Method for preparing back contact solar cell string, photovoltaic module and photovoltaic system

Abstract

The invention belongs to the field of solar cells, and provides a method for preparing a back contact solar cell string, a photovoltaic module and a photovoltaic system. The method comprises the following steps: providing a back contact solar cell, wherein the back contact solar cell is provided with main gate electrodes which are arranged at intervals; coating a conductive adhesive on the main gate electrode; and laying a welding strip on the main gate electrode along the extension direction of the main gate electrode, and carrying out first curing treatment, so that the welding strip is bonded with the main gate electrode through the cured conductive adhesive. According to the method provided by the embodiment of the invention, the back contact solar cell string with relatively good stability and relatively low contact resistance can be obtained.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a method for preparing a back-contact solar cell string, a photovoltaic module, and a photovoltaic system. Background Art

[0002] In the process of preparing photovoltaic cell modules, it is usually necessary to connect multiple cells with welding strips. However, for some types of photovoltaic cells, such as back-contact solar cells, the height of the positive and negative fine grid lines designed by the screen printing process is inconsistent with the height of the positive and negative main grid lines. Generally speaking, the main grid lines are slightly higher, usually with a height difference of 50μm to 150μm.

[0003] At present, the conventional method of interconnecting multiple solar cells with welding strips is to connect the strips with the positive and negative busbars by welding. However, due to the height difference between the thin busbars and the busbars, it is difficult for the strips to fully contact the busbars, which is not conducive to the welding between the strips and the busbars, resulting in welding failure or increased contact resistance, which in turn affects the power output of the solar cells.

[0004] Currently, the height difference between the main grid line and the thin grid line is solved by printing solder paste on the main grid line. However, since the main grid line is mainly composed of silver, the silver will dissolve in the solder paste during high temperature, which will cause the connected parts to fall off, resulting in welding failure and affecting the quality of photovoltaic modules.

[0005] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the invention

[0006] The embodiments of the present application provide a method for preparing a back-contact solar cell string, a photovoltaic module, and a photovoltaic system to solve technical problems such as welding failure between a welding ribbon and a grid electrode.

[0007] In a first aspect of an embodiment of the present application, a method for preparing a back-contact solar cell string is provided, the method comprising: A back-contact solar cell is provided, wherein the back-contact solar cell has main grid electrodes arranged at intervals; a conductive adhesive is applied on the main grid electrodes; a solder strip is laid on the main grid electrodes along the extension direction of the main grid electrodes, and a first curing treatment is performed to allow the solder strip to be bonded to the main grid electrodes through the cured conductive adhesive.

[0008] The method of the embodiment of the present application is simple to operate and can obtain a back-contact solar cell string with good stability and low contact resistance. When a photovoltaic module is assembled using the back-contact solar cell string, the stability of the photovoltaic module can be improved.

[0009] Conductive glue is used to combine the soldering strip and the main grid electrode at a relatively low temperature. The combination process is relatively tight and it is almost impossible for the grid wire metal (such as silver) in the main grid electrode to melt. This is because, on the one hand, the curing temperature of the conductive glue is relatively low (such as below 180°C), so that the soldering strip and the main grid electrode almost do not require a high-temperature welding process during the combination process, thereby reducing the problems of hidden cracks or even damage of the back contact solar cell caused by high temperature, and the high-temperature dissolution of the grid wire metal (such as silver) in the main grid electrode; on the other hand, the liquid conductive glue is in close contact with the solid main grid electrode, and the conductive glue has a high conductivity coefficient, which can reduce the cost of forming a battery string while also reducing the contact resistance between the back contact solar cells.

[0010] In addition, the conductive adhesive in the embodiment of the present application also has good mechanical properties and adaptability, and has good shear strength and adhesion after curing. When the back-contact solar cell string is used to prepare a photovoltaic module, a photovoltaic module with a stable combination of the welding strip and the main grid electrode can be obtained, thereby improving the power generation efficiency of the photovoltaic module.

[0011] According to an embodiment of the present application, the temperature of the first curing is 80-180°C.

[0012] According to an embodiment of the present application, the back-contact solar cell further comprises a fine grid electrode, which is vertically directed to the main grid electrode with the same polarity as the fine grid electrode, and an end of the fine grid electrode close to the main grid electrode with the opposite polarity is covered with insulating glue.

[0013] According to an embodiment of the present application, the insulating adhesive includes at least one of a thermosetting insulating adhesive and a UV curing insulating adhesive.

[0014] According to an embodiment of the present application, the covering method includes coating an insulating glue on a portion of the surface of the fine gate electrode and performing a second curing, wherein the second curing is performed under ultraviolet light irradiation, and the irradiation time is 1-6s.

[0015] According to an embodiment of the present application, coating the conductive paste on the main gate electrode includes: coating the conductive paste on a pad of the main gate electrode.

[0016] According to an embodiment of the present application, the conductive adhesive includes a resin mixture and a conductive filler.

[0017] According to an embodiment of the present application, the resin mixture includes at least one of a resin, a curing agent, a coupling agent, and a diluent.

[0018] According to an embodiment of the present application, the conductive filler includes at least one of copper, tungsten, gallium, nickel, silver and magnesium.

[0019] According to an embodiment of the present application, the resin includes at least one of bisphenol F epoxy resin, bisphenol A epoxy resin, aliphatic epoxy resin and acryl epoxy ester.

[0020] According to an embodiment of the present application, the curing agent includes at least one of ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, and diethylaminopropylamine.

[0021] According to an embodiment of the present application, the coupling agent includes at least one of alkenyltriethoxysilane, vinyltrimethoxysilane and 3-aminopropyltriethoxysilane.

[0022] According to an embodiment of the present application, the diluent includes at least one of ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, 1-4-cyclohexanedimethanol glycidyl ether and 1,4-butanediol glycidyl ether.

[0023] According to an embodiment of the present application, in the resin mixture, the mass ratio of the resin, the curing agent, the diluent and the coupling agent is 100:(10-30):(0.01-18):(0.01-3).

[0024] According to an embodiment of the present application, in the conductive adhesive, the mass ratio of the resin mixture to the conductive filler is 1:(1-9).

[0025] According to an embodiment of the present application, the height of the insulating glue is H 1 , the height of the conductive glue is H 2 , H 1 and H 2 The ratio between them satisfies 1≤H 2 / H 1 ≤1.5.

[0026] According to an embodiment of the present application, the time of the first curing treatment is 2-30 minutes.

[0027] According to a second aspect of the embodiments of the present application, a photovoltaic module is provided. The photovoltaic module includes a back-contact solar cell string. The back-contact solar cell string is prepared by the method described in the first aspect.

[0028] The photovoltaic module of the embodiment of the present application has good stability and low contact resistance, which can improve the power generation efficiency of the photovoltaic module. This is because, on the one hand, the welding strip and the main grid electrode are combined by low-temperature conductive adhesive, which can tightly combine the welding strip and the main grid to promote the welding strip to collect current; on the other hand, the conductive adhesive also has good mechanical properties and strong adaptability. In the process of forming the back-contact solar cell string, no high-temperature welding step is required, which can reduce the hidden cracks and even damage of the back-contact solar cell caused by high temperature.

[0029] The third aspect of the embodiments of the present application provides a photovoltaic system, including the photovoltaic module in any of the above embodiments. The photovoltaic system also has the advantages of the above photovoltaic modules, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments according to the present application and should not be regarded as limiting the scope of the present application.

[0031] Figure 1 is a schematic diagram of the structure of a back-contact solar cell in some embodiments; Figure 2 is a partial structural schematic diagram of a back-contact solar cell string in some embodiments; Figure 3 is an EL image of a cell of a back-contact solar cell string of Example 1; Figure 4 is a schematic diagram of the conductive adhesive and insulating adhesive structure of a back contact solar cell string in some embodiments; Figure 5 is a partial structural schematic diagram of a back-contact solar cell string in some other embodiments; Figure 6 is a schematic structural diagram of a back-contact solar cell in some embodiments; Description of reference numerals: 1: positive fine gate electrode; 2: positive main gate electrode; 3: first welding pad; 4: negative fine gate electrode; 5: negative main gate electrode; 6: second welding pad; 7: welding tape; 8: insulating glue; 9: conductive glue; 10: second electrode; 11: N-type silicon wafer; 12: phosphorus-doped layer; 13: boron-doped layer; 14: first anti-reflection layer; 15: passivation layer; 16: second anti-reflection layer; 17: first electrode. DETAILED DESCRIPTION

[0032] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the accompanying drawings, for clarity, the sizes of layers, regions, elements and their relative sizes may be exaggerated. Wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limitations on the present application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0033] It should be understood that when a layer is referred to as being "on, adjacent to, connected to, or coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other layer, or there may be intervening layers. Conversely, when a layer is referred to as being "directly on, directly adjacent to, directly connected to, or directly coupled to" another layer, there are no intervening layers. It should be understood that although the terms first, second, third, etc. may be used to describe various regions, layers, and / or portions, these regions, layers, and / or portions should not be limited by these terms. These terms are merely used to distinguish one region, layer, or portion from another region, layer, or portion. Therefore, without departing from the teachings of the present application, the regions, layers, or portions discussed below may be represented as regions, layers, or portions. When regions, layers, or portions are discussed, it does not mean that the present application necessarily has regions, layers, or portions.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broadly including quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0036] In a first aspect of the embodiments of the present application, a method for preparing a back-contact solar cell string is provided. The method comprises: (1) providing a back-contact solar cell having spaced main grid electrodes; (2) applying a conductive adhesive on the main grid electrodes; (3) laying a solder strip on the main grid electrodes along the extension direction of the main grid electrodes, and performing a first curing treatment so that the solder strip is bonded to the main grid electrodes through the cured conductive adhesive.

[0037] The method of the embodiment of the present application is simple to operate and can obtain a back-contact solar cell string with good stability and low contact resistance. When a photovoltaic module is assembled using the back-contact solar cell string, the stability of the photovoltaic module can be improved.

[0038] Conductive glue is used to combine the soldering strip and the main grid electrode at a relatively low temperature. The combination process is relatively tight and it is almost impossible for the grid wire metal (such as silver) in the main grid electrode to melt. This is because, on the one hand, the curing temperature of the conductive glue is relatively low (such as below 180°C), so that the soldering strip and the main grid electrode almost do not require a high-temperature welding process during the combination process, thereby reducing the problems of hidden cracks or even damage of the back contact solar cell caused by high temperature, and the high-temperature dissolution of the grid wire metal (such as silver) in the main grid electrode; on the other hand, the liquid conductive glue is in close contact with the solid main grid electrode, and the conductive glue has a high conductivity coefficient, which can reduce the cost of forming a battery string while also reducing the contact resistance between the back contact solar cells.

[0039] In addition, the conductive adhesive in the embodiment of the present application also has good mechanical properties and adaptability, and has good shear strength and adhesion after curing. When the back-contact solar cell string is used to prepare a photovoltaic module, a photovoltaic module with a stable combination of the welding strip and the main grid electrode can be obtained, thereby improving the power generation efficiency of the photovoltaic module.

[0040] According to an embodiment of the present application, in step (1), a back-contact solar cell is provided, wherein the back-contact solar cell has a spaced main grid electrode.

[0041] It can be understood that the PN junction and metal electrode contact of the back-contact solar cell are both located on the backlight side of the solar cell, so that there is no electrode blocking the front of the cell, thereby maximizing the use of incident light, reducing optical losses, obtaining more effective power generation area and higher photoelectric conversion efficiency.

[0042] In some embodiments, in step (1), the back-contact solar cell further comprises a fine gate electrode, the fine gate electrode is vertically directed to the main gate electrode with the same polarity as the fine gate electrode, and an end of the fine gate electrode close to the main gate electrode with the opposite polarity is covered with insulating glue.

[0043] Optionally, the back-contact solar cell includes a positive electrode and a negative electrode, the positive electrode includes a positive fine grid electrode, a positive main grid electrode and a welding pad located on the positive main grid electrode, the positive main grid electrode intersects with the positive fine grid electrode with the same polarity, and the positive main grid electrode is located on a side of the positive fine grid electrode away from the PN junction of the back-contact solar cell.

[0044] Optionally, the back-contact solar cell includes a positive electrode and a negative electrode, the negative electrode includes a negative electrode fine grid electrode, a negative electrode main grid electrode and a welding pad located on the negative electrode main grid electrode, the negative electrode main grid electrode intersects with the negative electrode fine grid electrode with the same polarity, and the negative electrode main grid electrode is located on a side of the negative electrode fine grid electrode away from the PN junction of the back-contact solar cell.

[0045] According to an embodiment of the present application, the back-contact solar cell further comprises fine grid electrodes distributed in a forked shape, the fine grid electrodes are alternately vertically directed to the main grid electrode, and an insulating glue is covered on one end of the fine grid electrode close to the main grid electrode of opposite polarity. The insulating glue is applied to form an insulating region between the main grid electrode and the fine grid electrode of opposite polarity, so as to reduce the probability of short circuit, thereby improving the stability of the back-contact solar cell string.

[0046] Optionally, the covering method includes coating an insulating glue on a portion of the surface of the fine gate electrode and performing a second curing to form an insulating region between the main gate electrode and the fine gate electrode with the opposite polarity. The insulating glue is covered on one end of the fine gate electrode close to the main gate electrode with the opposite polarity to achieve a regional insulation effect, so as to reduce the possibility of a short circuit between the main gate electrode and the fine gate electrode with the opposite polarity.

[0047] In some embodiments, the insulating adhesive comprises at least one of UV light-curing insulating adhesive and heat-curing insulating adhesive, which have good electrical insulation properties after curing.

[0048] Optionally, the UV light-curing insulating adhesive includes an epoxy system UV-curing insulating adhesive, an acrylic system UV-curing insulating adhesive, and the like.

[0049] Furthermore, the epoxy system UV curing insulating adhesive includes Henkel epoxy insulating adhesive E-90FL.

[0050] Optionally, the heat-curing insulating adhesive includes phenolic resin system insulating adhesive, epoxy resin system insulating adhesive, polyimide insulating adhesive, etc.

[0051] In some embodiments, the second curing is performed under ultraviolet light irradiation.

[0052] In some embodiments, the irradiation time is 1-6 seconds, such as 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, 6 seconds, etc. This can improve the bonding force between the insulating glue and the fine gate electrode, and can also improve the efficiency of the second curing.

[0053] According to an embodiment of the present application, in step (2), a conductive glue is applied on the main gate electrode. In this step, a conductive glue is applied on the main gate electrode. In this way, the height of the conductive glue can be made greater than the height of the insulating glue, so as to facilitate the subsequent laying and welding of the solder strip.

[0054] Optionally, the method of applying the conductive adhesive includes screen printing or dispensing.

[0055] Optionally, a conductive glue is coated on the pad of the main gate electrode, so that the amount of the conductive glue used can be reduced.

[0056] Furthermore, the pad (PAD point) is a region where the positive main gate electrode and the positive fine gate electrode intersect.

[0057] Alternatively, the pad is a region where the negative electrode main gate electrode intersects with the negative electrode fine gate electrode.

[0058] In some embodiments, in step (2), the conductive adhesive includes a resin mixture and a conductive filler.

[0059] In some embodiments, in step (2), the conductive filler is used to improve the conductivity of the conductive adhesive. Optionally, the conductive filler includes at least one of copper, tungsten, nickel, silver and magnesium.

[0060] In some embodiments, in step (2), the resin mixture includes at least one of a resin, a curing agent, a coupling agent, and a diluent.

[0061] Optionally, the resin includes at least one of bisphenol F epoxy resin, bisphenol A epoxy resin, aliphatic epoxy resin and acryl epoxy ester.

[0062] Optionally, the aliphatic epoxy resin includes Huntsman ARALDITE CY179-1, Huntsman ARALDITECY184, Huntsman EPALLOY 5000, and Huntsman EPALLOY 5001LC.

[0063] Optionally, the acrylic epoxy resin includes at least one of bisphenol A epoxy acrylate, novolac epoxy acrylate, and the like.

[0064] Optionally, the curing agent includes at least one of ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, and diethylaminopropylamine.

[0065] Optionally, the coupling agent includes at least one of alkenyltriethoxysilane, vinyltrimethoxysilane and 3-aminopropyltriethoxysilane.

[0066] Optionally, the dispersant includes at least one of diethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, 1-4-cyclohexanedimethanol glycidyl ether and 1,4-butanediol glycidyl ether.

[0067] In some embodiments, in step (2), in the resin mixture, the mass ratio of the resin, the curing agent, the diluent and the coupling agent is 100:(10-30):(0.01-18):(0.01-3), such as 100:20:1:1, 100:20:10:1.5, 100:30:18:3, etc. In this way, a resin mixture with good adhesion and tensile shear strength can be obtained.

[0068] In some embodiments, in step (2), the resin, the curing agent, the diluent and the coupling agent are mixed to obtain a resin mixture.

[0069] In some embodiments, in step (2), in the conductive adhesive, the mass ratio of the resin mixture to the conductive filler is 1:(1-9), such as 1:1, 1:4, 1:5, 1:6, 1:8, 1:9, etc. In this way, a conductive adhesive with good conductivity, adhesion, and tensile shear strength can be obtained.

[0070] Optionally, the mass ratio of the resin mixture to the conductive filler is 1:(1-5).

[0071] In some embodiments, a conductive paste is coated on the main gate electrode, and the height of the conductive paste is greater than the height of the insulating paste.

[0072] In some embodiments, in step (2), reference Figure 4 , the height H of the insulating glue 8 1 , the height H of the conductive adhesive 10 2 , H 1 and H 2 The ratio between them satisfies 1≤H 2 / H 1 ≤1.5, for example H 2 / H 1 The ratio is 1, 1.1, 1.25, 1.3, 1.5, etc. By printing insulating glue to cover the fine grid electrodes on both sides of the pad and printing additional conductive glue on the pad, not only the risk of battery grid breakage and the short circuit of heterogeneous grid lines when the welding strips are interconnected are reduced, but also the height difference between the welding strip and the pad due to the existence of insulating glue is eliminated, solving the problem of cold soldering when the welding strips are welded.

[0073] Understandably, H 1 and H 2 It refers to the height from the insulating glue or conductive glue to the surface of the battery cell in the thickness direction of the battery.

[0074] Optionally, the H 1 5-150μm, for example, 5μm, 20μm, 50μm, 80μm, 150μm, etc.

[0075] Optionally, the H 2 It is 50-200μm, for example, 50μm, 60μm, 80μm, 120μm, 200μm, etc.

[0076] As some examples, see Figure 4 and Figure 5 The fine gate electrodes with opposite polarities include a negative fine gate electrode 4 and a positive fine gate electrode 1. The negative fine gate electrode 4 is coated with an insulating glue 8. The positive fine gate electrode 1 intersects and contacts with the positive main gate electrode 2. The intersecting area is the pad 3 on the positive main gate electrode. The height H of the insulating glue 8 is 1 , the height H of the conductive adhesive 9 2 , H 1 and H 2 The ratio between them satisfies 1≤H 2 / H 1 ≤1.5. In this way, the soldering strip 7 is connected to the positive main grid electrode 2 through the conductive adhesive 9.

[0077] According to an embodiment of the present application, in step (3), a soldering tape is laid on the main gate electrode along the extension direction of the main gate electrode, and a first curing treatment is performed so that the soldering tape is bonded to the main gate electrode through the cured conductive adhesive. In this step, the main gate electrode and the soldering tape are connected together by curing the conductive adhesive at a low temperature (not higher than 180°C), and the height difference between the conductive wire and the pad due to the presence of the insulating adhesive is eliminated as much as possible during the connection process by controlling the height of the insulating adhesive and the conductive adhesive, thereby reducing the occurrence of problems such as cold soldering of the conductive wire and improving the welding effect.

[0078] In some embodiments, in step (3), a pre-pressing treatment is also performed before the first curing treatment, wherein the pre-pressing treatment is to use a welding rod to pre-press and fix the battery cell after the welding tape is laid, so as to facilitate the subsequent curing of the conductive adhesive by heating to form an interconnection.

[0079] In some embodiments, in step (4), the first curing treatment time is 2-30 minutes, such as 2 minutes, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 25 minutes, 30 minutes, etc. This can improve the adhesion and tensile shear strength of the conductive adhesive.

[0080] Optionally, the first curing treatment takes 2-20 minutes.

[0081] In some embodiments, in step (3), the temperature of the first curing is 80-180°C, such as 80°C, 120°C, 150°C, 180°C, etc. By curing the conductive adhesive at a low temperature (80-180°C), the main gate electrode and the soldering strip are connected together, and the height difference between the conductive wire and the soldering pad caused by the presence of the insulating adhesive is eliminated as much as possible during the connection process by controlling the height of the insulating adhesive and the conductive adhesive, thereby reducing the occurrence of problems such as cold soldering of the conductive wire and improving the welding effect.

[0082] In some embodiments, in step (3), the first curing treatment is performed in a drying oven or a tunnel kiln.

[0083] In some embodiments, the method for preparing a back-contact solar cell string further includes connecting a plurality of the back-contact solar cells via a welding ribbon to form a back-contact solar cell string.

[0084] It is understandable that a plurality of back-contact solar cells are connected via solder strips, and the number of the plurality of solar cells can be determined according to actual needs.

[0085] According to a second aspect of the embodiments of the present application, a photovoltaic module is provided. The photovoltaic module includes a back-contact solar cell string. The back-contact solar cell string is prepared by the method described in the first aspect.

[0086] The photovoltaic module of the embodiment of the present application has good stability and low contact resistance, which can improve the power generation efficiency of the photovoltaic module. This is because, on the one hand, the welding strip and the main grid electrode are combined by low-temperature conductive adhesive, which can tightly combine the welding strip and the main grid to promote the welding strip to collect current; on the other hand, the conductive adhesive also has good mechanical properties and strong adaptability. In the process of forming the back-contact solar cell string, no high-temperature welding step is required, which can reduce the hidden cracks and even damage of the back-contact solar cell caused by high temperature.

[0087] In some embodiments, reference Figure 1 The back contact solar cell comprises a positive fine grid electrode 1, a positive main grid electrode 2, a first pad 3, a negative fine grid electrode 4, a negative main grid electrode 5, and a second pad 6. The positive fine grid electrode 1 and the negative fine grid electrode 4 are distributed in a forked finger shape, the positive fine grid electrode 1 is vertically directed to the positive main grid electrode 2, a first pad 3 is arranged on the positive main grid electrode, and a conductive glue is applied on the first pad 3; the negative fine grid electrode 4 is vertically directed to the negative main grid electrode 5, a second pad 4 is arranged on the negative main grid electrode, and a conductive glue is applied on the second pad 4.

[0088] In some embodiments, reference Figure 2 The photovoltaic module includes a back-contact solar cell string. The welding strip 7, the insulating glue 8 and the conductive glue 9 are covered with the insulating glue 8 at one end of the fine grid electrode close to the main grid electrode with the opposite polarity, and the conductive glue 9 is arranged on the main grid electrode. The welding strip 7 is bonded to the main grid electrode through the cured conductive glue 9.

[0089] The third aspect of the embodiments of the present application provides a photovoltaic system, including the photovoltaic module in any of the above embodiments. The photovoltaic system also has the advantages of the above photovoltaic modules, which will not be described in detail here.

[0090] The above-mentioned photovoltaic system has a wide range of applications, not only limited to photovoltaic power stations, such as ground power stations, rooftop power stations and water power stations, but also includes various equipment and devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars and solar buildings. Of course, it is understandable that the application scenarios of photovoltaic systems are not limited to this, that is to say, photovoltaic systems can be used in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array may be an array combination of multiple photovoltaic components. For example, multiple photovoltaic components can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter and is converted into the alternating current required by the mains power grid, and then connected to the mains network to realize solar power supply.

[0091] Hereinafter, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited to the embodiments described herein.

[0092] The back contact solar cells used in the following examples and comparative examples are: refer to Figure 6, the back contact solar cell comprises: an N-type silicon wafer 11; a phosphorus doped layer 12; a boron doped layer 13; a first anti-reflection layer 14; a passivation layer 15; a second anti-reflection layer 16; a first electrode 17; and a second electrode 10. Specifically, the boron doped layer 13 and the phosphorus doped layer 14 are arranged in a forked finger shape on the back of the N-type silicon wafer 11; the first anti-reflection layer 14 is arranged in the isolation area between the boron doped layer 13 and the phosphorus doped layer 14, on the side of the boron doped layer 13 away from the N-type silicon wafer 11, and on the side of the phosphorus doped layer 14 away from the N-type silicon wafer 11; a passivation layer 15 is arranged on the front of the N-type silicon wafer; the second anti-reflection layer 16 is arranged on the side of the passivation layer 15 away from the N-type silicon wafer 11; the first electrode 17 is in contact with the phosphorus doped layer 12; and the second electrode 10 is in contact with the boron doped layer 13. Both the first electrode and the second electrode are silver metal electrodes. Among them, the thickness of the boron doped layer and the phosphorus doped layer is 120nm, and the passivation layer is 30nm. The thickness of the first anti-reflection layer was 75 nm, and the thickness of the second anti-reflection layer was 85 nm.

[0093] Example 1 S1: A silver paste is used to print interdigitated fine gate electrodes and a main gate electrode on the back of a back contact solar cell, wherein the fine gate electrodes intersect vertically with the main gate electrode of the same polarity, and the PAD point is the area on the main gate electrode where the fine gate electrode of the same polarity intersects with it; S2: Print UV curable insulating glue (Henkel epoxy insulating glue E-90FL) on one end of the fine gate electrode close to the main gate electrode with opposite polarity. After screen printing the insulating glue, irradiate it with UV light for 3 seconds to solidify and form an insulating glue film with a height of 80μm. S3: A conductive glue with a height of 100 μm is screen-printed on the PAD point of the main grid electrode of the battery; the conductive colloid is composed of resin (bisphenol A epoxy acrylate, CAS: 71281-65-7), curing agent (ethylenediamine), diluent (diethylene glycol glycidyl ether), coupling agent (triethoxysilane) and conductive filler (gallium-based liquid metal alloy), and the ratio of resin, curing agent, diluent and coupling agent in the resin mixture is 100:20:10:1.5, and the mass ratio of the resin mixture to the conductive filler is 1:5.

[0094] S4: Lay a soldering tape on the main gate electrode along the extension direction of the main gate electrode, pre-press it with a press, and cure it in an oven at 150° C. for 20 minutes, so that the soldering tape is bonded to the main gate electrode through the cured conductive adhesive.

[0095] S5: connecting the three back-contact solar cells via a welding ribbon to form a back-contact solar cell string.

[0096] Examples 2 and 3 A back-contact solar cell string is formed in the manner of Example 1, except that in S4: the curing temperatures are 80° C. and 180° C. respectively.

[0097] Examples 4 and 5 A back-contact solar cell string was formed in the same manner as in Example 1, except that the irradiation time was 1 s and 6 s respectively.

[0098] Example 6 A back-contact solar cell string is formed in the manner of Example 1, except that the ratio of the resin, the curing agent, the diluent, and the coupling agent in the resin mixture is 100:20:1:1.

[0099] Example 7 A back-contact solar cell string is formed in the manner of Example 1, except that the ratio of the resin, the curing agent, the diluent, and the coupling agent in the resin mixture is 100:30:18:3.

[0100] Examples 8 and 9 A back-contact solar cell string was formed in the manner of Example 1, except that the mass ratios of the resin mixture and the conductive filler were 1:1 and 1:9, respectively.

[0101] Examples 10-12 A back-contact solar cell string was formed in the manner of Example 1, except that the heights of the conductive glue were 60 μm, 80 μm, and 120 μm, respectively.

[0102] Examples 13 and 14 A back-contact solar cell string is formed in the manner of Example 1, except that in S4: the curing times are 5 minutes and 30 minutes respectively.

[0103] Embodiment 15 A back-contact solar cell string is formed in the same manner as in Example 1, except that step S2 is not performed.

[0104] Comparative Example 1 A back-contact solar cell string is formed in the manner of Example 1, except that in S4: the curing temperature is 250°C.

[0105] Comparative Example 2 A back-contact solar cell string is formed in the manner of Example 1, except that solder paste is used to bond and fix the solder strip to the main grid electrode.

[0106] Test Case The following performance tests were performed on the above-mentioned back-contact solar cell string, and the results are shown in Table 1.

[0107] Adhesion test method: refer to the method and requirements for photovoltaic module string welding tensile test specified in standard GB / T9535-2006; Tensile shear strength test method: refer to the test of adhesive tensile shear strength in standard GB / T7124-2008; Contact resistance test: refer to the contact resistance test method in standard ICE60512-27-100; Short circuit test: Direct short circuit method is used to test whether the battery of the module is short circuited; Cell EL (electroluminescence defect detection): After welding is completed, the cell EL is tested according to the IEC61215 standard to determine whether there is a cold weld, broken weld, or over-welding between the welding strip and the main grid electrode.

[0108] Table 1

[0109] It can be seen from the above table that by comparing Examples 1-15 with Comparative Examples 1-4, it can be seen that the battery string prepared by the method of the present application has good stability, which is manifested in the good adhesion between the welding strip and the main grid, the tensile shear strength, and the welding quality of the battery cell.

[0110] Compared with Example 1 and Comparative Example 1, it can be seen that the welding adhesion and tensile shear strength of the battery string of Example 1 are both good, and there is no cold solder joint phenomenon in the battery cell. This shows that if the curing temperature is too high, the bonding performance between the conductive adhesive and the welding strip and the main grid electrode will be affected.

[0111] Comparing Example 1 with Example 15, it can be seen that Example 15 does not perform the step of applying insulating glue, which may lead to the risk of short circuit at the contact position between the fine gate electrode with opposite polarity and the main gate electrode, and the protection strength is poor.

[0112] Comparing Example 1 with Comparative Example 2, it can be seen that the solder paste used in Comparative Example 2 will cause the silver in the main grid electrode to dissolve during the welding process, and the solder paste will also cause the adhesion and tensile shear strength between the solder strip and the main grid electrode to deteriorate, thereby causing cold solder joints in the battery cell.

[0113] Figure 3 This is an EL image of the cell of the back-contact solar cell string of Example 1. It can be seen that the welding between the welding ribbon and the main grid electrode is normal.

[0114] It should also be noted that the "some embodiments", "other embodiments", "embodiments", etc. mentioned in this application refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure or characteristic is described in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0115] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0116] It should also be noted that the above are only preferred embodiments of the present application, and the patent protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a back contact solar cell string, characterized in that: include: Providing a back-contact solar cell having main grid electrodes arranged at intervals; Applying conductive glue on the main gate electrode; A soldering tape is laid on the main gate electrode along the extension direction of the main gate electrode, and a first curing treatment is performed to allow the soldering tape to be bonded to the main gate electrode through the cured conductive adhesive.

2. The method according to claim 1, characterized in that The first curing temperature is 80-180°C; And / or, the first curing time is 2-30 minutes.

3. The method according to claim 1 or 2, characterized in that: The back contact solar cell further comprises a fine grid electrode distributed in an interdigitated shape, wherein the fine grid electrode is vertically directed to the main grid electrode having the same polarity as the fine grid electrode. An end of the fine gate electrode close to the main gate electrode with opposite polarity is covered with insulating glue.

4. The method according to claim 3, characterized in that The insulating adhesive includes at least one of a thermosetting insulating adhesive and a UV curing insulating adhesive.

5. The method according to claim 4, characterized in that The covering method includes coating an insulating glue on a part of the surface of the fine gate electrode and performing a second curing, The second curing is performed under ultraviolet light irradiation, and the irradiation time is 1-6s.

6. The method according to claim 3, characterized in that Applying the conductive glue on the main gate electrode includes: applying the conductive glue on the pad of the main gate electrode; And / or, the conductive adhesive comprises a resin mixture and a conductive filler; and / or, the resin mixture comprises at least one of a resin, a curing agent, a coupling agent and a diluent; And / or, the conductive filler includes at least one of copper, tungsten, gallium, nickel, silver and magnesium.

7. The method according to claim 6, characterized in that The resin includes at least one of bisphenol F epoxy resin, bisphenol A epoxy resin, aliphatic epoxy resin and acrylic epoxy ester; And / or, the curing agent includes at least one of ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, and diethylaminopropylamine; And / or, the coupling agent includes at least one of alkenyltriethoxysilane, vinyltrimethoxysilane and 3-aminopropyltriethoxysilane; And / or, the diluent includes at least one of ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, 1-4-cyclohexanedimethanol glycidyl ether and 1,4-butanediol glycidyl ether.

8. The method according to claim 7, characterized in that In the resin mixture, the mass ratio of the resin, the curing agent, the diluent and the coupling agent is 100:(10-30):(0.01-18):(0.01-3).

9. The method according to claim 6, characterized in that In the conductive adhesive, the mass ratio of the resin mixture to the conductive filler is 1:(1-9).

10. The method according to claim 3, characterized in that The height of the insulating glue is H1, the height of the conductive glue is H2, and the ratio between H1 and H2 satisfies 1≤H2 / H1≤1.

5.

11. A photovoltaic module, characterized in that: The invention comprises a back-contact solar cell string, wherein the back-contact solar cell string is prepared by the method according to any one of claims 1 to 10.

12. A photovoltaic system, characterized in that: The photovoltaic system comprises the photovoltaic assembly according to claim 11.

Images