Production method and production equipment of solar cell, solar cell and photovoltaic module

Abstract

The invention relates to the technical field of solar cells, in particular to a production method and production equipment of a solar cell, the solar cell and a photovoltaic module. The production method of the solar cell comprises the following steps: pre-sintering the solar cell printed with metal slurry; wherein the metal slurry is pre-sintered to form a metal electrode; controlling the solar cell to be at the target temperature; wherein the target temperature is higher than the normal temperature and lower than the rheological temperature of the metal slurry; and performing laser-induced sintering on the metal electrode on the solar cell at the target temperature. The production method of the solar cell can reduce lattice structure damage caused by laser, reduces a heat affected area caused by laser, and is beneficial to improving the conversion efficiency and prolonging the service life of the solar cell.

Description

Technical Field

[0001] The present application relates to the field of solar cell technology, and in particular to a solar cell production method, production equipment, solar cell and photovoltaic module. Background Art

[0002] Laser Induced Firing (LIF) technology refers to the use of laser to process metal electrodes during the formation of metal electrodes for solar cells. In order to achieve a specific temperature at the sintering point during laser induced sintering, the laser power is relatively high. The metal electrode is heated by a high-power laser, and then the temperature is quickly reduced to form a conductive contact that improves contact. However, high-power lasers can cause thermal stress, lattice structure damage, and a large heat-affected zone, which can shorten the life of solar cells and reduce efficiency. Summary of the invention

[0003] The embodiments of the present application disclose a solar cell production method, production equipment, solar cell and photovoltaic module, which can reduce the lattice structure damage caused by laser, reduce the heat affected area caused by laser, and are beneficial to improving the conversion efficiency and service life of the solar cell.

[0004] In order to achieve the above objectives, in a first aspect, the present application discloses a method for producing a solar cell, comprising the following steps:

[0005] Pre-sintering the solar cell printed with metal paste; wherein the metal paste forms a metal electrode after pre-sintering;

[0006] Controlling the solar cell to be at a target temperature; wherein the target temperature is higher than normal temperature and lower than the rheological temperature of the metal slurry;

[0007] The metal electrode on the solar cell at the target temperature is subjected to laser induced sintering.

[0008] In a possible implementation of the first aspect, the target temperature is T and the unit is ° C. The power of the laser in the laser induced sintering is P and the unit is W; wherein P = -0.13T+a, and a = 200~204.

[0009] In a possible implementation of the first aspect, the target temperature is 100° C. to 350° C.;

[0010] And / or, during the laser induced sintering, the sintering point temperature of the metal electrode is 1450° C. to 1650° C.;

[0011] And / or, the spot diameter of the laser in the laser induced sintering is 65 μm to 500 μm;

[0012] And / or, the power density of the laser in the laser induced sintering is 1×10 9 W / m 2 ~1×10 10 W / m 2 ;

[0013] And / or, the bias voltage applied to the solar cell during the laser induced sintering is 5V to 20V.

[0014] In a possible implementation of the first aspect, after the step of laser-induced sintering the metal electrode on the solar cell at the target temperature, the method for producing the solar cell further includes the following steps:

[0015] The solar cell is subjected to cooling annealing; wherein the cooling annealing of the solar cell is performed in an environment higher than room temperature and lower than the rheological temperature of the metal slurry.

[0016] In a possible implementation of the first aspect, the temperature reduction rate of the solar cell cooling annealing is 20° C. / s to 100° C. / s.

[0017] In a possible implementation of the first aspect, the steps of pre-sintering the solar cell printed with metal paste, controlling the solar cell to be at a target temperature, laser-induced sintering of the metal electrode on the solar cell at the target temperature, and cooling annealing the solar cell are performed sequentially in the same heating environment.

[0018] In a possible implementation of the first aspect, the heating environment has a connected pre-sintering area and a cooling area;

[0019] The production method of the solar cell also includes the following steps:

[0020] Conveying the solar cell through the pre-sintering area and the cooling area in sequence; wherein the temperature of the cooling area decreases along the conveying direction of the solar cell;

[0021] The step of pre-sintering the solar cell printed with metal paste is performed in the pre-sintering area;

[0022] The steps of controlling the solar cell to be at a target temperature, performing laser induced sintering on the metal electrode on the solar cell at the target temperature, and performing cooling annealing on the solar cell are performed in the cooling area.

[0023] In a possible implementation of the first aspect, the temperature of the pre-sintering area is 700° C. to 950° C.;

[0024] And / or, the temperature of the cooling zone is 100°C to 350°C.

[0025] In a second aspect, an embodiment of the present application discloses a production device for implementing the production method of the solar cell according to the first aspect, wherein the production device comprises:

[0026] A heating device, wherein a heating cavity is defined in the heating device; the heating cavity is configured to control the temperature of the solar cell;

[0027] an electrical connector, the electrical connector being disposed in the heating cavity, the electrical connector being configured to electrically connect the solar cell to apply a bias voltage to the solar cell; and

[0028] A laser is disposed on the heating device and is configured to perform laser induced sintering on the solar cells in the heating cavity.

[0029] In a possible implementation of the second aspect, the heating cavity includes a pre-sintering area and a cooling area, and the laser is disposed on the cooling area;

[0030] The pre-sintering area is configured to pre-sinter the solar cell printed with metal paste;

[0031] The cooling region is configured to perform cooling annealing on the solar cell.

[0032] In a possible implementation of the second aspect, the production equipment further includes:

[0033] A conveyor belt is disposed in the heating chamber, and is configured to convey the solar cells to pass through the pre-sintering area and the cooling area in sequence.

[0034] In a third aspect, an embodiment of the present application discloses a solar cell, comprising a silicon substrate, a doping layer and a metal electrode, wherein the doping layer is arranged on the light-receiving surface and / or the backlight surface of the silicon substrate, and the metal electrode is in ohmic contact with the doping layer. The solar cell is produced by the solar cell production method as described in the first aspect, or the solar cell is produced by the production equipment as described in the second aspect.

[0035] In a fourth aspect, an embodiment of the present application discloses a photovoltaic module, comprising a plurality of solar cells connected in series and / or in parallel, at least one of the solar cells being the solar cell described in the third aspect.

[0036] Compared with the prior art, the beneficial effects of the present application are as follows: the production method of the solar cell controls the solar cell at the target temperature before the laser-induced sintering of the metal electrode, thereby achieving a better sintering effect while also reducing the heat-affected zone and reducing the local thermal stress, thereby improving the performance of the solar cell, as follows:

[0037] During the laser induced sintering process, if a better sintering effect is to be achieved, the sintering point temperature of the metal electrode penetrating the glass layer and the solar cell needs to reach a specific temperature. In addition to the power of the laser, the decisive factor of the sintering point temperature also includes the overall temperature of the solar cell before laser induced sintering. By appropriately increasing the temperature of the solar cell before laser induced sintering, a better sintering effect can be achieved while reducing the laser power and / or laser irradiation time. The present application controls the temperature of the solar cell to be higher than room temperature and lower than the rheological temperature of the metal slurry before laser induced sintering, and then a lower power laser and / or a shorter laser irradiation time can be used to implement laser induced sintering to achieve a better sintering effect. The local high temperature formed by the laser on the metal electrode has a smaller temperature difference with the rest of the solar cell. The reduction in temperature difference is conducive to reducing thermal stress and reducing the heat-affected zone caused by local laser heating, thereby reducing the lattice mismatch and silicon wafer cracking caused by thermal stress, which is conducive to improving the conversion efficiency, mechanical stability and service life of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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.

[0039] Figure 1 A schematic diagram of the structure of a production device disclosed in an embodiment of the present application;

[0040] Figure 2 A schematic diagram of the structure of a solar cell disclosed in an embodiment of the present application;

[0041] Figure 3 Another schematic diagram of the structure of a solar cell disclosed in an embodiment of the present application;

[0042] Figure 4 This is a flow chart of a method for producing a solar cell disclosed in Example 2.

[0043] Description of reference numerals:

[0044] 100. Production equipment; 110. Heating device; 111. Heating cavity; 1111. Pre-sintering area; 1112. Cooling area; 120. Electrical connector; 130. Laser; 140. Conveyor belt; 150. Temperature sensor; 200. Solar cell; 210. Silicon substrate; 211. Light-receiving surface; 212. Backlight surface; 220. Doping layer; 230. Metal electrode; 240. Functional film; 250. Dielectric layer. DETAILED DESCRIPTION

[0045] 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.

[0046] In this application, the terms "disposed", "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 the specific circumstances.

[0047] 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.

[0048] Laser induced sintering is a method to improve the efficiency of solar cells. Before laser induced sintering, the solar cell is pre-sintered. Pre-sintering is to heat the metal slurry. As the temperature rises, the glass material in the metal slurry begins to soften and flow and corrode the functional film, such as the passivation film and / or anti-reflection film. The metal slurry opens the functional film and contacts the doping layer. After cooling, the glass material is transformed into a glass layer, and the metal components in the metal slurry are deposited in the glass layer to form metal crystallites, which then constitute the metal electrode. The solar cell is then taken out of the pre-sintering equipment. The solar cell has been cooled to room temperature before being transferred to the laser induced sintering equipment. Then the solar cell at room temperature is laser induced sintered. In order to achieve a better sintering effect, the sintering point temperature of the metal electrode needs to be stabilized at a specific temperature. The temperature should not be too low to avoid poor laser sintering effect; the temperature should not be too high, as too high temperature will damage the functional film.

[0049] When laser-induced sintering is performed on solar cells at room temperature, a high-power laser is required to heat the sintering point to a specific temperature. Laser-induced sintering is a local heating process. The local high temperature in the laser-treated area has a large temperature difference from the rest of the solar cell, which leads to uneven heating and stress concentration of the solar cell, causing thermal stress. Thermal stress can cause lattice mismatch between the metal electrode and the surrounding silicon substrate, causing defects such as cracks in the silicon substrate at the metal electrode. High-power lasers can also increase the heat-affected area, which in turn reduces the mechanical stability and conversion efficiency of the solar cell.

[0050] In summary, using high-power lasers for laser-induced sintering of solar cells at room temperature will cause thermal stress and increase the heat-affected zone, thereby shortening the life of the solar cells and reducing the conversion efficiency.

[0051] Based on the above analysis, the solar cell production method provided in the embodiment of the present application controls the temperature of the solar cell to be higher than room temperature and lower than the rheological temperature of the metal slurry before laser induced sintering, and thus can implement laser induced sintering using a lower power laser and / or a shorter laser irradiation time to reduce the temperature difference between the laser processed area and the rest of the solar cell, thereby reducing the lattice structure damage caused by excessive temperature difference. In addition, it can also reduce the heat affected zone induced by the laser, which is beneficial to improving the conversion efficiency and service life of the solar cell.

[0052] The technical solution of the present invention will be described below in conjunction with embodiments and drawings.

[0053] In a first aspect, the present application discloses a method for producing a solar cell, comprising the following steps:

[0054] The solar cell printed with the metal paste is pre-sintered; wherein the metal paste is pre-sintered to form a metal electrode. The solar cell in this step refers to a solar cell to be made into a metal electrode, for example, a solar cell precursor after being plated with a passivation film or an anti-reflection film. The metal paste can be a silver-containing paste.

[0055] The solar cell is controlled to be at a target temperature; wherein the target temperature is higher than normal temperature and lower than the rheological temperature of the metal slurry.

[0056] It should be noted that the term "normal temperature" refers to room temperature, which is defined as a temperature between 15°C and 25°C. When the rheological temperature refers to the temperature range at which the metal slurry exhibits rheological properties, the rheological temperature below the metal slurry specifically refers to the temperature below the lower limit of the rheological temperature range. The temperature of the solar cell can be controlled by either increasing the temperature, decreasing the temperature, or maintaining the original temperature.

[0057] Laser-induced sintering of metal electrodes on solar cells at target temperature.

[0058] The production method of the solar cell controls the solar cell at a target temperature before laser-induced sintering of the metal electrode, thereby achieving a better sintering effect while also reducing the heat-affected zone and reducing local thermal stress, thereby improving the performance of the solar cell, as follows:

[0059] During the laser induced sintering process, if a better sintering effect is to be achieved, the metal electrode penetrates the glass layer and the sintering point temperature of the solar cell needs to reach a specific temperature. The term "sintering point" specifically refers to the point where the metal material and silicon of the metal electrode melt and diffuse each other during the laser induced sintering process. In addition to the power of the laser, the decisive factor of the sintering point temperature also includes the overall temperature of the solar cell before laser induced sintering. By appropriately increasing the temperature of the solar cell before laser induced sintering, a better sintering effect can be achieved while reducing the laser power and / or laser irradiation time. This application is to control the temperature of the solar cell to be higher than room temperature and lower than the rheological temperature of the metal slurry before laser induced sintering, so that a lower power laser and / or a shorter laser irradiation time can be used to implement laser induced sintering to achieve a better sintering effect. The local high temperature formed by the laser on the metal electrode has a smaller temperature difference with the rest of the solar cell. The reduction in temperature difference is conducive to reducing thermal stress and reducing the heat-affected zone caused by local laser heating, thereby reducing the lattice mismatch and silicon wafer cracking caused by thermal stress, which is conducive to improving the conversion efficiency, mechanical stability and service life of the solar cell.

[0060] For different types of solar cells and / or different types of metal pastes, the target temperatures are different. In order to quickly match the laser power parameters, the inventors have found that there is a linear relationship between the laser power and the target temperature. Furthermore, the target temperature is T and the unit is ℃, and the power of the laser in laser induced sintering is P and the unit is W; wherein, P = -0.13T + a, and a = 200 ~ 204 includes any point value within the numerical range, such as 200, 202.8 or 204. It should be noted that in the above relationship, P and T represent values ​​without units. Exemplarily, for different types of metal pastes, the rheological temperatures are different, and the target temperatures T are different. Using the above relationship: P = -0.13T + a, the corresponding laser power can be quickly matched, and laser induced sintering is performed using the matched laser power, and the performance and reliability of the obtained solar cell are better.

[0061] Preferably, the target temperature is 100° C. to 350° C., including any point value within the temperature range, such as 100° C., 200° C. or 350° C. The target temperature range can effectively reduce the laser power and reduce the impact of high temperature on solar cells.

[0062] Preferably, during laser induced sintering, the sintering point temperature of the metal electrode is 1450° C. to 1650° C., including any point value within the temperature range, such as 1450° C., 1550° C. or 1650° C. When the above sintering point temperature is reached during laser induced sintering, the sintering effect is better.

[0063] Preferably, the spot diameter of the laser in laser induced sintering is 65 μm to 500 μm, including any point value within the diameter range, such as 65 μm, 250 μm or 500 μm. The laser spot in the above diameter range combined with the laser of the above power is conducive to reaching the above sintering point temperature during laser induced sintering.

[0064] Preferably, the power density of the laser in the laser induced sintering is 1×10 9 W / m 2 ~1×10^10 / m 2 Including any point value within the power density range, for example, 1×10 9 W / m 2 , 5×10 9 W / m 2 or 1×10 10 W / m 2 The combination of the laser with the above power density and the laser spot with the above diameter range is conducive to reaching the above sintering point temperature during laser induced sintering.

[0065] Preferably, the bias voltage applied to the solar cell during laser induced sintering is 5V to 20V, including any value within the bias voltage range, such as 5V, 15V or 20V. In the laser induced sintering process, the local laser beam forms induced carriers, which, combined with the bias voltage, form a local current. The local current leads to a heating point, i.e., a sintering point. Sintering occurs at the corresponding location, and the metal material and silicon form a eutectic diffusion to form a contact point. The above bias voltage range is conducive to reaching the above sintering point temperature during laser induced sintering.

[0066] In a possible implementation of the first aspect, after the step of laser-induced sintering the metal electrode on the solar cell at the target temperature, the method for producing the solar cell further includes the following steps:

[0067] The solar cell is subjected to cooling annealing; wherein the cooling annealing of the solar cell is performed in an environment higher than room temperature and lower than the rheological temperature of the metal slurry.

[0068] Specifically, in the related art, after completing the laser induced sintering, the solar cell is cooled down at room temperature. The cooling rate of the laser treated area is relatively fast, and the growth time of the product of laser induced sintering, that is, the silver particles, is relatively short, resulting in a smaller size of the silver particles. The silver particles include silver particles composed of single silver, or alloy particles of silver and silicon. The smaller the size of the silver particles formed, the worse its stability and heat resistance. When the solar cell is further processed, such as string welding, packaging, stability testing and other subsequent processing, the gain generated at the cell end does not reflect a significant performance improvement at the component end.

[0069] The solar cell of the present application is cooled and annealed in an environment higher than room temperature and lower than the rheological temperature of the metal slurry, and the cooling rate of the laser-processed area is slowed down. The slower the cooling rate, the larger the size of the silver particles formed, which is more conducive to improving the stability of the silver particles forming the contact points, thereby improving the stability of the solar cell. On the other hand, the present application controls the cooling rate of the cooling annealing, and can also perform synchronous low-temperature annealing on the metal grid lines after laser sintering to reduce thermal stress.

[0070] Preferably, the cooling rate of the solar cell cooling annealing is 20°C / s to 100°C / s, including any point value within the cooling rate range, such as 20°C / s, 60°C / s or 100°C / s. The cooling rate can obtain silver particles of sufficient size and can also take into account faster production efficiency.

[0071] Furthermore, in the solar cell production method of the present application, the steps of pre-sintering the solar cell printed with metal paste, controlling the solar cell to be at a target temperature, laser-induced sintering of the metal electrode on the solar cell at the target temperature, and cooling and annealing the solar cell are sequentially performed in the same heating environment. It should be noted that the same heating environment may refer to a heating cavity in the same production equipment.

[0072] In the related art, pre-sintering and laser-induced sintering are often performed in two different devices, namely high-temperature sintering equipment and laser sintering equipment. The solar cell is pre-sintered in the high-temperature sintering equipment and then transferred to the laser sintering equipment for laser-induced sintering. The disadvantage is that the equipment cost is high. Pre-sintering requires heating the solar cell and the metal electrode, and then heating them again during laser-induced sintering after cooling, which not only complicates the process but also causes high heating energy consumption.

[0073] In the solar cell production method of the present application, pre-sintering, temperature control, laser-induced sintering and cooling annealing are carried out sequentially in the same heating environment, so that the integration of the entire metal electrode production process is improved, and the entire production process can be completed in one production equipment, thereby reducing equipment costs, improving production efficiency and reducing the energy consumption required for heating.

[0074] Further, in the solar cell production method of the present application, the heating environment has a connected pre-sintering area and a cooling area;

[0075] The production method of the solar cell also includes the following steps:

[0076] The solar cells are transported through the pre-sintering area and the cooling area in sequence; wherein the temperature of the cooling area decreases along the transport direction of the solar cells;

[0077] The step of pre-sintering the solar cell printed with the metal paste is performed in the pre-sintering area;

[0078] The steps of controlling the solar cell to be at a target temperature, performing laser induced sintering on the metal electrode on the solar cell at the target temperature, and performing cooling annealing on the solar cell are performed in the cooling zone.

[0079] In the production method of solar cells of the present application, the solar cells are sequentially conveyed through a pre-sintering area and a cooling area, and pre-sintering, temperature control, laser-induced sintering and cooling annealing are sequentially completed, so that the secondary sintering of the metal electrode can be realized in an assembly line process, with higher processing efficiency, less energy consumption, and reduced process difficulty and processing cost.

[0080] Optionally, the temperature of the pre-sintering area is 700° C. to 950° C., including any point value within the temperature range, such as 700° C., 800° C. or 950° C. This temperature range can ensure that the metal paste can open the functional film during pre-sintering and reduce the impact of high temperature on the solar cell.

[0081] Optionally, the temperature of the cooling area is 100° C. to 350° C., including any point value within the temperature range, such as 100° C., 200° C. or 350° C. This temperature range can effectively reduce the laser power and the influence of high temperature on the solar cell. The metal electrode is annealed and cooled within this temperature range, which can also effectively reduce thermal stress.

[0082] Second, see Figure 1 The embodiment of the present application discloses a production device 100 for implementing the production method of solar cells as described in the first aspect.

[0083] The production equipment 100 includes a heating device 110 , an electrical connection 120 and a laser 130 .

[0084] A heating cavity 111 is defined in the heating device 110. The heating cavity 111 is configured to control the temperature of the solar cell 200. Optionally, the heating method of the heating device 110 may be resistance wire heating, infrared light heating or hot air heating.

[0085] The electrical connector 120 is disposed in the heating chamber 111, and is configured to electrically connect the solar cell 200 to apply a bias voltage to the solar cell 200. For example, the electrical connector 120 is an electrode probe, and the number of the electrode probes is preferably plural.

[0086] The laser 130 is disposed on the heating device 110 , and the laser 130 is configured to perform laser induced sintering on the solar cells 200 in the heating cavity 111 .

[0087] Furthermore, the heating chamber 111 includes a pre-sintering area 1111 and a cooling area 1112, and the laser 130 is disposed on the cooling area 1112. The pre-sintering area 1111 and the cooling area 1112 each include a plurality of temperature zones whose temperatures can be adjusted. The temperature of each temperature zone is monitored by a temperature sensor 150.

[0088] The pre-sintering region 1111 is configured to pre-sinter the solar cell 200 printed with the metal paste, and the cooling region 1112 is configured to cool and anneal the solar cell 200 .

[0089] Preferably, the production equipment 100 further includes a conveyor belt 140, which is disposed in the heating chamber 111, and is configured to convey the solar cells 200 sequentially through the pre-sintering area 1111 and the cooling area 1112, and the conveying direction of the conveyor belt 140 is the X direction shown in the figure. Optionally, the temperature of the cooling area 1112 decreases along the X direction, and the temperature of the pre-sintering area 1111 increases along the X direction.

[0090] The solar cell 200 is transported on the conveyor belt 140, passing through the pre-sintering area 1111 and the cooling area 1112 in sequence to complete pre-sintering, temperature control, laser induced sintering and cooling annealing in sequence, realizing assembly line processing with higher processing efficiency, less energy consumption, and reduced process difficulty and processing cost.

[0091] Furthermore, the electrical connector 120 can be disposed on the conveyor belt 140. After the solar cell 200 is positioned and placed on the conveyor belt 140, the solar cell 200 is positioned and docked with the electrical connector 120 on the conveyor belt 140 and the solar cell 200 and the electrical connector 120 remain in position during the conveyance process. It should be noted that when the solar cell 200 is provided with a metal electrode only on the backlight surface, such as a back contact solar cell, only one set of electrical connectors 120 is required. If metal electrodes are provided on both the light-receiving surface and the backlight surface of the solar cell 200, such as a passivated contact solar cell, two sets of electrical connectors 120 are required. Figure 1As shown, one group of electrical connectors 120 is arranged on the surface of the conveyor belt 140, and the conveyor belt 140 is a crawler conveyor belt; another group of electrical connectors 120 is fixed to the side of the conveyor belt 140 through a bracket and moves synchronously with the conveyor belt 140. This group of electrical connectors 120 can be driven to retract and retract by a high-temperature resistant motor or a spring.

[0092] Thirdly, see Figure 2 and Figure 3 The present application embodiment discloses a solar cell 200, which includes a silicon substrate 210, a doping layer 220 and a metal electrode 230, wherein the doping layer 220 is disposed on a light-receiving surface 211 and / or a backlight surface 212 of the silicon substrate 210. Figure 2 In the embodiment, the doping layer 220 is disposed on the backlight surface 212, that is, the back contact solar cell. Figure 3 In the embodiment, the doping layer 220 is arranged on the light-receiving surface 211 and the backlight surface 212, for example, a passivation contact solar cell, when used as a passivation contact solar cell, a dielectric layer 250 made of silicon oxide is arranged between at least one doping layer 220 and the silicon substrate 210. The metal electrode 230 is in ohmic contact with the doping layer 220, and the solar cell 200 is produced by the production method of the solar cell 200 as described in the first aspect, or the solar cell 200 is produced by the production equipment 100 as described in the second aspect.

[0093] Optionally, the metal electrode 230 is a silver electrode, and the doped layer 220 may be a doped polysilicon layer or a doped amorphous silicon layer, or the doped layer 220 is directly formed on the silicon substrate 210 by element diffusion, such as boron diffusion or phosphorus diffusion.

[0094] It should be noted that the doping layer 220 may not be directly formed on the surface of the silicon substrate 210. For example, a dielectric layer may be formed between the doping layer 220 and the surface of the silicon substrate 210. On the other hand, the light-receiving surface 211 and / or the backlight surface 212 of the silicon substrate 210 are not limited to Figure 2 and Figure 3 Furthermore, the surface of the doped layer 220 facing away from the silicon substrate 210 may also be covered with a functional film 240, such as a passivation film and / or an anti-reflection film. When the functional film 240 is provided, the metal electrode 230 passes through the functional film 240 and makes ohmic contact with the doped layer 220.

[0095] In a fourth aspect, an embodiment of the present application discloses a photovoltaic module, comprising a plurality of solar cells connected in series and / or in parallel, at least one solar cell being the solar cell described in the third aspect.

[0096] The technical solution of the present invention will be described below in conjunction with embodiments.

[0097] Example 1

[0098] Reference Figure 1 This embodiment provides a production device 100, which includes a heating device 110, an electrical connector 120, a laser 130 and a conveyor belt 140.

[0099] A heating chamber 111 is defined in the heating device 110 . The heating chamber 111 is configured to control the temperature of the solar cell 200 .

[0100] The electrical connector 120 is disposed in the heating chamber 111 , and is configured to electrically connect the solar cell 200 to apply a bias voltage to the solar cell 200 .

[0101] The laser 130 is disposed on the heating device 110 , and the laser 130 is configured to perform laser induced sintering on the solar cells 200 in the heating cavity 111 .

[0102] The conveyor belt 140 is disposed in the heating chamber 111 , and the conveyor belt 140 is configured to convey the solar cells 200 to sequentially pass through the pre-sintering area 1111 and the cooling area 1112 .

[0103] Example 2

[0104] Reference Figure 4 This embodiment provides a method for producing solar cells, using the production equipment of embodiment 1. The heating chamber 111 of the production equipment has eight temperature zones. In this embodiment, the temperatures of temperature zones 1 to 8 are set as follows: temperature zone 1, 85°C; temperature zone 2, 400°C; temperature zone 3, 850°C; temperature zone 4, 600°C; temperature zone 5, 450°C; temperature zone 6, 350°C; temperature zone 7, 200°C; temperature zone 8, 150°C. Among them, temperature zones 1 to 5 are pre-sintering areas 1111. Temperature zones 6 to 8 are cooling areas 1112.

[0105] The production method of the solar cell comprises the following steps:

[0106] S1. Pre-sintering the solar cell printed with metal paste, wherein the metal paste is pre-sintered to form a metal electrode.

[0107] S2. Control the solar cell to be at a target temperature. The target temperature is higher than the normal temperature and lower than the rheological temperature of the metal slurry. In this embodiment, the normal temperature is 25°C and the target temperature is 350°C.

[0108] S3. Laser induced sintering is performed on the metal electrode on the solar cell at the target temperature. The sintering point temperature of the laser and the metal electrode in the laser induced sintering is 1550°C. The spot diameter of the laser is 500μm. The power of the laser is 155W. The power density of the laser in the laser induced sintering is 3×10 9 W / m 2 The bias voltage applied to the solar cell is 15V.

[0109] S4, cooling and annealing the solar cell. The cooling and annealing of the solar cell is performed in an environment higher than room temperature and lower than the rheological temperature of the metal slurry. The cooling and annealing of the solar cell has a temperature drop rate lower than 50°C / s.

[0110] Steps S1 to S4 are performed sequentially in the same heating environment, which is the heating chamber of Example 1, that is, the heating environment has a connected pre-sintering area and a cooling area.

[0111] The production method of the solar cell also includes the following steps:

[0112] The conveyor belt of Example 1 is used to convey the solar cells through the pre-sintering area and the cooling area in sequence. The temperature of the cooling area decreases along the conveying direction of the solar cells. The temperature of the pre-sintering area is 700°C to 950°C, and the temperature of the cooling area is 100°C to 350°C. Step S1 is performed in the pre-sintering area, and steps S2, S3 and S4 are performed in the cooling area.

[0113] Example 3

[0114] The difference between this embodiment and embodiment 2 is that: in step S4, the solar cell is cooled and annealed at room temperature. The temperature drop rate of the solar cell cooling and annealing exceeds 100° C. / s.

[0115] Comparative Example 1

[0116] The solar cell production method of this comparative example comprises the following steps:

[0117] Step 1: Use high temperature sintering equipment to pre-sinter the solar cells printed with metal paste.

[0118] Step 2: Use laser sintering equipment to perform laser induced sintering on the metal electrode of the solar cell at room temperature. The laser power is 200W and the power density of the laser in laser induced sintering is 1×10 10 W / m 2 .

[0119] Step 3: Cooling and annealing the solar cell at room temperature.

[0120] The solar cells in Examples 2 and 3 and Comparative Example 1 after cooling and annealing were subjected to electrical performance tests, where the solar cells at this time were solar cells at the cell end. The solar cells were subjected to electrical performance tests again after being serially welded, where specifically, serial welding refers to welding multiple solar cells in series using a welding ribbon, and the solar cells after serial welding are solar cells at the module end. The test results are shown in Table 1.

[0121] Table 1: Solar cell electrical performance test results

[0122]

[0123]

[0124] As can be seen from Table 1, in Example 2, since the temperature of the solar cell is controlled to be higher than room temperature and lower than the rheological temperature of the metal slurry before laser induced sintering, laser induced sintering can be performed using a lower power laser to reduce the temperature difference between the laser processing area and the rest of the solar cell, thereby reducing the lattice structure damage caused by excessive temperature difference. In addition, the heat affected area caused by the laser can be reduced. The solar cell after cooling annealing has good contact resistance, fill factor, open circuit voltage and conversion efficiency. In addition, in Example 2, the cooling rate of cooling annealing is controlled, the cooling rate of the laser processing area is slowed down, the size of the silver particles formed is larger, and the metal grid after laser sintering can also be synchronously annealed at low temperature to reduce thermal stress. The stability and heat resistance of the silver particles are good. After the solar cell is further serially welded, the gain generated by the solar cell at the cell end can still be maintained at the component end. The fill factor, short-circuit current density and conversion efficiency of Example 2 after serial welding are slightly reduced, which shows that the solar cell of Example 2 can still maintain gain at the component end.

[0125] Compared with Example 2, Comparative Example 1 performs laser sintering at room temperature, and a high-power laser is required to heat the sintering point to a specific temperature, which leads to uneven heating and stress concentration of the solar cell. Due to the increase in the heat-affected zone and the influence of residual thermal stress, the open circuit voltage of Comparative Example 1 decreases relative to Example 2, and the contact resistance increases, which ultimately leads to a decrease in conversion efficiency. And because Comparative Example 1 is annealed at room temperature, the growth time of the silver particles is short, resulting in a small size of the silver particles. The smaller the size of the formed silver particles, the worse its stability and heat resistance. After the solar cell is further series-welded, the gain generated by the solar cell at the cell end does not reflect a significant performance improvement at the component end. Since the silver particles have smaller grains and a lower melting point, the silver particles are more easily destroyed by the high temperature during series welding. Therefore, the contact resistance of the solar cell in Comparative Example 1 increases after series welding, and the open circuit voltage, fill factor and short-circuit current density decrease, which leads to a significant decrease in conversion efficiency.

[0126] Compared with Example 2, Example 3 is annealed at room temperature, and the growth time of silver particles is shorter, resulting in small silver particle size. The smaller the size of the formed silver particles, the worse their stability and heat resistance. After the solar cells are further soldered, the gain generated by the solar cells at the cell end does not reflect a significant performance improvement at the component end. Since the silver particles have smaller grains and lower melting points, the silver particles are more easily damaged by the high temperature during soldering. Therefore, the contact resistance increases significantly after soldering, and the fill factor and conversion efficiency both decrease significantly.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for producing a solar cell, characterized in that: The following steps are involved: Pre-sintering the solar cell printed with metal paste; wherein the metal paste forms a metal electrode after pre-sintering; Controlling the solar cell to be at a target temperature; wherein the target temperature is higher than normal temperature and lower than the rheological temperature of the metal slurry; The metal electrode on the solar cell at the target temperature is subjected to laser induced sintering.

2. The method for producing a solar cell according to claim 1, characterized in that: The target temperature is T and the unit is °C, the power of the laser in the laser induced sintering is P and the unit is W; wherein, P=-0.13T+a, and a=200-204.

3. The method for producing a solar cell according to claim 1 or 2, characterized in that: The target temperature is 100°C to 350°C; And / or, during the laser induced sintering, the sintering point temperature of the metal electrode is 1450° C. to 1650° C.; And / or, the spot diameter of the laser in the laser induced sintering is 65 μm to 500 μm; And / or, the power density of the laser in the laser induced sintering is 1×10 9 W / m 2 ~1×10 10 W / m 2 ; And / or, the bias voltage applied to the solar cell during the laser induced sintering is 5V to 20V.

4. The method for producing a solar cell according to claim 1 or 2, characterized in that: After the step of laser-induced sintering the metal electrode on the solar cell at the target temperature, the method for producing the solar cell further comprises the following steps: The solar cell is subjected to cooling annealing; wherein the cooling annealing of the solar cell is performed in an environment higher than room temperature and lower than the rheological temperature of the metal slurry.

5. The method for producing a solar cell according to claim 4, characterized in that: The cooling rate of the solar cell cooling annealing is 20°C / s to 100°C / s.

6. The method for producing a solar cell according to claim 4, characterized in that: The steps of pre-sintering the solar cell printed with metal paste, controlling the solar cell to be at a target temperature, laser-induced sintering of the metal electrode on the solar cell at the target temperature, and cooling annealing the solar cell are performed sequentially in the same heating environment.

7. The method for producing a solar cell according to claim 6, characterized in that: The heating environment has a connected pre-sintering area and a cooling area; The production method of the solar cell also includes the following steps: Conveying the solar cell through the pre-sintering area and the cooling area in sequence; wherein the temperature of the cooling area decreases along the conveying direction of the solar cell; The step of pre-sintering the solar cell printed with metal paste is performed in the pre-sintering area; The steps of controlling the solar cell to be at a target temperature, performing laser induced sintering on the metal electrode on the solar cell at the target temperature, and performing cooling annealing on the solar cell are performed in the cooling area.

8. The method for producing a solar cell according to claim 7, characterized in that: The temperature of the pre-sintering area is 700°C to 950°C; And / or, the temperature of the cooling zone is 100°C to 350°C.

9. A production equipment, characterized in that: For implementing the method for producing a solar cell according to any one of claims 1 to 8, the production equipment comprises: A heating device, wherein a heating cavity is defined in the heating device; the heating cavity is configured to control the temperature of the solar cell; an electrical connector, the electrical connector being disposed in the heating chamber and configured to electrically connect the solar cell to apply a bias voltage to the solar cell; and A laser is disposed on the heating device and is configured to perform laser induced sintering on the solar cells in the heating cavity.

10. The production equipment according to claim 9, characterized in that The heating cavity comprises a pre-sintering area and a cooling area, and the laser is arranged on the cooling area; The pre-sintering area is configured to pre-sinter the solar cell printed with metal paste; The cooling region is configured to perform cooling annealing on the solar cell.

11. The production equipment according to claim 10, characterized in that The production equipment also includes: A conveyor belt is disposed in the heating chamber, and is configured to convey the solar cells to pass through the pre-sintering area and the cooling area in sequence.

12. A solar cell, characterized in that: The solar cell includes a silicon substrate, a doped layer and a metal electrode, wherein the doped layer is arranged on the light-receiving surface and / or the backlight surface of the silicon substrate, and the metal electrode is in ohmic contact with the doped layer. The solar cell is produced by the solar cell production method described in any one of claims 1 to 8, or the solar cell is produced by the production equipment described in any one of claims 9 to 11.

13. A photovoltaic module, characterized in that: The invention comprises a plurality of solar cells connected in series and / or in parallel, and at least one of the solar cells is the solar cell according to claim 12.

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