CN220914252U

CN220914252U - Photovoltaic module

Info

Publication number: CN220914252U
Application number: CN202322549808.2U
Authority: CN
Inventors: 秦年年; 陶武松; 王路闯
Original assignee: Zhejiang Jinko Solar Co Ltd; Jinko Solar Haining Co Ltd
Current assignee: Zhejiang Jinko Solar Co Ltd; Jinko Solar Haining Co Ltd
Priority date: 2023-09-19
Filing date: 2023-09-19
Publication date: 2024-05-07
Anticipated expiration: 2033-09-19

Abstract

The application relates to the technical field of photovoltaics, in particular to a photovoltaic module, which comprises a plurality of battery pieces, wherein the back surface of a silicon substrate of each battery piece is provided with a first main grid line and a second main grid line which extend along a first direction, and the first main grid line and the second main grid line are alternately arranged along a second direction and have opposite polarities; the end parts and/or the cutting edges of the adjacent battery pieces are arranged in a stacked mode to form a stacked area, and the adjacent end parts and/or the cutting edges are connected through welding strips arranged on the main grid lines; the end face or the cutting face of the battery piece, the back face of the other battery piece and the welding strip are enclosed to form a gap, and a supporting piece is filled in the gap. According to the photovoltaic module, the end parts and/or the cutting edges of the adjacent battery pieces are arranged in a stacked mode, gaps between the end parts and/or the cutting edges of the adjacent battery pieces are removed, the light conversion area of the photovoltaic module is increased, and the generated energy is improved; meanwhile, the supporting piece is filled in the gap, the welding strip is supported by the supporting piece, the problem that the welding strip breaks when the stress is overlarge during lamination is avoided, and the assembly quality is improved.

Description

Photovoltaic module

[ Field of technology ]

The application relates to the technical field of photovoltaics, in particular to a photovoltaic module.

[ Background Art ]

The back contact battery is characterized in that two electrode metal grid lines (comprising two electrode main grid lines and two electrode thin grid lines) and PN junctions on the battery piece are positioned on the back surface of the battery piece, and the two electrode metal grid lines are alternately distributed at intervals. The back contact battery with the structure can reduce optical loss and has higher short-circuit current Jsc because the front side (light conversion surface) of the battery piece is free of shielding of structures such as two-pole metal grid lines and the like; meanwhile, the back of the battery piece can tolerate a wider bipolar metal grid line to reduce the series resistance Rs of the battery piece, so that the filling factor FF is improved; in addition, the front surface field of the battery piece and the open-circuit voltage gain caused by good passivation effect are added, so that the output power of the back contact battery is increased, and the conversion efficiency of the back contact battery is high, and therefore, the back contact battery has good commercialization prospect.

The existing back contact battery comprises a plurality of battery pieces, and the battery pieces are connected through welding strips to form a battery string so as to obtain a high-efficiency output assembly. But adjacent battery pieces have a certain gap when the battery pieces are connected through welding strips, and the gap can not finish light conversion, so that the light conversion area is reduced.

[ utility model ]

In view of the above, the application provides a photovoltaic module, which removes gaps between adjacent battery pieces by stitch welding technology to improve the generated energy; and filling a supporting piece in the lamination area of the welding strip and the adjacent battery piece to support the welding strip.

The application provides a photovoltaic module, which comprises a plurality of battery pieces, wherein each battery piece comprises a silicon substrate, a first main grid line and a second main grid line which extend along a first direction are arranged on the back surface of the silicon substrate, and the first main grid lines and the second main grid lines are alternately arranged along a second direction and have opposite polarities;

The end parts and/or the cutting edges of the adjacent battery pieces are arranged in a stacked mode to form a stacking area, and the end parts and/or the cutting edges of the adjacent battery pieces are connected through welding strips arranged on the first main grid line and the second main grid line; the end face or the cutting face of the battery piece, the back face of the other battery piece and the welding strip are enclosed to form a gap, and a supporting piece is filled in the gap.

With reference to the first aspect, the solder strips include, but are not limited to, one or more of a round wire solder strip, a triangular solder strip, a flat solder strip, and a profiled solder strip.

With reference to the first aspect, the support member is one or more of EVA support bar, POE support bar and PET support bar, PVB support bar, EPE support bar and EP support bar.

With reference to the first aspect, a cross-sectional area of the single support member along the second direction is less than or equal to a cross-sectional area of the single void along the second direction.

With reference to the first aspect, the battery piece is a whole battery piece or a cut piece of the whole battery piece.

In combination with the first aspect, a width a of the stacking area of adjacent battery pieces along the first direction satisfies: a is more than or equal to 0.05mm and less than or equal to 0.5mm.

In combination with the first aspect, the silicon substrate is further provided with a first thin grid line and a second thin grid line which extend along a second direction, and the first thin grid line and the second thin grid line are alternately arranged along the first direction;

The first thin grid line is connected with the first main grid line, the second thin grid line is connected with the second main grid line, the polarities of the first thin grid line and the first main grid line are the same, and the polarities of the second thin grid line and the second main grid line are the same.

With reference to the first aspect, a distance between the first thin grid line or the second thin grid line located at the end or the cutting edge of the battery piece and the end or the cutting edge of the battery piece is b, wherein b > a.

In combination with the first aspect, welding spots are arranged on the first main grid line and the second main grid line at intervals along the first direction, and the welding strips connected with the adjacent battery pieces are connected through the welding spots.

In combination with the first aspect, the photovoltaic module further comprises photovoltaic glass, a first adhesive film, a second adhesive film and a photovoltaic backboard, wherein a plurality of battery pieces are stitch welded to form a battery string, and the photovoltaic glass, the first adhesive film, the battery string, the second adhesive film and the photovoltaic backboard are assembled into the photovoltaic module.

After the scheme is adopted, the application has the following beneficial effects:

According to the photovoltaic module provided by the application, the end parts and/or the cutting edges of the adjacent battery pieces are arranged in a stacked manner, so that gaps between the end parts and/or the cutting edges of the adjacent battery pieces are removed, the light conversion area of the photovoltaic module is increased, and the generated energy is further improved; meanwhile, the supporting piece is filled in the gap enclosed by the welding strip and the battery piece, the welding strip is supported by the supporting piece, the problem that the welding strip breaks when the stress is overlarge during lamination can be avoided by the buffer effect of the supporting piece, and the assembly quality is improved.

[ Description of the drawings ]

Fig. 1 is a schematic structural diagram of a photovoltaic module provided by the present application;

fig. 2 is a top view of a portion of the structure of the photovoltaic module provided by the present application;

Fig. 3 is a schematic structural view of a photovoltaic module in which a supporting member does not completely fill a gap;

FIG. 4 is an enlarged view of FIG. 3 at A;

fig. 5 is a schematic structural view of a support member filling a void in a photovoltaic module according to the present application;

fig. 6 is an enlarged view at B in fig. 5.

The attached drawings are identified:

1. A first battery piece; 2. a second battery piece; 3. welding a belt; 4. a support; 5. photovoltaic glass; 6. a first adhesive film; 7. a second adhesive film; 8. a photovoltaic backsheet.

[ Detailed description ] of the invention

For a better understanding of the technical solution of the present application, the following detailed description of the embodiments of the present application refers to the accompanying drawings.

It should be understood that the described embodiments are merely some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be understood that the term "and/or" as used herein is merely one relationship describing the association of the associated objects, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

It should be noted that, the terms "upper", "lower", "left", "right", and the like in the embodiments of the present application are described in terms of the angles shown in the drawings, and should not be construed as limiting the embodiments of the present application. In the context of this document, it will also be understood that when an element is referred to as being "on" or "under" another element, it can be directly on the other element or be indirectly on the other element through intervening elements.

In some embodiments, the composition of the photovoltaic module comprises a laminate and a frame, the laminate comprising photovoltaic glass 5, a first adhesive film 6, a plurality of sets of cell strings, a second adhesive film 7, and a photovoltaic backsheet 8; the battery strings comprise a plurality of battery pieces which are arranged in series, the battery pieces are whole battery pieces or cutting pieces of one N of the whole battery pieces, the types of the battery pieces can be selected according to actual needs, and the battery strings are not limited herein. The photovoltaic glass 5, the first adhesive film 6, the plurality of groups of battery strings, the second adhesive film 7 and the photovoltaic backboard 8 are subjected to lamination procedures to obtain a laminated piece, and at the moment, the laminated piece is assembled with the frame to form the photovoltaic module.

Further, the battery piece used in the application can be a single-sided light conversion battery piece or a double-sided light conversion battery piece. The single-sided light conversion cell refers to a cell that can only receive light from the front side and convert the light into electric power; the double-sided light conversion cell refers to a cell capable of receiving light from both sides and converting the light into electric power, that is, a cell capable of receiving not only direct irradiation of sunlight from the front side to convert it into electric power but also light such as reflected light or scattered light from the ground from the back side, thereby improving the power generation efficiency of the photovoltaic module. The cell of other light conversion regions may be selected, and the light conversion type of the cell may be selected according to actual needs, which is not limited herein.

Furthermore, the metal grid lines for collecting current on the battery piece are all arranged on the back surface of the battery piece, namely, the photovoltaic module adopts the back contact battery piece, and the metal grid lines are specifically as follows: the two-pole metal grid lines (including two-pole main grid lines and two-pole fine grid lines) and PN junctions on the battery piece are all positioned on the back surface of the battery piece, and the two-pole metal grid lines are alternately distributed at intervals. The back contact battery with the structure can reduce optical loss and has higher short-circuit current Jsc because the front side (light conversion surface) of the battery piece is free of shielding of structures such as two-pole metal grid lines and the like; meanwhile, the back of the battery piece can tolerate a wider bipolar metal grid line to reduce the series resistance Rs of the battery piece, so that the filling factor FF is improved; and the open-circuit voltage gain caused by the front surface field of the battery piece and the good passivation effect is added, so that the output power of the back contact battery is increased, and the conversion efficiency of the back contact battery is high.

Meanwhile, the back contact battery comprises a plurality of battery pieces, and the battery pieces are connected through welding strips to form a battery string so as to obtain the high-efficiency output assembly.

But adjacent battery pieces have a certain gap when the prior battery pieces are connected through welding strips, and the gap can not finish light conversion, so that the light conversion area of the photovoltaic module is reduced.

In view of the above, the present application provides a photovoltaic module, which includes a plurality of battery pieces, the battery pieces include a silicon substrate, a first main grid line and a second main grid line extending along a first direction are disposed on a back surface of the silicon substrate, and the first main grid line and the second main grid line are alternately arranged along a second direction and have opposite polarities;

The end parts and/or the cutting edges of the adjacent battery pieces are arranged in a stacked mode to form a stacking area, and the end parts and/or the cutting edges of the adjacent battery pieces are connected through welding strips 3 arranged on the first main grid line and the second main grid line; wherein, the end face or the cutting face of the battery piece, the back face of the other battery piece and the welding strip 3 are enclosed to form a gap, and a supporting piece 4 is filled in the gap.

In the scheme, the photovoltaic module is arranged by stacking the end parts and/or the cutting edges of the adjacent battery pieces, so that gaps between the end parts and/or the cutting edges of the adjacent battery pieces are removed, the light conversion area of the photovoltaic module is increased, and the generated energy is further improved; meanwhile, the supporting piece 4 is filled in the gap enclosed by the welding strip 3 and the battery piece, the welding strip 3 is supported by the supporting piece 4, the problem that the welding strip 3 breaks when being excessively stressed during lamination can be avoided by the buffer effect of the supporting piece 4, and the assembly quality is improved.

It should be noted that, the first direction in the present application refers to the length direction of the battery pieces, that is, the serial direction of the battery pieces in the battery string, and the second direction refers to the width direction of the battery pieces, that is, the parallel direction of the plurality of battery strings.

In some embodiments, the rows of the first main grid lines and the second main grid lines on the back surface of the battery piece extend along the first direction, and are alternately distributed along the second direction. It should be noted that, along the second direction, the initial main gate line is the first main gate line, or the second main gate line may be selected according to actual needs, which is not limited herein.

Meanwhile, the back of the battery piece further comprises a first thin grid line and a second thin grid line which extend along the second direction, namely, the first main grid line, the second main grid line, the first thin grid line and the second thin grid line are all positioned on the back of the battery piece. Specifically, the first thin gate lines and the second thin gate lines are alternately arranged along a first direction; the first thin grid line is connected with the first main grid line, the second thin grid line is connected with the second main grid line, the polarities of the first thin grid line and the first main grid line are the same, and the polarities of the second thin grid line and the second main grid line are the same. It can be understood that the first main gate line may be selected as the positive main gate line, the second main gate line may be selected as the negative main gate line, or the second main gate line may be selected as the positive main gate line, or the first main gate line may be selected as the negative main gate line, which may be selected according to actual needs, and is not limited herein.

At this time, through the cooperation of the first thin grid line and the first main grid line and the cooperation of the second thin grid line and the second main grid line, the light converted current can be collected to the first main grid line and the second main grid line through the first thin grid line and the second thin grid line.

In some embodiments, in order to obtain a more efficient output assembly and ensure light conversion efficiency, the battery pieces of the application adopt stitch welding technology and are connected through the welding strip 3 to form a battery string, so as to improve the generating capacity of the photovoltaic assembly, eliminate gaps among the battery pieces, increase the light conversion area of the photovoltaic assembly, and further improve the light conversion efficiency. As shown in fig. 1 and 2, two adjacent battery cells (first battery cell 1 and second battery cell 2, respectively) are exemplified.

Specifically, the first battery sheet 1 and the second battery sheet 2 form a stacking region along the first direction, and the width a of the stacking region is 0.05mm to 0.5mm, alternatively, the width of the stacking region may be specifically 0.05mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, or the like, which may be selected according to actual needs, and is not limited herein. If the width of the stacking area of the adjacent battery pieces is too small, the connection stability of the first battery piece 1 and the second battery piece 2 is reduced, and the problem of edge damage caused by too large compressive stress of the edges of the battery pieces is generated in the lamination process; if the width of the stacking area of the adjacent battery pieces is too large, the light conversion area of the battery pieces can be reduced, and the generating capacity and the light conversion efficiency of the photovoltaic module are reduced.

Meanwhile, the distance between the first thin grid line or the second thin grid line positioned at the end part or the cutting edge of the battery piece and the end part or the cutting edge of the battery piece is b, wherein b is more than a. It will be appreciated that the distance between the first thin grid line or the second thin grid line and the end or the cut edge of the battery piece meets the above requirement, so that when adjacent battery pieces are stacked, the stacking area covers the first thin grid line or the second thin grid line, and the first thin grid line or the second thin grid line cannot function.

In some embodiments, adjacent battery cells, which are completed in lamination, may be connected into a battery string by the solder tape 3. Specifically, a plurality of welding spots are arranged on the first main grid line and the second main grid line at intervals, and the interval distance between adjacent welding spots can be selected according to actual needs, so that the method is not limited. The welding strips 3 connecting the adjacent battery pieces are connected through welding points, so that a battery string is obtained, and the welding strips can collect currents of a plurality of battery pieces.

The solder ribbon 3 used in the present application includes, but is not limited to, one or more of a round wire solder ribbon 3, a triangular solder ribbon 3, a flat solder ribbon 3 and a special-shaped solder ribbon 3, and may be selected according to actual needs without limitation. Preferably, the solder strip 3 is a flat solder strip 3, and compared with solder strips 3 with other shapes, the flat solder strip 3 is easier to have a Z-shaped bent shape in the process of connecting adjacent battery pieces so as to generate gaps, and the support piece 4 can protect the solder strip 3 in the subsequent processing process of filling the support piece 4. Specific: the end face or the cutting face of the laminated battery piece, the back face of the other battery piece and the welding strip 3 enclose to form a gap, as shown in fig. 3, a supporting piece 4 is filled in the gap, the supporting piece 4 is made of an elastic material with an undefined shape, the buffering action of the elastic material can deform to support the deformation of the welding strip 3, the problem that the welding strip 3 breaks when being excessively stressed during lamination is avoided, and the assembly quality is improved.

In order to prevent bubbles from being generated in the battery string due to the fact that the supporting member 4 cannot be fully filled in the gaps in the subsequent lamination process, the supporting member 4 can be filled after the welding strips 3 are connected through welding points, at the moment, adjacent battery pieces are inclined along the direction perpendicular to the welding strips 3, so that the volume of the gaps is increased, the supporting member 4 is filled in the gaps, the welding strips 3 are supported, and the situation that the supporting member 4 cannot be fully filled in the gaps in the subsequent lamination process is avoided.

In some embodiments, the support 4 used in the present application is one or more selected from EVA support bar, POE support bar and PET support bar, PVB support bar, EPE support bar and EP support bar, which may be selected according to actual needs, and is not limited herein. Meanwhile, the cross-sectional area of the single supporting member 4 along the second direction is smaller than or equal to the cross-sectional area of the single gap along the second direction, and it can be understood that if the cross-sectional area of the supporting member 4 is larger than the cross-sectional area of the gap, when lamination is completed in the process of filling the supporting member 4, the supporting member 4 with overlarge volume can jack up the welding strip 3, and the welding quality of adjacent battery pieces is affected.

At this time, the battery string with the welded tape 3 connected may be subjected to a lamination process with the remaining accessories, as shown in fig. 5 and 6, in which the supporting member 4 is melted by heat and uniformly filled in the gaps, eliminating the gaps between the supporting member 4, the welded tape 3 and the stacked adjacent battery sheets; and during lamination, part of the support 4 is melt-bonded together with at least one of the first adhesive film 6 and the second adhesive film 7.

In addition, since the battery sheet is extremely fragile and is easily broken when pressed, the photovoltaic glass 5 and the photovoltaic back sheet 8 cannot be directly attached thereto, and therefore the first adhesive film 6 and the second adhesive film 7 are required to have an adhesive function in between. In practical use, the first adhesive film 6 and the second adhesive film 7 are used for encapsulating the battery strings arranged at intervals, specifically, the first adhesive film 6, the battery strings and the second adhesive film 7 are laminated to obtain a combination, and then the combination is heated to a certain temperature, so that the first adhesive film 6 and the second adhesive film 7 are bonded with the battery piece after being melted.

It should be noted that, the first adhesive film 6 and the second adhesive film 7 used in the present application may be an ethylene-vinyl acetate copolymer (EVA) adhesive film, a polyethylene octene co-elastomer (POE) adhesive film, or a polyethylene terephthalate (PET) adhesive film, and may also be a PVB adhesive film, an EPE adhesive film (EVA and POE three-layer co-extruded adhesive film), an EP adhesive film (EVA and POE two-layer co-extruded adhesive film), or other types of adhesive films, which may be selected according to actual needs, and are not limited herein. Preferably, the first adhesive film 6 and the second adhesive film 7 used in the application are EVA adhesive films, the EVA adhesive films are non-adhesive at normal temperature, have good flexibility, transparency and surface glossiness, stable chemical properties, good ageing resistance and ozone resistance, no toxicity, and are subjected to hot pressing under certain conditions to undergo fusion bonding and crosslinking curing, and the cured adhesive films have excellent light transmittance, bonding strength, thermal stability, air tightness and ageing resistance, so that the light conversion performance of the photovoltaic module is not affected when a plurality of groups of battery strings are encapsulated.

The photovoltaic glass 5 is arranged on one side, far away from the battery piece, of the first adhesive film 6, and the photovoltaic glass 5 is also called 'photoelectric glass', has good light transmittance and high hardness, and can adapt to large day and night temperature difference and severe weather environment after being covered on the first adhesive film 6, so that the battery piece is protected. The photovoltaic glass 5 used in the application can be ultrawhite photovoltaic embossed glass, ultrawhite processing float glass or TCO glass, and the like, and can also be other types of photovoltaic glass 5, and can be selected according to actual needs, and is not limited in this regard.

The photovoltaic backboard 8 is arranged on one side, far away from the battery piece, of the second adhesive film 7, and the photovoltaic backboard 8 also plays roles in protecting and supporting the battery piece, has good weather resistance, water resistance, corrosion resistance, insulativity and the like, can isolate the photovoltaic module from surrounding photovoltaic environments, and can effectively protect and support the battery piece, so that the impact strength of the photovoltaic module is increased. The photovoltaic backsheet 8 used in the present application may be glass, rolled glass or ultra-white rolled glass.

In actual use, the battery piece is manufactured into a battery string by adopting a stitch welding technology, and the supporting piece 4 is filled in a gap formed between the adjacent battery string and the welding strip 3; and then placing the laminated photovoltaic glass 5, the first adhesive film 6, a plurality of groups of battery strings, the second adhesive film 7 and the photovoltaic backboard 8 into a laminating machine, vacuumizing to extract air in the assembly, heating to melt the first adhesive film 6 and the second adhesive film 7, and bonding the batteries, the glass and the photovoltaic backboard 8 together to obtain the laminated piece. In the process, the supporting pieces 4 filled in the gaps surrounded by the welding strips 3 and the battery pieces are heated and melted and then uniformly filled in all parts of the gaps, the welding strips 3 are supported by the supporting pieces 4, the problem that the welding strips 3 break when being excessively stressed during lamination can be avoided by the buffer effect of the supporting pieces 4, and the assembly quality is improved.

After the lamination piece is bonded, the photovoltaic module can be obtained through assembling the frame, and finally the photovoltaic module is fixed on the bracket through the pressing block for use. The support is a special support body designed and installed for supporting, fixing and rotating the photovoltaic module, the support can be divided into a fixed support and a tracking support according to the structure, the direction of the fixed support is fixed, the manufacturing cost is low, the tracking support can rotate the photovoltaic module according to the illumination intensity to reduce the included angle between the module and the direct sunlight, more solar irradiation is obtained, the power generation efficiency can be effectively improved, and the manufacturing cost is high; the material can be divided into an aluminum alloy bracket, a carbon steel bracket or a stainless steel bracket, and the structure and the material of the bracket can be selected according to actual needs, and the structure and the material are not limited. When in actual use, the photovoltaic bracket can fix the photovoltaic module in a certain direction, arrangement mode and interval according to the topography, climate and solar resource conditions, and it can be understood that the photovoltaic module can better receive sunlight after being fixed by the bracket.

While the foregoing is directed to embodiments of the present application, other and further embodiments of the application may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. The photovoltaic module is characterized by comprising a plurality of battery pieces, wherein each battery piece comprises a silicon substrate, a first main grid line and a second main grid line which extend along a first direction are arranged on the back surface of the silicon substrate, and the first main grid lines and the second main grid lines are alternately arranged along a second direction and have opposite polarities;

2. The photovoltaic assembly of claim 1, wherein the solder strips include, but are not limited to, one or more of round wire solder strips, delta solder strips, flat solder strips, and profiled solder strips.

3. The photovoltaic assembly of claim 1, wherein the support is one or more of the group consisting of, but not limited to, EVA support bar, POE support bar and PET support bar, PVB support bar, EPE support bar and EP support bar.

4. The photovoltaic assembly of claim 1, wherein a cross-sectional area of an individual support along the second direction is less than or equal to a cross-sectional area of an individual void along the second direction.

5. The photovoltaic module of claim 1, wherein the cell is a unitary cell or a cut piece of a unitary cell.

6. The photovoltaic module of claim 1, wherein the width a of the stacking region of adjacent cells along a first direction satisfies: a is more than or equal to 0.05mm and less than or equal to 0.5mm.

7. The photovoltaic module according to claim 6, wherein the silicon substrate is further provided with first thin grid lines and second thin grid lines extending along a second direction, and the first thin grid lines and the second thin grid lines are alternately arranged along the first direction;

8. The photovoltaic module of claim 7, wherein the first thin-grid line or the second thin-grid line at the end or cut edge of the cell sheet is at a distance b from the end or cut edge of the cell sheet, wherein b > a.

9. The photovoltaic module of claim 1, wherein, along a first direction, welding spots are arranged on the first main grid line and the second main grid line at intervals, and the welding strips connecting adjacent battery pieces are connected through the welding spots.

10. The photovoltaic module of claim 1, further comprising photovoltaic glass, a first adhesive film, a second adhesive film, and a photovoltaic back sheet, wherein a plurality of the battery cells are stitch welded to form a battery string, and wherein the photovoltaic glass, the first adhesive film, the battery string, the second adhesive film, and the photovoltaic back sheet are assembled into the photovoltaic module.