Solar cell processing method, solar cell and photovoltaic module
Through a solar cell treatment method including primary sintering, secondary sintering and controlled cooling treatment, the problem of large contact resistance between silver electrode and silicon contact is solved, and the photoelectric conversion performance of the solar cell is improved.
Patent Information
- Application Number
- CN202410776362.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-17
- Publication Date
- 2025-03-07
AI Technical Summary
In the prior art, the contact resistance between the silver electrode and the silicon contact is relatively large, which affects the photoelectric performance of the solar cell.
A solar cell treatment method is adopted, including primary sintering treatment, secondary sintering treatment and controlled cooling treatment. The specific steps are: firstly, the pre-made silver gate wire is prepared by pre-sintering treatment of 600°C to 700°C; then the solar cell with pre-made silver gate wire is irradiated with laser light and a reverse bias voltage is applied to form a secondary sintered silver gate wire with a silver dendrite structure; finally, the solar cell is placed in a chamber containing a non-oxidizing gas, and the D50 of the nano silver particles is controlled to be 20 nm to 100 nm.
By reducing the contact resistance between the silver electrode and the silicon contact, the photoelectric conversion performance of the solar cell is improved.
Smart Images
Figure CN119584667A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of solar cells, and in particular to a solar cell processing method, a solar cell and a photovoltaic module. Background Art
[0002] Solar cells are devices that convert solar energy into electrical energy. They are clean and pollution-free and have been widely used in the power generation industry.
[0003] In the related art, the electrodes of solar cells are usually silver electrodes. Although silver electrodes have high conductivity, how to control the contact resistance at the interface between the silver electrode contacts and the silicon contacts during the electrode preparation process to improve the conductivity of the silver electrode, thereby improving the photoelectric performance of the solar cell, has become a technical problem that needs to be solved urgently. Summary of the invention
[0004] In order to solve the above technical problems, the present application discloses a solar cell processing method, a solar cell and a photovoltaic module to reduce the contact resistance between the silver electrode contacts and the silicon contacts so as to improve the photoelectric performance of the solar cell.
[0005] In a first aspect, the present application provides a solar cell processing method, the method comprising:
[0006] Primary sintering treatment: printing silver paste onto the pattern of the silver grid lines corresponding to the solar cell, and pre-sintering the silver grid lines at 600°C to 700°C to prepare prefabricated silver grid lines;
[0007] Secondary sintering treatment: laser irradiation is performed on the solar cell with prefabricated silver grid lines, and a reverse bias voltage is applied to the solar cell while the laser irradiation is performed to form secondary sintered silver grid lines with a silver dendrite structure;
[0008] Controlling the temperature reduction treatment: placing the solar cell with the secondary sintered silver grid line in a chamber containing a non-oxidizing gas, so that the D50 of the nano-silver particles in the silver dendrite structure is 20nm to 100nm;
[0009] The thermal conductivity of the non-oxidizing gas at 0° C. is 0.015 W / (m·K) to 0.024 W / (m·K).
[0010] In some embodiments of the present application, in the volume-based particle size distribution of the nanosilver particles, when the volume accumulation reaches 50% from the small particle size side, the distance of the shortest line segment on the spherical surface connecting two adjacent nanosilver particles is D, and D≤15nm.
[0011] In some embodiments of the present application, in the secondary sintered silver grid lines, a plurality of the nanosilver particles aggregate to form silver dendrites, and the silver dendrites are used to constitute silver electrode contacts of the solar cell.
[0012] In some embodiments of the present application, during the secondary sintering process of the solar cell, the solar cell with the prefabricated silver grid lines is placed in a chamber containing a non-oxidizing gas, so that the prefabricated silver grid lines during the secondary sintering process are simultaneously placed in a sintering atmosphere environment of the non-oxidizing gas, and the thermal conductivity of the non-oxidizing gas at 0°C is 0.015W / (m·K) to 0.024W / (m·K).
[0013] In some embodiments of the present application, the non-oxidizing gas includes at least one of carbon dioxide, nitrogen and argon.
[0014] In some embodiments of the present application, the volume fraction of the non-oxidizing gas in the chamber is not less than 80%.
[0015] In some embodiments of the present application, the process of controlling the temperature reduction treatment includes:
[0016] The solar cell with the secondary sintered silver grid lines is placed in a chamber containing the non-oxidizing gas and having a target temperature of 25° C. to 300° C., so that the D50 of the nano-silver particles in the silver dendrite structure is 20 nm to 100 nm.
[0017] In some embodiments of the present application, the method further comprises:
[0018] The environment where the solar cell is located is heated to the target temperature by at least one heating method selected from convection heating, radiation heating and conduction heating.
[0019] In some embodiments of the present application, the process of controlling the temperature reduction treatment includes:
[0020] The solar cell with the secondary sintered silver grid lines is placed in a chamber containing the non-oxidizing gas and having a target pressure of 0.01 bar to 5 bar, so that the D50 of the nano-silver particles in the silver dendrite structure is 20 nm to 100 nm.
[0021] In some embodiments of the present application, the process of controlling the temperature reduction treatment includes:
[0022] The solar cell with the secondary sintered silver grid line is placed on a table surface in a chamber containing the non-oxidizing gas, the thermal conductivity of the table is 0.001W / (m·K) to 100W / (m·K), and the D50 of the nanosilver particles in the silver dendrite structure is 20nm to 100nm.
[0023] In some embodiments of the present application, the material of the countertop includes at least one of soft porcelain, aluminum silicate, rubber and plastic.
[0024] In some embodiments of the present application, the peak temperature of the pre-sintering treatment of the silver grid line is 600°C to 700°C.
[0025] In a second aspect, the present application provides a solar cell obtained by processing the solar cell processing method described in the first aspect.
[0026] In some embodiments of the present application, the solar cell includes any one of a TOPCon solar cell, an IBC solar cell, and a PERC solar cell.
[0027] In a third aspect, the present application provides a photovoltaic module, wherein the photovoltaic module includes the solar cell as described in the first aspect, or the photovoltaic module includes the solar cell prepared by the preparation method as described in the second aspect.
[0028] Compared with the prior art, this application has at least the following beneficial effects:
[0029] The solar cell processing method, solar cell and photovoltaic module provided by the present application are to treat the solar cell after secondary sintering, that is, place the solar cell with secondary sintered silver grid wire in a chamber containing non-oxidizing gas, so that the D50 of the nanosilver particles in the silver dendrite structure is 20nm to 100nm. Compared with the existing solar cell silver grid wire, the nanosilver particles in the silver grid wire of the present application have a larger D50, that is, the average particle size of the nanosilver particles of the present application is larger, and therefore has a smaller specific surface area and lower specific surface energy, which can improve the stability of the nanosilver particles, reduce the risk of silver dendrite fracture, and improve the contact stability between the silver electrode contact and the silicon contact, thereby reducing the contact resistance at the contact interface between the silver electrode contact and the silicon contact, and improving the photoelectric conversion performance of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0031] Figure 1 Schematic diagram of the change of thermal conductivity of air, carbon dioxide and nitrogen with temperature;
[0032] Figure 2 This application is a schematic diagram of the structure of a secondary sintering treatment device in one embodiment;
[0033] Figure 3 Schematic diagram of the relationship between the thermal conductivity of carbon dioxide gas and the temperature and pressure;
[0034] Figure 4 This is a schematic diagram of the structure of a solar cell with silver grid lines in one embodiment of the present application;
[0035] Figure 5 This is a schematic structural diagram of a solar cell with silver grid lines in another embodiment of the present application;
[0036] Figure 6 A scanning electron microscope (SEM) image of nanosilver particles in the silver grid wire of the embodiment of the present application;
[0037] Figure 7 This is a SEM image of nanosilver particles in the silver grid lines of TOPCon solar cells in the related art.
[0038] Description of reference numerals:
[0039] 1-housing, 2-secondary sintering treatment device, 3-table, 4-protective cover, 5-pipeline, 6-oxygen concentration detection device, 7-pressure sensor, 8-temperature sensor, 9-fan, 10-solar cell, 20-interface passivation layer, 30-first doping layer, 40-second doping layer, 100-silicon substrate, 101-light receiving surface, 102-backlight surface. DETAILED DESCRIPTION
[0040] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only 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 creative work are within the scope of protection of this application.
[0041] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.
[0042] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.
[0043] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0044] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.
[0045] In the related art, although the silver grid line can be prepared by light injection combined with a low-temperature sintering process, the particle size of the nanosilver particles in the formed silver grid line is small, resulting in the risk of fracture of the silver dendrites composed of the nanosilver particles, which in turn leads to an increase in the contact resistance at the contact interface between the silver electrode contact and the silicon contact, affecting the photoelectric conversion performance of the solar cell. For example, for a conventional air atmosphere, due to the high thermal conductivity of air (0.24W / (m·K) at 0°C), the cooling rate is fast, and the formed nanosilver particles are small. When the size of the nanosilver particles drops to the nanometer size level, physical properties different from those of the bulk material will appear, such as the melting point will drop, and the nanosilver particles will pre-melt when the surface is reheated. Therefore, the smaller the size of the nanosilver particles, the higher the sintering activity of the nanosilver particles, and the smaller the nanosilver particles are, the easier it is to melt, resulting in the melting of the silver dendrites used for electrical connection between the silver grid line and the silicon contact, thereby increasing the contact resistance at the contact interface between the silver electrode contact and the silicon contact.
[0046] In view of this, in a first aspect, the present application provides a solar cell processing method, the method comprising:
[0047] Primary sintering treatment: printing silver paste onto the pattern of the silver grid lines corresponding to the solar cell, drying and pre-sintering treatment at 600°C to 700°C to prepare prefabricated silver grid lines, which are obtained after primary sintering treatment.
[0048] Secondary sintering treatment: laser irradiation is performed on the solar cell with prefabricated silver grid lines, and a reverse bias voltage is applied to the solar cell during the laser irradiation to form secondary sintered silver grid lines with a silver dendrite structure, wherein the secondary sintered silver grid lines include a silver dendrite structure obtained by a crystallization process of multiple nano-silver particles.
[0049] Controlled cooling treatment: placing the solar cell with secondary sintered silver grid lines in a chamber containing a non-oxidizing gas, so that the D50 of the nanosilver particles in the silver dendrite structure is 20nm to 100nm, and the thermal conductivity of the non-oxidizing gas at 0°C is 0.015W / (m·K) to 0.024W / (m·K).
[0050] Here, D50 represents the volume average particle size, that is, the particle size at which the cumulative volume from the small particle size side is 50% in the particle size distribution of nanosilver particles from small particle size to large particle size. The D50 of the nanosilver particles can be measured using a laser scattering diffraction particle size distribution measuring apparatus (manufactured by Beckman Coulter) and the like.
[0051] Solar cells with silver grid lines may include, but are not limited to, passivated contact (TOPCon) solar cells, all-back contact (IBC) solar cells, passivated emitter and back contact (PERC) solar cells, and the like.
[0052] In the secondary sintering process, a reverse bias voltage is applied while laser irradiation is performed, wherein the reverse bias voltage can enhance the built-in electric field strength of the solar cell PN junction. The laser generates a large number of photogenerated carriers in the solar cell. The photogenerated carriers are quickly separated under the action of the enhanced built-in electric field, and accumulate at the electrode contacts and silicon contacts (i.e., silver-silicon contacts) to generate heat, causing the silver therein to melt.
[0053] In the controlled cooling treatment step, by placing the solar cell with the secondary sintered silver grid line in a chamber containing a non-oxidizing gas, and the thermal conductivity of the non-oxidizing gas at 0°C is 0.015W / (m·K) to 0.024W / (m·K), the cooling rate of the solar cell can be slowed down, which is beneficial to the formation and growth of nanosilver particles at the contact interface between the electrode contact and the silicon contact of the solar cell (hereinafter referred to as the silver-silicon contact interface), thereby forming larger nanosilver particles. After measurement, the D50 of the formed nanosilver particles is 20nm to 100nm, which has a smaller specific surface area and lower specific surface energy. In summary, the present application provides a method for treating a solar cell, which can increase the D50 of nanosilver particles, improve the stability of nanosilver particles, reduce the risk of breakage of silver dendrites, and improve the stability of contact between the silver electrode contact and the silicon contact, thereby reducing the contact resistance at the contact interface between the silver electrode contact and the silicon contact, and improving the photoelectric conversion efficiency of the solar cell.
[0054] The present application has no particular restrictions on the parameters of laser irradiation and reverse bias voltage, as long as the secondary sintering process can be performed. For example, the laser power is 5W to 200W, the wavelength is 300nm to 1200nm, the pulse frequency is 20Hz to 50Hz, the pulse width is 55ms to 65ms, and the reverse bias voltage ranges from 5V to 40V.
[0055] In an optional embodiment, in the volume-based particle size distribution of the nanosilver particles, when the volume accumulation reaches 50% from the small particle size side, the distance of the shortest line segment on the spherical surface between two adjacent nanosilver particles is D, D≤15nm; preferably, D≤10nm. The inventors have also found that the distance between the nanosilver particles will also affect the contact resistance at the contact interface, thereby affecting the photoelectric conversion performance of the solar cell. Nanosilver particles are usually spherical, and the D of the nanosilver particles of the present application is within the above range, indicating that the nanosilver particles have a smaller distance between them, so that the number of nanosilver particles per unit volume area is greater, which is beneficial to reduce the contact resistance at the contact interface and improve the photoelectric conversion efficiency of the solar cell.
[0056] In an optional embodiment, in the secondary sintered silver grid line, multiple nanosilver particles are aggregated to form silver dendrites, and the silver dendrites are used to form silver electrode contacts of solar cells. It is understandable that multiple nanosilver particles can form silver dendrites after being aggregated in a linear shape, and the silver dendrites are used to form silver electrode contacts of solar cells, so that the contact resistance between the silver electrode contacts and the silicon contacts is lower, which is beneficial to the improvement of the photoelectric conversion efficiency of the solar cell.
[0057] In an optional embodiment, during the secondary sintering process of the solar cell, the solar cell with the prefabricated silver grid line is placed in a chamber containing a non-oxidizing gas, so that the prefabricated silver grid line during the secondary sintering process is also placed in a sintering atmosphere of the non-oxidizing gas, and the thermal conductivity of the non-oxidizing gas at 0°C can also be 0.015W / (m·K) to 0.024W / (m·K). In this way, when the nanosilver particles are aggregated into silver dendrites under the action of the secondary sintering process, the nanosilver particles will not be oxidized into Ag with a higher resistivity. x O y Particles are beneficial to reducing the contact resistance at the contact interface and improving the photoelectric conversion efficiency of solar cells.
[0058] In an optional embodiment, the non-oxidizing gas includes at least one of carbon dioxide, nitrogen and argon.
[0059] Figure 1 Schematic diagram of the change of thermal conductivity of air, carbon dioxide and nitrogen with temperature. Figure 1, under normal pressure conditions, the thermal conductivity of carbon dioxide is less than that of air when it is below 590°C, and the nanosilver particles will not be oxidized within the temperature range of the controlled cooling treatment; and although the thermal conductivity of nitrogen is similar to that of air, nitrogen does not contain active oxygen components, which can also reduce the probability of oxidation reactions of nanosilver particles during secondary sintering and controlled cooling treatments. The present application uses at least one of the above-mentioned non-oxidizing gases, which can not only slow down the cooling rate of the solar cell during the cooling treatment to form larger nanosilver particles and improve the crystal structure stability of the silver dendrites, but also because the non-oxidizing gas atmosphere does not contain active oxygen components, it can also reduce the probability of oxidation reactions of nanosilver particles, further improving the conductivity of the nanosilver particles.
[0060] In an optional embodiment, the volume fraction of the non-oxidizing gas in the chamber is not less than 80%. For example, the volume fraction of the non-oxidizing gas in the chamber is 80% to 100%, and the volume fraction of air is 0% to 20%. In this way, the oxygen in the chamber is exhausted as much as possible, thereby reducing the degree of oxidation of the nano-silver particles. However, as the volume fraction of air in the chamber decreases, the cost of exhausting air increases. From the perspective of reducing the degree of oxidation of the nano-silver particles and reducing manufacturing costs, the volume fraction of the non-oxidizing gas in the chamber is preferably 80% to 97%.
[0061] In the present application, the concentration of oxygen in the chamber can be detected by an oxygen concentration detection device. Since the volume fraction of oxygen in the air is 21%, after the volume fraction of oxygen is detected, the volume fraction of air in the chamber can be calculated based on it, thereby determining the volume fraction of non-oxidizing gas in the chamber.
[0062] The present application has no particular limitation on the method of forming the non-oxidizing gas atmosphere. For example, the non-oxidizing gas may be introduced into the chamber of the secondary sintering treatment device for placing the solar cells through a pipeline.
[0063] Figure 2 FIG. 1 is a schematic diagram of the structure of a secondary sintering treatment device in an embodiment. Figure 2The secondary sintering treatment device includes a machine housing 1, a secondary sintering treatment device 2 is arranged in the machine housing, a table 3 is arranged below the secondary sintering treatment device, and a solar cell 10 is laid flat on the table; the secondary sintering treatment device is also provided with a protective cover 4, and the protective cover can use a commonly used heat-insulating material on the market, such as a heat-insulating material of model ZC200, ZC220 or ZC325, which has the functions of pressure resistance and heat preservation, and the protective cover covers the table to form a sealed chamber; the secondary sintering treatment device also includes a plurality of pipelines 5, and the plurality of pipelines 5 are used to pass the same or different non-oxidizing gases into the chamber to adjust the composition of the gas in the chamber. An oxygen concentration detection device 6, a pressure sensor 7 and a temperature sensor 8 are arranged in the protective cover, wherein the oxygen concentration detection device is used to detect the concentration of oxygen; the pressure sensor is used to detect the ambient pressure; and the temperature sensor is used to detect the ambient temperature. A fan 9 and a corresponding air duct are also arranged below the table 3 for exhaust, and a valve can also be arranged in the air duct for opening and closing the air duct. In addition, the area indicated by the dotted line below the secondary sintering treatment device is the laser scanning area, and the arrow shows the gas flow direction.
[0064] In an optional embodiment, the process of controlling the temperature reduction treatment includes:
[0065] The solar cell with the secondary sintered silver grid line is placed in a chamber containing a non-oxidizing gas and a target temperature of 25° C. to 300° C., so that the D50 of the nano-silver particles in the silver dendrite structure is 20 nm to 100 nm.
[0066] The inventors have found that by placing a solar cell that has undergone secondary sintering, that is, a solar cell with secondary sintered silver grid lines, in a chamber with the above parameters, the cooling rate of the solar cell can be slowed down during the cooling process, especially the cooling rate at the contact interface, thereby forming larger nanosilver particles.
[0067] The present application can control the temperature of the environment in which the solar cell is located within the above-mentioned target temperature range through a variety of methods. In an optional embodiment, the environment in which the solar cell is located can be heated to the target temperature by at least one of convection heating, radiation heating and conduction heating. The present application has no particular restrictions on the specific implementation of convection heating, radiation heating and conduction heating, as long as the purpose of heating the chamber temperature of the present application can be achieved. For example, the heating of the device can be achieved by heating an inert gas such as carbon dioxide or nitrogen, and using these gases to convect in the chamber; or, the radiation heating of the device can be achieved by electromagnetic radiation or the like; or, the conduction heating of the device can be achieved by heating the base.
[0068] In an optional embodiment, the process of controlling the temperature reduction treatment includes:
[0069] The solar cell with the secondary sintered silver grid line is placed in a chamber containing non-oxidizing gas and the target pressure is 0.01 bar to 5 bar, so that the D50 of the nano silver particles in the silver dendrite structure is 20nm to 100nm.
[0070] The inventors have found that by placing a solar cell that has undergone secondary sintering, that is, a solar cell with secondary sintered silver grid lines, in a chamber with the above-mentioned parameters, the cooling rate of the solar cell can be slowed down during the cooling process, which is conducive to the formation of larger nano-silver particles, thereby reducing the risk of silver dendrites breaking, further improving the stability of silver dendrites, and also helping to reduce the contact resistance at the contact interface, thereby improving the photoelectric conversion performance of the solar cell.
[0071] In an optional embodiment, the solar cell with the secondary sintered silver grid wire can also be placed in a non-oxidizing gas atmosphere with the above-mentioned thermal conductivity, and the target pressure in the non-oxidizing gas atmosphere is controlled to be 1 bar to 10 bar and the target temperature is controlled to be 50°C to 300°C. This can further slow down the cooling rate of the solar cell during the cooling treatment process, which is conducive to the formation of larger nanosilver particles, reducing the risk of breakage of silver dendrites, further improving the stability of silver dendrites, and also conducive to further reducing the contact resistance at the contact interface, thereby further improving the photoelectric conversion performance of the solar cell.
[0072] Figure 3 This is a schematic diagram showing the relationship between the thermal conductivity of carbon dioxide gas and the temperature and pressure. Figure 3 When the temperature of carbon dioxide gas is lower than 180°C, the thermal conductivity of carbon dioxide gas varies greatly under different pressure conditions; when the temperature is lower than 180°C, with the increase of pressure, the thermal conductivity shows a rapid increasing trend under the same temperature conditions; after the temperature is higher than 180°C, no matter how the pressure changes, its thermal conductivity is almost linearly related to the increase in temperature, and under different pressure conditions, the thermal conductivity at the same temperature is almost the same. The present application controls the target pressure and target temperature in the non-oxidizing gas atmosphere within the above range, so as to slow down the cooling rate of the solar cell during the cooling process, especially the cooling rate at the contact interface, which is conducive to the formation of larger nanosilver particles, thereby reducing the risk of silver dendrite fracture, further improving the stability of silver dendrites, and facilitating the further reduction of contact resistance at the contact interface, thereby further improving the photoelectric conversion performance of the solar cell.
[0073] The present application can adjust the pressure of the environment where the solar cell is located within the above target pressure range in a variety of ways. In an optional embodiment, the pressure of the environment where the solar cell is located can be adjusted to the target pressure by using a vacuum pump to ensure the pressure difference between the intake and exhaust.
[0074] In an optional embodiment, the process of controlling the temperature reduction treatment includes:
[0075] A solar cell with secondary sintered silver grid lines is placed on a table surface in a chamber containing non-oxidizing gas, the thermal conductivity of the table surface is 0.001W / (m·K) to 100W / (m·K), and the D50 of the nanosilver particles in the silver dendrite structure is 20nm to 100nm.
[0076] The inventors have found that by placing a solar cell that has undergone secondary sintering, that is, a solar cell with secondary sintered silver grid lines, on a table surface in a chamber with the above parameters, the cooling rate of the solar cell can be slowed down during the cooling process, which is conducive to the formation of larger nano-silver particles.
[0077] In an optional embodiment, the material of the countertop includes at least one of a soft porcelain material, an aluminum silicate material, rubber and plastic. Compared with the traditional brass material (thermal conductivity is 108.9W / (m·K)), the above-mentioned material of the present application has a lower thermal conductivity, which is beneficial to further slow down the cooling rate of the solar cell during the cooling process. Exemplarily, the above-mentioned soft porcelain material includes but is not limited to lightweight metal porous material (MCM) flexible split bricks, MCM flexible clay boards, MCM flexible stones, MCM flexible glazed bricks, etc.; aluminum silicate materials include but are not limited to the following models: HY-type, HY-number, HZSM; rubber includes but is not limited to nitrile rubber, chloroprene rubber, silicone rubber; plastic includes but is not limited to polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyimide (PI) and polytetrafluoroethylene (PTFE).
[0078] In an optional embodiment, the peak temperature of the pre-sintering treatment of the silver grid line is 600°C to 700°C. The sintering temperature of the silver grid line of the present application is lower than the existing high-temperature sintering (sintering peak temperature is about 800°C), which can reduce the damage of the silver paste to the passivation film layer on the surface of the solar cell, thereby improving the passivation effect of the solar cell.
[0079] In a second aspect, the present application provides a solar cell processed by the processing method described in the first aspect.
[0080] The solar cell with silver grid lines of the present application may include a silicon substrate, one side of the silicon substrate is stacked with an interface passivation layer and a first doping layer, and the other side of the silicon substrate is stacked with a second doping layer.
[0081] In one embodiment, reference Figure 4 The backlight surface 102 of the silicon substrate 100 has an interface passivation layer 20 and a first doping layer 30 stacked, and the light-receiving surface 101 of the silicon substrate has a second doping layer 40; in another embodiment, reference Figure 5 The light-receiving surface 101 of the silicon substrate 100 has an interface passivation layer 20 and a first doping layer 30 stacked in layers, and the backlight surface 102 of the silicon substrate has a second doping layer 40 .
[0082] The silicon substrate may be of a first conductivity type, the doping element of the first doping layer may be of a second conductivity type, and one of the first conductivity type and the second conductivity type may be an N type and the other may be a P type. For example, when the first conductivity type is an N type, the second conductivity type may be a P type; when the first conductivity type is a P type, the second conductivity type may be an N type.
[0083] The silicon substrate of the present application may be a pre-treated silicon substrate, for example, a texturing-treated silicon substrate.
[0084] In an optional implementation, the interface passivation layer and the first doping layer are made by PECVD, and the thickness of the first doping layer is 20 nm to 150 nm.
[0085] The material of the interface passivation layer of the present application may include a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide or titanium oxide. Specifically, the interface passivation layer may be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent passivation properties, can minimize the recombination loss of minority carriers on the surface of the semiconductor substrate, and is a film with excellent durability for subsequent high-temperature processes. In order to better provide interface passivation for the substrate, the thickness of the interface passivation layer can be 0.1nm to 5nm. For example, the thickness of the interface passivation layer can be 0.1nm, 0.5nm, 1nm, 1.5nm, 2nm, 3nm, 4nm, 5nm, etc., however, the present application is not limited thereto, and the thickness of the interface passivation layer can have various values. As a barrier for electrons and holes, the interface passivation layer can be combined with the polysilicon layer to prevent minority carriers from passing through. The interface passivation layer can also have a pinhole channel effect, allowing the carriers in the solar cell to move freely, and the selective passage of the majority carriers through the heavily doped polysilicon is beneficial to reduce the recombination loss of the minority carriers. In addition, the interface passivation layer can be used as a diffusion barrier to prevent the dopant of the doped polysilicon layer from diffusing into the semiconductor substrate.
[0086] In an optional embodiment, the solar cell includes any one of a passivated contact solar cell, a full back electrode contact solar cell, a passivated emitter and a back contact solar cell, and the solar cell may be a solar cell obtained after secondary sintering.
[0087] The solar cell provided by the present application has nanosilver particles in the silver grid lines with a larger D50, that is, the average particle size of the nanosilver particles of the present application is larger, and therefore has a smaller specific surface area and a lower specific surface energy, thereby improving the stability of the nanosilver particles and reducing the risk of breakage of silver dendrites, thereby reducing the contact resistance at the contact interface and having a higher photoelectric conversion performance.
[0088] In a third aspect, the present application provides a photovoltaic module, which includes the solar cell described in the second aspect.
[0089] The present application also provides a photovoltaic module, which is used to convert received light energy into electrical energy and transmit it to an external load. The photovoltaic module includes: at least one battery string, which is formed by connecting a plurality of the above-mentioned solar cells; a packaging film, which is used to cover the surface of the battery string; and a cover plate, which is used to cover the surface of the packaging film away from the battery string.
[0090] The solar cell and its processing method, and photovoltaic module of the embodiment of the present application are further explained below in conjunction with more specific embodiments.
[0091] Example
[0092] Carbon dioxide gas is introduced into the chamber of the secondary sintering treatment device through a pipeline, and the oxygen concentration in the chamber is detected by an oxygen concentration detection device, and the volume fraction of the carbon dioxide gas in the chamber is controlled to be 80% accordingly, so as to form a carbon dioxide gas atmosphere; the temperature and pressure in the chamber are detected by a temperature sensor and a pressure sensor respectively, so that the chamber temperature is 25°C and the pressure is 1 bar; a TOPCon solar cell with silver grid lines after the primary sintering treatment is placed on the table surface of the chamber, and then laser irradiation is performed, with a laser power of 20W, a wavelength of 1064nm, a pulse period of 3ms, and a pulse irradiation time of 10ms, and a reverse bias voltage of 10V is applied to the solar cell during irradiation, and then the laser irradiation and reverse bias voltage are stopped, and the gas atmosphere, temperature and pressure in the chamber are maintained, so that the solar cell after the secondary sintering treatment is cooled, so that the silver grid lines form silver dendrites containing nano silver particles. According to SEM analysis, the D50 of the nano silver particles is 24nm. Among them, the thickness of the silicon substrate is 130μm, the thickness of the interface passivation layer is 1.6nm, the thickness of the first doping layer is 50nm, the thickness of the second doping layer is 100nm, the thickness of the passivation layer is 5nm, the thickness of the anti-reflection layer is 80nm, the peak temperature of the pre-sintering treatment is 700℃; the table material is brass.
[0093] from Figure 6 It can be seen that in the silver grid lines of the embodiment, the number of nano silver particles with large particle size is greater; Figure 7It can be seen that in the silver grid lines of the TOPCon solar cells in the related art, the number of nanosilver particles with large particle size is small, indicating that the solar cells processed by the solar cell processing method of the present application have larger nanosilver particles in the silver grid lines, which is beneficial to reduce the contact resistance at the contact interface, thereby improving the photoelectric conversion performance of the solar cell.
[0094] The above is a detailed introduction to a solar cell processing method, a solar cell and a photovoltaic module disclosed in the embodiments of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core inventions of the embodiments of the present application. At the same time, for those skilled in the art, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.
Claims
1. A solar cell processing method, characterized in that: The method comprises: Primary sintering treatment: printing silver paste onto the pattern of the silver grid lines corresponding to the solar cell, and pre-sintering the silver grid lines at 600°C to 700°C to prepare prefabricated silver grid lines; Secondary sintering treatment: laser irradiation is performed on the solar cell with prefabricated silver grid lines, and a reverse bias voltage is applied to the solar cell while the laser irradiation is performed to form secondary sintered silver grid lines with a silver dendrite structure; Controlling the temperature reduction treatment: placing the solar cell with the secondary sintered silver grid line in a chamber containing a non-oxidizing gas, so that the D50 of the nano-silver particles in the silver dendrite structure is 20nm to 100nm; The thermal conductivity of the non-oxidizing gas at 0° C. is 0.015 W / (m·K) to 0.024 W / (m·K).
2. The solar cell processing method according to claim 1, characterized in that: In the volume-based particle size distribution of the nanosilver particles, when the volume accumulation reaches 50% from the small particle size side, the distance of the shortest line segment on the spherical surface connecting two adjacent nanosilver particles is D, and D≤15nm.
3. The solar cell processing method according to claim 1, characterized in that: In the secondary sintered silver grid lines, a plurality of the nano silver particles are aggregated to form silver dendrites, and the silver dendrites are used to form silver electrode contacts of the solar cell.
4. The solar cell processing method according to claim 1, characterized in that: During the secondary sintering process of the solar cell, the solar cell with the prefabricated silver grid lines is placed in a chamber containing a non-oxidizing gas, so that the prefabricated silver grid lines during the secondary sintering process are simultaneously placed in a sintering atmosphere environment of the non-oxidizing gas, and the thermal conductivity of the non-oxidizing gas at 0°C is 0.015W / (m·K) to 0.024W / (m·K).
5. The solar cell processing method according to claim 1 or 4, characterized in that: The non-oxidizing gas includes at least one of carbon dioxide, nitrogen and argon.
6. The solar cell processing method according to claim 1 or 4, characterized in that: The volume fraction of the non-oxidizing gas in the chamber is not less than 80%.
7. The solar cell processing method according to any one of claims 1 to 4, characterized in that: The process of controlling the temperature reduction treatment comprises: The solar cell with the secondary sintered silver grid lines is placed in a chamber containing the non-oxidizing gas and having a target temperature of 25° C. to 300° C., so that the D50 of the nano-silver particles in the silver dendrite structure is 20 nm to 100 nm.
8. The solar cell processing method according to claim 7, characterized in that: The method further comprises: The environment where the solar cell is located is heated to the target temperature by at least one heating method selected from convection heating, radiation heating and conduction heating.
9. The solar cell processing method according to any one of claims 1 to 4, characterized in that: The process of controlling the temperature reduction treatment comprises: The solar cell with the secondary sintered silver grid lines is placed in a chamber containing the non-oxidizing gas and having a target pressure of 0.01 bar to 5 bar, so that the D50 of the nano-silver particles in the silver dendrite structure is 20 nm to 100 nm.
10. The solar cell processing method according to any one of claims 1 to 4, characterized in that: The process of controlling the temperature reduction treatment comprises: The solar cell with the secondary sintered silver grid line is placed on a table surface in a chamber containing the non-oxidizing gas, the thermal conductivity of the table is 0.001W / (m·K) to 100W / (m·K), and the D50 of the nanosilver particles in the silver dendrite structure is 20nm to 100nm.
11. The solar cell processing method according to claim 10, characterized in that: The material of the table top includes at least one of soft porcelain, aluminum silicate material, rubber and plastic.
12. The solar cell processing method according to any one of claims 1 to 4, characterized in that: The peak temperature of the pre-sintering treatment of the silver grid line is 600°C to 700°C.
13. A solar cell, characterized in that: The solar cell is obtained by processing according to any one of claims 1 to 12.
14. The solar cell according to claim 13, characterized in that: The solar cell includes any one of a TOPCon solar cell, an IBC solar cell, and a PERC solar cell.
15. A photovoltaic module, characterized in that: Comprising the solar cell as claimed in any one of claims 13 to 14.