Battery string and method of manufacturing the same, photovoltaic module

Abstract

This application discloses a battery string and its fabrication method, as well as a photovoltaic module. The fabrication method of the battery string includes the following steps: providing a plurality of battery cells, electrical connectors, and a protective layer; wherein adjacent battery cells are partially overlapped, each battery cell includes a current collecting layer, the electrical connectors are connected to the current collecting layers of the battery cells, and the electrical connectors have a designated area to be broken by a laser; the protective layer is disposed between the battery cells and the electrical connectors, and the protective layer corresponds to the designated area; the laser is applied to the designated area to break the electrical connector; wherein the protective layer includes a film layer with an absorbance greater than or equal to 50%, and / or a film layer with a reflectance greater than or equal to 65%; when the laser is an infrared laser, the protective layer includes a film layer with an absorbance greater than or equal to 50% and a film layer with a reflectance greater than or equal to 65%. This application can effectively enhance the protection effect of the battery cells when the laser breaks the electrical connectors, reducing the possibility of battery cell damage or breakage.

Description

Technical Field

[0001] This application relates to the technical field of solar cells, and more particularly to a cell string and its fabrication method, and a photovoltaic module. Background Technology

[0002] For back-contact solar cells with multiple grid lines, electrical connectors are typically welded to the back of the cells. After welding, a laser is used to break the connectors, enabling series-parallel connection of the cells. However, with the development of cascading technology, cells are now arranged with negative spacing, meaning the edges of adjacent cells overlap. During the laser breaking process, the high energy of the laser can easily penetrate the connectors and directly affect the cells below them, causing damage or even severance to the cells beneath the connectors. This severely impacts the module's yield and reliability. Summary of the Invention

[0003] To enhance the protection of solar cells when lasers break electrical connectors and effectively reduce the occurrence of damage or breakage of solar cells, this application provides a solar cell string, its preparation method, and a photovoltaic module.

[0004] In a first aspect, embodiments of this application provide a method for preparing a battery string.

[0005] A method for fabricating a battery string includes the following steps: providing a plurality of battery cells, electrical connectors, and a protective layer; wherein adjacent battery cells partially overlap, each battery cell includes a current collecting layer, the electrical connectors are connected to the current collecting layers of the plurality of battery cells, and the electrical connectors have a designated area to be laser-broken, the protective layer is disposed between the battery cells and the electrical connectors, and the protective layer corresponds to the designated area. The laser is applied to the designated area to break the electrical connection. The protective layer comprises a film layer with an absorbance of 50% or more and / or a film layer with a reflectance of 65% or more; when the laser is an infrared laser, the protective layer comprises a film layer with an absorbance of 50% or more and a film layer with a reflectance of 65% or more.

[0006] As an optional implementation, in the embodiments of this application, the protective layer includes a single-layer structure or a stacked structure; When the protective layer is a single-layer structure, the single-layer structure is a light-absorbing and heat-absorbing adhesive layer or a reflective adhesive layer, wherein the light absorption rate of the light-absorbing and heat-absorbing adhesive layer is greater than or equal to 50%, and / or the reflectivity of the reflective adhesive layer is greater than or equal to 65%. When the protective layer is the laminated structure, the laminated structure includes a light-absorbing and heat-absorbing adhesive layer and a reflective adhesive layer, wherein the light absorption rate of the light-absorbing and heat-absorbing adhesive layer is greater than 50%, and the reflectivity of the reflective adhesive layer is greater than 65%.

[0007] As an optional implementation, in the embodiments of this application, when the laser is a green laser, the protective layer includes the single-layer structure or the stacked structure.

[0008] As an optional implementation, in the embodiments of this application, when the protective layer is the stacked structure, the light-absorbing and heat-absorbing adhesive layer is close to the battery cell, and the reflective adhesive layer is located on the side of the light-absorbing and heat-absorbing adhesive layer away from the battery cell.

[0009] As an optional implementation, in the embodiments of this application, the material of the protective layer includes a resin adhesive, which includes at least one of epoxy resin adhesive, modified epoxy resin adhesive, acrylate adhesive, modified acrylic resin adhesive, silicone resin adhesive, polyimide resin adhesive, and phenolic resin adhesive. And / or, The curing method of the protective layer includes at least one of thermosetting, UV curing, or a combination of thermosetting and UV curing.

[0010] As an optional implementation, in the embodiments of this application, when the protective layer includes a light-absorbing and heat-absorbing adhesive layer, the light-absorbing and heat-absorbing adhesive layer includes light-absorbing filler and / or heat-absorbing filler, wherein: The light-absorbing filler includes at least one of carbon black, graphene, carbon nanotubes, phthalocyanine, phosphocyanine, Fe3O4, and copper sulfide. The heat-absorbing filler includes at least one of aerogel, mica powder, vermiculite, and calcium silicate.

[0011] As an optional implementation, in the embodiments of this application, the laser is a green laser, and the light-absorbing and heat-absorbing adhesive layer further includes polyene organic pigments.

[0012] As an optional implementation, in the embodiments of this application, when the protective layer includes a reflective adhesive layer, the reflective adhesive layer includes a reflective filler, and the reflective filler includes at least one of titanium dioxide, core-SiO2 shell-Al2O3 composite pigment, rare earth oxide, hollow glass microspheres, ceramic microspheres, barium sulfate, and alumina. And / or, When the laser is an infrared laser, the wavelength of the infrared laser is 1064 nm; when the laser is a green laser, the wavelength of the green laser is 532 nm. And / or, The laser includes continuous laser or pulsed laser; And / or, The angle between the incident direction of the laser and the electrical connector is 60°~120°; And / or, The protective layer is located near the overlapping area of ​​the adjacent battery cells; And / or, The steps of providing the battery cell include: firstly, setting the protective layer on the current collecting layer of the battery cell, and then welding the electrical connector on the current collecting layer, wherein the welding position of the electrical connector is staggered from the position where the protective layer is set; And / or, The solar cell includes a back-contact solar cell, and the back surface of the back-contact solar cell has a first current-collecting sublayer and a second current-collecting sublayer. The first current-collecting sublayer and the second current-collecting sublayer have opposite electrical properties, and the first current-collecting sublayer is close to the second current-collecting sublayer. The electrical connectors are respectively disposed on the first busbar layer and the second busbar layer; The protective layer is an insulating layer, and the width of the protective layer is greater than or equal to the width of the electrical connector; in: The first current collection sublayer and the second current collection sublayer are arranged in an interdigitated structure. The first current collection sublayer includes a first bus gate layer and a first collector gate layer connected to the first bus gate layer. The second current collection sublayer includes a second bus gate layer and a second collector gate layer connected to the second bus gate layer. The first collector gate layer is close to the second bus gate layer, and the second collector gate layer is close to the first bus gate layer. or, The first current collection sub-layer may be only a first bus gate layer, and the second current collection sub-layer may be only a second bus gate layer. The first bus gate layer and the second bus gate layer are arranged close to each other.

[0013] Secondly, embodiments of this application provide a battery string.

[0014] A battery string, prepared by the method of the first aspect, comprises: A plurality of the aforementioned battery cells, wherein adjacent battery cells are arranged in a partially overlapping manner; The electrical connector connects to a plurality of the battery cells, and the electrical connector has a designated area to be broken by the laser. The protective layer is disposed between the battery cell and the electrical connector, and the position of the protective layer corresponds to the designated area. The protective layer includes a film layer with an absorbance of ≥50% and / or a film layer with a reflectance of ≥65%.

[0015] Thirdly, embodiments of this application provide a photovoltaic module.

[0016] A photovoltaic module comprising a battery string as described in the second aspect.

[0017] Compared with the prior art, the beneficial effects of this application are as follows: This application provides a method for fabricating a battery string. By setting a protective layer with specific absorbance and / or specific reflectance between the battery cells and electrical connectors, it effectively solves the problem that the battery cells are easily damaged or even cut when lasers break the electrical connectors when they are partially overlapped, thereby improving the reliability and production yield of the module. Specifically, the protective layer of this application is set corresponding to the designated area on the electrical connector to be broken by the laser. This allows the protective layer to effectively absorb laser energy using a film layer with an absorbance greater than or equal to 50%, or to reflect laser energy using a film layer with a reflectance greater than or equal to 65%, thereby significantly reducing the impact of laser energy on the battery cells. Especially for infrared lasers that require higher energy to break the electrical connectors, the protective layer must simultaneously meet the above-mentioned specific absorbance and specific reflectance requirements to achieve efficient reflection and full absorption of laser energy, thereby providing more effective protection for the battery cells and significantly reducing the risk of damage or cut to the battery cells. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a structural schematic diagram disclosed in the embodiments of this application, illustrating a first positional relationship between the battery cell, electrical connector, and protective layer; Figure 2 This is a structural schematic diagram disclosed in the embodiments of this application, illustrating a second positional relationship between the battery cell, electrical connector, and protective layer; Figure 3 This is a schematic diagram of the structure of the first type of battery string formed after the laser welding ribbon is broken, as disclosed in the embodiments of this application. Figure 4 This is a schematic diagram of the structure of the second type of battery string formed after the laser welding ribbon is broken, as disclosed in the embodiments of this application. Figure 5 This is a schematic diagram of the structure of the first protective layer structure disposed on the battery cell, as disclosed in the embodiments of this application. Figure 6 This is a schematic diagram illustrating a second protective layer structure disposed on a battery cell, as disclosed in the embodiments of this application. Figure 7 This is a schematic diagram illustrating a third protective layer structure disposed on a battery cell, as disclosed in the embodiments of this application. Figure 8 This is a schematic diagram of the structure of the first type of electrical connector and protective layer disclosed in this application disposed on the back contact solar cell; Figure 9 This is a schematic diagram of the structure of the second type of electrical connector and protective layer disclosed in the embodiments of this application disposed on the back contact solar cell.

[0020] Icons: 1. Battery cell; 11. Current collection layer; 111. First current collection sub-layer; 1111. First busbar layer; 1112. First current collection sub-layer; 112. Second current collection sub-layer; 1121. Second busbar layer; 1122. Second current collection layer; 2. Electrical connector; 21. Designated area; 3. Protective layer; 31. Light-absorbing and heat-absorbing adhesive layer; 32. Reflective adhesive layer. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The technical solution of this application will be further described below with reference to the embodiments and accompanying drawings.

[0023] In a first aspect, embodiments of this application provide a method for preparing a battery string.

[0024] A method for preparing a battery string, referring to Figures 1 to 4 This includes the following steps: Provide such as Figure 1 or Figure 2 The diagram shows several battery cells 1, electrical connectors 2, and a protective layer 3; wherein adjacent battery cells 1 partially overlap, each battery cell 1 includes a current collecting layer 11, the electrical connectors 2 are connected to the current collecting layers 11 of the battery cells 1, and the electrical connectors 2 have a designated area 21 to be laser-broken (i.e., corresponding to...). Figure 1The portion of the electrical connector 2 enclosed by the dashed box in the middle), the protective layer 3 is disposed between the battery cell 1 and the electrical connector 2, and the position of the protective layer 3 corresponds to the designated area 21; The laser is applied to the designated area 21 to break the electrical connector 2; after the electrical connector 2 is broken, the structural diagram of the combination of the battery cell 1 and the electrical connector 2 can be referred to Figure 3 or Figure 4 Looking at them from left to right, Figure 3 The diagram illustrates how the laser severed the electrical connector 2 located on the left-hand battery cell 1. Figure 4 The diagram illustrates how a laser can sever electrical connector 2 located on the right-side battery cell 1.

[0025] The protective layer 3 includes a film layer with an absorbance of 50% or more and / or a film layer with a reflectance of 65% or more; when the laser is an infrared laser, the protective layer 3 includes a film layer with an absorbance of 50% or more and a film layer with a reflectance of 65% or more.

[0026] In this application, adjacent solar cells 1 are arranged in a partially overlapping manner, allowing more solar cells 1 to be arranged within a unit module area, thereby increasing the power density of the module. Furthermore, this application provides a protective layer 3 between the solar cells 1 and the electrical connector 2, with the protective layer 3 corresponding to a designated area 21 on the electrical connector 2. This protective layer 3 effectively blocks laser energy, reducing damage to the solar cells 1 during laser interruption of the electrical connector 2 and lowering the risk of the solar cells 1 being cut during laser processing, thereby improving the reliability and yield of the solar cells 1.

[0027] Specifically, the protective layer 3 includes a film layer with an absorbance of ≥50%, which can effectively absorb the laser energy when the electrical connector 2 is interrupted, preventing the laser energy from being directly transmitted to the battery cell 1 and causing damage or breakage. Alternatively, the protective layer 3 includes a film layer with a reflectivity of ≥65%, which can reflect the laser energy that interrupts the electrical connector 2, reducing the energy transmitted to the battery cell 1. When the protective layer 3 simultaneously satisfies both an absorbance of ≥50% and a reflectivity of ≥65%, it can reflect the laser energy that interrupts the electrical connector 2 and absorb the remaining energy, thereby better protecting the battery cell 1.

[0028] When the light absorption rate of the protective layer 3 is less than 50% and / or the reflectivity is less than 65%, the protective layer 3 has insufficient laser energy processing capability, which will still cause the battery cell 1 to be damaged or cut off.

[0029] Specifically, when the laser is an infrared laser, the electrical connector 2 has a high reflectivity and low absorption rate due to its high infrared laser reflection. To achieve the desired interruption effect, higher laser energy is typically required when using an infrared laser to break the electrical connector 2. Correspondingly, breaking the electrical connector 2 with a laser also means that more laser energy will act on the battery cell 1. The side of the current collection layer 11 closest to the electrical connector 2 needs to reflect and absorb laser energy more effectively. This requires the protective layer 3 to meet both an absorption rate greater than or equal to 50% and a reflectivity greater than or equal to 65% to provide optimal protection for the battery cell 1.

[0030] It should be noted that when the protective layer 3 includes a film layer with an absorbance greater than or equal to 50% and a film layer with a reflectance greater than or equal to 65%, it can be a single layer that meets both the requirements of absorbance greater than or equal to 50% and reflectance greater than or equal to 65%, or it can be two layers that meet the requirements of absorbance greater than or equal to 50% and reflectance greater than or equal to 65% respectively.

[0031] Reflectivity (R) refers to the percentage of laser energy reflected by the protective layer 3 at a specific wavelength to the total incident laser energy. Reflectivity reflects the reflectivity of the protective layer 3 in this application to reflect laser energy and can be measured using a UV-Vis-NIR spectrophotometer. Specifically, during the reflectivity test, the prepared protective layer 3 sample is placed in the integrating sphere sample window of the UV-Vis-NIR spectrophotometer, using a standard white plate as a reference. The incident light is incident perpendicularly or nearly perpendicularly, and the integrating sphere collects reflected light from all directions. Furthermore, the test wavelength needs to be selected according to the laser type: for green lasers, the test wavelength is set to 532 nm ± 10 nm; for infrared lasers, the test wavelength is set to 1064 nm ± 10 nm.

[0032] Absorbance (A) refers to the percentage of laser energy absorbed by the protective layer 3 material at a specific wavelength relative to the total incident laser energy. Absorbance reflects the absorption capacity of the protective layer 3 for laser energy. Absorbance can also be measured using a UV-Vis-NIR spectrophotometer. Specifically, during absorbance testing, the reflectance and transmittance of the protective layer 3 are first tested. The reflectance is tested according to the aforementioned reflectance testing method. Transmittance is calculated by placing the sample in the optical path, measuring the light energy transmitted through the sample, and then calculating the transmittance (T). If the sample is designed to be opaque or its thickness is sufficient to block laser transmission, the transmittance is considered 0. Finally, the absorbance (A) is calculated using the formula: A = 1. R T. When transmittance T=0, A=1 R.

[0033] The absorbance of this application is greater than or equal to 50%, meaning that at the corresponding laser wavelength, the percentage of laser energy absorbed by the protective layer 3 is not less than 50% of the total incident laser energy. This indicates that the protective layer 3 can convert at least half of the incident laser energy into heat energy or other forms of energy and retain it within the film layer, reducing the laser energy that penetrates to the solar cell 1. The reflectance of this application is greater than or equal to 65%, meaning that at the corresponding laser wavelength, the percentage of laser energy reflected by the protective layer 3 is not less than 65% of the total incident laser energy. This indicates that the film layer can reflect most of the incident laser energy, reducing the impact of the incident laser energy on the solar cell 1. For example, the absorbance of the protective layer is 50%, 60%, 70%, 80%, 90%, 95%, 99%, etc.; the reflectance of the protective layer is 65%, 75%, 85%, 95%, 99%, etc.

[0034] Furthermore, the electrical connector 2 can be a solder strip. The solder strip can be connected to the current collection layer 11 of the battery cell 1 by soldering, thereby achieving better electrical connection function.

[0035] Reference Figures 5 to 7 In some embodiments, the protective layer 3 includes a single-layer structure or a stacked structure; Reference Figure 3 and Figure 4 When the protective layer 3 is a single-layer structure, the single-layer structure is as follows: Figure 5 The light-absorbing and heat-absorbing adhesive layer 31 shown or as shown Figure 6 The reflective adhesive layer 32 shown has an absorptivity of 50% or greater than or equal to that of the light-absorbing and heat-absorbing adhesive layer 31, and / or a reflectivity of 65% or greater than or equal to that of the reflective adhesive layer 32. Reference Figure 7 When the protective layer 3 is a laminated structure, the laminated structure includes a light-absorbing and heat-absorbing adhesive layer 31 and a reflective adhesive layer 32. The light absorption rate of the light-absorbing and heat-absorbing adhesive layer 31 is greater than 50%, and the reflectivity of the reflective adhesive layer 32 is greater than 65%.

[0036] When the protective layer 3 is a single-layer structure, it is suitable for processing scenarios with low laser energy (such as using green lasers) or low protection requirements. When the protective layer 3 is a multi-layer structure, the light-absorbing and heat-absorbing adhesive layer 31 and the reflective adhesive layer 32 can work together to achieve a better protective effect, which is suitable for processing scenarios with high laser energy (such as using infrared lasers) or high protection requirements.

[0037] In some embodiments, when the laser is a green laser, the protective layer 3 includes a single-layer structure or a stacked structure.

[0038] Because the electrical connector 2 has a low reflectivity to green light and a better absorption effect, green laser can effectively break the electrical connector 2 at a lower power compared to infrared laser. This means that the laser energy acting on the solar cell 1 is relatively low. Therefore, using a single-layer structure that meets either an absorbance of 50% or higher or a reflectance of 65% or higher as the protective layer 3 is sufficient to meet the protection requirements. To further improve the protection level of the solar cell 1, a single-layer structure that simultaneously meets either an absorbance of 50% or higher or a reflectance of 65% or higher can also be used, or a stacked structure formed by combining a film layer that meets an absorbance of 50% or higher and a film layer that meets a reflectance of 65% or higher can be used.

[0039] Reference Figure 7 In some embodiments, when the protective layer 3 is a stacked structure, the light-absorbing and heat-absorbing adhesive layer 31 is close to the battery cell 1, and the reflective adhesive layer 32 is located on the side of the light-absorbing and heat-absorbing adhesive layer 31 away from the battery cell 1. By placing the reflective adhesive layer 32 on the light-absorbing and heat-absorbing adhesive layer 31, the incident laser energy can be efficiently reflected first, thereby reducing the laser energy entering the interior of the protective layer 3. Subsequently, the light-absorbing and heat-absorbing adhesive layer 31 absorbs the energy that penetrates the reflective adhesive layer 32 and blocks the heat transfer to the battery cell 1. This allows the functions of the reflective adhesive layer 32 and the light-absorbing and heat-absorbing adhesive layer 31 to work together better. Compared with a single-layer structure or a reverse stacked structure (heat absorption followed by reflection), this can more effectively reduce the heat conduction of laser energy to the battery cell 1 and provide a better heat insulation and protection effect.

[0040] The protective layer 3 of this application can be selected from a variety of resin adhesives. In some embodiments, the material of the protective layer 3 includes a resin adhesive, which includes at least one of epoxy resin adhesive, modified epoxy resin adhesive, acrylate adhesive, modified acrylic resin adhesive, silicone resin adhesive, polyimide resin adhesive, and phenolic resin adhesive. Specifically, different types of resin adhesives can be selected according to different processing environments and weather resistance requirements.

[0041] It should be noted that the resin adhesive is a common commercially available product, and it is sufficient as long as the light absorption or reflectance produced by the resin adhesive meets the requirements of the protective layer 3 of this application.

[0042] Protective layer 3 is obtained by curing the aforementioned resin adhesive. In some embodiments, the curing method of protective layer 3 includes at least one of thermosetting, UV curing, or a combination of thermosetting and UV curing. When protective layer 3 is a dark adhesive layer containing opaque fillers (such as carbon black), UV curing alone may result in incomplete internal curing due to the difficulty of light penetration. In this case, thermosetting or a combination of thermosetting and UV curing can be selected to effectively solve the problem of incomplete curing of dark adhesive layers, significantly improve the curing degree and mechanical strength of protective layer 3, and ensure the stability of protective layer 3 under laser impact.

[0043] In some embodiments, when the protective layer 3 includes a light-absorbing and heat-absorbing adhesive layer 31, the light-absorbing and heat-absorbing adhesive layer 31 includes light-absorbing fillers and / or heat-absorbing fillers, wherein: The light-absorbing filler includes at least one of carbon black, graphene, carbon nanotubes, phthalocyanine, phosphocyanine, Fe3O4, and copper sulfide; The heat-absorbing filler includes at least one of the following: aerogel, mica powder, vermiculite, and calcium silicate.

[0044] Fillers such as carbon black, graphene, carbon nanotubes, phthalocyanine, phosphine, Fe3O4, and copper sulfide exhibit high absorption rates for lasers of different wavelengths. This allows the light-absorbing and heat-absorbing adhesive layer 31, containing these fillers, to meet the requirement of an absorption rate greater than or equal to 50%. Simultaneously, materials such as aerogel, mica powder, vermiculite, and calcium silicate have low thermal conductivity and good high-temperature resistance. This enables the light-absorbing and heat-absorbing adhesive layer 31 to construct a thermal barrier while absorbing laser energy, effectively preventing heat transfer to the solar cell 1 and reducing the risk of damage to the solar cell 1 due to localized overheating.

[0045] In some embodiments, the laser is a green laser, and the light-absorbing and heat-absorbing adhesive layer 31 also includes polyene organic pigments.

[0046] The inclusion of polyene organic pigments can enhance the light absorption rate of the light-absorbing and heat-absorbing adhesive layer 31 for green light. Furthermore, the lower laser energy required for the green laser to break the electrical connector 2 maintains the molecular structure stability of the polyene organic pigments in the light-absorbing and heat-absorbing adhesive layer 31, preventing the polyene organic pigments from failing due to high-energy laser irradiation.

[0047] In some embodiments, when the protective layer 3 includes a reflective adhesive layer 32, the reflective adhesive layer 32 includes reflective fillers, which include at least one of titanium dioxide, core-SiO2-shell-Al2O3 composite pigments, rare earth oxides, hollow glass microspheres, ceramic microspheres, barium sulfate, and alumina. The use of highly reflective fillers such as titanium dioxide and hollow glass microspheres allows the reflective adhesive layer 32 containing these fillers to better meet the requirements of this application for efficient reflection of incident laser energy, thereby reducing the heat entering the reflective adhesive layer 32 and being transferred to the solar cell 1 at the source.

[0048] This application allows the use of different types of lasers to act on a designated area 21 on the electrical connector 2. Examples include infrared lasers and green lasers. In some embodiments, when the laser is an infrared laser, the wavelength is 1064 nm; when the laser is a green laser, the wavelength is 532 nm.

[0049] In some embodiments, the laser includes a continuous laser or a pulsed laser. Both continuous and pulsed lasers can generate sufficient laser energy to break the electrical connector 2. However, compared to the extremely high instantaneous power of pulsed lasers (up to tens of thousands of watts), continuous lasers have stable instantaneous power, causing less damage to the battery during the breaking of the electrical connector 2, and effectively reducing the risk of mechanical and thermal shock.

[0050] In some embodiments, the angle between the incident direction of the laser and the electrical connector 2 is 60° to 120°. This facilitates the maximum concentration of laser energy on the designated area 21 to be broken by the laser in the electrical connector 2, improving cutting efficiency; at the same time, it can reduce the ineffective scattering area of ​​the laser on the surface of the battery cell 1, shrink the heat-affected zone, and thus further reduce the potential thermal damage to the battery cell 1 material around the designated area 21 to be broken by the laser. Exemplarily, the angle between the incident direction of the laser and the electrical connector 2 is 60°, 80°, 100°, 120°, etc.

[0051] Reference Figure 1 In some embodiments, the protective layer 3 is located near the overlapping area of ​​adjacent battery cells 1.

[0052] The designated area 21 to be laser-broken in the electrical connector 2 is usually close to the overlapping area of ​​the adjacent battery cell 1. Therefore, the protective layer 3 is correspondingly set in the overlapping area of ​​the adjacent battery cell 1 to provide better protection for the battery cell 1.

[0053] And / or, The steps for providing the battery cell 1 include: first, setting a protective layer 3 on the current collecting layer 11 of the battery cell 1; then, welding electrical connectors 2 onto the current collecting layer 11, with the welding positions of the electrical connectors 2 staggered from the positions where the protective layer 3 is set. The protective layer 3 is pre-set on the current collecting layer 11 to facilitate the coating and curing operations of the protective layer 3; then, electrical connectors 2 are welded to the remaining positions on the current collecting layer 11, ensuring that the welding positions of the electrical connectors 2 are staggered from the positions where the protective layer 3 is set.

[0054] Reference Figure 8 or Figure 9In some embodiments, the solar cell 1 includes a back-contact solar cell, the back surface of which has a first current-collecting sublayer 111 and a second current-collecting sublayer 112, the first current-collecting sublayer 111 and the second current-collecting sublayer 112 having opposite electrical properties, and the first current-collecting sublayer 111 being close to the second current-collecting sublayer 112. The first current collection sublayer 111 includes a first bus gate layer 1111, and the second current collection sublayer 112 includes a second bus gate layer 1121; Electrical connectors 2 are respectively disposed on the first busbar layer 1111 and the second busbar layer 1121; The protective layer 3 is an insulating layer, and the width of the protective layer 3 is greater than or equal to the width of the electrical connector 2.

[0055] Specifically, such as Figure 8 As shown, the first current collection sublayer 111 and the second current collection sublayer 112 are arranged in an interdigitated structure. The first current collection sublayer 111 includes a first bus gate layer 1111 and a first collector gate layer 1112 connected to the first bus gate layer 1111. The second current collection sublayer 112 includes a second bus gate layer 1121 and a second collector gate layer 1122 connected to the second bus gate layer 1121. The first collector gate layer 1112 is close to the second bus gate layer 1121, and the second collector gate layer 1122 is close to the first bus gate layer 1111. or, like Figure 9 As shown, the first current collection sub-layer 111 may consist only of the first bus gate layer 1111, and the second current collection sub-layer 112 may consist only of the second bus gate layer 1121. In this case, the first bus gate layer 1111 and the second bus gate layer 1121, which are electrically opposite, are arranged close to each other. Electrical connectors 2 are respectively disposed on the first busbar layer 1111 and the second busbar layer 1121; The protective layer 3 is an insulating layer, and the width b of the protective layer 3 is greater than or equal to the width a of the electrical connector 2.

[0056] In a back-contact solar cell, the first current-collecting sublayer 111 and the second current-collecting sublayer 112, which have opposite polarities, are close to each other. To ensure the protective effect of the protective layer 3 on the solar cell 1 when the electrical connector 2 is broken by a laser, the width of the protective layer 3 is usually not less than the width of the electrical connector 2. This makes it easy for the wider protective layer 3 to contact the current-collecting sublayer with the opposite polarity to the busbar layer (such as the first busbar layer 1111) when it covers the busbar layer. For example, when the current-collecting layer 11 is as follows... Figure 8In the structure shown, the protective layer 3 covers the second bus gate layer 1121, which is close to the first collector gate layer 1112 with opposite polarity. The protective layer 3 used in this application is an insulating layer, which effectively prevents the protective layer 3 from simultaneously contacting both the second bus gate layer 1121 and the first collector gate layer 1112 close to it, thus preventing a short circuit caused by the opposite polarity of the bus gate layer and collector gate layer in the backlight surface.

[0057] When the current collection layer 11 is as follows Figure 9 In the structure shown, the protective layer 3 covers the second bus gate layer 1121, which is close to the first bus gate layer 1111 with opposite polarity. The protective layer 3 used in this application is an insulating layer, which effectively prevents the protective layer 3 from simultaneously contacting both the second bus gate layer 1121 and the first bus gate layer 1111 close to it, thus preventing a short circuit between the bus gate layers with opposite polarity in the backlight surface.

[0058] It should be noted that, as Figure 8 As shown, the width b of the protective layer 3 and the width a of the electrical connector 2 can be measured along the width direction of the electrical connector 2.

[0059] Furthermore, such as Figure 8 As shown in this application, the electrical connector 2 disposed on the first busbar layer 1111 extends along the length direction of the first busbar layer 1111, and the electrical connector 2 disposed on the second busbar layer 1121 extends along the length direction of the second busbar layer 1121. This facilitates the welding connection between the electrical connector 2 on the back surface side of the multi-busbar back-contact solar cell and the current collection layer 11.

[0060] Meanwhile, after laser treatment, the protective layer 3 can be retained on the battery cell 1 without the need for post-processing such as water washing, which can reduce the process steps and reduce the impact of removing the protective layer 3 on the battery reliability and yield.

[0061] Secondly, embodiments of this application provide a battery string.

[0062] A battery string, fabricated using the method described in the first aspect, comprises: Several solar cells 1 are arranged with partial overlap between adjacent solar cells 1; Electrical connector 2, which connects to a plurality of battery cells 1, and has a designated area 21 to be broken by laser; The protective layer 3 is disposed between the battery cell 1 and the electrical connector 2, and the position of the protective layer 3 corresponds to the designated area 21. The protective layer 3 includes a film layer with an absorbance greater than or equal to 50% and / or a film layer with a reflectance greater than or equal to 65%.

[0063] The battery string prepared by the method mentioned in the first aspect can effectively maintain the efficiency stability of the battery string and reduce the risk of damage or even severance to the battery cell 1 when the designated area 21 of the electrical connector 2 is broken by laser.

[0064] Thirdly, embodiments of this application provide a photovoltaic module.

[0065] A photovoltaic module comprising a string of cells as mentioned in the second aspect.

[0066] The technical solution of this application will be further described below with reference to more specific embodiments.

[0067] Example 1 This application provides a method for preparing a battery string, which includes the following steps: Provided are several solar cells, solder ribbons and a protective layer; wherein, the solar cells include a current collection layer, the solder ribbons are connected to the current collection layers of several solar cells, and the electrical connectors have a designated area to be laser-broken, and the protective layer is disposed between the solar cells and the solder ribbons, and the position of the protective layer corresponds to the designated area; Using a laser to target a designated area, the solder strip is broken; The protective layer is a single-layer light-absorbing and heat-absorbing adhesive layer. The relevant settings of the protective layer scheme, such as laser wavelength, resin type, curing method, filler and light absorption rate of the light-absorbing and heat-absorbing adhesive layer, are shown in Table 1.

[0068] Examples 2 to 8 This application provides a method for preparing a battery string, which differs from Example 1 in that the protective layer scheme is different, as shown in Table 1, while the rest is consistent with Example 1.

[0069] Example 9 This application provides a method for preparing a battery string, which differs from Example 1 in that the protective layer is a stacked light-absorbing and heat-absorbing adhesive layer and a reflective adhesive layer. The light-absorbing and heat-absorbing adhesive layer is close to the battery cell, and the reflective adhesive layer is located on the side of the light-absorbing and heat-absorbing adhesive layer away from the battery cell. The specific arrangement of the light-absorbing and heat-absorbing adhesive layer and the reflective adhesive layer is shown in Table 1. The rest is consistent with Example 1.

[0070] Example 10 This application provides a method for preparing a battery string, which differs from Example 1 in that a 1064 nm infrared laser is used instead of a 532 nm green laser. The protective layer consists of a stacked light-absorbing and heat-absorbing adhesive layer and a reflective adhesive layer. The light-absorbing and heat-absorbing adhesive layer is close to the solar cell, and the reflective adhesive layer is located on the side of the light-absorbing and heat-absorbing adhesive layer away from the solar cell. The specific arrangement of the light-absorbing and heat-absorbing adhesive layer and the reflective adhesive layer is shown in Table 1. The rest is consistent with Example 1.

[0071] Comparative Examples 1 to 3 This application provides a method for preparing a battery string, which differs from Example 1 in that the protective layer scheme is different, as shown in Table 1, while the rest is consistent with Example 1.

[0072] Comparative Examples 4 to 5 This application provides a method for preparing a battery string, which differs from Example 10 in that a 1064 nm infrared laser is used instead of a 532 nm green laser; and the protective layer scheme is different, as shown in Table 1. The rest is the same as Example 10.

[0073] experiment Battery cell damage test Visually inspect the surface of the solar cells for traces of laser cutting. If there are no traces of laser cutting on the surface of the solar cell, the damage is recorded as "no damage". If there are traces of laser cutting on the surface of the solar cell, the damage is recorded as "damaged". If the solar cell is directly cut by laser, the damage is recorded as "cut".

[0074] It should be noted that although the protective layer in this application is mostly a colored adhesive layer, which may obstruct the view to some extent, during testing, if the laser energy is sufficient to damage the solar cell, the protective layer on top of the solar cell will inevitably be damaged first. Therefore, when damage occurs, the protective layer will show obvious laser damage marks, and the damage to the solar cell can be directly observed even without removing the protective layer. In cases of severe damage, the solar cell is directly cut off. Therefore, when visually inspecting the surface of the solar cell for laser cutting marks, it is not necessary to forcibly remove the protective layer for effective judgment.

[0075] The laser wavelength, protective layer configuration, and cell damage conditions of the above embodiments and comparative examples are shown in Table 1.

[0076] Table 1

[0077] As can be seen from the test results of Examples 1 to 10 in Table 1, the protective layer of Examples 1 to 10 can effectively reflect the laser energy of the designated area where the solder ribbon is broken, thereby effectively protecting the solar cell and reducing the damage to the solar cell caused by the laser breaking the solder ribbon.

[0078] A comparison of the test results of Example 1 and Comparative Example 1 shows that the protective layer of Comparative Example 1 did not have functional filler, which made the light absorption and reflectivity of Comparative Example 1 not meet the requirements of this application. Consequently, the protective layer of Comparative Example 1 could not provide effective protection for the solar cell when the laser breaks the solder strip, resulting in the solar cell being broken.

[0079] A comparison of the test results of Example 1 and Comparative Example 2 shows that the light absorption rate of the light-absorbing and heat-absorbing adhesive layer used in Comparative Example 2 is less than 50%, resulting in poor protection of the solar cell when the solder ribbon is broken by the laser, leading to damage to the solar cell. Combined with the test results of Comparative Example 3, it can be seen that the reflectivity of the reflective adhesive layer used in Comparative Example 3 is less than 65%, also resulting in insufficient protection of the solar cell when the solder ribbon is broken by the laser, leading to damage to the solar cell.

[0080] A comparison of the test results of Example 10 and Comparative Example 4 shows that Comparative Example 4 used a single-layer light-absorbing and heat-absorbing adhesive layer as a protective layer. Although the light absorption rate of this adhesive layer was relatively high, its protective effect on the solar cell was still poor when the infrared laser broke the solder ribbon, resulting in the solar cell being cut. A comparison of the test results of Comparative Example 5 shows that Comparative Example 5 used a single-layer reflective adhesive layer as a protective layer. Although the reflectiveness of this adhesive layer was relatively high, its protective effect on the solar cell was also insufficient when the infrared laser broke the solder ribbon, resulting in the solar cell being cut.

[0081] The technical solutions disclosed in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a battery string, characterized in that, Includes the following steps: A plurality of battery cells, electrical connectors, and a protective layer are provided; wherein, adjacent battery cells partially overlap, each battery cell includes a current collecting layer, the electrical connectors are connected to the current collecting layers of the plurality of battery cells, and each electrical connector has a designated area to be broken by a laser, the protective layer is disposed between the battery cells and the electrical connectors, and the protective layer corresponds to the designated area. The laser is applied to the designated area to break the electrical connection. The protective layer comprises a film layer with an absorbance of 50% or more and / or a film layer with a reflectance of 65% or more; when the laser is an infrared laser, the protective layer comprises a film layer with an absorbance of 50% or more and a film layer with a reflectance of 65% or more.

2. The method for preparing a battery string according to claim 1, characterized in that, The protective layer may include a single-layer structure or a multi-layer structure; When the protective layer is a single-layer structure, the single-layer structure is a light-absorbing and heat-absorbing adhesive layer or a reflective adhesive layer, wherein the light absorption rate of the light-absorbing and heat-absorbing adhesive layer is greater than or equal to 50%, and / or the reflectivity of the reflective adhesive layer is greater than or equal to 65%. When the protective layer is the laminated structure, the laminated structure includes a light-absorbing and heat-absorbing adhesive layer and a reflective adhesive layer, wherein the light absorption rate of the light-absorbing and heat-absorbing adhesive layer is greater than 50%, and the reflectivity of the reflective adhesive layer is greater than 65%.

3. The method for preparing a battery string according to claim 2, characterized in that, When the laser is a green laser, the protective layer includes the single-layer structure or the stacked structure.

4. The method for preparing a battery string according to claim 2, characterized in that, When the protective layer is the stacked structure, the light-absorbing and heat-absorbing adhesive layer is close to the battery cell, and the reflective adhesive layer is located on the side of the light-absorbing and heat-absorbing adhesive layer away from the battery cell.

5. The method for preparing a battery string according to claim 1, characterized in that, The protective layer is made of a resin adhesive, which includes at least one of epoxy resin adhesive, modified epoxy resin adhesive, acrylate adhesive, modified acrylic resin adhesive, silicone resin adhesive, polyimide resin adhesive, and phenolic resin adhesive. And / or, The curing method of the protective layer includes at least one of thermosetting, UV curing, or a combination of thermosetting and UV curing.

6. The method for preparing a battery string according to claim 1, characterized in that, When the protective layer includes a light-absorbing and heat-absorbing adhesive layer, the light-absorbing and heat-absorbing adhesive layer includes light-absorbing fillers and / or heat-absorbing fillers, wherein: The light-absorbing filler includes at least one of carbon black, graphene, carbon nanotubes, phthalocyanine, phosphocyanine, Fe3O4, and copper sulfide. The heat-absorbing filler includes at least one of aerogel, mica powder, vermiculite, and calcium silicate.

7. The method for preparing a battery string according to claim 6, characterized in that, The laser is a green laser, and the light-absorbing and heat-absorbing adhesive layer also includes polyene organic pigments.

8. The method for preparing a battery string according to claim 1, characterized in that, When the protective layer includes a reflective adhesive layer, the reflective adhesive layer includes a reflective filler, and the reflective filler includes at least one of titanium dioxide, core-SiO2 shell-Al2O3 composite pigment, rare earth oxide, hollow glass microspheres, ceramic microspheres, barium sulfate, and alumina. And / or, When the laser is an infrared laser, the wavelength of the infrared laser is 1064 nm; when the laser is a green laser, the wavelength of the green laser is 532 nm. And / or, The laser includes continuous laser or pulsed laser; And / or, The angle between the incident direction of the laser and the electrical connector is 60°~120°; And / or, The protective layer is located near the overlapping area of ​​the adjacent battery cells; And / or, The steps of providing the battery cell include: firstly, setting the protective layer on the current collecting layer of the battery cell, and then welding the electrical connector on the current collecting layer, wherein the welding position of the electrical connector is staggered from the position where the protective layer is set; And / or, The solar cell includes a back-contact solar cell, and the back surface of the back-contact solar cell has a first current-collecting sublayer and a second current-collecting sublayer. The first current-collecting sublayer and the second current-collecting sublayer have opposite electrical properties, and the first current-collecting sublayer is close to the second current-collecting sublayer. The protective layer is an insulating layer, and the width of the protective layer is greater than or equal to the width of the electrical connector; in: The first current collection sublayer and the second current collection sublayer are arranged in an interdigitated structure. The first current collection sublayer includes a first bus gate layer and a first collector gate layer connected to the first bus gate layer. The second current collection sublayer includes a second bus gate layer and a second collector gate layer connected to the second bus gate layer. The electrical connectors are respectively disposed on the first bus gate layer and the second bus gate layer. The first collector gate layer is close to the second bus gate layer, and the second collector gate layer is close to the first bus gate layer. or, The first current collection sublayer may be only a first bus gate layer, and the second current collection sublayer may be only a second bus gate layer. The electrical connectors are respectively disposed on the first bus gate layer and the second bus gate layer, and the first bus gate layer and the second bus gate layer are disposed close to each other.

9. A battery string, characterized in that, The battery string is prepared by the method described in any one of claims 1-8, and the battery string comprises: A plurality of the aforementioned battery cells, wherein adjacent battery cells are arranged in a partially overlapping manner; The electrical connector connects to a plurality of the battery cells, and the electrical connector has a designated area to be broken by the laser. The protective layer is disposed between the battery cell and the electrical connector, and the position of the protective layer corresponds to the designated area. The protective layer includes a film layer with an absorbance of ≥50% and / or a film layer with a reflectance of ≥65%.

10. A photovoltaic module, characterized in that, Includes the battery string as described in claim 9.

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