Back contact solar cell and back contact photovoltaic module

Abstract

The invention relates to the technical field of solar cells, in particular to a back contact solar cell and a back contact photovoltaic module. The back contact solar cell comprises a cell body, a bonding pad group and a collector grid line. The bonding pad groups with the two polarities are alternately arranged on the back surface of the battery body at intervals along a first direction; each bonding pad group comprises a plurality of bonding pads which are arranged at intervals along the second direction and have the same polarity. The current collection grid lines with two polarities are arranged on the back surface of the battery body, and each bonding pad is connected with at least one current collection grid line with the same polarity and is arranged at intervals with the current collection grid line with the opposite polarity. In the first direction, the battery body is provided with first battery edges which are oppositely arranged, the bonding pads in the bonding pad set closest to the first battery edges are edge bonding pads, the distance between the edge bonding pads and the closest first battery edges is D1, the size of the battery body in the first direction is D2, and 0.043% < D1 / D2 < 0.870%. And the conversion efficiency of the back contact solar cell is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a back contact solar cell and a back contact photovoltaic module. BACKGROUND

[0002] The edge region of the back contact solar cell has a poor current collection effect, which affects the conversion efficiency of the back contact solar cell, and causes the power of the back contact photovoltaic module using the back contact solar cell to decrease. SUMMARY

[0003] Embodiments of the present application disclose a back contact solar cell and a back contact photovoltaic module, which can improve the conversion efficiency of the back contact solar cell.

[0004] To achieve the above-mentioned purpose, in a first aspect, embodiments of the present application disclose a back contact solar cell, comprising:

[0005] a cell body;

[0006] a plurality of pad groups of two polarities, which are alternately and spacedly arranged on the back surface of the cell body along a first direction; each of the pad groups comprises a plurality of pads of the same polarity, which are spacedly arranged along a second direction, and the first direction intersects the second direction; and

[0007] a plurality of current collecting grid lines of two polarities, which are arranged on the back surface of the cell body, and each of the pads is connected to at least one current collecting grid line of the same polarity and is spaced from the current collecting grid line of the opposite polarity;

[0008] along the first direction, the cell body has oppositely arranged first cell edges, the pads in the pad group closest to each of the first cell edges are edge pads, the distance between the edge pads and the closest first cell edge is D1, and the size of the cell body in the first direction is D2, wherein 0.043% < D1 / D2 < 0.870%.

[0009] In a possible implementation manner of the first aspect, 0.1mm < D1 < 2mm.

[0010] In a possible implementation manner of the first aspect, 0.1mm < D1 < 1mm.

[0011] In a possible implementation manner of the first aspect, a direct electrical connection is formed between the edge pads and the current collecting grid lines.

[0012] In a possible implementation manner of the first aspect, along the first direction, the edge pads are connected to the current collecting grid lines only at an end away from the closest first cell edge.

[0013] On the back of the battery body, the area between the edge pad and the nearest first battery edge is a grid-free area.

[0014] In a possible implementation of the first aspect, the back-contact solar cell further includes busbars, each of which extends along the second direction; wherein each busbar is connected to all the pads in each pad group; or, each busbar is connected to a portion of the pads in each pad group; or...

[0015] The back-contact solar cell is a non-busbar solar cell.

[0016] In a possible implementation of the first aspect, when the back contact solar cell further includes a busbar, the total area of ​​the busbar and the pad projected onto the cell body is S1, and the area of ​​the back side of the cell body is S2, wherein 0.05% ≤ S1 / S2 ≤ 6.2%.

[0017] When the back-contact solar cell is a non-busbar solar cell, the total area of ​​the pads projected onto the cell body is S1, and the area of ​​the back side of the cell body is S2, wherein 0.05% ≤ S1 / S2 ≤ 6.2%.

[0018] In a possible implementation of the first aspect, each of the collector grid lines extends along the first direction, and the collector grid lines of the two polarities are arranged alternately in a row along the second direction;

[0019] The multiple columns of collector grid lines are arranged at intervals along the first direction, and there is a discontinuity between adjacent columns of collector grid lines;

[0020] Apart from the edge pads, the other pad groups are respectively disposed in each of the discontinuous regions, and the pads included in these pad groups are inner pads;

[0021] On both sides of each of the discontinuous regions, the collector grid lines with the same polarity as the inner pads are called same polarity collector grid lines; along the first direction, there is an overlap break between two adjacent same polarity collector grid lines, and each of the inner pads is respectively disposed at each of the overlap breaks, and the two ends of the inner pads overlap with the two same polarity collector grid lines respectively.

[0022] In a possible implementation of the first aspect, on both sides of each of the discontinuous regions, the collector grid lines with opposite polarity to the inner pads are opposite polarity collector grid lines; along the first direction, there is an isolation break between the two opposite polarity collector grid lines.

[0023] Wherein, along the first direction, the width W1 of the isolation break is greater than the width W2 of the overlapping break.

[0024] In a possible implementation manner of the first aspect, 0.3mm≤W1≤1.2mm; and / or,

[0025] 0.15mm≤W2≤0.7mm.

[0026] In a possible implementation manner of the first aspect, the shape of the solder pad comprises a square, a diamond, an oval, an H shape, a T shape, a trapezoid; and / or,

[0027] The number of the solder pad groups is greater than or equal to 30 groups and less than or equal to 120 groups; and / or,

[0028] The distance between two adjacent solder pad groups is D3, where 1.5mm≤D3≤8mm.

[0029] In a second aspect, the embodiments of the present application disclose a back contact photovoltaic module, comprising:

[0030] a plurality of electrically connected back contact solar cells, at least one of the back contact solar cells being the back contact solar cell of the first aspect; and

[0031] a plurality of solder strips, each of the solder strips being welded with each of the solder pad groups, and the solder strip welded on the edge solder pad being an edge solder strip, the distance between the edge solder strip and the first cell edge being D4, where 0.043%<D4 / D2<0.870%.

[0032] In a possible implementation manner of the second aspect, 0.1mm<D4<2mm.

[0033] In a possible implementation manner of the second aspect, 0.1mm<D4<1mm.

[0034] In a possible implementation manner of the second aspect, along the second direction, the cell body has a second cell edge oppositely arranged, and a welding position of the solder strip closest to the second cell edge is a starting welding point.

[0035] The distance between the starting welding point and the second cell edge closest to the starting welding point is D5, where 0.5mm≤D5≤7mm.

[0036] In a third aspect, the embodiments of the present application disclose a back contact photovoltaic module, comprising:

[0037] a plurality of electrically connected back contact solar cells, at least one of the back contact solar cells being the back contact solar cell of the first aspect; and

[0038] A plurality of solder strips, each of the solder strips is welded with each of the pad groups, along the first direction, each of the pad groups is arranged at intervals with adjacent pad groups of opposite polarity, and no insulating glue is arranged between them.

[0039] In a possible implementation of the third aspect, each of the current collecting grid lines extends along the first direction, and the current collecting grid lines of two polarities are alternately arranged at intervals along the second direction to form a column;

[0040] A plurality of columns of the current collecting grid lines are arranged at intervals along the first direction, and each of the columns of the current collecting grid lines has an interval region between adjacent columns of the current collecting grid lines;

[0041] Each of the pad groups except the edge pad is arranged in each of the interval regions, and the pads of the pad groups are inner side pads;

[0042] On both sides of each of the interval regions, the current collecting grid line opposite in polarity to the inner side pad is a heteropolarity current collecting grid line; along the first direction, there is an isolation break between adjacent two of the heteropolarity current collecting grid lines;

[0043] In the isolation break, along the first direction, the width of the isolation break is W1, and the width of the solder strip is W3, where W1>W3.

[0044] In a fourth aspect, the embodiments of the present application disclose a back contact photovoltaic module, comprising:

[0045] A plurality of electrically connected back contact solar cells, at least one of the back contact solar cells is the back contact solar cell of the first aspect; and

[0046] A plurality of solder strips, each of the solder strips is welded with each of the pad groups;

[0047] In the welding area of the solder strip and the pad, along the direction away from the cell body, the cell body is sequentially stacked with a pad, a silver-tin alloy layer, a first tin-lead alloy layer, a conductive metal-tin alloy layer, a conductive metal layer, and a second tin-lead alloy layer.

[0048] The thickness of the silver-tin alloy layer is T1, and the thickness of the second tin-lead alloy layer is T2; where 2.5<T2 / T1<300.

[0049] In a possible implementation of the fourth aspect, the thickness T1 of the silver-tin alloy layer is 0.1 μm-10 μm; and / or,

[0050] The first tin-lead alloy layer does not contain bismuth elements; and / or,

[0051] The material of the conductive metal layer is selected from at least one of copper or aluminum.

[0052] In a possible implementation manner of the fourth aspect, the collector grid lines of the two polarities are alternately and spacedly arranged into a column along the second direction;

[0053] The plurality of columns of the collector grid lines are spacedly arranged along the first direction, and there is an interruption region between two adjacent columns of the collector grid lines;

[0054] Except for the edge pad, each of the remaining pad groups is respectively arranged in each of the interruption regions, and the pads of the pad groups are inner pads;

[0055] On both sides of each of the interruption regions, the collector grid lines of the same polarity as the inner pads are homopolar collector grid lines; along the first direction, there is an overlap break between two of the homopolar collector grid lines, each of the inner pads is respectively arranged in each of the overlap breaks, and the inner pads are respectively overlapped with the two collector grid lines at two ends thereof;

[0056] Along the first direction, a width of the overlap break is W2, and a width of the solder strip is W3, where W2> W3.

[0057] Compared with the prior art, the application has at least the following beneficial effects:

[0058] In the back contact solar cell of the application, the pad groups of the two polarities are alternately and spacedly arranged on the back surface of the cell body along the first direction. Each pad group includes a plurality of pads of the same polarity which are spacedly arranged along the second direction. Each pad is connected with at least one collector grid line of the same polarity and is spacedly arranged with a collector grid line of the opposite polarity. In this way, the pads and the collector grid lines connected with the pads can be distributed on the back surface of the cell body along the first direction and the second direction, which is beneficial to better carrier collection and current conduction of the cell body.

[0059] On this basis, a spacing between the edge pad and the nearest first cell edge is D1, and a size of the cell body in the first direction is D2, where 0.043% < D1 / D2 < 0.870%.

[0060] When D1 / D2 satisfies the above ratio range, the spacing between the edge pad and the nearest first cell edge is close enough, so that the collector grid line connected with the edge pad is close enough to the first cell edge, which is beneficial to expand the carrier collection area of the collector grid line and shorten the transmission distance of the carrier near the first cell edge to the edge pad. The shorter the transmission distance is, the smaller the series resistance loss of the carrier due to resistance in the cell body is, and the higher the conversion efficiency of the back contact solar cell is.

[0061] And, the distance between the edge pad and the closest edge of the first cell is not too close, thereby leaving enough engineering allowance for printing of the edge pad to reduce the risk of printing the edge pad outside the cell body.

[0062] In this way, the back contact solar cell can have higher conversion efficiency and reduce the risk of abnormal printing of the edge pad. BRIEF DESCRIPTION OF DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0064] Figure 1 A structure diagram of a back contact solar cell;

[0065] Figure 2A A structure diagram of a back contact solar cell (the back contact solar cell is a solar cell without busbar lines) disclosed in an embodiment of the present application;

[0066] Figure 2B A structure diagram of a back contact solar cell; Figure 2A A local enlarged view of the A area shown in FIG. 1;

[0067] Figure 3 A simulation diagram of the conversion efficiency of the back contact solar cell disclosed in an embodiment of the present application and D1;

[0068] Figure 4 A sectional view of a back contact solar cell disclosed in an embodiment of the present application;

[0069] Figure 5 A structure diagram of a back contact solar cell (all the pads in each pad group are connected with each busbar line) disclosed in an embodiment of the present application;

[0070] Figure 6 A structure diagram of a back contact solar cell (each busbar line is connected with a part of pads in each pad group) disclosed in an embodiment of the present application;

[0071] Figure 7 A connection diagram of an inner pad with a same-polarity current collecting busbar line and a different-polarity current collecting busbar line disclosed in an embodiment of the present application;

[0072] Figure 8 A structure diagram of a deformed pad disclosed in an embodiment of the present application;

[0073] Figure 9AA structural schematic diagram of a back contact photovoltaic module disclosed in an embodiment of the present application;

[0074] Figure 9B A structural schematic diagram of a back contact photovoltaic module disclosed in an embodiment of the present application; Figure 9A A partial enlarged view of the B region shown in FIG. 1;

[0075] Figure 10 A sectional view of a back contact photovoltaic module disclosed in an embodiment of the present application at a soldering region of a solder pad and a solder ribbon;

[0076] Figure 11 A method flow chart of a manufacturing method of a back contact photovoltaic module disclosed in an embodiment of the present application;

[0077] Figure 12 Another method flow chart of a manufacturing method of a back contact photovoltaic module disclosed in an embodiment of the present application;

[0078] Figure 13 A structural schematic diagram of an automatic string soldering device disclosed in an embodiment of the present application;

[0079] Figure 14 A schematic diagram of a structure obtained after a rotatable carrier adsorbs a cell in an embodiment of the present application;

[0080] Figure 15 A structural schematic diagram of a back contact solar cell disclosed in an embodiment of the present application;

[0081] Figure 16 A schematic diagram of a target placement angle of a cell after a rotatable carrier is circumferentially unfolded in an embodiment of the present application;

[0082] Figure 17 A schematic diagram of a state of a robot placing a cell in an embodiment of the present application;

[0083] Figure 18 A schematic diagram of a second included angle disclosed in an embodiment of the present application;

[0084] Figure 19 A schematic diagram of a state of winding a conductive wire in an embodiment of the present application;

[0085] Figure 20 A schematic diagram of a state of coating a curable adhesive in an embodiment of the present application;

[0086] Figure 21 A schematic diagram of a state of curing a curable adhesive in an embodiment of the present application;

[0087] Figure 22 A schematic diagram of a distribution of a cured adhesive strip disclosed in an embodiment of the present application;

[0088] Figure 23 A state diagram when welding the conductive wire and the first gate line is disclosed in an embodiment of the present application;

[0089] Figure 24 Another structure diagram of a back contact photovoltaic module is disclosed in an embodiment of the present application;

[0090] Figure 25 A partial cross-sectional diagram of a back contact photovoltaic module is disclosed in an embodiment of the present application;

[0091] Figure 26 Another partial cross-sectional diagram of a back contact photovoltaic module is disclosed in an embodiment of the present application;

[0092] Figure 27 A diagram of a second correction angle is disclosed in an embodiment of the present application.

[0093] Explanation of reference signs:

[0094] 1. Back contact solar cell; 101, first cell edge; 102, gate line free area; 103, second cell edge; 11, cell body; 111, silicon substrate; 112, doped layer; M12, pad group; 12, pad; 12a, edge pad; 12b, inner pad; 13, current collecting gate line; 13a, same polarity current collecting gate line; 13b, different polarity current collecting gate line; 131, overlap break; 132, isolation break; 14, bus bar; 15, inner pad; 16, connecting gate line; 17, encapsulation adhesive layer; M1, cell string to be welded;

[0095] X, first direction; Y, second direction;

[0096] D1, distance between edge pad and closest first cell edge; D2, dimension of cell body in first direction; D3, distance between two adjacent pad groups; D4, distance between edge solder strip and first cell edge; D5, distance between starting point and closest second cell edge; D6, first distance; D7, second distance; D8, third distance; D9, fourth distance; D10, fifth distance; D11, sixth distance; W1, width of isolation break; W2, width of overlap break; W3, width of solder strip; W4, preset maximum offset of solder strip; T1, thickness of first tin-based alloy layer; T2, thickness of second tin-based alloy layer; θ1, first included angle; θ2, second included angle; Δθ2, second correction angle;

[0097] 2. Solder strip; 2a, edge solder strip; 2b, middle solder strip; 201, starting point; 21, silver-tin alloy layer; 22, first tin-lead alloy layer; 23, conductive metal-tin alloy layer; 24, conductive metal layer; 25, second tin-lead alloy layer;

[0098] 3. Rotatable carrier; 31. Manipulator; 4. Guide mechanism; 5. Gluing mechanism; 51. Cured adhesive strip; 6. Curing lamp box; 7. Infrared lamp box. DETAILED DESCRIPTION

[0099] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0100] In the present application, the positions or location relationships indicated by the terms "upper", "inner", "outer", "lateral", "longitudinal" and the like are based on the positions or location relationships shown in the drawings. These terms are mainly used for better describing the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific position, or to be constructed and operated in a specific position.

[0101] In addition, in addition to being used to indicate the positions or location relationships, the above-mentioned terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. Those of ordinary skill in the art can understand the specific meanings of these terms in the present application according to the specific circumstances.

[0102] In addition, the terms "provided", "connected", "linked" should be understood broadly. For example, it can be fixedly connected, detachably connected, or integrally constructed; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication between two devices, elements or components. Those of ordinary skill in the art can understand the specific meanings of the above-mentioned terms in the present application according to the specific circumstances.

[0103] In addition, the terms "first", "second" and the like are mainly used to distinguish different devices, elements or components (the specific types and structures can be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, the meaning of "multiple" is two or more.

[0104] The inventor found in actual research that the edge region of the back contact solar cell has stress concentration phenomenon and is more prone to hidden cracks under external force. During the welding process, the pressure pin presses the solder strip on the solder pad, and the solder pad bears concentrated load. If the solder pad is arranged at the edge of the cell, the stress concentration effect will further amplify the influence of external force, and hidden cracks at the edge are prone to occur. Therefore, in order to avoid this phenomenon of poor welding at the edge region, the edge solder pad is usually arranged at a position far away from the edge of the cell, for example, the distance between the edge solder pad and the edge of the cell is more than 2 mm.

[0105] Reference Figure 1 , Figure 1 is a schematic diagram of a structure of a back contact solar cell 1. Since the distance between the edge solder pad and the edge of the cell is large, in order to fully collect the current on the back of the cell, it is necessary to arrange a current collecting grid line 13 and a bus bar grid line 14 between the edge solder pad and the edge of the cell. The bus bar grid line 14 outside the edge solder pad does not participate in welding, so the current of the current collecting grid line 13 needs to be collected to the bus bar grid line 14, and then collected to the edge solder pad through the connecting grid line 16. The current transmission path can refer to Figure 1 , the current transmission path of the current collecting grid line 13 is indicated by an arrow (→) in Figure 1 . The edge solder pad is equivalent to the inward retraction of the connected current collecting grid line 13 and bus bar grid line 14, which is called an inward retracted solder pad 15 in the industry.

[0106] It can be understood that this part of the current collecting grid line 13 is not directly electrically connected with the inward retracted solder pad 15, but indirectly electrically connected. This also leads to the problem that this part of the current collecting grid line 13 has a long current transmission path and large current transmission loss.

[0107] Based on the above analysis, the embodiment of the present application provides a back contact solar cell, the distance between the edge solder pad and the nearest first edge of the cell is close enough, so that the current collecting grid line connected to the edge solder pad is close enough to the first edge of the cell, which is beneficial to expand the carrier collection area of the current collecting grid line, shorten the transmission distance of the carrier near the first edge of the cell to the edge solder pad. The shorter the transmission distance, the smaller the series resistance loss of the carrier due to resistance in the cell body, and the higher the conversion efficiency of the back contact solar cell. Moreover, since the current collecting area of the current collecting grid line is already close enough to the first edge of the cell, the current collecting grid line no longer needs to collect current beyond the outside of the edge solder pad, and can form a direct electrical connection with the edge solder pad. In addition, compared with the edge design with the connecting grid line 16 and the inward retracted solder pad 15, the carrier transmission path in the present application is shortened, so that the transmission loss of the carrier is further reduced, and the edge EL (Electroluminescence, electroluminescence) blackening problem is solved.

[0108] The technical solutions of the present application will be described below in conjunction with the embodiments and the drawings.

[0109] Figure 2A is a structural schematic diagram of a back contact solar cell disclosed by an embodiment of the present application. For the convenience of understanding, the first direction X is Figure 2A the lateral direction of the paper, and also corresponds to the length direction of the current collecting grid line 13, and the second direction Y is Figure 2A the longitudinal direction of the paper. Of course, the second direction Y does not necessarily have to be perpendicular to the first direction X, and can also be approximately perpendicular, for example, the included angle between the two is 80°, 85°, 87° or 89°.

[0110] Please refer to Figure 2A , the embodiment of the present application discloses a back contact solar cell 1, which comprises a cell body 11, two kinds of polar pad groups M12 and two kinds of current collecting grid lines 13.

[0111] The two kinds of polar pad groups M12 are alternately and spacedly arranged on the back surface of the cell body 11 along the first direction X. Each pad group M12 comprises a plurality of pads 12 with the same polarity which are spacedly arranged along the second direction Y, and the first direction X intersects the second direction Y.

[0112] The two kinds of current collecting grid lines 13 are arranged on the back surface of the cell body 11, and each pad 12 is connected to at least one current collecting grid line 13 with the same polarity and is spaced from the current collecting grid line 13 with the opposite polarity.

[0113] In the first direction X, the cell body 11 has oppositely arranged first cell edges 101, the pad in the pad group M12 closest to each first cell edge 101 is an edge pad 12a, the spacing between the edge pad 12a and the closest first cell edge 101 is D1, and the size of the cell body 11 in the first direction X is D2, wherein 0.043% < D1 / D2 < 0.870%.

[0114] The beneficial effects of the back contact solar cell 1 of the present application will be described below.

[0115] In the back contact solar cell 1 of the present application, the two polarities of the pad groups M12 are alternately and spacedly arranged on the back surface of the cell body 11 in the first direction X, specifically, the pad group M12 of the positive polarity and the pad group M12 of the negative polarity are alternately and spacedly arranged in the first direction X. Each pad group M12 includes a plurality of pads 12 of the same polarity which are spacedly arranged in the second direction Y. Each pad 12 is connected to at least one current collecting grid line 13 of the same polarity and is spaced from the current collecting grid line 13 of the opposite polarity. In this way, the pads 12 and the current collecting grid lines 13 connected to the pads 12 can be relatively uniformly and densely distributed on the back surface of the cell body 11 in the first direction X and the second direction Y, which is conducive to better carrier collection and confluence of the cell body 11 and reduces the resistance loss caused by the transmission of the carriers in the cell body 11.

[0116] On this basis, the distance between the edge pad 12a and the closest first cell edge 101 is D1, and the size of the cell body 11 in the first direction X is D2, wherein 0.043% < D1 / D2 < 0.870%. For example, D1 / D2 is 0.044%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.869%.

[0117] When D1 / D2 satisfies the above ratio range, the distance between the edge pad 12a and the closest first cell edge 101 is close enough, so that the current collecting grid line 13 connected to the edge pad 12a is close enough to the first cell edge 101, which is conducive to expanding the carrier collection area of the current collecting grid line 13 and shortening the transmission distance of the photo-generated carriers near the first cell edge 101 to the edge pad 12a. The shorter the transmission distance, the smaller the series resistance loss caused by the resistance of the carriers in the cell body 11, and the higher the conversion efficiency of the back contact solar cell 1.

[0118] In addition, the distance between the edge pad 12a and the closest first cell edge 101 is not too close, so as to leave enough engineering allowance for the printing of the edge pad 12a to reduce the risk of the edge pad 12a being printed out of the cell body 11.

[0119] In this way, the back contact solar cell 1 can not only have a higher conversion efficiency, but also reduce the risk of abnormal printing of the edge pad 12a.

[0120] The distance D1 between the edge pad and the closest first cell edge will be described in detail below.

[0121] It should be noted that, since the battery body 11 of the present application has two oppositely arranged first battery edges 101, for each edge pad 12a, the closest first battery edge 101 means the one of the two first battery edges 101 that is closest to the edge pad 12a.

[0122] Please refer to Figure 2A and Figure 3 Optionally, 0.1mm < D1 < 2mm. D1 is for example 0.1mm, 0.3mm, 0.5mm, 0.7mm, 0.9mm, 1.1mm, 1.3mm, 1.5mm, 1.7mm, 1.9mm or 1.99mm.

[0123] It should be noted that, for the industrialization specification of the back contact solar cell 1 with the dimension along the first direction X being 166mm, 182mm or 210mm, when D1 < 2mm, the distance between the edge pad 12a and the closest first battery edge 101 is close enough, so that the current collecting grid line 13 connected to the edge pad 12a is close enough to the first battery edge 101, which is beneficial to expand the carrier collection area of the current collecting grid line 13 and shorten the transmission distance of the photo-generated carriers near the first battery edge 101 to the edge pad 12a. The shorter the transmission distance is, the smaller the series resistance loss of the carriers in the battery body 11 due to the resistance is, which is beneficial to improve the conversion efficiency of the back contact solar cell 1.

[0124] In addition, when D1 > 0.1mm, the edge pad 12a will not be too close to the first battery edge 101, so as to leave enough engineering allowance for the printing of the edge pad 12a, so as to reduce the risk of the paste of the edge pad 12a being printed out of the battery body 11. Furthermore, when D1 > 0.1mm, enough placement accuracy allowance is provided for the placement offset of the solder ribbon 2 on the edge pad 12a, so as to avoid the solder ribbon 2 being placed out of the back contact solar cell 1 when being placed, thereby avoiding the solder ribbon 2 contacting other back contact solar cells 1 or metal components to cause electric leakage, which is beneficial to improve the welding yield of the back contact photovoltaic module.

[0125] Further, 0.1mm < D1 < 1mm. When D1 satisfies the above distance range, the current collection range of the current collecting grid line 13 on the edge pad 12a is further expanded, which can make full use of the region of the battery body 11 with the width of 1mm from the first battery edge 101, so as to further improve the conversion efficiency of the back contact solar cell 1. Figure 3 As shown in Figure 3The simulation diagram between the conversion efficiency of the back contact solar cell disclosed in the embodiments of the present application and D1 (the distance between the edge bonding pad 12a and the closest first cell edge 101) can be seen that when D1 < 1 mm, the conversion efficiency of the back contact solar cell is not obviously improved with the change of D1, which indicates that the back contact solar cell has approached the optimal conversion efficiency at this time.

[0126] The edge bonding pad and the current collecting grid line of the present application will be described in detail below.

[0127] In some embodiments, referring to Figure 2A and Figure 2B , the edge bonding pad 12a and the current collecting grid line 13 form a direct electrical connection.

[0128] In the present application, the term "direct electrical connection" means that there is no other electrode structure between the edge bonding pad 12a and the current collecting grid line 13 to improve the current transmission efficiency, reduce the current transmission loss, and thus improve the conversion efficiency of the back contact solar cell 1 and reduce the edge EL blackening problem of the back contact solar cell 1.

[0129] More specifically, the way to achieve a direct electrical connection is, for example, lapping or butt joint. Lapping means that the partial area of the current collecting grid line 13 and the partial area of the edge bonding pad 12a overlap each other to make them directly contact, thereby forming a direct electrical connection. Butt joint means that the partial area of the current collecting grid line 13 and the partial area of the edge bonding pad 12a are butted together to make them directly contact, thereby forming a direct electrical connection.

[0130] In some embodiments, referring to Figure 2A and Figure 2B , along the first direction X, the edge bonding pad 12a is connected to the current collecting grid line 13 only from one end away from the closest first cell edge 101. The connection mode is, for example, a direct electrical connection.

[0131] In addition, on the back surface of the cell body 11, the area between the edge bonding pad 12a and the closest first cell edge 101 is a grid line free area 102.

[0132] For the convenience of understanding, the one end of the edge bonding pad 12a away from the closest first cell edge 101 will be referred to as the inner side end of the edge bonding pad 12a below. Correspondingly, the other end of the edge bonding pad 12a along the first direction X is the outer side end.

[0133] In the present application, the edge bonding pad 12a is close enough to the first cell edge 101, and the current collecting grid line 13 connected to the inner side end of the edge bonding pad 12a is also close enough to the first cell edge 101, thereby being able to fully collect the current on the back surface of the cell body 11. It should be noted that in the present application, the current is the macroscopic manifestation of the directional movement of charge carriers.

[0134] In this way, the back contact solar cell 1 of the present application can sufficiently collect the current on the back surface of the cell body 11 even if no grid lines are provided at the outer end of the edge pad 12a, so that the area between the edge pad 12a and the closest first cell edge 101 becomes a grid line free area 102.

[0135] In the present application, the term "grid line free area 102" refers to an area without printed grid lines, such as current-carrying grid lines, bus bar grid lines, interconnection grid lines, or connection grid lines.

[0136] The back contact solar cell 1 of the present application helps to reduce the risk of grid lines being printed outside the cell body 11 by providing the grid line free area 102. Moreover, the grid line free area 102 is also conducive to reducing the edge leakage phenomenon and the carrier recombination phenomenon, as will be described below.

[0137] The cell body of the present application will be described below.

[0138] In some embodiments, referring to Figure 4 , the cell body 11 includes a silicon substrate 111 and two types of doped layers 112.

[0139] The two types of doped layers 112 are arranged at intervals on the back surface of the silicon substrate 111. The current collecting grid lines 13 of various polarities form ohmic contacts with the doped layers 112 of corresponding doping types, respectively.

[0140] Since no grid lines are provided in the area between the edge pad 12a and the closest first cell edge 101, the present application can remove the doped layers around the periphery of the first cell edge 101 to reduce the edge leakage phenomenon and the carrier recombination phenomenon caused by the doped layers.

[0141] In the present application, the back contact solar cell can be provided with bus bar grid lines or without bus bar grid lines, which will be described in detail below.

[0142] In some embodiments, referring back to Figure 2A , the back contact solar cell 1 is a bus bar grid line free solar cell, also known as a main grid free solar cell. The bus bar grid line free solar cell does not need to print bus bar grid lines 14, which can reduce the amount of silver paste used and is also conducive to improving the contact properties of the metal electrode, thereby improving the fill factor and conversion efficiency of the back contact solar cell.

[0143] Further, when the back contact solar cell 1 is a bus bar grid line free solar cell, the total area of the orthographic projection of the pad 12 on the cell body 11 is S1, and the area of the back surface of the cell body 11 is S2, wherein 0.05%≤S1 / S2≤6.2%.

[0144] It can be understood that the soldering area of the back contact solar cell 1 is the total area of the normal projection of the soldering pads 12 on the solar cell body 11. As analyzed above, S1 / S2 is the soldering area ratio. When 0.05%≤S1 / S2≤6.2%, the warpage of the solar cell 1 caused by the mismatch of the thermal expansion coefficients of the materials involved in the soldering can be controlled within a small range, for example, 4 mm. Considering that the silicon substrate is relatively hard, when the warpage of the solar cell caused by the soldering is greater than 4 mm, it may cause the solar cell to crack during the packaging of the module. Therefore, controlling the warpage of the solar cell within a small range can improve the packaging yield of the back contact photovoltaic module.

[0145] It should be noted that the warpage of the solar cell refers to the maximum height of the back contact solar cell 1 with respect to the reference plane on which the back contact solar cell 1 is placed after the soldering is completed.

[0146] Optionally, the number of the soldering pad groups M12 is greater than or equal to 30 groups and less than or equal to 120 groups, for example, 30 groups, 40 groups, 50 groups, 60 groups, 70 groups, 80 groups, 100 groups, or 120 groups. When the back surface of the back contact solar cell 1 is provided with the soldering pad groups M12 within the above range, the distance between the soldering pad groups M12 is relatively small, and the current collected by the current collecting grid lines 13 can be transmitted to the soldering pad groups M12 in a shorter distance and then be collected by the soldering ribbon, thereby reducing the ohmic loss of the current during the transmission in the current collecting grid lines 13, which is conducive to improving the conversion efficiency of the back contact solar cell 1.

[0147] In addition, considering that the warpage of the back contact solar cell 1 is proportional to the number of the soldering pad groups M12, the soldering pad groups M12 within the above range can control the warpage of the solar cell within a small range, for example, less than 4 mm, thereby reducing the packaging failure rate of the back contact photovoltaic module caused by the large warpage of the solar cell, and further improving the packaging yield and reliability of the back contact photovoltaic module.

[0148] Optionally, the distance between the adjacent two soldering pad groups M12 is D3, where 1.5 mm≤D3≤8 mm. D3 is, for example, 1.5 mm, 2 mm, 4 mm, 6 mm, 7 mm, or 8 mm. When the distance D3 between the adjacent two soldering pad groups M12 satisfies the above distance range, the current collected by the current collecting grid lines 13 can be transmitted to the soldering pad groups M12 in a shorter distance, thereby reducing the ohmic loss caused by the transmission of the current in the current collecting grid lines 13.

[0149] It should be noted that the distance between the adjacent two soldering pad groups M12 refers to the distance between the centers of the adjacent two soldering pad groups M12 along the first direction X.

[0150] In some embodiments, please refer to Figure 5and Figure 6 The back contact solar cell 1 further comprises busbar lines 14, each of which extends along the second direction Y. In the present application, the busbar lines 14 can also be welded with the solder ribbons 2, thereby increasing the soldering area of the solder ribbons 2 and improving the pull-off force of the solder ribbons 2 and thus the soldering reliability. In the present application, the busbar lines 14 have various connection modes with the pad groups M12, which will be described below.

[0151] In one example, as shown in Figure 5 each of the busbar lines 14 is connected with all the pads 12 in each of the pad groups M12. In this example, all the pads 12 in each of the pad groups M12 are interconnected by the busbar lines 14, so that even if some of the pads 12 are disconnected from the solder ribbons 2, the current on these pads 12 can still be collected by the other pads 12 in the same pad group M12 through the busbar lines 14, avoiding the situation that the current cannot be collected.

[0152] In another example, as shown in Figure 6 each of the busbar lines 14 is connected with a part of the pads 12 in each of the pad groups M12. For example, each of the busbar lines 14 is connected with one, two, three or four of the pads 12 in each of the pad groups M12. The busbar lines 14 connected to each of the pad groups M12 can be one or more.

[0153] In this way, the pad groups M12 can increase the soldering area through the busbar lines 14, and when a plurality of pads 12 are connected by the busbar lines 14, the plurality of pads 12 can also be interconnected by the busbar lines 14, avoiding the situation that the current collected by the current collecting lines connected to a single pad cannot be collected when the pad is not soldered properly. Compared with the previous example, the total area of the busbar lines 14 in the present example can be smaller, thereby reducing the amount of silver paste and improving the bifaciality of the back contact solar cell.

[0154] Further, when the back contact solar cell 1 further comprises the busbar lines 14, the total area of the normal projection of the busbar lines 14 and the pads 12 on the cell body 11 is S1, and the area of the back surface of the cell body 11 is S2, wherein 0.05%≤S1 / S2≤6.2%.

[0155] As mentioned above, both the busbar grid lines 14 and the pads 12 are involved in soldering, and the total area S1 of the busbar grid lines 14 and the pads 12 in the orthographic projection on the battery body 11 corresponds to the soldering area. In the present application, the ratio S1 / S2 of S1 to the area S2 of the back surface of the battery body 11 is the soldering area ratio. The inventors have found that the warpage of the back contact solar cell 1 is in direct proportion to the soldering area ratio, and when S1 / S2≤6.2%, the warpage of the back contact solar cell 1 can be controlled within a small range, for example, the warpage of the back contact solar cell 1 is controlled within 4 mm. Considering that the silicon substrate is relatively hard, when the warpage of the cell caused by soldering is greater than 4 mm, it may cause the cell to crack during the packaging of the module, and therefore, controlling the warpage of the back contact solar cell 1 within a small range can improve the packaging yield of the back contact photovoltaic module.

[0156] Furthermore, 0.05%≤S1 / S2, which indicates that the back contact solar cell 1 has a large enough soldering area, which means that the contact between the solder strip 2 and the back contact solar cell 1 is more sufficient, which helps to reduce the contact resistance and improve the soldering pull-off force, and thus improve the output power and reliability of the back contact photovoltaic module using the back contact solar cell 1.

[0157] The inner pads 12b and the collector grid lines 13 of the present application will be described below.

[0158] In some embodiments, referring to Figure 2A and Figure 7 , each collector grid line 13 extends along the first direction X, and the collector grid lines 13 of the two polarities are alternately and spacedly arranged in a column along the second direction Y. In the present application, the first direction X can be perpendicular to the second direction Y. For example, the first direction X is the length direction of the battery body 11, and the second direction Y is the width direction of the battery body 11. In this way, the collector grid lines 13 of the two polarities are distributed on the back surface of the battery body 11 along the first direction X and the second direction Y, which is conducive to efficiently collecting the current on the back surface of the battery body 11.

[0159] On this basis, a plurality of columns of collector grid lines 13 are spacedly arranged along the first direction X, and each two adjacent columns of collector grid lines 13 have an intermittent area therebetween. Except for the edge pads 12a, each pad group M12 is respectively arranged in each intermittent area, and the pads 12 included in each pad group M12 are inner pads 12b.

[0160] Among them, on both sides of each intermittent area, the collector grid lines 13 of the same polarity as the inner pads 12b are the same-polarity collector grid lines 13a. Along the first direction X, each two adjacent same-polarity collector grid lines 13a have a lap joint gap 131 therebetween, each inner pad 12b is arranged in each lap joint gap 131, and the two ends of each inner pad 12b are respectively lapped with the two same-polarity collector grid lines 13a.

[0161] More specifically, when the inner side pad 12b is a positive pad 12, the same polarity busbar 13a refers to a positive busbar 13. Conversely, when the inner side pad 12b is a negative pad 12, the same polarity busbar 13a refers to a negative busbar 13.

[0162] It can be understood that two same polarity busbars 13a are directly connected to the same inner side pad 12b by lapping, so as to improve current transmission efficiency, reduce current transmission loss, and further improve the conversion efficiency of the back contact solar cell 1.

[0163] Since the same polarity busbar 13a and the inner side pad 12b are stacked together when lapped, the height of the lapped area is higher than the rest of the inner side pad 12b, thereby forming a height difference. Therefore, in the embodiment of the present application, the solder strip 2 can be placed in the lapped gap 131, thereby being staggered with the lapped area. In this way, the solder strip 2 contacts the area with a higher height of the solder pad 12, and is staggered with the area having a height difference on the solder pad 12, so that the solder strip 2 can better adhere to and be welded to the solder pad 12.

[0164] Further, on both sides of each intermittent area, the busbar 13 opposite to the polarity of the inner side pad 12b is a different polarity busbar 13b. Along the first direction X, the two different polarity busbars 13b have an isolation gap 132 therebetween.

[0165] Among them, along the first direction X, the width W1 of the isolation gap 132 is greater than the width W2 of the lapped gap 131.

[0166] In this way, the solder strip 2 welded on the inner side pad 12b can be as far away from the different polarity busbar 13b as possible to avoid short circuit phenomenon.

[0167] It can be understood that when the inner side pad 12b is a positive pad 12, the different polarity busbar 13b refers to a negative busbar 13. Conversely, when the inner side pad 12b is a negative pad 12, the different polarity busbar 13b refers to a positive busbar 13.

[0168] Optionally, 0.15mm≤W2≤0.7mm. The width W2 of the overlap break 131 is, for example, 0.15mm, 0.2mm, 0.3mm, 0.5mm or 0.7mm. Since the projection width of the solder strip 2 on the battery sheet is 0.15mm-0.25mm, and the preset maximum offset of the solder strip 2 is <0.1mm, the overlap break 131 in the above width range can accommodate the solder strip 2 in the above width range, and has an engineering allowance for the offset of the solder strip 2, so that the solder pad 12 can be placed in the overlap break 131, and the solder strip 2 does not contact the same-polarity current collecting grid line 13a to cause silver etching reaction to cause grid breakage.

[0169] In the present application, the silver etching reaction refers to the reaction between the tin-based alloy on the solder strip 2 and the silver in the grid line, which will cause the loss of silver and affect the conductivity of the grid line. Especially when the tin-based alloy material completely reacts with the metal material (such as Ag) on the solder pad to cause the soldering area to have no metal material, which leads to grid breakage or poor soldering in the soldering area, and cannot provide effective transmission medium for the carriers.

[0170] In addition, the solder strip 2 can be staggered with the overlap area on the solder pad 12, so that the solder strip 2 is better attached to the solder pad 12, and the soldering effect is better.

[0171] Furthermore, since the length of the solder pad 12 along the first direction X needs to be greater than the width W2 of the overlap break 131 to simultaneously overlap with two same-polarity current collecting grid lines 13a, the overlap break 131 in the above width range makes the length of the solder pad 12 not too long, which is beneficial to reduce the light-shielding area of the solder pad 12 and the amount of silver paste used during printing.

[0172] Optionally, 0.3mm≤W1≤1.2mm. W1 is, for example, 0.3mm, 0.6mm, 0.9mm or 1.2mm. When the width W1 of the isolation break 132 meets the above width range, the opposite-polarity current collecting grid line 13b can avoid the solder strip 2 in the above width range and has sufficient offset engineering allowance for the placement of the solder strip 2, thereby avoiding short circuit phenomenon. In this way, the opposite-polarity current collecting grid line 13b can achieve insulation and isolation from the solder strip 2 even without coating insulating glue. In addition, the isolation break 132 in the above width range is not too wide to avoid the opposite-polarity current collecting grid line 13b being too short to affect the collection efficiency of the carriers.

[0173] For example, as shown in Figure 7 the shape of the solder pad includes a square. The square solder pad has uniform width at each part, and can form good soldering with the square solder pad when the solder strip is offset.

[0174] For another example, as shown in Figure 8 (A), the shape of the solder pad 12 also includes a rhombus. As shown in Figure 8The shape of the solder pad 12 further comprises a rectangle as shown in (B). As shown in (B), the shape of the solder pad 12 further comprises an ellipse. As shown in (B), the shape of the solder pad 12 further comprises an H shape. As shown in (B), the shape of the solder pad 12 further comprises a T shape. As shown in (B), the shape of the solder pad 12 further comprises a trapezoid. Figure 8 Figure 8 Figure 8

[0175] The solder pad 12 in the shape of a rectangle or an ellipse is wide in the middle and narrow at both ends, and the solder pad 12 in the shape of a rectangle or an ellipse can be welded with the solder ribbon 2 by using the wider middle part, thereby forming a good welding effect, and the solder pad 12 in the shape of a rectangle or an ellipse is narrow at both ends, which can reduce the amount of silver paste used when printing. The solder pad 12 in the shape of an H is wide at both ends, which can provide sufficient offset engineering allowance for printing the same-polarity current collecting grid line 13a.

[0176] Please refer to Figure 9A The embodiment of the present application discloses a back contact photovoltaic module, which comprises a plurality of back contact solar cells 1 connected in an electrical manner and a plurality of solder ribbons 2. At least one back contact solar cell 1 is the back contact solar cell 1 disclosed by the embodiment of the present application.

[0177] Each solder ribbon 2 is welded with each solder pad group M12, and the solder ribbon 2 welded on the edge solder pad 12a is an edge solder ribbon 2a, and the distance between the edge solder ribbon 2a and the closest first cell edge 101 is D4, wherein 0.043% < D4 / D2 < 0.870%.

[0178] The beneficial effects of the back contact photovoltaic module of the present application will be described below.

[0179] When D4 / D2 satisfies the above ratio range, D4 / D2 is, for example, 0.044%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.869%. The distance between the edge solder ribbon 2a and the first cell edge 101 is close enough, so that the current on the edge solder pad 12a can be transmitted to the edge solder ribbon 2a through a shorter transmission path. The shorter the transmission path, the smaller the series resistance loss caused by the resistance of the transmission medium itself in the edge solder pad 12a and the edge solder ribbon 2a, and the higher the power density of the back contact photovoltaic module.

[0180] In addition, the distance between the edge solder ribbon 2a and the closest first cell edge 101 is not too close, so as to leave enough placement engineering allowance for the edge solder ribbon 2a, so as to avoid the phenomenon that the edge solder ribbon 2a is placed outside the back contact solar cell 1 and cannot collect current.

[0181] In this way, the back contact photovoltaic module can have a higher power density and can reduce the risk of electric leakage of the edge solder ribbon 2a.

[0182] ​​​The distance D4 between the edge tab 2a and the first cell edge 101 will be described in detail below.

[0183] Optionally, 0.1mm < D4 < 2mm. D4 is for example 0.11mm, 0.3mm, 0.5mm, 0.7mm, 0.9mm, 1.1mm, 1.3mm, 1.5mm, 1.7mm, 1.9mm or 1.99mm. For the industrialization specification of the back contact solar cell 1 with the dimension along the first direction X being 166mm, 182mm or 210mm, when D4 < 2mm, the distance between the edge tab 2a and the nearest first cell edge 101 is close enough, so that the current on the edge pad 12a can be transmitted to the edge tab 2a with a shorter transmission path. The shorter the transmission distance is, the smaller the series resistance loss caused by the bulk resistance of the transmission medium in the edge pad 12a and the edge tab 2a is, and the higher the power density of the back contact photovoltaic module is.

[0184] And when 0.1mm < D4, the distance between the edge tab 2a and the nearest first cell edge 101 is not too close, so that there is enough margin for the edge tab 2a to be placed, to avoid the phenomenon that the edge tab 2a is placed outside the back contact solar cell 1 and cannot collect current.

[0185] Further, 0.1mm < D4 < 1mm. When D4 < 1mm, the current collection range of the current collection grid line 13 on the edge pad 12a is further expanded, and the cell body 11 area with the width of 1mm from the first cell edge 101 can be fully utilized, further improving the conversion efficiency of the back contact solar cell 1. At the same time, the current on the edge pad 12a can be transmitted to the edge tab 2a with a shorter transmission path, further improving the power density of the back contact photovoltaic module.

[0186] The starting point 201 of the tab 2 of the present application will be described in detail below.

[0187] In some embodiments, along the second direction Y, the cell body 11 has oppositely arranged second cell edges 103, and the welding position of the tab 2 closest to the second cell edge 103 is the starting point 201.

[0188] It should be noted that the starting point 201 is often located on the pad closest to the second cell edge 103 in the pad group.

[0189] Wherein, the distance between the starting point 201 and the nearest second cell edge 103 is D5, and 0.5mm ≤ D5 ≤ 5mm.

[0190] When the distance D5 between the soldering point 201 and the closest second cell edge 103 satisfies the above distance range, the current collecting grid line 13 close to the second cell edge 103 has a shorter current transmission path to the current transmission path of the soldering point 201, which is beneficial to reduce the series resistance loss caused by current transmission. Moreover, since the second cell edge 103 is the weak part of the back contact solar cell 1, when the distance D5 between the soldering point 201 and the closest second cell edge 103 satisfies the above distance range, the mechanical pressure caused by the soldering of the solder strip 2 can be avoided to break the back contact solar cell 1.

[0191] With reference to Figure 9A and Figure 9B The embodiment of the present application discloses a back contact photovoltaic module, which comprises a plurality of electrically connected back contact solar cells 1 and a plurality of solder strips 2. At least one back contact solar cell 1 is the back contact solar cell 1 of the first aspect. Each solder strip 2 is welded with each solder pad group M12.

[0192] Among them, along the first direction X, each solder pad group M12 is spaced apart from the adjacent and opposite polarity current collecting grid line 13, and there is no insulating glue between the two.

[0193] The beneficial effects of the back contact photovoltaic module of the present application are described below.

[0194] The present application realizes insulation isolation by spacing each solder pad group M12 from the adjacent and opposite polarity current collecting grid line 13, and does not need to set insulating glue between the two for insulation, which is beneficial to reduce the material cost and simplify the production steps.

[0195] Moreover, the shrinkage stress in the curing process of the insulating glue is one of the important reasons for the warping of the back contact solar cell 1. Then, the back contact solar cell 1 of the present application can avoid forming shrinkage stress on the back of the back contact solar cell 1 by canceling the insulating glue, which is beneficial to reduce the warping degree of the back contact solar cell 1, and further reduce the welding failure phenomenon caused by the large warping degree of the back contact solar cell 1.

[0196] More specifically, along the first direction X, the width of the isolation fracture 132 is W1, and the width of the solder strip 2 is W3, wherein W1>W3.

[0197] Since the width W1 of the isolation fracture 132 is greater than the width W3 of the solder strip 2, the isolation fracture 132 has enough engineering allowance for the offset of the solder strip 2 when placed. The width W1 of the isolation fracture 132 can be set according to the offset amount of the solder strip. In this way, even if the solder strip 2 is offset when placed, the solder strip 2 can still be spaced apart from the heteropolarity current collecting grid line 13b on both sides of the isolation fracture, thereby realizing insulation isolation. In this way, the back contact photovoltaic module no longer needs to set insulating glue for insulation.

[0198] Please refer to Figure 9A and Figure 10 The embodiment of the present application also discloses a back contact photovoltaic module, comprising a plurality of electrically connected back contact solar cells 1 and a plurality of solder strips 2. Each solder strip 2 is welded with each solder pad group M12.

[0199] In the welding area of the solder strip 2 and the solder pad 12, in the direction away from the cell body 11, the cell body 11 is sequentially stacked with the solder pad 12, the silver-tin alloy layer 21, the first tin-lead alloy layer 22 and the conductive metal-tin alloy layer 23, the conductive metal layer 24 and the second tin-lead alloy layer 25.

[0200] The thickness of the silver-tin alloy layer 21 is T1, and the thickness of the second tin-lead alloy layer 25 is T2; wherein 2.5 < T2 / T1 < 300.

[0201] The beneficial effects of the back contact photovoltaic module of the present application are described below.

[0202] The solder strip 2 of the present application can be placed on the lap joint fracture 131 to stagger the lap joint area of the two same-polarity current collecting grid lines 13a, so that the solder strip 2 can be more accurately attached and welded with the solder pad 12, and thus it is not necessary to fill the tin paste between the solder strip 2 and the solder pad 12 or between the solder strip 2 and the current collecting grid line 13.

[0203] Since the tin paste will cause the silver-tin alloy layer 21 to be too thick, and the present application does not fill the tin paste, the thickness T1 of the silver-tin alloy layer 21 is relatively thin, and T1 satisfies the following relationship 2.5 < T2 / T1 < 300, and T2 / T1 is for example 2.6, 3, 10, 20, 30, 40, 50, 60, 80, 100, 150, 200, 250 or 299. The thinner silver-tin alloy layer 21 can reduce the material usage of the grid line material, and also can reduce the process, so as to achieve the economic benefit of reducing the production cost without sacrificing the power density of the back contact photovoltaic module.

[0204] Optionally, the thickness T1 of the silver-tin alloy layer 21 is 0.1 μm to 10 μm, for example 0.1 μm, 0.5 μm, 1 μm, 2 μm, 5 μm, 8 μm or 10 μm. The silver-tin alloy layer 21 with the thickness range can form a good combination after being welded with the solder pad 12, so as to reduce the false welding and delamination phenomenon. Moreover, the silver-tin alloy layer 21 with the thickness range will not be too thick to cause the waste of the grid line material, so as to achieve the purpose of reducing the cost and saving the process.

[0205] It can be understood that since the present application does not fill the tin paste, the first tin-lead alloy layer 22 does not contain bismuth element, so as to avoid the use of rare elements, especially in the case of large-scale photovoltaic product market usage, which can greatly reduce the industrialization cost.

[0206] Optionally, the conductive metal layer 24 is made of at least one of copper or aluminum. Copper and aluminum have low resistivity, which can reduce the resistance transmission loss in the current transmission process of the back contact photovoltaic module. Moreover, copper and aluminum are low in cost, which can also reduce the production cost of the photovoltaic product.

[0207] It should be noted that when the conductive metal layer 24 is copper, the conductive metal-tin alloy layer 23 is a copper-tin alloy layer. When the conductive metal layer 24 is aluminum, the conductive metal-tin alloy layer 23 is an aluminum-tin alloy layer.

[0208] In some embodiments, for the solder ribbon 2 and the current collecting grid line 13 connected to the same pad 12, the two are arranged at intervals.

[0209] That is, the solder ribbon 2 and the current collecting grid line 13 are arranged at intervals in the overlap region with the pad 12, so that the solder ribbon 2 can better fit the pad 12, and thus it is not necessary to fill the solder paste between the solder ribbon 2 and the pad 12.

[0210] Further, along the first direction X, the width of the overlap break 131 is W2, and the width of the solder ribbon 2 is W3, where W2 > W3.

[0211] In this way, the width W2 of the overlap break 131 provides a margin for the offset of the solder ribbon 2, and the width W2 of the overlap break 131 can be set according to the offset amount of the solder ribbon 2. Even if the solder ribbon 2 is offset, the solder ribbon 2 can still be arranged at intervals in the overlap region with the current collecting grid line 13 and the pad 12, and the solder ribbon 2 can fit the pad 12 after being placed, without the need to fill the solder paste before welding.

[0212] In contrast, in the welding process of the related art, it is often necessary to fill the solder paste between the solder ribbon and the pad to enable the solder ribbon to form good contact with the pad, and the use of the solder paste increases the manufacturing cost of the back contact photovoltaic module.

[0213] Moreover, the welding process in the related art is difficult to achieve the distance between the edge solder ribbon and the first cell edge D4 satisfying 0.043% < D4 / D2 < 0.870%. This is because in the welding process of the related art, the press needle is used to press the solder ribbon on the pad, and the pad bears concentrated load. If the pad is close to the first cell edge, the stress concentration effect will further amplify the influence of external force, and edge hidden cracks are prone to occur. In order to avoid such edge area welding defects, the pad is usually arranged at a position far from the first cell edge.

[0214] In addition, in the welding process of the related art, the offset amount of the solder ribbon is large, and the risk of cross-contact of the solder ribbon is large. In order to reduce the risk of cross-contact short circuit, it is often necessary to arrange an insulating adhesive between the pad group and the heteropolar current collecting grid line.

[0215] In contrast, the welding process of the present application does not need to press the bonding wire to the pad to weld the bonding wire to the pad, reduces the risk of edge crack, and the edge pad can be closer to the edge of the first battery, so that the edge bonding wire can also be closer to the edge of the first battery, and the distance D4 between the edge bonding wire and the edge of the first battery satisfies 0.043% < D4 / D2 < 0.870%.

[0216] Furthermore, the welding process of the present application can make the bonding wire wrap over the pad group with high precision, effectively reduce or eliminate the risk of the bonding wire contacting the current collecting grid line, and there is no need to print polymer insulating glue. Moreover, the alignment precision between the bonding wire and the pad group is improved, which is also conducive to the formation of surface contact between the bonding wire and the pad group, and even without filling the solder paste between the two, a good contact can be formed.

[0217] The welding process of the present application will be described in detail below.

[0218] Referring to Figure 11 Some embodiments of the present application provide a manufacturing method of a back contact photovoltaic module, which can include the following steps S100-S500.

[0219] S100, matching a to-be-welded battery string and providing a rotatable carrier. The to-be-welded battery string includes a plurality of back contact solar cells arranged in sequence in a second direction, and a plurality of pad groups provided on the back contact solar cells. The plurality of pad groups are alternately and spacedly arranged on the back of the battery body along a first direction. Each of the pad groups includes a plurality of pads with the same polarity and spacedly arranged along the second direction. The first direction intersects the second direction.

[0220] S200, obtaining a circumferential dimension of the rotatable carrier, and determining a target placement angle of the back contact solar cell when placed along the circumference of the rotatable carrier based on the circumferential dimension and a distance between two adjacent target pad groups in the back contact solar cell.

[0221] Optionally, the rotatable carrier includes but is not limited to a cylindrical roller. The rotatable carrier can rotate at a uniform speed.

[0222] Optionally, each of the pad groups is arranged at equal intervals in the first direction, and the target pad group can be any pad group.

[0223] Optionally, the distances between at least some adjacent pad groups are different, and the target pad group can be selected from the pad groups in the key area as needed. For example, the back contact solar cell includes a main area and an edge area, the distance between the adjacent pad groups located in the main area is a first distance, the distance between the adjacent pad groups located in the edge area is a second distance, and the first distance and the second distance are different. The two adjacent target pad groups can be any two pad groups located in the main area.

[0224] S300, place the back contact solar cell on the rotatable carrier according to the target placement angle.

[0225] Optionally, the target placement angle of each back contact solar cell can be determined one by one.

[0226] Optionally, the structure of each back contact solar cell is the same, and the target placement angle of each back contact solar cell can be placed according to the target placement angle of any one back contact solar cell.

[0227] Optionally, the rotatable carrier can vacuum adsorb the back contact solar cell to realize the placement and fixation of the back contact solar cell on the rotatable carrier.

[0228] S400, spiral the solder strip on the pad group of each back contact solar cell along the circumference of the rotatable carrier.

[0229] S500, weld the solder strip and the pad group to form a cell string.

[0230] In the embodiments of the present application, the rotatable carrier can be provided to match the cell string to be welded, and the target placement angle of the back contact solar cell when placed along the circumference of the rotatable carrier is determined according to the circumferential size of the rotatable carrier and the spacing between the adjacent two target pad groups in the back contact solar cell; then, the back contact solar cell is placed on the rotatable carrier according to the target placement angle, so that a single solder strip can be spirally wound on the pad group of each back contact solar cell along the circumference of the rotatable carrier, the alignment of the solder strip and the pad group is realized, and the welding of the solder strip and the pad group is carried out subsequently, so as to obtain the cell string. The embodiments of the present application can establish a reference coordinate system based on the rotatable carrier, and realize the welding between the solder strip and the pad group by the way of pre-determining the target placement angle, placing the back contact solar cell according to the target placement angle, and self-aligning the solder strip, which is beneficial to realize the size alignment of the solder strip relative to the pad group at the sub-millimeter level, effectively eliminate the inertial deviation caused by the high-speed back-and-forth placement of the mechanical hand for multiple solder strips, and does not need to be isolated by the insulating glue and compensated by the metal solder, so as to facilitate to increase the number of pad groups, reduce the spacing between the pad groups, improve the welding precision, and further realize the high-precision, low-resistance and low-cost cell interconnection process, and ensure and improve the production yield and long-term reliability of the back contact photovoltaic module.

[0231] In some embodiments of the present application, please refer to Figure 12 , the manufacturing method of the back contact photovoltaic module further comprises a step S600.

[0232] S600, pattern the solder strip to form a plurality of sub-solder strips.

[0233] Here, the connection relationship between the sub-solder strip and the pad group can be patterned to divide the solder strip into a plurality of sub-solder strips.

[0234] For example, the patterning process of the solder strip includes, but is not limited to, a cutting process.

[0235] In the embodiments of the present application, after the single solder strip is spirally wound on the pad groups of the back contact solar cells and the solder strip is welded with the pad groups, the multiple sub-solder strips are obtained by cutting the solder strip, so that the repeated solder strip alignment and placement and welding procedures can be avoided, and the production efficiency and yield can be improved.

[0236] It should be noted that in some embodiments of the present application, the matching of the to-be-welded cell string in step S100 and the provision of the rotatable carrier can include the following steps S110-S130.

[0237] S110, obtaining an unfolded length of the to-be-welded cell string in a second direction.

[0238] Here, the unfolded length of the to-be-welded cell string can be different due to different assembly patterns of the to-be-welded cell string.

[0239] Optionally, the unfolded length of the to-be-welded cell string includes, but is not limited to, 728mm-1570mm, for example, the unfolded length can be 728mm, 1176mm or 1570mm, etc.

[0240] S120, determining a target circumference based on the unfolded length; the target circumference is greater than or equal to the unfolded length.

[0241] S130, providing a rotatable carrier with a circumference of the target circumference.

[0242] In the embodiments of the present application, the rotatable carrier with a circumference greater than or equal to the unfolded length of the to-be-welded cell string can be used to unfold and lay the to-be-welded cell string on the outer surface of the rotatable carrier in one direction, so that a single solder strip can be spirally wound on the pad groups of each back contact solar cell in the to-be-welded cell string.

[0243] In some examples, only one to-be-welded cell string can be placed on the rotatable carrier; or, the axial dimension of the rotatable carrier is large, and multiple to-be-welded cell strings can be placed along the axial direction, wherein the solder strip corresponds to the to-be-welded cell string one by one.

[0244] It is worth mentioning that in some embodiments, the material of the rotatable carrier is related to its moment of inertia. The above target circumference can also be determined in combination with the unfolded length of the to-be-welded cell string and the material of the rotatable carrier to more accurately select the rotatable carrier.

[0245] Optionally, the rotatable carrier is a cylindrical roller, and the material density of the cylindrical roller is greater than 7g / cm 3The material of the cylindrical roller can be, for example, a metal material such as stainless steel or aluminum alloy, etc. In addition, the cylindrical roller can be a hollow roller or a solid roller.

[0246] In some examples, the radius of the cylindrical roller is defined as R, and the circumference is defined as C, so C=2πR, and R≥115 mm.

[0247] For the sake of clarity, the manufacturing method of the back contact photovoltaic module provided by the embodiments of the present application is described below. Figure 13 An exemplary structural diagram of an automatic string welding device is provided. The manufacturing method of the back contact photovoltaic module is described in detail in some of the following embodiments in combination with the device. Figure 13 The manufacturing method of the back contact photovoltaic module is described in detail in combination with the device.

[0248] Please refer to Figure 13 and Figure 14 In the loading station, the battery string M1 to be welded can be matched, a rotatable carrier 3 can be provided, and after the target placement angle θ corresponding to the back contact solar cell 1 is determined, the back contact solar cell 1 is placed on the rotatable carrier 3 according to the target placement angle θ. The target placement angle θ corresponding to the back contact solar cell 1 can be determined in various ways.

[0249] In some embodiments of the present application, please refer to Figure 15 and Figure 16 In step S200, the target placement angle of the back contact solar cell when placed along the circumference of the rotatable carrier is determined based on the circumferential dimension and the spacing between the two adjacent target pad groups in the back contact solar cell, which can include the following steps S210 and S220.

[0250] S210, the spacing between the two adjacent target pad groups is defined as D3, the circumferential dimension is C, and the first included angle is θ1.

[0251] S220, according to the formula: θ1=arcsin(D3 / C), the first included angle θ1 is determined; wherein the target placement angle θ is equal to the first included angle θ1, i.e. θ=θ1.

[0252] In some examples, taking the back contact solar cell 1 shown in Figure 15 as an example, a plurality of pad groups M12 are provided on the back contact solar cell 1, and the plurality of pad groups M12 are, for example, arranged at equal intervals in the first direction. Assuming that each back contact solar cell 1 in the battery string M1 to be welded has been sequentially placed on the circumferential surface of the rotatable carrier 3 according to the target placement angle θ, then as shown in Figure 16As shown in FIG. 1, after the circumferential surface of the rotatable carrier 3 is laid flat, the solder strip 2 is spirally wound on the pad groups M12 of each back contact solar cell 1, and the solder strip 2 can form a helical track with a pitch D3 and a rise angle θ on the circumferential surface of the rotatable carrier 3, that is, the winding pitch of the solder strip 2 can be equal to the distance between adjacent pad groups in the same back contact solar cell 1. Moreover, Figure 16 The two A point positions shown in FIG. 1 are the same when the circumferential surface of the rotatable carrier 3 is a cylindrical surface. Based on this, when the distance between adjacent two target pad groups is defined as D3, the circumferential dimension of the rotatable carrier 3 is C, and the first included angle is θ1, then the first included angle θ1 = arcsin(D3 / C). In the embodiments of the present application, the target placement angle θ is set to be equal to the first included angle θ1, which can ensure that a single solder strip is spirally wound between the pad groups M12 of each back contact solar cell 1.

[0253] It can be understood that in embodiments in which the distances between some adjacent pad groups are different, the back contact solar cell 1 can be placed according to the target placement angle θ, and the solder strip 2 can be spirally wound on the circumferential surface of the rotatable carrier 3 to align with each pad group M12.

[0254] For example, 0° ≤ absolute value of the target placement angle ≤ 1°.

[0255] Here, the target placement angle matching the placement direction of the back contact solar cell 1 relative to the edge of the end face of the rotatable carrier 3 can be positive or negative; for example, it can be positive when the back contact solar cell 1 is placed in a clockwise deflection relative to the edge of the end face of the rotatable carrier 3, and it can be negative when the back contact solar cell 1 is placed in a counterclockwise deflection relative to the edge of the end face of the rotatable carrier 3.

[0256] In some examples, the absolute value of the target placement angle ranges from 0.051° to 0.638°. The target placement angle may, for example, be 0.051°, 0.087°, 0.195°, 0.389°, or 0.638°.

[0257] In some examples, taking the rotatable carrier 3 as a cylindrical drum with a radius R = 375 mm and the distance D3 = 8 mm between adjacent two target pad groups in the same back contact solar cell 1 as an example, the target placement angle θ = θ1 = 0.389° can be obtained by the formula θ1 = arcsin(D3 / C). Similarly, matching different values of the radius in the cylindrical drum and different values of the distance between adjacent two target pad groups in the same back contact solar cell 1, the target placement angle can also be obtained based on the foregoing calculation formula.

[0258] In some embodiments of the present application, the spacing between two adjacent target pad groups in the same back contact solar cell is not greater than the product of the number of pad groups in the back contact solar cell minus one and 230 mm.

[0259] In some embodiments, it is understood that the back contact solar cell 1 is generally placed on the rotatable carrier 3 by a mechanical arm 31 of a robot. Specifically, the mechanical arm 31 generally places the back contact solar cell 1 at a corresponding position by using the position data of the back contact solar cell 1 and the position of the rotatable carrier 3 obtained through visual positioning. Then, the back contact solar cell 1 is fixed by the rotatable carrier 3. Figure 13 and Figure 17 It is understood that the back contact solar cell 1 is generally placed on the rotatable carrier 3 by a mechanical arm 31 of a robot. Specifically, the mechanical arm 31 generally places the back contact solar cell 1 at a corresponding position by using the position data of the back contact solar cell 1 and the position of the rotatable carrier 3 obtained through visual positioning. Then, the back contact solar cell 1 is fixed by the rotatable carrier 3.

[0260] Here, it is understood that the mechanical arm 31 and the rotatable carrier 3 generally have a small angular deviation when picking up the back contact solar cell 1 and positioning. Therefore, in some other embodiments of the present application, referring to Figure 18 The first mark point Mark1 and the second mark point Mark2 can be arranged on the back contact solar cell 1 along the second direction (i.e., the direction in which the pad groups extend) to measure and determine the first correction angle based on the first mark point Mark1 and the second mark point Mark2, so as to compensate for the angular deviation of the mechanical arm 31 and the rotatable carrier 3 when picking up the back contact solar cell 1 and positioning. The shape, material and implementation form of the first mark point Mark1 and the second mark point Mark2 are not limited in the embodiments of the present application, and any shape, material and implementation form that can be measured and recognized are acceptable.

[0261] Correspondingly, the step S200 of determining the target placement angle of the back contact solar cell when placed along the circumferential direction of the rotatable carrier based on the circumferential dimension and the spacing between two adjacent target pad groups in the back contact solar cell can include the following steps S210' to S240'.

[0262] S210', defining the spacing between two adjacent target pad groups as D3, the circumferential dimension of the rotatable carrier as C, and the first included angle as θ1; and determining the first included angle θ1 according to the formula: θ1=arcsin(D3 / C).

[0263] S220', placing the back contact solar cell on the rotatable carrier according to the first included angle.

[0264] S230', obtaining the first distance from the first mark point to the reference reference line, the second distance from the second mark point to the reference reference line, and the third distance between the first mark point and the second mark point, and determining the first correction angle based on the first distance, the second distance and the third distance.

[0265] Optionally, the reference baseline is a virtual straight line, an extension direction of the reference baseline is parallel to an axis of the rotatable carrier, and the reference baseline, the first mark point Mark1 and the second mark point Mark2 can be located in a same plane parallel to a surface of the back contact solar cell.

[0266] S240', determining a target placement angle according to the first included angle and the first correction angle.

[0267] For example, as shown in Figure 18 In step S230', determining the first correction angle based on the first distance, the second distance and the third distance can include steps S231-S233.

[0268] S231, defining the first distance as D6, the second distance as D7, the third distance as D8, the second included angle as θ2, and the first correction angle as Δθ1.

[0269] S232, determining the second included angle θ2 according to the formula θ2=arcsin[(D6-D7) / D8].

[0270] S233, determining the first correction angle Δθ1 according to the formula Δθ1=θ1-θ2.

[0271] Correspondingly, in step S240', the target placement angle θ is equal to the sum of the first included angle θ1 and the first correction angle Δθ1; that is, θ=θ1+Δθ1.

[0272] In the embodiments of the present application, after the back contact solar cell is placed on the rotatable carrier according to the first included angle, the actual placement angle (i.e., the second included angle θ2) of the back contact solar cell can be measured and obtained based on the first mark point Mark1 and the second mark point Mark2, so that the first correction angle Δθ1 can be determined based on Δθ1=θ1-θ2. In this way, after the first included angle θ1 is compensated according to the first correction angle Δθ1 to determine the target placement angle θ (i.e., θ=θ1+Δθ1), the actual placement angle of the back contact solar cell can be the first included angle θ1 when the robot places the back contact solar cell according to the target placement angle, so that the single solder ribbon can be aligned and wound between the solder pads M12 on each back contact solar cell 1.

[0273] Optionally, the compensation and correction of the target placement angle θ based on the first correction angle Δθ1 can be performed each time the robot adsorbs and places the back contact solar cell.

[0274] Please refer to Figure 13 and Figure 19It is understood that after the back contact solar cells 1 are placed in the loading station, the obtained structure can be sequentially conveyed to the wire winding station. In the wire winding station, the single solder strip 2 is first pulled and positioned to the starting soldering point of the busbar of the rotatable carrier 3 by the solder strip clamping jaw, then the rotatable carrier 3 is controlled to rotate at a constant speed, the solder strip winding mechanism is controlled to move at a constant speed in a straight line, and the solder strip 2 can be wound on the pad group of each back contact solar cell 1 by the solder strip clamping jaw under the guidance of the guide mechanism 4. For example, the pad groups M12 in each back contact solar cell 1 are arranged at equal intervals in the first direction, and the solder strip 2 can form a helical trajectory with a pitch D3 and an angle θ on the circumferential surface of the rotatable carrier 3.

[0275] In some embodiments of the present application, after the solder strip is helically wound on the pad group of each back contact solar cell in step S400, before the solder strip and the pad group are welded in step S500, the manufacturing method of the back contact photovoltaic module can further include steps S410 and S420.

[0276] S410, after winding the solder strip, a plurality of areas to be coated with adhesive of the obtained structure are coated with a solidifiable adhesive; wherein the areas to be coated with adhesive extend in the first direction, and the plurality of areas to be coated with adhesive are distributed at intervals in the second direction.

[0277] Here, the number, position and coating process of the areas to be coated with adhesive can be matched with the requirements and set by adjusting the parameters.

[0278] For example, please refer to Figure 13 and Figure 20 It is understood that after the winding of the solder strip 2 is completed, the obtained structure can be sequentially conveyed to the adhesive coating station. In the adhesive coating station, the solidifiable adhesive is coated on each area to be coated with adhesive by the adhesive coating mechanism 5. The solidifiable adhesive is a high molecular fixed adhesive, which is used to fix the solder strip after solidification to prevent the solder strip from shifting position before welding.

[0279] S420, solidifying the solidifiable adhesive to form a solidified adhesive strip; the solidified adhesive strip fixedly connects the solder strip and the back contact solar cell.

[0280] Optionally, the solidification process of the solidifiable adhesive includes a light solidification process or a heat solidification process.

[0281] In some examples, please refer to Figure 13 and Figure 21 It is understood that after the adhesive coating, the obtained structure can be sequentially conveyed to the light curing station. In the light curing station, the solidifiable adhesive is irradiated with ultraviolet light by the curing lamp box 6, so that the solidifiable adhesive forms a solidified adhesive strip after solidification.

[0282] In other examples, the solidification process of the solidifiable adhesive is a heat solidification process, which can be heated by infrared light, for example.

[0283] Optionally, the heating temperature of the heat curing process ranges from 100°C to 300°C, for example, 100°C, 150°C, 200°C or 300°C, etc.

[0284] In some examples, the heating temperature of the heat curing process ranges from 120°C to 150°C, for example, 120°C, 130°C, 140°C or 150°C, etc.

[0285] Optionally, the heating duration of the heat curing process ranges from 1 minute to 60 minutes, for example, 1 minute, 5 minutes, 10 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes, etc.

[0286] In some examples, the heating duration of the heat curing process ranges from 10 minutes to 30 minutes, for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes, etc.

[0287] For example, as shown in Figure 22 , the extending direction of the cured adhesive tape 51 is perpendicular to the extending direction of the solder tape 2. At least two cured adhesive tapes 51 can be formed on each coil of the solder tape 2.

[0288] In some embodiments of the present application, the step S500 of welding the solder tape and the pad group to form the battery string can include the following steps S510 and S520.

[0289] S510, placing the resulting structure after winding the solder tape in a heating environment.

[0290] For example, please understand Figure 13 and Figure 23 After fixing the solder tape 2, the resulting structure can be sequentially conveyed to the welding station. In the welding station, the heating environment can be provided by controlling the heating of the infrared light box 7.

[0291] S520, heating the solder tape based on the heating environment to weld the solder tape and the pad group to form the battery string.

[0292] Here, it can be understood that the solder tape and the pad group are both made of metal materials. By heating the solder tape, the metallization connection (i.e. welding) between the solder tape and the pad group can be achieved.

[0293] Optionally, the heating temperature provided by the heating environment ranges from 100°C to 500°C, for example, 100°C, 120°C, 150°C, 250°C, 300°C, 400°C or 500°C, etc.

[0294] In some examples, the heating temperature provided by the heating environment ranges from 150 °C to 250 °C, for example, can be 150 °C, 180 °C, 200 °C, 220 °C or 250 °C, etc.

[0295] Optionally, when the curing process of the curable glue is a thermal curing process, the heating structure used by the curable glue can be the same infrared lamp box as the heating structure used when the soldering solder strip and the solder pad group are combined.

[0296] From the above, it can be understood that Figure 13 that after the solder strip and the solder pad group are combined, the resulting structure can be sequentially conveyed to the unloading station to remove the battery string at the unloading station.

[0297] From the above, the manufacturing method of the back contact photovoltaic module provided by the embodiments of the present application can be based on Figure 13 The automatic string welding equipment shown in the figure is completed by station cycle. After the workbench in the automatic string welding equipment is rotated to the specified station, the corresponding structure will automatically trigger the work.

[0298] In some embodiments, the patterning process of the solder strip is performed after the battery string is removed at the unloading station.

[0299] In some embodiments, referring to Figure 12 , the manufacturing method of the back contact photovoltaic module further includes the following step S700.

[0300] S700, coating an encapsulation glue layer to encapsulate the battery string.

[0301] Optionally, referring to Figure 24 and Figure 25 It can be understood that the back contact solar cell 1 is provided with a plurality of current collecting grid lines 13 connected to each solder pad 12 respectively. The plurality of current collecting grid lines 13 extend along the first direction X and are arranged at intervals in the second direction Y. The middle solder strip 2b after the solder strip patterning is isolated from the current collecting grid line 13 connected to the adjacent solder pad 12 by the encapsulation glue layer 17.

[0302] Optionally, referring to Figure 24 and Figure 26 It can be understood that the middle solder strip 2b after the solder strip patterning is isolated from the current collecting grid line 13 connected to the adjacent solder pad 12 by the air gap G.

[0303] It should be noted that after the step S500 of welding the solder rib and the pad group to form the battery string, due to the coating (e.g. Teflon tape) on the surface of the rotatable carrier and the position tolerance between different mechanisms inside the automatic string welding equipment, a stable system angle deviation is easily introduced in the battery string, and the system angle deviation is related to the target placement angle of the back contact solar cell, i.e. the system angle deviation is relatively stable at the same placement position of the back contact solar cell. Based on this, in some embodiments of the present application, please refer to Figure 24 , the back contact solar cell 1 is provided with a plurality of current collecting grid lines 13 connected with each pad group M12 respectively. The plurality of current collecting grid lines 13 extend along a first direction and are arranged at intervals in a second direction, for example, equidistantly arranged. Each current collecting grid line 13 can be an equal length grid line for example. The manufacturing method of the back contact photovoltaic module can further include the following steps S710-S740.

[0304] S710, determine a to-be-tested pad group, and select two target current collecting grid lines from the current collecting grid lines connected with the to-be-tested pad group.

[0305] S720, obtain the end point positions of the two target current collecting grid lines on the same side of the corresponding solder rib, which are defined as a first end point position and a second end point position respectively, for example, the end point 1 and the end point 2 shown in Figure 27 .

[0306] S730, respectively obtain a fourth distance from the first end point position to the corresponding solder rib, a fifth distance from the second end point position to the corresponding solder rib, and a sixth distance between the first end point position and the second end point position, and determine a second correction angle based on the fourth distance, the fifth distance and the sixth distance.

[0307] S740, update the target placement angle of the back contact solar cell in the next to-be-welded battery string based on the second correction angle.

[0308] In some embodiments of the present application, please refer to Figure 27 , the step S730 of determining the second correction angle based on the fourth distance, the fifth distance and the sixth distance can include the following steps S731 and S732.

[0309] S731, define the fourth distance as D9, the fifth distance as D10, the sixth distance as D11, and the second correction angle as Δθ2.

[0310] S732, determine the second correction angle Δθ2 according to the formula Δθ2 = arcsin[(D10-D9) / D11].

[0311] Correspondingly, in step S740, the target placement angle θ' of the back contact solar cell in the next to be welded cell string is equal to the sum of the target placement angle θ of the back contact solar cell in the current to be welded cell string and the second correction angle Δθ2; that is, θ' = θ + Δθ2.

[0312] It can be understood that, in combination with the relevant description in some of the foregoing embodiments, when the target placement angle θ of the back contact solar cell in the current to be welded cell string is θ1, the target placement angle θ' of the back contact solar cell in the next to be welded cell string is θ1+ Δθ2. When the target placement angle θ of the back contact solar cell in the current to be welded cell string is θ1+ Δθ1, the target placement angle θ' of the back contact solar cell in the next to be welded cell string is θ1+ Δθ1+ Δθ2.

[0313] In the embodiments of the present application, after the welding is completed and the to-be-measured bonding pad group and the two target current collecting grid lines are determined, the second correction angle Δθ2 can be determined based on the distances from the end point positions, i.e., end point 1 and end point 2, of the two target current collecting grid lines to the solder strip. Figure 27 It can be understood that the second correction angle Δθ2 can effectively represent the relative deflection between the bonding pad group M12 and the solder strip 2 under the influence of the system angle deviation. It should be noted that, for the convenience of understanding, Figure 27 In the embodiments of the present application, the bonding pad group M12 is represented by its center line in the first direction.

[0314] In this way, the target placement angle θ' of the back contact solar cell in the next to be welded cell string is compensated according to the second correction angle Δθ2, so that the system angle deviation can be effectively compensated in the process of the next to be welded cell string, thereby further improving the alignment accuracy between the solder strip and the bonding pad group M12.

[0315] Alternatively, the compensation and correction of the target placement angle θ' of the back contact solar cell in the next to be welded cell string based on the second correction angle Δθ2 can be performed for the first to be welded cell string in each batch of to be welded cell strings, or for a preset number of to be welded cell strings. In other words, for the same batch of to be welded cell strings, the system angle deviation can be completely compensated in the angle correction of one or a small number of to be welded cell strings.

[0316] In addition, the determination of the to-be-measured bonding pad group in the above step S710 can be implemented by using the following two implementation manners.

[0317] In some embodiments of the present application, the region average method can be used to determine the to-be-measured bonding pad group. For example, the determination of the to-be-measured bonding pad group in step S710 can include the following steps S711 and S712.

[0318] S711, a plurality of detection regions are divided on the back contact solar cell.

[0319] S712, randomly or according to a preset rule, selecting a preset number of pad groups in each detection area as the to-be-tested pad groups.

[0320] Correspondingly, in step S740, the target placement angle of the back contact solar cell in the next to-be-welded battery string is updated based on the second correction angle, which can be expressed as: the target placement angle of the back contact solar cell in the next to-be-welded battery string is updated based on the average value of the second correction angles corresponding to each to-be-tested pad group. That is, in the embodiment in which the to-be-tested pad groups are multiple, the second correction angles corresponding to the to-be-tested pad groups can be obtained one by one, and then the average value of the second correction angles is calculated to update the target placement angle of the back contact solar cell in the next to-be-welded battery string based on the average value of the second correction angles.

[0321] In some embodiments of the present application, the to-be-tested pad group can be determined by using a specific position method. For example, in step S710, the to-be-tested pad group can be determined by selecting the to-be-tested pad group in the key area of the back contact solar cell, wherein the key area includes: the starting area or the middle area of the pad groups along the winding direction of the solder ribbon. That is, along the winding direction of the solder ribbon, the first pad group at the starting area can be selected as the to-be-tested pad group, or one or more pad groups at the middle area can be selected as the to-be-tested pad group. It can be understood that in the example in which the pad groups are multiple, the second correction angle can be the average value of the second correction angles corresponding to each to-be-tested pad group.

[0322] From the above, the embodiments of the present application can converge the landing point error of the solder ribbon to within ±0.15 mm by dynamically and iteratively correcting the target placement angle of the back contact solar cell. That is, the maximum offset between the center line of the solder ribbon and the center line of the pad group is not greater than 0.15 mm.

[0323] In some examples, the landing point error of the solder ribbon can be converged to within ±0.10 mm; that is, the maximum offset between the center line of the solder ribbon and the center line of the pad group is not greater than 0.10 mm.

[0324] In some examples, the landing point error of the solder ribbon can be converged to within ±0.05 mm; that is, the maximum offset between the center line of the solder ribbon and the center line of the pad group is not greater than 0.05 mm.

[0325] In addition, in some embodiments of the present application, the width of the solder ribbon is ≥0.1 mm; for example, it can be 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 0.6 mm or 1.0 mm, etc.

[0326] In summary, the manufacturing method of the back contact photovoltaic module provided by the embodiments of the present application can have the following technical advantages (1)~(7).

[0327] (1) Significantly improves the alignment accuracy between the solder strip and the solder pad group. For example, in the embodiments of the present application, the solder strip is spirally wound, and the target placement angle of the back contact solar cell is dynamically corrected, which can converge the landing point error of the solder strip to within ±0.15 mm, or even within ±0.05 mm.

[0328] (2) The number of main grids is not limited. For example, in the embodiments of the present application, a single solder strip can be wound to cover all the solder pad groups, and there is no physical constraint between the width of the solder head and the solder strip supply channel, which can easily support a high-density grid line design of ≥30 solder pad groups, leaving enough space for the efficiency improvement of the back contact photovoltaic module.

[0329] (3) Effectively reduces the series resistance and power loss. For example, in the embodiments of the present application, without the need for insulation glue isolation and metal solder backfilling, the solder point interface between the solder strip and the solder pad group can be ensured to be single and dense, thereby reducing the series resistance and power loss.

[0330] (4) Simplifies the welding process and improves the production rhythm. The production process of the present application is reduced from three steps of "printing glue-solidifying-solder reflow" to one step of continuous wire winding welding, which can improve the production rhythm and simultaneously reduce the BOM cost and energy consumption.

[0331] (5) There is no need for insulation glue isolation and metal solder compensation. For example, in the embodiments of the present application, the solder strip can be wound above the solder pad group with high precision, effectively reducing or eliminating the risk of cross-contact of the solder strip, without the need for printing polymer insulation glue, and without the need for secondary metal solder backfilling process due to the step difference of the insulation glue.

[0332] (6) Enhances the long-term reliability of the cell string. The present application has no organic glue volatilization and secondary heterogeneous solder joint, which can have better thermal-mechanical matching of the welding interface. Moreover, the current density of the solder strip can be reduced due to the increase in the number of solder pad groups, and the risk of hot spots can be reduced.

[0333] (7) More environmentally friendly and safe. In the embodiments of the present application, there is no need to use solvent-based insulation glue, which can avoid the emission pollution of volatile organic compounds (VOC) and the management of workshop odor; without metal solder compensation, the amount of solder used is reduced, which can reduce the potential exposure of lead, bismuth and other metals.

[0334] Finally, it should be pointed out that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A back contact solar cell, characterized by, The back contact solar cell comprises: a battery body; two kinds of pad groups of different polarities, which are alternately and spacedly arranged on the back surface of the battery body along a first direction; each of the pad groups comprises a plurality of pads of the same polarity which are spacedly arranged along a second direction, and the first direction intersects the second direction; and two kinds of current collecting grid lines of different polarities, which are arranged on the back surface of the battery body, and each of the pads is connected with at least one current collecting grid line of the same polarity and is spaced from the current collecting grid line of the opposite polarity; along the first direction, the battery body has oppositely arranged first battery edges, the pads in the pad group closest to each of the first battery edges are edge pads, the distance between the edge pads and the closest first battery edge is D1, and the size of the battery body in the first direction is D2, wherein 0.043% < D1 / D2 < 0.870%.

2. The back contact solar cell of claim 1, wherein 0.1mm < D1 < 2mm.

3. The back contact solar cell of claim 2, wherein, 0.1mm < D1 < 1mm.

4. The back contact solar cell of claim 1, wherein The edge pads and the current collecting grid lines form a direct electrical connection.

5. The back contact solar cell of claim 1, wherein Along the first direction, only one end of the edge pad away from the closest first battery edge is connected with the current collecting grid line; On the back surface of the battery body, the area between the edge pad and the closest first battery edge is a grid line free area.

6. The back contact solar cell of claim 1, wherein, The back contact solar cell further comprises bus grid lines, each of which extends along the second direction; wherein each of the bus grid lines is connected with all the pads in each of the pad groups; or each of the bus grid lines is connected with a part of the pads in each of the pad groups; or The back contact solar cell is a bus grid line free solar cell.

7. The back contact solar cell of claim 6, wherein, When the back contact solar cell further comprises bus grid lines, the total area of the orthographic projection of the bus grid lines and the pads on the battery body is S1, and the area of the back surface of the battery body is S2, wherein 0.05% ≤ S1 / S2 ≤ 6.2%; When the back contact solar cell is a bus grid line free solar cell, the total area of the orthographic projection of the pads on the battery body is S1, and the area of the back surface of the battery body is S2, wherein 0.05% ≤ S1 / S2 ≤ 6.2%.

8. The back contact solar cell according to any one of claims 1 to 7, characterized in that Each of the current collecting grid lines extends along the first direction, and the current collecting grid lines of the two kinds of polarities are alternately and spacedly arranged into a column along the second direction; A plurality of columns of the current collecting grid lines are spacedly arranged along the first direction, and each of the columns of the current collecting grid lines has an interruption area between two adjacent columns of the current collecting grid lines; Each of the pad groups except the edge pad group is arranged in each of the interruption areas, and the pads included in these pad groups are inner side pads; On both sides of each of the interruption areas, the current collecting grid lines of the same polarity as the inner side pads are same polarity current collecting grid lines; along the first direction, each of the same polarity current collecting grid lines has an overlap break between two adjacent same polarity current collecting grid lines, each of the inner side pads is arranged in each of the overlap breaks, and the two ends of the inner side pad are respectively overlapped with two same polarity current collecting grid lines.

9. The back contact solar cell of claim 8, wherein, The current collecting grid lines opposite to the inner side pad polarity on both sides of the discontinuous area are heteropolar current collecting grid lines; along the first direction, the two heteropolar current collecting grid lines have an isolated discontinuous part therebetween; Wherein, along the first direction, the width W1 of the isolated discontinuous part is greater than the width W2 of the overlapping discontinuous part.

10. The back contact solar cell of claim 9, wherein, 0.3mm≤W1≤1.2mm; and / or, 0.15mm≤W2≤0.7mm.

11. The back contact solar cell according to any one of claims 1 to 7, characterized in that The shape of the pad includes square, diamond, oval, H-shaped, T-shaped, trapezoidal; and / or, The number of the pad groups is greater than or equal to 30 groups and less than or equal to 120 groups; and / or, The distance between the adjacent two pad groups is D3, wherein 1.5mm≤D3≤8mm.

12. A back contact photovoltaic module characterized by, It comprises: a plurality of electrically connected back contact solar cells, at least one of the back contact solar cells is the back contact solar cell according to any one of claims 1 to 11; and a plurality of solder strips, each of the solder strips is welded with each of the pad groups, and the solder strip welded on the edge pad is an edge solder strip, the distance between the edge solder strip and the first cell edge is D4, wherein 0.043%<D4 / D2<0.870%.

13. The back contact photovoltaic assembly of claim 12, wherein, 0.1mm<D4<2mm.

14. The back contact photovoltaic module of claim 13, wherein, 0.1mm<D4<1mm.

15. The back contact photovoltaic module of any of Claims 12 to 14, wherein, Along the second direction, the cell body has oppositely arranged second cell edges, and the welding position of the solder strip closest to the second cell edge is a starting welding point; Wherein, the distance between the starting welding point and the closest second cell edge is D5, wherein 0.5mm≤D5≤7mm.

16. A back contact photovoltaic module characterized by, It comprises: a plurality of electrically connected back contact solar cells, at least one of the back contact solar cells is the back contact solar cell according to any one of claims 1 to 7 and 11; and a plurality of solder strips, each of the solder strips is welded with each of the pad groups, and along the first direction, each of the pad groups is arranged with the adjacent, opposite polarity current collecting grid line, and there is no insulating glue between them.

17. The back contact photovoltaic assembly of claim 16, wherein, Each of the current collecting grid lines extends along the first direction, and the current collecting grid lines of the two polarities are alternately and spaced arranged into a column along the second direction; A plurality of columns of the current collecting grid lines are spaced arranged along the first direction, and the adjacent two columns of the current collecting grid lines have discontinuous areas therebetween; Except for the edge pad, each of the remaining pad groups is arranged in each of the discontinuous areas, and the pads of these pad groups are inner side pads; On both sides of each of the discontinuous areas, the current collecting grid lines opposite to the inner side pad polarity are heteropolar current collecting grid lines; along the first direction, the adjacent two heteropolar current collecting grid lines have an isolated discontinuous part therebetween; Wherein, along the first direction, the width of the isolated discontinuous part is W1, and the width of the solder strip is W3, wherein W1>W3.

18. A back contact photovoltaic module characterized by, It comprises: a plurality of electrically connected back contact solar cells, at least one of the back contact solar cells is the back contact solar cell according to any one of claims 1 to 7 and 11; and a plurality of solder strips, each of the solder strips is welded with each of the pad groups; The silver-tin alloy layer is arranged between the first tin-lead alloy layer and the conductive metal layer, and the second tin-lead alloy layer is arranged on the conductive metal layer. The thickness of the silver-tin alloy layer is T1, and the thickness of the second tin-lead alloy layer is T2; wherein 2.5 < T2 / T1 < 300.

19. The back contact photovoltaic assembly of claim 18, wherein, The thickness T1 of the silver-tin alloy layer is 0.1 μm to 10 μm. The first tin-lead alloy layer does not contain bismuth element. The conductive metal layer is made of at least one of copper or aluminum. Each of the current collecting grid lines extends along the first direction, and the current collecting grid lines of the two polarities are alternately and spacedly arranged into a column along the second direction. A plurality of columns of the current collecting grid lines are spacedly arranged along the first direction, and there is an intermittent area between two adjacent columns of the current collecting grid lines.

20. The back contact photovoltaic assembly of claim 18, wherein, Each of the pad groups other than the edge pad is arranged in each of the intermittent areas, and the pads of the pad groups are inner pads. On both sides of each of the intermittent areas, the current collecting grid lines of the same polarity as the inner pads are homopolar current collecting grid lines; along the first direction, there is an overlapping break between two homopolar current collecting grid lines, each of the inner pads is arranged in each of the overlapping breaks, and the inner pads are respectively overlapped with the two current collecting grid lines at both ends. Along the first direction, the width of the overlapping break is W2, and the width of the solder strip is W3, wherein W2 > W3. ​ ​

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