Back-contact battery and photovoltaic module

Abstract

The present invention provides a back-contact battery and a photovoltaic module. The back-contact battery includes a battery body having opposite first and second surfaces; a first electrode and a second electrode disposed on the first surface of the battery body, the first electrode and the second electrode being alternately arranged at intervals in a first direction and extending in a second direction; a connection conductor disposed on the first surface, the connection conductor extending in the first direction, an insulating layer being provided between the connection conductor and the first electrode and being connected to the second electrode; the connection conductor includes a first portion located between two adjacent insulating layers along the first direction and a second portion whose projection on the first surface coincides with the projection of the first electrode, the surface of the first portion facing away from the battery body has a first average roughness, and the surface of the second portion facing away from the battery body has a second average roughness, wherein the second average roughness is less than the first average roughness.

Description

Technical Field

[0001] At least one embodiment of the present invention relates to the field of photovoltaic technology, and particularly to a back-contact battery and a photovoltaic module. Background Art

[0002] In a back-contact battery, a positive secondary grid and a negative secondary grid are respectively disposed on different doping regions of the backlight surface of the battery body, and then the current generated by the battery body is collected by connecting to the main grid of the same polarity.

[0003] The main grid and the secondary grid are arranged in different directions. Therefore, while the main grid is connected to the secondary grid of the same polarity, it also spans the secondary grids of different polarities. To prevent short circuits caused by the main grid connecting the secondary grids of different polarities, an insulating layer needs to be provided between the main grid and the secondary grids of different polarities, that is, the overlapping part of the printed main grid and the secondary grids of different polarities is formed on the insulating layer.

[0004] Based on the material characteristics of the insulating layer, the surface of the insulating layer facing away from the battery body protrudes from the battery body and is relatively smooth, which is conducive to the accumulation of more paste of the printed main grid in the area between adjacent insulating layers. In this way, the part of the main grid located in this area can be made thicker, which is conducive to improving the reliability of the electrical connection between the main grid and the secondary grid of the same polarity. However, the surface of this part facing away from the battery body often forms a generally arched shape and is relatively smooth. This smooth surface is not conducive to forming an effective connection with the external interconnection strip, and it is easy to cause problems such as poor contact between the main grid and the interconnection strip. Summary of the Invention

[0005] To solve at least one of the above and other technical problems in the prior art, the present invention provides a back-contact battery and a photovoltaic module, which are conducive to setting a bonding layer on the connecting conductor to improve the reliability of the connection between the connecting conductor and the electrical connector.

[0006] An embodiment of the present invention provides a back-contact battery, including a battery body having opposite first and second surfaces; a first electrode and a second electrode disposed on the first surface of the battery body, the first electrode and the second electrode being alternately arranged at intervals in a first direction and extending in a second direction, the first direction intersecting the second direction; a connecting conductor disposed on the first surface, the connecting conductor extending in the first direction, an insulating layer being provided between the connecting conductor and the first electrode and being connected to the second electrode; the connecting conductor including a first part located between two adjacent insulating layers along the first direction and a second part whose projection on the first surface coincides with the projection of the first electrode, the surface of the first part facing away from the battery body having a first average roughness, and the surface of the second part facing away from the battery body having a second average roughness, wherein the second average roughness is less than the first average roughness.

[0007] In the case of adopting the above embodiment, the second average roughness is configured to be smaller than the first average roughness, that is, the second portion is smoother, has less surface undulations, and has better flatness than the first portion. The relatively rough first portion is conducive to connection with external electrical connectors or solder, and has better welding quality. The relatively smooth second portion is conducive to preventing the connecting conductor from piercing the insulating layer covering the first electrode when it is welded or laminated with the external electrical connector, thereby avoiding leakage and short circuit.

[0008] In some exemplary embodiments, the first average roughness is greater than or equal to 5 micrometers.

[0009] When adopting the above-mentioned embodiment, the first average roughness is configured to be greater than or equal to 5 microns, which is beneficial to forming a larger contact area when the connecting conductor is welded with the external electrical connector or solder, so as to more effectively reduce the contact resistance, and help form a larger area of ​​the intermetallic compound layer to provide greater pull-out resistance.

[0010] In some exemplary embodiments, the second average roughness is less than 10 micrometers.

[0011] When adopting the above-mentioned embodiment, in addition to making the raised portion formed on the surface of the second part smaller to avoid piercing the insulating layer, limiting the second average roughness can also prevent the occurrence of solder bridges, cold welding or reduced welding quality caused by uneven distribution of solder thereon.

[0012] In some exemplary embodiments, a surface of the first portion facing away from the first surface has a plurality of first protrusions, and a maximum height of the plurality of first protrusions along a direction perpendicular to the first surface is greater than or equal to 8 micrometers.

[0013] In the case of the above embodiment, the first protrusion formed on the first portion has a greater height (and greater surface undulations), which helps to improve the joining force between the electrical connector and the connecting conductor, increase the contact area, and reduce the contact resistance.

[0014] In some exemplary embodiments, a ratio of a thickness of the first portion to a thickness of the second portion is between 4-10.

[0015] When adopting the above-mentioned embodiment, the thickness of the first part is related to the thickness of the second part. The thicker first part can ensure the reliability of welding, and the thinner second part can realize the electrical transmission of adjacent isotropic fine grids along the extension direction of the connecting conductor, thereby preventing the problem of partial poor joining. A second part that is too thin is not conducive to the transmission of current, and a second part that is too thick will lead to waste of materials. The present application achieves a balance between material cost and electrical transmission effect by setting the thickness ratio to 4-10.

[0016] In some exemplary embodiments, the thickness of the first portion is greater than or equal to 25 micrometers.

[0017] When the above embodiment is adopted, setting the first part thicker is beneficial to maintaining its reliability with the external electrical connector in the welding state, reducing the risk of poor welding, and under the condition of unchanged width, it can also increase the cross-sectional area of ​​the connecting conductor to reduce the resistance of the connecting conductor.

[0018] In some exemplary embodiments, the thickness of the second portion is 5 micrometers to 15 micrometers.

[0019] In the case of the above embodiment, when the thickness of the first part is greater than or equal to 25 microns, the second part should be set to a suitable thickness. If it is set too thin, such as the upper limit value corresponding to the thickness ratio of 10, it is not conducive to the current transmission of two adjacent fine grids; and if it is set too thick, such as the lower limit value corresponding to the thickness ratio of 4, it not only wastes the material of the connecting conductor, but also has little improvement on electrical conduction, and may cause the connecting conductor to extend in the width direction during printing, and then cause overlap with another opposite fine grid to cause a short circuit.

[0020] In some exemplary embodiments, the connecting conductor further includes a third portion that overlaps with a projection of the insulating layer in an orthographic projection of the first surface; and a thickness of the first portion is greater than a thickness of the third portion.

[0021] In the case of the above-mentioned embodiment, the first part is used as the main connection point between the connecting conductor and the external electrical connector. Setting it thicker is beneficial to making the joint position with the electrical connector have better welding quality; correspondingly, the third part is not particularly thick, which can make the surface of the connecting conductor roughly flush, so as to reduce the warping deformation of the electrical connector after lamination.

[0022] In some exemplary embodiments, the thickness of the third portion is less than or equal to 25 micrometers.

[0023] In some exemplary embodiments, the width of the first electrode is 30 micrometers to 100 micrometers; and / or the width of the second electrode is 30 micrometers to 100 micrometers.

[0024] The portion of the battery body located between the adjacent first electrode and the second electrode forms an isolation region; the insulating layer covers a portion of the isolation region.

[0025] When forming a relatively narrow electrode by printing methods such as screen printing, the insulating layer extends to the isolation region, covering the side portion of the first electrode in the first direction, which is beneficial to maintaining the insulation effect between the first electrode, the second electrode and the connecting conductor. At the same time, a sufficient width is reserved to ensure that the connecting conductor can be in full contact with the second electrode.

[0026] In some exemplary embodiments, the width of the first electrode is 300 micrometers to 600 micrometers; and / or, the width of the second electrode is 300 micrometers to 600 micrometers. When forming a relatively wide electrode by means such as electroplating and deposition, when the first surface is the backlight surface of the back-contact cell, there is no need to consider its light-shielding loss. On this basis, setting relatively wide first and second electrodes can increase the area ratio of the first and second electrodes to the area of the first surface. In this way, the current collection efficiency can be effectively improved, especially the collection efficiency of minority carriers in the minority carrier doping region. Moreover, setting electrodes with a larger width can also increase their cross-sectional area, effectively reducing the series resistance. In addition, the relatively wide first and second electrodes can also distribute the electric field more evenly and provide support for the cell body, which is beneficial to improving the structural strength of the back-contact cell.

[0027] In some exemplary embodiments, a portion of the cell body located between the adjacent first electrode and the second electrode forms an isolation region; the insulating layer covers the isolation region and extends onto the second electrode. For relatively wide first and second electrodes, the insulating layer extends onto the electrodes of opposite polarities. On the one hand, it can ensure the insulation of the isolation region, and on the other hand, it can also ensure that the width of the electrodes of the same polarity is smaller, so that the connecting conductor can save paste at this position while ensuring a sufficient height of the first part.

[0028] An embodiment of the present invention further provides a back-contact cell, including a cell body having opposite first and second surfaces; a first electrode and a second electrode disposed on the first surface of the cell body, the first electrode and the second electrode are alternately arranged at intervals in the first direction and extend in the second direction; a connecting conductor disposed on the first surface, the connecting conductor extends in the first direction, an insulating layer is disposed between the connecting conductor and the first electrode and is connected to the second electrode; the connecting conductor includes a first part located between two adjacent insulating layers in the first direction, and the surface of the first part facing away from the cell body has a plurality of first protrusions, and the maximum height of the plurality of first protrusions is greater than or equal to 8 micrometers.

[0029] In the case of adopting the above implementation manner, the height of the first protrusions formed on the first part is relatively large (the surface undulation is also relatively large), which helps to improve the bonding force between the electrical connector and the connecting conductor, increase the contact area, and at the same time reduce the contact resistance.

[0030] In some exemplary embodiments, the connecting conductor further includes a second portion that overlaps with a projection of the first electrode in an orthographic projection of the first surface, and a ratio of a thickness of the first portion to a thickness of the second portion is between 4-10.

[0031] When adopting the above-mentioned embodiment, the thickness of the first part is related to the thickness of the second part. The thicker first part can ensure the reliability of welding, and the thinner second part can realize the electrical transmission of adjacent isotropic fine grids along the extension direction of the connecting conductor, thereby preventing the problem of partial poor joining. A second part that is too thin is not conducive to the transmission of current, and a second part that is too thick will lead to waste of materials. The present application achieves a balance between material cost and electrical transmission effect by setting the thickness ratio to 4-10.

[0032] In some exemplary embodiments, the thickness of the first portion is greater than or equal to 25 micrometers.

[0033] When the above embodiment is adopted, setting the first part thicker is beneficial to maintaining its reliability with the external electrical connector in the welding state, reducing the risk of poor welding, and under the condition of unchanged width, it can also increase the cross-sectional area of ​​the connecting conductor to reduce the resistance of the connecting conductor.

[0034] In some exemplary embodiments, the thickness of the second portion is 5 micrometers to 15 micrometers.

[0035] In the case of the above embodiment, when the thickness of the first part is greater than or equal to 25 microns, the second part should be set to a suitable thickness. If it is set too thin, such as the upper limit value corresponding to the thickness ratio of 10, it is not conducive to the current transmission of two adjacent fine grids; and if it is set too thick, such as the lower limit value corresponding to the thickness ratio of 4, it not only wastes the material of the connecting conductor, but also has little improvement on electrical conduction, and may cause the connecting conductor to extend in the width direction during printing, and then cause overlap with another opposite fine grid to cause a short circuit.

[0036] In some exemplary embodiments, the connecting conductor further includes a third portion that coincides with a projection of the insulating layer in an orthographic projection of the first surface; and a thickness of the first portion is greater than a thickness of the third portion.

[0037] In the case of the above-mentioned embodiment, the first part is used as the main connection point between the connecting conductor and the external electrical connector. Setting it thicker is beneficial to making the joint position with the electrical connector have better welding quality; correspondingly, the third part is not particularly thick, which can make the surface of the connecting conductor roughly flush, so as to reduce the warping deformation of the electrical connector after lamination.

[0038] In some exemplary embodiments, a portion of the battery body located between the adjacent first electrode and the second electrode forms an isolation region; the insulating layer covers the isolation region and extends onto the second electrode.

[0039] In the case of adopting the above-described embodiment, on the premise that the width of the battery body is limited, the wider the widths of the first electrode and the second electrode are set, the smaller the distance between the first electrode and the second electrode in the first direction becomes. For this reason, covering the entire isolation region with the insulating layer and extending it onto the second electrode can not only be used to maintain the insulation between the first electrode and the second electrode in the first direction, but also prevent the connection conductor from entering the isolation region to avoid leakage caused by an excessive electric field strength in the isolation region.

[0040] An embodiment of the present invention further provides a photovoltaic module, including: a back-contact battery; an electrical connector electrically connecting the connection conductors of at least two of the above-mentioned back-contact batteries.

[0041] In the case of adopting the above-described embodiment, the electrical connector electrically connects the connection conductors of one polarity of one back-contact battery and at the same time electrically connects the connection conductors of the other polarity of another back-contact battery, so that a plurality of back-contact batteries can be connected in series to form a battery string.

[0042] In some exemplary embodiments, a bonding layer is provided between the above-mentioned electrical connector and the above-mentioned connection conductor, and the bonding layer is continuous along the extending direction of the electrical connector.

[0043] In the case of adopting the above-described embodiment, the bonding layer and the first part of the connection conductor form a good connection and electrical connection relationship.

[0044] In some exemplary embodiments, an air gap is formed between the above-mentioned bonding layer and the third part of the connection conductor.

[0045] In the case of adopting the above-described embodiment, since the bonding layer has formed a good connection and electrical connection relationship with the first part of the connection conductor, for this reason, the part where the air gap is formed may not be connected to the third part. In this way, it is beneficial to reduce the material consumption for forming the bonding layer.

[0046] In some exemplary embodiments, a plurality of first bonding portions are provided between the above-mentioned electrical connector and the above-mentioned connection conductor, and the plurality of the first bonding portions are arranged at intervals in the first direction.

[0047] In the case of adopting the above-described embodiment, the plurality of first bonding portions arranged at intervals are beneficial to reducing the material consumption for forming the first bonding portions.

[0048] In some exemplary embodiments, the first bonding portion is provided on the first part of the connection conductor.

[0049] In the case of adopting the above-mentioned embodiment, the first joint portion is mainly disposed on the first portion, so that the joint layer is discrete and discontinuous in the first direction. This not only plays the role of reducing the amount of material used to form the joint layer as described above, but also prevents the short-circuit problem caused by excessive or improper distribution of the joint layer.

[0050] In some exemplary embodiments, the photovoltaic module includes a second joint portion, and the second joint portion is located above at least two first electrodes.

[0051] In the case of adopting the above-mentioned embodiment, the second joint portion is continuously disposed on at least two first electrodes and the second electrode located between two first electrodes, which is beneficial to form a good electrical connection with the connection conductor and the electrical connector, and helps to reduce the contact resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a schematic diagram of a back-contact battery from a top view perspective according to an exemplary embodiment of the present invention;

[0053] Figure 2 is Figure 1 a partial cross-sectional view of the A1-A2 portion of the shown exemplary embodiment;

[0054] Figure 3 is a schematic diagram of a back-contact battery from a top view perspective according to another exemplary embodiment of the present invention;

[0055] Figure 4 is a schematic diagram of a back-contact battery from a top view perspective according to still another exemplary embodiment of the present invention;

[0056] Figure 5 is Figure 1 a partial cross-sectional view of the B1-B2 portion of the shown exemplary embodiment;

[0057] Figure 6 is a partial cross-sectional view of a photovoltaic module according to an exemplary embodiment of the present invention, showing the first joint portion;

[0058] Figure 7 is a partial cross-sectional view of a photovoltaic module according to another exemplary embodiment of the present invention, showing the second joint portion.

[0059] In the said drawings, the meanings of the reference numerals are specifically as follows:

[0060] 1. Battery body;

[0061] 2. Second electrode;

[0062] 3. First electrode;

[0063] 4. Insulating layer;

[0064] 5. Connecting conductor;

[0065] 51. First protrusion;

[0066] 6. Electrical connector;

[0067] 7. Bonding layer;

[0068] 71. First bonding portion;

[0069] 72. Second bonding portion;

[0070] 8. Air gap. Detailed implementation manners

[0071] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in detail with reference to specific embodiments and the accompanying drawings.

[0072] The terms used herein are merely for describing specific embodiments and are not intended to limit the present invention. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0073] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0074] In the case of using expressions such as "at least one of A, B, and C, etc.", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include, but is not limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C. In the case of using expressions such as "at least one of A, B, or C, etc.", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include, but is not limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C.

[0075] In a back-contact battery (i.e., BC battery), different doping regions on the backlight side are alternately distributed. Correspondingly, the auxiliary grids arranged on different doping regions are also alternately distributed and have different conduction types. To collect the current collected by the auxiliary grids, some back-contact batteries are also provided with a main grid (i.e., Busbar) that intersects the auxiliary grids. In addition to connecting to the auxiliary grids of the same polarity, the arranged main grid also needs to cross the auxiliary grids of different polarities. Therefore, it is necessary to electrically isolate the main grid from the auxiliary grids of different polarities.

[0076] Currently, there are mainly two ways to electrically isolate the main grid from the auxiliary grids of different polarities. One is to set the auxiliary grid into a discontinuous structure so that the main grid passes through the disconnection parts formed by the auxiliary grids of different polarities. The other is to use an auxiliary grid with a continuous structure and provide an insulating layer between the overlapping parts of the main grid and the auxiliary grids of different polarities.

[0077] The latter of the above methods can more effectively avoid electrical contact between the auxiliary grids of different polarities than the former, which is beneficial to reducing the short-circuit current and leakage current. Based on the material characteristics of the insulating layer (such as insulating glue, silicon oxide, silicon nitride or other materials), the surface of the insulating layer is smooth, and the middle part is more convex than the two sides. In this way, it is beneficial to make the part of the main grid between two adjacent insulating layers thicker than the part on the insulating layer. However, the surface of the part of the main grid above the insulating layer facing away from the battery body often forms a relatively smooth curved surface, and this smooth curved surface is not conducive to forming an effective connection with the external interconnection strip through solder.

[0078] In view of this, how to provide a back-contact battery and a photovoltaic module that are beneficial to effectively connecting the main grid with the external interconnection strip has become an urgent technical problem to be solved.

[0079] Figure 1 is a schematic top view of a back-contact battery according to an exemplary embodiment of the present invention. Figure 2 is Figure 1 a partial cross-sectional view of the A1-A2 part of the shown exemplary embodiment.

[0080] The back-contact battery provided according to the present invention, as Figure 1 and Figure 2 shown, the back-contact battery of the present invention can be a traditional IBC battery (interdigitated back-contact battery), or a TBC battery (TOPCon back-contact battery), an HBC battery (heterojunction back-contact battery), or a hybrid back-contact battery (i.e., the PN passivation therein is of different passivation materials, for example, it can be a combination of polysilicon passivation and amorphous / microcrystalline passivation).

[0081] The above-mentioned back-contact battery includes a battery body 1, and the battery body 1 at least includes a substrate and a doped layer on the substrate. The substrate has a rectangular or square structure, and its long side or side length is between 182 - 240 mm. Preferably, it can be (182 ± 2) * (191 ± 2) mm, (182 ± 2) * (210 ± 2) mm, (210 ± 2) * (210 ± 2) mm.

[0082] The battery body 1 of the above-mentioned IBC battery (interdigitated back-contact battery) includes a first doped semiconductor part and a second doped semiconductor part that are alternately and spaced apart along a first direction on the substrate to form an interdigitated doped part structure. One of the first doped semiconductor part and the second doped semiconductor part is n-type doped, and the other is p-type doped. Electrode structures are respectively arranged at intervals in the first doped semiconductor part and the second doped semiconductor part.

[0083] The battery body 1 of the above-mentioned TBC battery (TOPCon back-contact battery) includes a tunneling oxide layer provided on the substrate, and a first doped semiconductor part and a second doped semiconductor part formed by a doped polysilicon layer. Among them, the TOPCon structure formed by the stacked tunneling oxide layer and doped polysilicon layer can provide higher carrier lifetime and lower surface recombination compared with the IBC battery, which is beneficial to improving the photoelectric conversion efficiency of the TBC battery.

[0084] The battery body 1 of the above-mentioned HBC battery (heterojunction back-contact battery) includes an n-type doped layer and a p-type doped layer stacked on the substrate to form a heterojunction structure. Among them, the n-type doped layer includes but is not limited to microcrystalline silicon or amorphous silicon (to provide electrons), and the p-type doped layer can also use microcrystalline silicon or amorphous silicon (such as using boron as a dopant to provide holes). The HBC battery helps to improve the carrier lifetime and reduce the surface recombination. Further, a conductive oxide layer (i.e., TCO) can also be provided between the surfaces of the n-type doped layer and the p-type doped layer and the electrodes, which is beneficial to collecting the carriers in the doped region and can also play a certain antireflection role.

[0085] The battery body 1 of the above-mentioned hybrid back-contact battery can adopt a layer structure similar to that of the IBC battery or the TBC battery, and a corresponding passivation layer structure is configured on this basis, such as a combination of at least two of polysilicon passivation, amorphous silicon passivation, and microcrystalline silicon passivation.

[0086] Based on the back-contact battery of any of the above embodiments, the above-mentioned back-contact battery further includes a first surface provided on the battery body 1 (such as the backlight surface of the battery body 1, that is Figure 1The first electrode 3, the second electrode 2, and the connecting conductor 5 on the surface facing the viewing angle shown; the corresponding second surface is the light-receiving surface). The first electrode 3 and the second electrode 2 (which can also be called fine grids, collector grid lines, sub-grids, etc., the first electrode 3 and the second electrode 2 have different polarities and are respectively used to extract majority carriers or minority carriers of different doped regions), the first electrode 3 and the second electrode 2 are alternately arranged at intervals along the first direction (such as Figure 1 the up-down direction shown), and extend along the second direction (such as Figure 1 the left-right direction shown), and the first direction intersects the second direction.

[0087] The connecting conductor 5 (which can be called the main grid in some cases and is used to collect the current collected by the first electrode 3 or the second electrode 2), the connecting conductor 5 extends along the first direction, an insulating layer 4 is provided between the connecting conductor 5 and the first electrode 3, and it is connected to the second electrode 2. The connecting conductor 5 includes a first part located between two adjacent insulating layers 4 along the first direction and a second part whose projection in the front projection on the first surface coincides with the projection of the first electrode 3. The surface of the first part facing away from the battery body 1 has a first average roughness, and the surface of the second part facing away from the battery body 1 has a second average roughness, where the second average roughness is less than the first average roughness.

[0088] It should be noted that the average roughness refers to the average distance by which the profile near the outside of the battery cell (near the connecting part) deviates from the reference line (the base reference line of multiple protrusions) within the sampling length (such as Figure 2 the N part shown), and is used to reflect the overall roughness level of the surface. The larger the value of the average roughness, the rougher the surface, the smaller the surface undulation, and the better the flatness. Specifically, during measurement, it is necessary to measure the values of points at 20 different positions respectively on a sampling length of at least 50 microns continuously on the cross-section (such as the cross-sectional pattern in Figure 2 ) and calculate the average value.

[0089] In a schematic embodiment, taking the battery body 1 with an n-type silicon substrate as an example, the first electrode 3 is arranged on the n-type doped region, and the corresponding second electrode 2 is arranged on the p-type doped region. Corresponding to the corresponding doped regions, the first electrode 3 serves as the positive electrode of the back-contact battery, and the second electrode 2 serves as the negative electrode of the back-contact battery. Similarly, the first electrode 3 can also be arranged on the p-type doped region to serve as the negative electrode, and the second electrode 2 can also be arranged on the n-type doped region to serve as the positive electrode.

[0090] In a schematic embodiment, such as Figure 1As shown, the insulating layer 4 includes, but is not limited to, insulating small pieces configured to be generally rectangular. Specifically, the width of the insulating small piece should be configured to be greater than the width of the connecting conductor 5, so that the portion of the connecting conductor 5 that coincides with the first electrode 3 in the front projection direction of the battery body 1 is completely covered, to electrically isolate the connecting conductor 5 and the first electrode 3. Among them, the insulating layer 4 can be made of inorganic materials such as silicon oxide, silicon nitride, etc., or can be made of organic materials such as insulating glue, etc. The thickness of the insulating layer 4 is not greater than 60 μm, for example, it can be 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, etc. Its thickness should not be too large to prevent the first part from being overly low-lying, resulting in poor soldering, or requiring more connecting conductor materials to offset the height difference.

[0091] In a schematic embodiment, as Figure 1 shown, a plurality of insulating small pieces (i.e., the insulating layer 4) are provided on the first electrode 3. Specifically, the plurality of insulating small pieces on each first electrode 3 are arranged at intervals along the first direction (such as Figure 1 the up and down direction shown), to be disposed at the position where the connecting conductor 5 and each first electrode 3 are laminated.

[0092] In a schematic embodiment, as Figure 2 shown, the insulating small pieces located above the first electrode 3 often form a cross-sectional shape that is generally arched (i.e., the middle part on the first electrode 3 bulges upward, and the edge parts on both sides of the middle part are thinner). Further, the connecting conductor 5 extends along the first direction (such as Figure 2 the left and right direction shown), and is formed above the insulating layer 4 and between adjacent insulating layers 4. Among them, Figure 2 only shows schematically that the connecting conductor 5 straddles two insulating layers 4. It should be understood that the connecting conductor 5 can straddle each insulating layer 4 arranged along the first direction.

[0093] In a schematic embodiment, as Figure 2 shown, in the front projection of the first surface (such as Figure 2 the upper surface shown) of the battery body 1, the second part (such as Figure 2 the M part shown) where the connecting conductor 5 coincides with the first electrode 3 also forms a curved surface along with the slope of the surface of the insulating layer 4 facing away from the battery body 1 (such as Figure 2 the upper surface shown). Specifically, the second average roughness (i.e., Ra2, which is the roughness of the curved surface) of this second part is less than the first average roughness (i.e., Ra1), that is, the second part is smoother, has smaller surface undulations, and better flatness than the first part. Preferably, the concavo-convex structure formed by the second part should be more uniform, and the largest convex part should also be smaller. In this way, it is beneficial to prevent the second part from piercing the insulating layer 4 when the connecting conductor 5 is welded or laminated with an external electrical connection member (such as a solder strip), thereby avoiding the occurrence of leakage and short-circuit situations.

[0094] In such an embodiment, the second average roughness is configured to be less than the first average roughness, that is, the second part is smoother than the first part. The relatively rough first part is conducive to making the solder (including but not limited to solder paste) adhere to the connecting conductor 5 and form a larger contact area, so as to effectively reduce the contact resistance; in addition, when welding with an external electrical connector (such as a solder strip), it also helps to form an intermetallic compound layer (i.e., IMC) with a larger area to provide a greater tensile force and have better welding quality.

[0095] Figure 3 It is a schematic diagram of a top view of a back-contact battery according to another exemplary embodiment of the present invention.

[0096] In another exemplary embodiment, as Figure 3 shown, a partial main-gridless battery structure. Specifically, the battery body 1 includes a C region located at the edge (such as Figure 3 the regions located at the upper and lower parts of the battery body 1 shown), and a D region located in the middle (such as Figure 3 the region between the two C regions shown). The connecting conductor 5 is provided in the C region of the battery body 1 to be used as an end main grid. Among them, the configuration of the connecting conductor 5 with the first electrode 3, the second electrode 2 and the insulating layer 4 is similar to that of the foregoing embodiment and will not be elaborated here. The connecting conductor 5 is not provided in the D region of the battery body 1 so that a completely main-gridless structure is formed in this region. Generally speaking, along the extending direction of the connecting conductor 5, the width of the C region is much smaller than the width of the D region, and among them, in a single C region, the length of the connecting conductor 5 along its extending direction can be 3-12 mm.

[0097] In such an embodiment, the connecting conductor 5 is only provided at the edge part of the battery body 1 for connecting with an electrical connector (such as a solder strip). In this way, the edge current of the battery body 1 can be collected through the connecting conductor 5 to prevent the hidden crack caused by the joint position of the electrical connector and the electrode (i.e., the first electrode and the second electrode) being too close to the edge of the battery body 1.

[0098] In yet another exemplary embodiment, not shown in the figures, the back-contact battery of the present invention may be a battery structure without a main grid (i.e., 0BB). Specifically, the first electrode 3 and the second electrode 2 on the first surface of the battery body 1 (which may also be called fine grids, collector grid lines, sub-grids, etc., and the first electrode 3 and the second electrode 2 have different polarities and are respectively used to extract majority carriers or minority carriers from different doped regions) are directly connected to an external electrical connection member (which may also be called a solder strip or an interconnection bar and is used to connect at least two back-contact batteries in series) without passing through the main grid. At this time, the connecting conductor 5 can be regarded as a bonding layer connecting the solder strip or can also be regarded as a main grid structure connecting the first electrode 3 or the second electrode 2.

[0099] On this basis, the connecting conductor 5 is disposed between the first electrode 3 or the second electrode 2 and the electrical connection member, and it can be used as a bonding layer (which can be solder, solder paste, such as solder, for welding the sub-grid and the solder strip; or it can be a conductive adhesive layer, such as conductive silver paste, conductive glue, etc., for conducting bonding of the sub-grid and the solder strip), so as to form a good welding relationship between the electrode (i.e., the first electrode 3 or the second electrode 2) and the electrical connection member.

[0100] The connecting conductor 5 is prefabricated at a specific position of the battery body 1. Further, during the process of welding the electrode to the electrical connection member, the electrical connection member has a bonding layer, and this bonding layer melts and merges with the connecting conductor 5 to form an intermetallic compound (i.e., IMC).

[0101] According to an embodiment of the present invention, as Figure 2 shown, the first average roughness is greater than or equal to 5 microns.

[0102] According to an embodiment of the present invention, as Figure 2 shown, the second average roughness is less than 10 microns. In an exemplary embodiment, as Figure 2 shown, the first part (such as the Figure 2 shown N part) of the connecting conductor 5 located between two adjacent insulating layers 4 has a surface (such as the Figure 2 shown upper surface) facing away from the battery body 1 that forms a substantially curved surface. Specifically, the first average roughness (i.e., Ra1, which is the surface roughness of the curved surface) of this surface includes but is not limited to being configured to be greater than or equal to 5 microns, i.e., Ra1 ≥ 5μm. Further, the largest protruding part in this first part (i.e., the N part) includes but is not limited to being greater than or equal to 8 microns. It should be understood that the embodiments of the present invention are not limited thereto.

[0103] For example, the surface of the first part facing away from the battery body 1 can also be configured with an average roughness of 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 10μm, 20μm, and any other average roughness greater than 5μm, which is appropriate to meet the corresponding welding and electrical requirements.

[0104] In a schematic embodiment, to form the connecting conductor 5 having the above-mentioned first average roughness, an organic component with a weight component greater than 5% (and containing 2%-5% epoxy resin) can be configured in the paste for printing the main grid (such as silver paste), and then sintering at 500-800 °C can be carried out. During the sintering process, due to the decomposition and overflow of the organic material, the surface of the formed connecting conductor will present a rough surface, that is, the roughness is more than 5 microns. It should be understood that the embodiments of the present invention are not limited thereto.

[0105] For example, it can also be achieved by other processes such as scraping and spraying. In such an embodiment, by setting the first average roughness of the first part (i.e., the N part) of the connecting conductor 5 to be greater than or equal to 5 microns, a relatively rough surface can be formed on the first part. In this way, when the connecting conductor is welded to an external electrical connector or solder, it is beneficial to form a larger contact area, so as to effectively reduce the contact resistance, and contribute to the formation of a larger intermetallic compound layer to provide a greater tensile force. And by configuring the second roughness to be less than 10 microns, the protrusions formed on the surface of the second part can be made smaller, so as to avoid the situation of piercing the insulating layer due to the protrusions protruding too much from the surface. For example, the surface of the second part facing away from the battery body 1 can also be configured with an average roughness of 1μm, 2μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 9μm and any other average roughness less than 10 microns, but at the same time, it is necessary to ensure that it is less than the average roughness of the surface of the first part facing away from the battery body 1.

[0106] According to an embodiment of the present invention, as Figure 2 shown, the surface of the first part facing away from the first surface (such as Figure 2 the upper surface shown) has a plurality of first protrusions 51, and the maximum height of the plurality of first protrusions 51 perpendicular to the first surface is greater than or equal to 8 microns.

[0107] According to an embodiment of the present invention, as Figure 2 shown, the ratio of the thickness of the first part to the thickness of the second part is between 4-10.

[0108] In such an embodiment, the height of the first protrusions 51 formed on the first part is relatively large, which helps to improve the bonding force between the electrical connector and the connecting conductor, increase the contact area, and at the same time reduce the contact resistance. The thickness of the first part and the thickness of the second part are related. If it is too thin, it is not conducive to current transmission, and if it is too thick, it will cause material waste.

[0109] According to an embodiment of the present invention, as Figure 2 shown, the thickness of the first part is greater than or equal to 25 microns.

[0110] In such an embodiment, setting the first part thicker is beneficial to maintaining its reliability with the external electrical connector in the welding state, reducing the risk of poor welding, and under the condition of unchanged width, it can also increase the cross-sectional area of ​​the connecting conductor to reduce the resistance of the connecting conductor.

[0111] According to an embodiment of the present invention, Figure 2 As shown, the thickness of the second portion is 5 micrometers to 15 micrometers.

[0112] According to an embodiment of the present invention, Figure 2 As shown, the connecting conductor 5 also includes a third portion that coincides with the projection of the insulating layer 4 in the orthographic projection of the first surface. The thickness of the first portion is greater than that of the third portion (e.g. Figure 2 The thickness of the O part is shown.

[0113] According to an embodiment of the present invention, Figure 2 As shown, the third part (such as Figure 2 The thickness of the third portion (shown as the O portion) is less than or equal to 25 microns. The width of the third portion along the first direction is 300-800 microns, that is, the width of each insulating layer 4 along the first direction is 300-800 microns, thereby achieving insulation of the opposite-sex electrodes, while ensuring that the spacing between the two insulating layers 4 in the first direction can expose the same-sex electrodes to be connected to the conductor 5, wherein the spacing between the two insulating layers 4 in the first direction is 100-500 microns, that is, the width of the first portion is 100-500 microns.

[0114] In an illustrative embodiment, Figure 2 As shown, the first part (such as Figure 2 The surface of the battery body 1 (as shown in the N part) away from the battery body 1 Figure 2 The upper surface shown in FIG. 1 is not smooth, and therefore, the thickness of the first portion can be understood as the average thickness of the first portion. Further, the third portion (such as FIG. 1 ) where the connecting conductor 5 overlaps with the insulating layer 4 Figure 2 The O portion shown in FIG. 1 includes a second portion (such as Figure 2 The M part shown in the figure), the second part has a thickness (even if the connecting conductor 5 will not be disconnected in the second part), and the thickness of the third part gradually increases from the upper surface of the insulating layer 4 to both sides. For this reason, the thickness of the third part can also be understood as the average thickness of the third part. The average thickness refers to the average value of the thickness of the corresponding layer in the region along the direction perpendicular to the surface of the battery, which should at least ensure the average thickness value of multiple thicknesses in the middle position and multiple thicknesses at the boundary connected to the first part.

[0115] According to an embodiment of the present invention, Figure 1 and Figure 2As shown, the width of the first electrode 3 is from 30 micrometers to 100 micrometers. And / or, the width of the second electrode 2 is from 30 micrometers to 100 micrometers.

[0116] In such an embodiment, setting the widths of the first electrode 3 and the second electrode 2 to be relatively narrow helps to improve the fill factor and output power of the back contact cell, and helps to optimize the current flow path to reduce current congestion and potential loss points.

[0117] In such an embodiment, setting the first part to be relatively thick is beneficial to maintaining the reliability of its electrical connection with the external electrical connector in the welded state, reducing the risk of poor welding, and under the condition of constant width, it can also increase the cross-sectional area of the connecting conductor to reduce the resistance of the connecting conductor. In the case of adopting the above embodiment, for the first part with a thickness greater than or equal to 25 micrometers, the second part should be set with an appropriate thickness. If it is set too thin, such as corresponding to the upper limit value of the thickness ratio of 10, it is not conducive to the current transmission between two adjacent fine grids; if it is set too thick, such as corresponding to the lower limit value of the thickness ratio of 4, it not only wastes the material of the connecting conductor, but also has a small improvement in electrical conduction, and may cause the connecting conductor to extend in the width direction during printing, and then cause short circuit due to overlapping with the opposite fine grid.

[0118] In a schematic embodiment, the first electrode 3 and the second electrode 2 can be formed by printing methods such as screen printing, such as Figure 1 and Figure 2 As shown, at this time, the widths of both the first electrode 3 and the second electrode 2 can be from 30 micrometers to 100 micrometers. Specifically, the first electrode 3 is disposed on the majority carrier (i.e., the majority carriers) doped region, and the second electrode 2 is disposed on the minority carrier (i.e., the minority carriers) doped layer. Further, the width of the first electrode 3 (i.e., w1) is configured to be less than the width of the second electrode 2 (i.e., w2), that is, 30μm ≤ w1 ≤ 100μm, 30μm ≤ w2 ≤ 100μm, and w1 < w2.

[0119] In such an embodiment, taking the cell body with an n-type silicon wafer as the substrate as an example, electrons are the majority carriers and holes are the minority carriers. Correspondingly, the p-type doped region is used as the minority carrier region for collecting minority carriers, that is, holes; correspondingly, the n-type doped region is used as the majority carrier region for collecting majority carriers, that is, electrons. Based on the characteristics of the back contact cell, when collecting minority carriers through the second electrode 2, holes will also be laterally transported in the substrate. During this process, holes are prone to carrier recombination with the majority carriers in the majority carrier region. Therefore, setting the second electrode 2 located in the minority carrier doped region to be wider can more effectively improve the collection efficiency of the second electrode 2 for minority carriers.

[0120] In a schematic embodiment, the first electrode 3 and the second electrode 2 can be directly electrically connected to the corresponding doped regions, or a transparent conductive oxide (i.e., TCO) layer can be provided between the electrodes (i.e., the first electrode 3 and the second electrode 2) and the corresponding doped regions. Based on the collection efficiency of minority carriers as described above, the minority carrier doped region and / or the transparent conductive oxide layer located on the minority carrier doped region can also be designed to be wider accordingly to further improve the collection efficiency of minority carriers. Among them, the first electrode 3 and / or the second electrode 2 are formed on the battery body 1 by, but not limited to, electroplating, evaporation, chemical vapor deposition, etc.

[0121] Similarly, taking the battery body with a p-type silicon wafer as the substrate as an example, electrons are minority carriers and holes are majority carriers. Therefore, the electrode located on the minority carrier doped region should also be set wider, and the specific effect will not be elaborated here. It should be understood that the embodiments of the present invention are not limited thereto.

[0122] For example, the widths of the first electrode 3 and the second electrode 2 can be set to be approximately equal.

[0123] Again, for example, the width of the first electrode 3 can be set to be greater than the width of the second electrode 2. Specifically, it should be appropriate to meet the collection requirements of the corresponding photo-generated carriers, which will not be elaborated here.

[0124] According to an embodiment of the present invention, as Figure 1 and Figure 2 shown, the portion of the battery body 1 located between the adjacent first electrode 3 and the second electrode 2 forms an isolation region. The insulating layer 4 covers a part of the isolation region.

[0125] In a schematic embodiment, as Figure 2 shown, the portion between the first electrode 3 and the second electrode 2 along the first direction forms an isolation region. Specifically, the insulating layer 4 extends from the upper part of the first electrode 3 to the isolation region and is spaced from the second electrode 2. The portion between the insulating layer 4 and the second electrode is covered by the connecting conductor 5 (the covered portion is only the region within the width range of the connecting conductor 5) to maintain the insulation effect between the first electrode 3 and the second electrode 2 (and the connecting conductor 5), and at the same time, leave enough width to ensure that the connecting conductor can be in full contact with the second electrode. Figure 4 is a schematic diagram of a top view of a back-contact battery according to another schematic embodiment of the present invention. Figure 5 is Figure 1 a partial cross-sectional view of the B1 - B2 portion of the schematic embodiment shown.

[0126] According to an embodiment of the present invention, the first electrode 3 and the second electrode 2 can be formed by a deposition process such as electroplating, as Figure 4 and Figure 5As shown, at this time, the width of the first electrode 3 is from 300 microns to 600 microns. And / or, the width of the second electrode 2 is from 300 microns to 600 microns.

[0127] In a schematic embodiment, as Figure 4 and Figure 5 shown, the widths of both the first electrode 3 and the second electrode 2 can be from 300 microns to 600 microns. Specifically, the first electrode 3 is disposed on a majority carrier doped region, and the second electrode 2 is disposed on a minority carrier doped layer. Further, the width of the first electrode 3 (i.e., w1) is configured to be less than the width of the second electrode 2 (i.e., w2), that is, 300μm ≤ w1 ≤ 600μm, 300μm ≤ w2 ≤ 600μm, and w1 < w2. Further, the sum of the areas of the first electrode 3 and the second electrode 2 on the first surface (such as the surface facing the viewing angle as Figure 4 shown) includes but is not limited to 50% or more of the total area of the first surface.

[0128] In this embodiment, setting the width of the second electrode 2 wider produces a technical effect similar to that of the embodiments shown in the above Figure 1 and Figure 2 wherein the electrode (i.e., the second electrode 2) located on the minority carrier doped region is set wider to improve the collection effect of minority carriers. Therefore, it will not be elaborated here.

[0129] In such an embodiment, the first surface is the backlight surface of the back contact battery, so there is no need to consider its light shielding loss. On this basis, by increasing the widths of the first electrode 3 and the second electrode 2 and the area ratio of the first surface they occupy, the current collection efficiency can be effectively improved, especially the collection efficiency of minority carriers on the minority carrier doped region. Moreover, setting electrodes with a larger width can also increase their cross-sectional areas and effectively reduce the series resistance. In addition, the wider first electrode 3 and second electrode 2 can also distribute the electric field more evenly and provide support for the battery body 1, which is still beneficial to improving the structural strength of the battery body.

[0130] According to an embodiment of the present invention, as Figure 4 and Figure 5 shown, the portion of the battery body 1 located between the adjacent first electrode 3 and second electrode 2 forms an isolation region. The insulating layer 4 covers the isolation region and extends onto the second electrode 2.

[0131] On the premise that the width of the battery body 1 is limited, if the widths of the first electrode 3 and the second electrode 2 are set wider, the distance between the first electrode 3 and the second electrode 2 in the first direction will be smaller. Therefore, the entire isolation region is covered with an insulating layer 4 and extends above the second electrode 2, which can be used to maintain the insulation between the first electrode 3 and the second electrode 2 in the first direction and prevent the connection conductor 5 from entering the isolation region, so as to avoid leakage caused by excessive electric field strength in the isolation region.

[0132] In a schematic embodiment, as Figures 1 to 5 shown, the back contact battery further includes a fourth electrode (which can also be called the main grid), the fourth electrode extends along the first direction, and is alternately and spaced apart from the connection conductor 5 along the second direction (such as Figure 1 the left - right direction shown), and the fourth electrode and the connection conductor 5 have different polarities. Specifically, the fourth electrode is connected to the first electrode 3 and is used to collect the current collected by the first electrode 3. Further, an insulating layer 4 is also correspondingly provided between the fourth electrode and the second electrode 2, and the part of the fourth electrode located between two adjacent insulating layers 4 also correspondingly forms a first part and a second part. Among them, the first part and the second part of the fourth electrode can adopt an implementation manner similar to that of the connection conductor 5 and have similar effects, so this will not be elaborated here.

[0133] According to the back contact battery provided by the present invention, as Figure 1 and Figure 2 shown, it includes a battery body 1, a first electrode 3, a second electrode 2, and a connection conductor 5. The battery body 1 has a relative first surface (such as the backlight surface of the battery body 1, that is, Figure 1 the surface facing the viewing angle shown; the corresponding second surface is the light - receiving surface) and a second surface. The first electrode 3 and the second electrode 2 (which can also be called fine grids, collector grid lines, sub - grids, etc., the first electrode 3 and the second electrode 2 have different polarities and are respectively used to extract the majority carriers or minority carriers of different doping regions) are provided on the first surface of the battery body 1, and the first electrode 3 and the second electrode 2 are alternately and spaced apart in sequence along the first direction (such as Figure 1 the up - down direction shown) and extend along the second direction. The connection conductor 5 is provided on the first surface, the connection conductor 5 extends along the first direction (such as Figure 1 the left - right direction shown), an insulating layer 4 is provided between the connection conductor 5 and the first electrode 3, and it is connected to the second electrode 2. The connection conductor 5 includes a first part (such as Figure 2 the N part shown) located between two adjacent insulating layers 4 along the first direction, and the surface of the first part facing away from the battery body 1 has a plurality of first protrusions 51, and the maximum height of the plurality of first protrusions 51 is greater than or equal to 8 micrometers.

[0134] In such an embodiment, the height of the first protrusion 51 formed on the first part is relatively large, which helps to improve the bonding force between the electrical connector 6 and the connecting conductor 5, increase the contact area, and reduce the contact resistance at the same time.

[0135] According to an embodiment of the present invention, as Figure 2 shown, the connecting conductor 5 further includes a second part (such as the M part shown in Figure 2 ) whose projection in the front projection of the first surface coincides with the projection of the first electrode 3. The ratio of the thickness of the first part to the thickness of the second part is between 4 and 10.

[0136] In such an embodiment, the thickness of the first part is related to the thickness of the second part. If it is too thin, it is not conducive to current transmission. If it is too thick, it will cause waste of materials.

[0137] In addition, as an independent embodiment, as Figure 2 shown, the connecting conductor 5 further includes a second part (such as the M part shown in Figure 2 ) whose projection in the front projection of the first surface coincides with the projection of the first electrode 3. The ratio of the thickness of the first part to the thickness of the second part is between 4 and 10. In the case of adopting the above independent embodiment, without considering the roughness or the height of the maximum protrusion of the connecting conductor 5 (of course, other contents of the embodiments of the present invention can be applied to this independent embodiment), the thickness of the first part is related to the thickness of the second part. The relatively thick first part can ensure the reliability of welding, and the relatively thin second part can realize the electrical transmission of adjacent same-sex fine grids along the extending direction of the connecting conductor, preventing partial bonding problems. If the second part is too thin, it is not conducive to current transmission. If it is too thick, it will cause waste of materials. The present application realizes the balance between material cost and electrical transmission effect by setting the thickness ratio to 4 - 10.

[0138] According to an embodiment of the present invention, as Figure 1 and Figure 2 shown, the thickness of the first part is greater than or equal to 25 microns. Its height can be slightly less than the height of the insulating layer 4, but it should not be too low to prevent the solder tape from being unable to obtain a reliable connection even through the bonding layer. Generally, the height difference between the lowest position of the first part and the highest position of the insulating layer 4 is between 10 and 50 microns, so as to ensure a good connection with the solder tape on the basis of using less connecting conductor material.

[0139] In such an embodiment, setting the first part thicker is beneficial to maintaining the reliability of the external electrical connector in the welding state, reducing the risk of poor welding, and under the condition of unchanged width, the cross-sectional area of ​​the connecting conductor can also be increased to reduce the resistance of the connecting conductor. In the case of the above embodiment, for the thickness of the first part greater than or equal to 25 microns, the second part should be set to a suitable thickness. If it is set too thin, such as corresponding to the upper limit value of the thickness ratio of 10, it is not conducive to the current transmission of two adjacent fine grids; and if it is set too thick, such as corresponding to the lower limit value of the thickness ratio of 4, it not only wastes the material of the connecting conductor, but also has little improvement on electrical conduction, and may cause the connecting conductor to extend in the width direction during printing, which then leads to overlapping with another opposite fine grid to cause a short circuit.

[0140] According to an embodiment of the present invention, Figure 1 and Figure 2 As shown, the thickness of the second portion is 5 micrometers to 15 micrometers.

[0141] In such an embodiment, for the thickness of the first part being greater than or equal to 25 microns, the second part should be set to a suitable thickness. If it is set too thin, such as the upper limit value corresponding to the thickness ratio of 10, it is not conducive to the current transmission of two adjacent fine grids; and if it is set too thick, such as the lower limit value corresponding to the thickness ratio of 4, it not only wastes the material of the connecting conductor, but also has little improvement on the electrical conduction, and may cause the connecting conductor to extend in the width direction during printing, and then cause overlap with another opposite fine grid to cause a short circuit.

[0142] According to an embodiment of the present invention, Figure 1 and Figure 2 As shown, the connecting conductor 5 also includes a first surface (such as Figure 2 The third part (as shown in the upper surface) of the orthographic projection of the insulating layer coincides with the projection of the insulating layer Figure 2 The first part (as shown in Figure 2 The thickness of the M portion) shown is greater than the thickness of the third portion.

[0143] In such an embodiment, the first part is used as the main connection point between the connecting conductor and the external electrical connector. Setting it thicker is beneficial to making the joint position with the electrical connector have better welding quality; correspondingly, the third part is not particularly thick, which can make the surface of the connecting conductor roughly flush, so as to reduce the warping deformation of the electrical connector after lamination.

[0144] According to an embodiment of the present invention, Figure 4 and Figure 5 As shown, the portion of the battery body 1 located between the adjacent first electrode 3 and the second electrode 2 forms an isolation region; the insulating layer covers the isolation region and extends onto the second electrode 2 .

[0145] In such an embodiment, on the premise that the width of the battery body 1 is limited, if the widths of the first electrode 3 and the second electrode 2 are set wider, the distance between the first electrode 3 and the second electrode 2 in the first direction will be smaller. Therefore, the entire isolation area is covered with the insulating layer 4 and extends above the second electrode 2, which can not only be used to maintain the insulation between the first electrode 3 and the second electrode 2 in the first direction, but also prevent the connecting conductor 5 from entering the isolation area to avoid leakage caused by excessive electric field strength in the isolation area.

[0146] Figure 6 is a partial cross-sectional view of a photovoltaic module according to an exemplary embodiment of the present invention, showing the first joint portion. Figure 7 is a partial cross-sectional view of a photovoltaic module according to another exemplary embodiment of the present invention, showing the second joint portion.

[0147] Based on the same inventive concept, the present invention also provides a photovoltaic module, as Figure 6 and Figure 7 shown, including a back-contact battery and an electrical connector 6 (which can also be called a solder ribbon or an interconnection strip for connecting at least two back-contact batteries in series). The electrical connector 6 electrically connects the connecting conductors 5 of at least two back-contact batteries, and a joint layer 7 (which can also be called solder, solder paste, such as solder, for filling between the facing surfaces of the connecting conductor 5 and the electrical connector 6 in a molten state to form a metal connection with good electrical conductivity) is provided between the electrical connector 6 and the connecting conductor 5. Specifically, the electrical connector 6 connects the connecting conductor 5 of one polarity (such as the positive electrode) of a back-contact battery, and at the same time connects the connecting conductor 5 of the other polarity (such as the negative electrode) of another adjacent back-contact battery.

[0148] According to an embodiment of the present invention, as Figure 6 shown, a plurality of first joint portions 71 are provided between the electrical connector 6 and the connecting conductor 5, and the plurality of first joint portions 71 are arranged at intervals in the first direction. The plurality of first joint portions 71 are relatively sparse, and the plurality of first joint portions 71 are discretely arranged below the electrical connector 6 and are not connected to each other.

[0149] According to an embodiment of the present invention, as Figure 6 shown, the first joint portion 71 is provided on the first part of the connecting conductor 5.

[0150] In an exemplary embodiment, as Figure 6 shown, a plurality of first joint portions 71 are arranged at intervals between the electrical connector 6 (i.e., the solder ribbon) and the surface of the connecting conductor 5 facing away from the battery body 1 (such as Figure 6 the upper surface shown). Among them, Figure 6Only a first joint portion 71 is schematically shown. It should be understood that a first joint portion 71 can be provided on each first portion of the connecting conductor 5. It should be understood that the embodiments of the present invention are not limited thereto.

[0151] For example, PAD points (also called pads) can be provided on at least a part of the first portions of the connecting conductor 5. The width of the PAD can be configured to be greater than the width of other parts of the connecting conductor 5, or form some special shapes, such as a rectangular portion, a rhombic portion, etc. protruding from the main body of the connecting conductor 5 in the second direction. In this way, it is beneficial to further increase the contact area between the first joint portion 71 (i.e., solder) and the connecting conductor 5.

[0152] In such an embodiment, the plurality of first joint portions 71 are spaced and discretely distributed in the first direction, which is beneficial to reducing the consumption of the first joint portion 71. Among them, the specific number and position of the first joint portion 71 can be set according to actual welding requirements. In addition to setting the first joint portion 71 on the first portion of the connecting conductor 5, it can also be set on the second portion or the third portion of the connecting conductor 5.

[0153] According to an embodiment of the present invention, as Figure 7 shown, the photovoltaic module includes a second joint portion 72, and the second joint portion 72 is located above at least two first electrodes 3.

[0154] In a schematic embodiment, as Figure 7 shown, the second joint portion 72 extends in the first direction above each first electrode 3 and the second electrode 2.

[0155] According to an embodiment of the present invention, as Figure 7 shown, a joint layer 7 is provided between the electrical connector 6 and the connecting conductor 5. The joint layer 7 is continuous along the extending direction of the electrical connector 6. The second joint portion 72 can be formed by densely arranging a plurality of first joint portions 71 and finally being melted and connected into one body to form Figure 7 the joint layer 7.

[0156] According to an embodiment of the present invention, as Figure 7 shown, the connecting conductor 5 includes a third portion whose projection in the positive projection of the first surface of the battery body 1 coincides with the projection of the insulating layer 4. An air gap 8 is formed between the joint layer 7 and the third portion of the connecting conductor 5.

[0157] In a schematic embodiment, as Figure 7As shown, the second joint portion 72 is continuously provided between the electrical connector 6 (i.e., the solder tape) and the connection conductor 5. Among them, before being pressed by the electrical connector 6, the second joint portion 72 can be discretely provided on the connection conductor 5, and then made thinner by pressing (specific pressing methods include but are not limited to adhesive film bonding and pressing, a press head machine, or any other method), and extended along the first direction. Specifically, the second joint portion 72 is spaced from the top of the insulating layer, forming an air gap 8. In such an embodiment, since the second joint portion 72 has formed a good connection and electrical connection relationship with the first and third parts (except the second part) of the first electrode 3, the part forming the air gap 8 may not be connected to the third part. In this way, it is beneficial to reduce the amount of the second joint portion 72 (i.e., solder paste).

[0158] In another exemplary embodiment, not shown in the figure, the second joint portion 72 can be continuously provided on the connection conductor 5 (such as in the form of a strip) on the connection conductor 5, and after pressing, it will basically completely fill the space between the electrical connector 6 and the connection conductor 5 (i.e., basically no air gap as shown in 6 will be formed). In this way, compared with Figure 6 and Figure 7 the embodiment shown, it can form a better electrical connection between the electrical connector 6 and the connection conductor 5, providing a greater tensile force, but also consuming a correspondingly larger amount of the second joint portion 72 (i.e., solder paste). Therefore, the specific arrangement of the joint layer 7 should be comprehensively set according to the required electrical connection performance and tensile force of the photovoltaic module.

[0159] It should also be noted that the directional terms mentioned in the embodiments, such as "up", "down", "front", "back", "left", "right", etc., are only for reference to the drawings and do not limit the protection scope of the present invention. Throughout the drawings, the same elements are denoted by the same or similar reference numerals. When it may cause confusion in understanding the present invention, conventional structures or configurations will be omitted.

[0160] The embodiments of the present invention have been described above. However, these embodiments are only for illustrative purposes and do not limit the scope of the present invention. Although the embodiments have been described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art can make various substitutions and modifications, and these substitutions and modifications should all fall within the scope of the present invention.

Claims

1. A back contact battery, characterized in that: include: A battery body (1) having a first surface and a second surface opposite to each other; A first electrode (3) and a second electrode (2) are arranged on a first surface of the battery body (1), the first electrode (3) and the second electrode (2) are arranged alternately and spaced in sequence along a first direction and extend along a second direction, the first direction intersecting the second direction; a connecting conductor (5) disposed on the first surface, the connecting conductor (5) extending along the first direction, an insulating layer (4) being disposed between the connecting conductor (5) and the first electrode (3), and connected to the second electrode (2); The connecting conductor (5) comprises a first portion located between two adjacent insulating layers (4) along the first direction and a second portion overlapping with a projection of the first electrode (3) in an orthographic projection of the first surface, wherein a surface of the first portion facing away from the battery body (1) has a first average roughness, and a surface of the second portion facing away from the battery body (1) has a second average roughness, wherein the second average roughness is smaller than the first average roughness.

2. The back contact cell according to claim 1, characterized in that: The first average roughness is greater than or equal to 5 micrometers.

3. The back contact battery according to claim 2, characterized in that: The second average roughness is less than 10 micrometers.

4. The back contact cell according to claim 1, characterized in that: The surface of the first portion facing away from the first surface has a plurality of first protrusions (51), and the maximum height of the plurality of first protrusions (51) along a direction perpendicular to the first surface is greater than or equal to 8 micrometers.

5. The back contact cell according to claim 1, characterized in that: The ratio of the thickness of the first portion to the thickness of the second portion is between 4-10.

6. The back contact cell according to claim 5, characterized in that: The thickness of the first portion is greater than or equal to 25 micrometers.

7. The back contact cell according to claim 6, characterized in that: The second portion has a thickness of 5 micrometers to 15 micrometers.

8. The back contact cell according to claim 1, characterized in that: The connecting conductor (5) further comprises a third portion which coincides with the projection of the insulating layer (4) in the orthographic projection of the first surface; The thickness of the first portion is greater than the thickness of the third portion.

9. The back contact battery according to claim 8, characterized in that The thickness of the third portion is less than or equal to 25 micrometers.

10. The back contact cell according to claim 1, characterized in that: Along the first direction, the width of the first electrode (3) is 30 micrometers to 100 micrometers; And / or, the width of the second electrode (2) is 30 micrometers to 100 micrometers.

11. The back contact cell according to claim 1 or 10, characterized in that: The portion of the battery body (1) located between the adjacent first electrode (3) and the second electrode (2) forms an isolation region; The insulating layer (4) covers a portion of the isolation region.

12. The back contact cell according to claim 1, characterized in that: The width of the first electrode (3) is 300 micrometers to 600 micrometers; And / or, the width of the second electrode (2) is 300 micrometers to 600 micrometers.

13. The back contact cell according to claim 1 or 12, characterized in that: The portion of the battery body (1) located between the adjacent first electrode (3) and the second electrode (2) forms an isolation region; The insulating layer (4) covers the isolation region and extends onto the second electrode (2).

14. A back contact battery, characterized in that: include: A battery body (1) having a first surface and a second surface opposite to each other; A first electrode (3) and a second electrode (2) are arranged on a first surface of the battery body (1), the first electrode (3) and the second electrode (2) being arranged alternately and spaced in sequence along a first direction and extending along a second direction; a connecting conductor (5) disposed on the first surface, the connecting conductor (5) extending along the first direction, an insulating layer (4) being disposed between the connecting conductor (5) and the first electrode (3), and connected to the second electrode (2); The connecting conductor (5) comprises a first portion located between two adjacent insulating layers (4) along the first direction, the surface of the first portion facing away from the battery body (1) having a plurality of first protrusions (51), and a maximum height of the plurality of first protrusions (51) being greater than or equal to 8 micrometers.

15. The back contact cell according to claim 14, characterized in that The connecting conductor (5) further comprises a second portion which coincides with the projection of the first electrode (3) in the orthographic projection of the first surface, and the ratio of the thickness of the first portion to the thickness of the second portion is between 4 and 10.

16. The back contact cell according to claim 15, characterized in that The thickness of the first portion is greater than or equal to 25 micrometers.

17. The back contact cell according to claim 16, characterized in that: The second portion has a thickness of 5 micrometers to 15 micrometers.

18. The back contact cell according to claim 14, characterized in that The connecting conductor (5) further comprises a third portion which coincides with the projection of the insulating layer (4) in the orthographic projection of the first surface; The thickness of the first portion is greater than the thickness of the third portion.

19. The back contact cell according to any one of claims 14 to 18, characterized in that: The portion of the battery body (1) located between the adjacent first electrode (3) and the second electrode (2) forms an isolation region; The insulating layer (4) covers the isolation region and extends onto the second electrode (2).

20. A photovoltaic module, characterized in that: include: A back contact battery as claimed in any one of claims 1 to 19; An electrical connector (6) electrically connects at least two connection conductors (5) of the back contact cells.

21. The photovoltaic module according to claim 20, characterized in that: A bonding layer (7) is provided between the electrical connection member (6) and the connection conductor (5), and the bonding layer (7) is continuous along the extension direction of the electrical connection member (6).

22. The photovoltaic module according to claim 21, characterized in that: The connecting conductor (5) includes a third portion that coincides with a projection of the insulating layer (4) in an orthographic projection of the first surface of the battery body (1); An air gap (8) is formed between the bonding layer (7) and the third portion of the connecting conductor (5).

23. The photovoltaic module according to claim 20, characterized in that: A plurality of first joining portions (71) are arranged between the electrical connector (6) and the connecting conductor (5), and the plurality of first joining portions (71) are arranged at intervals along a first direction.

24. The photovoltaic module according to claim 23, characterized in that: The first joint portion (71) is arranged on a first portion of the connecting conductor (5).

25. The photovoltaic module according to claim 21, characterized in that: It comprises a second bonding portion (72), wherein the second bonding portion (72) is located on at least two first electrodes (3).

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