1:1 mass ratio. The polymer pore-forming agent is expanded microspheres. The microwave absorbing material is oleic acid-coated tellurium powder.

[0119] The preparation method of the conductive paste in this embodiment is the same as that in Embodiment 1.

[0120] Example 3

[0121] This embodiment provides a conductive paste and its preparation method.

[0122] The conductive paste comprises the following components by mass fraction:

[0123] The composition includes 82% silver powder, 2.4% bismuthate glass powder, 15% organic carrier, 0.1% polymer pore-forming agent, and 0.5% microwave absorbing material. The organic carrier is a mixture of terpineol and ethyl cellulose in a 1:1 mass ratio. The polymer pore-forming agent is expanded microspheres. The microwave absorbing material is oleic acid-coated antimony powder.

[0124] The preparation method of the conductive paste in this embodiment is the same as that in Embodiment 1.

[0125] Example 4

[0126] This embodiment provides a conductive paste and its preparation method.

[0127] The conductive paste comprises the following components by mass fraction:

[0128] The composition consists of 82% silver powder, 5% bismuthate glass powder, 9% organic carrier, 1% polymer pore-forming agent, and 3% microwave absorbing material. The organic carrier is a mixture of terpineol and ethyl cellulose in a 1:1 mass ratio. The polymer pore-forming agent is polymethyl methacrylate particles. The microwave absorbing material is oleic acid-coated tungsten trioxide nanoparticles.

[0129] The preparation method of the conductive paste in this embodiment is the same as that in Embodiment 1.

[0130] Example 5

[0131] This embodiment provides a solar cell (TOPCon cell) and its preparation method.

[0132] The method for preparing a solar cell includes the following steps:

[0133] Step 1: Provide N-type doped single-crystal silicon, and perform texturing and cleaning on both sides of the single-crystal silicon to form a textured structure, thereby obtaining a silicon substrate.

[0134] Step 2: Using boron trichloride as the boron source, a boron diffusion process is performed on the front side of the silicon substrate to form the emitter.

[0135] Step 3: Remove the borosilicate glass layer on the back of the silicon substrate and polish the back side.

[0136] Step 4: A tunneling layer is formed on the back side of the silicon substrate by a thermal oxidation process.

[0137] Step 5: An intrinsic amorphous silicon layer is deposited on the back side using PECVD process, and a diffusion process is performed using phosphorus oxychloride as the phosphorus source to form a doped polycrystalline silicon layer.

[0138] Step 6: Remove the borosilicate glass, phosphosilicate glass layer and front polycrystalline silicon layer by RCA cleaning.

[0139] Step 7: Deposit an aluminum oxide layer on the front side and a silicon nitride layer on both sides to form a front passivation layer and a back passivation layer.

[0140] Step 8: Conductive paste is screen-printed onto the front and back passivation layers, followed by laser-assisted sintering and thermal sintering. The conductive paste used is the one provided in Example 1. The laser used for laser-assisted sintering has a wavelength of 1064 nm, a power of 200 W, and a scanning speed of 60 m / s. The thermal sintering process is performed at a temperature of 550 °C for 90 s.

[0141] Example 6

[0142] The method for preparing the solar cell provided in this embodiment is basically the same as the steps in Embodiment 5, except that the conductive paste used is the conductive paste provided in Embodiment 2.

[0143] Example 7

[0144] The method for preparing the solar cell provided in this embodiment is basically the same as the steps in Embodiment 5, except that the conductive paste used is the conductive paste provided in Embodiment 3.

[0145] Example 8

[0146] The method for preparing the solar cell provided in this embodiment is basically the same as the steps in Embodiment 5, except that the conductive paste used is the conductive paste provided in Embodiment 4.

[0147] Comparative Example 1

[0148] The method for preparing the solar cell provided in this embodiment is basically the same as the steps in Embodiment 5, with the following differences:

[0149] (1) The conductive paste comprises the following components by mass fraction: 84.5% silver powder, 2.1% bismuthate glass powder, and 12.4% organic carrier. The organic carrier is a mixture of terpineol and ethyl cellulose in a mass ratio of 1:1. (2) The power of laser-assisted sintering is 350W.

[0150] Ten solar cells each from the above-described embodiments and comparative examples were taken, and the average value of the results was taken after performance testing. The test results are shown in Table 1.

[0151] Table 1 Performance test results of solar cells

[0152]

[0153] As can be seen from the results in Table 1, the solar cells prepared by conductive paste containing microwave absorbing materials and polymer pore-forming agents in Examples 5-8 have significantly improved electrical performance compared to the cells prepared by conventional conductive paste without microwave absorbing materials and polymer pore-forming agents in Comparative Example 1.

[0154] The conductive paste used in Comparative Example 1 requires high laser power for sintering due to the limited absorption rate of laser energy by metal particles. This not only increases energy consumption but also easily damages the passivation layer on the battery surface, leading to a decrease in the battery's open-circuit voltage. Furthermore, the uneven distribution of traditional pastes on the textured surface and inconsistent laser energy absorption result in poor uniformity of the contact points formed after laser activation, leading to over- or under-burning phenomena and limiting the improvement of fill factor and photoelectric conversion efficiency. In contrast, the conductive pastes used in Examples 5-8 effectively solve these problems through the combined action of microwave absorbing materials and polymer pore-forming agents. The microwave absorbing materials efficiently absorb laser light and release heat, causing the particulate polymer pore-forming agent to rapidly vaporize, forming a cavity structure within the conductive paste. This creates multiple reflection cavities, extending the optical path to improve laser energy absorption, thereby reducing the laser power required for sintering, minimizing damage to the battery's passivation layer, and improving the battery's open-circuit voltage. Meanwhile, the microscopic high pressure generated by the vaporization of the polymer pore-forming agent drives molten metal particles to impact the battery surface at high speed, improving the physical contact and embedding depth between the metal and silicon materials, forming more and more uniform ohmic contact points, optimizing the fill factor and photoelectric conversion efficiency, and the battery short-circuit current density is also improved due to the improved electrode contact uniformity and reduced passivation layer damage.

[0155] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0156] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A conductive paste, characterized in that, The material comprises metal powder, glass powder, organic carrier, microwave absorbing material, and polymer pore-forming agent. The microwave absorbing material is capable of absorbing laser light and releasing heat. The mass fraction of the metal powder is 82%~88%, the mass fraction of the glass powder is 1%~5%, the mass fraction of the organic carrier is 8%~15%, the mass fraction of the microwave absorbing material is 0.5%~3%, and the mass fraction of the polymer pore-forming agent is 0.1%~1%.

2. The conductive paste as described in claim 1, characterized in that, The polymer pore-forming agent has a particulate structure with a D50 particle size of 1μm to 5μm.

3. The conductive paste as described in claim 1, characterized in that, The thermal decomposition temperature of the polymer pore-forming agent is 200℃~500℃.

4. The conductive paste as described in claim 1, characterized in that, The polymer pore-forming agent is made of one or more of polymethyl methacrylate, polystyrene, polylactic acid, polyvinyl butyral, and expanded microspheres. The expanded microspheres include a thermoplastic polymer shell and volatile alkanes disposed in the thermoplastic polymer shell.

5. The conductive paste as described in claim 1, characterized in that, The microwave absorbing material includes one or more of tellurium, antimony, and tungsten trioxide.

6. The conductive paste as described in claim 1, characterized in that, The microwave absorbing material has a granular structure with a D50 particle size of 1μm to 5μm. The surface of the microwave absorbing material is provided with a coating layer, and the coating layer material includes one or more of surfactants, silane coupling agents, polymer dispersants, and organic acids.

7. The conductive paste as described in claim 6, characterized in that, The surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, alkylphenol polyoxyethylene ether phosphate, hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether. And / or, the silane coupling agent comprises one or more of aminopropylalkoxysilane, glycidyl etheroxypropylalkoxysilane, mercaptopropylalkoxysilane, vinylalkoxysilane, and methacryloxypropylalkoxysilane; And / or, the polymer dispersant includes one or more of polyvinylpyrrolidone and polyvinyl alcohol; And / or, the organic acid includes one or more of oleic acid, stearic acid, palmitic acid and linoleic acid.

8. The conductive paste according to any one of claims 1 to 7, characterized in that, The metal powder includes one or more of the following: silver powder, aluminum powder, copper powder, nickel powder, silver-coated copper powder, and silver-coated nickel powder.

9. A method for preparing a conductive paste, wherein the conductive paste is the conductive paste according to any one of claims 1 to 8, characterized in that, Includes the following steps: The organic carrier and the glass powder are stirred and mixed to obtain a first mixture; The first mixture is rolled and mixed with the metal powder to obtain a second mixture; The second mixture is rolled and mixed with the microwave absorbing material to obtain a third mixture; The third mixture is rolled and mixed with the polymer pore-forming agent to obtain the fourth mixture.

10. A method for preparing a solar cell, characterized in that, Includes the following steps: Provide battery body; A conductive paste is coated on the battery body, wherein the conductive paste is the conductive paste according to any one of claims 1 to 8 or the conductive paste prepared by the preparation method according to claim 9; The conductive paste is subjected to laser-assisted sintering to form a first sintered product.

11. The method for preparing a solar cell as described in claim 10, characterized in that, The laser used in the laser-assisted sintering process has a wavelength of 1000nm~1300nm and a power of 170W~230W.

12. The method for preparing a solar cell as described in claim 10 or 11, characterized in that, It also includes the following steps: The first sintered product is subjected to heating and sintering treatment to form a second sintered product.

13. The method for preparing a solar cell as described in claim 12, characterized in that, The temperature for the heating and sintering process is 500℃~600℃.

14. A solar cell, characterized in that, It is prepared by the preparation method according to any one of claims 10 to 13.

15. A photovoltaic module, characterized in that, It includes a first encapsulation component, a second encapsulation component, and the solar cell of claim 14, wherein the solar cell is disposed between the first encapsulation component and the second encapsulation component.

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