CN108538948A - Solar cell grid line structure, solar battery sheet and solar energy stacked wafer moudle - Google Patents

Abstract

The invention provides a solar cell grid structure, a solar battery sheet and a solar laminate assembly. The grid structure includes a plurality of auxiliary grid lines arranged on a silicon wafer, and a main grid line perpendicular to the auxiliary grid lines; the main grid line It consists of a grid-like porous structure. When conductive glue is coated on the busbar, part of the conductive glue is filled in the mesh holes. Since the materials that make up the conductive glue and the busbars have good electrical conductivity, when the above-mentioned grid lines are dense enough, using a grid pattern instead of a solid pattern will not have a serious impact on the electrical performance of the component. The deformation of the conductive glue and the diffusion on the suede surface of the cell covered with silicon nitride are limited within the grid pattern due to the restriction of the busbar grid pattern, thereby avoiding the occurrence of glue overflow and glue seepage.

Description

Solar cell grid wire structure, solar cell sheet and solar laminated module

technical field

The invention belongs to the field of solar cells, and in particular relates to a solar cell grid structure, a solar cell and a solar stack assembly.

Background technique

A solar cell is a device that uses the photovoltaic effect to directly convert light energy into direct current. According to different photoelectric conversion materials, solar cells include monocrystalline silicon, polycrystalline silicon, amorphous silicon thin films, cadmium telluride thin films, copper indium gallium tin thin films, gallium arsenide, fuel sensitization, perovskite, stacked layers, etc. . The most common of these are crystalline silicon solar cells, including monocrystalline silicon solar cells and polycrystalline silicon solar cells. Solar cells are usually in the shape of a sheet. The side that absorbs light energy and converts it into electricity is called the light-absorbing side or front side, and the other side is called the back side. For some solar cells, the back side can also absorb and convert light energy into electrical energy. These solar cells are called bifacial cells.

The electrode patterns on the front and back of the crystalline silicon solar cell are prepared by metallizing the surface of the solar cell. The commonly used metallization method is to print the conductive paste containing silver particles on the surface of the battery by screen printing and sintering, and the electrode pattern can be changed by changing the screen pattern design of the screen printing.

In addition to the electrode area of crystalline silicon solar cells, the front side is usually a silicon nitride film, and the back side is usually screen-printed aluminum paste and sintered to form an aluminum back field. For some special solar cells, such as double-sided P-type silicon PERC cells or double-sided N-type silicon PERT cells that can absorb light on both the front and back sides, the surface of the back electrode and the area other than the metallized fine grid lines is also a silicon nitride film. For a double-sided HJT battery, that is, a heterojunction battery, the surface of the front and back electrodes and the area other than the gate line is a transparent conductive oxide film, such as indium tin oxide ITO.

A photovoltaic device that can be used for a long time is obtained by electrically interconnecting multiple solar cells and encapsulating them in glass or organic polymers, which is called a photovoltaic module. The interconnection method of cells in crystalline silicon photovoltaic modules is commonly arranged by arranging the cells sequentially, using tin-coated solder strips containing copper substrates as interconnection strips, and one end of the interconnection strips is welded to the front busbar of the first cell , and the other end of the interconnection bar is welded on the back electrode of the adjacent second battery sheet. The two ends of the second interconnection bar are respectively welded to the front main grid line of the second battery piece and the back grid line of the third battery piece, and so on. In this way, all the battery slices are connected in series.

The laminated module adopts another technology of cell interconnection. As shown in Figure 1, the busbar electrode on the front of the same solar cell and the back silver electrode on the back are respectively located on the left and right sides of the cell, and one side of solar cell A is placed under another cell B, so that The busbar electrodes on the front side of battery sheet A overlap with the electrodes on the back side of cell sheet B. A conductive material is used to form a conductive connection between the two electrodes. At the same time, the other side of battery sheet B is placed under battery sheet C, so that the busbar electrode on the front side of B and the electrode on the back of C overlap each other, and a conductive material is used between the two electrodes to form a conductive electrode. connect. In the same way, M cells can be interconnected sequentially to form a cell string (5≤M≤120).

The lamination interconnection method can also be used to form interconnections between M slices of solar cells (5≤M≤120). Interconnected cells Solar cell slicing refers to cutting a complete or incomplete solar cell into small pieces by mechanical, laser or other means. The shape of the solar cell slice can be a polygon such as a rectangle or a triangle, a curved figure such as a circle, a sector, an ellipse, or an irregular figure. The number of slices that can be cut into a solar cell is K slices, where 1≤K≤20.

For a square or rectangular solar battery sheet, it can be cut into K rectangular slices with the same shape and size, where 1≤K≤20.

For quasi-rectangular solar cells with chamfers, they can be cut into K pieces of sliced cells, where 1≤K≤20, and some sliced cells are quasi-rectangular with 1 or 2 chamfers, and some sliced cells is a rectangle without chamfers. For example, Figure 2 is a way of cutting a solar cell sheet into five sliced cells, the leftmost and rightmost sliced cells have chamfered corners, and the middle three sliced cells have no chamfered corners.

The conductive material between the electrodes of adjacent battery sheets in the same battery string in the stack assembly includes materials such as conductive glue, conductive tape, solder tape or solder paste. According to the characteristics of the conductive material, the corresponding preparation method should be selected. For battery strings that use conductive glue to form electrical interconnections, glue dispensing or screen printing can be used.

The main components of conductive adhesive include resin material matrix and conductive filler. The filler therein is usually silver or silver-containing particles. Compared with the commonly used tin-coated copper tape, the conductive adhesive can not only form a good mechanical adhesion and conductive connection with the silver electrode, but also some conductive adhesives can also be used with other surfaces of the battery, such as silicon nitride film layers, or Silicon materials form a good bond.

Since silver is a precious metal, solar cell pastes and conductive adhesives containing silver are relatively expensive. Cheap metal materials such as copper, aluminum, nickel, or non-metallic conductive materials such as various carbon materials, indium tin oxide, etc. can be used to replace the silver in the paste or conductive glue, or by changing the design of the metal pattern on the battery surface or conducting The design of glue pattern can reduce the usage of silver paste or conductive glue accordingly.

If the lamination process is not properly controlled, glue overflow or glue leakage will occur. Adhesive overflow means that both the matrix and the filler of the conductive adhesive overflow the overlapping part of the two cells, and the adhesive seepage means that the matrix of the conductive adhesive seeps out of the overlapping part of the two cells, but the filler does not. Glue overflow and bleeding will affect the long-term reliability of laminated components and should be avoided in actual production.

As shown in Figure 3, photovoltaic laminated modules can be divided into horizontal and vertical types according to the arrangement direction of battery strings. The battery string parallel to the short side of the module is called a horizontal laminated module, and the battery string parallel to the long side of the module is called a vertical laminated module.

A circuit diagram of a laminated assembly using two parallel diodes is shown in Figure 4. Multiple laminated batteries are connected in series and parallel to form a battery string. Each battery string is connected in parallel with a bypass diode. Two such battery strings Groups are concatenated into components. The laminated assembly using this circuit can be of vertical or horizontal type.

Use double-sided laminated cells or double-sided laminated cell slices, such as the aforementioned P-type silicon double-sided PERC laminated cells, N-type silicon double-sided PERT laminated cells, or HJT laminated cells, through the aforementioned laminated cells process, double-sided laminated components can be obtained.

In the laminated assembly, it is divided into N long battery strings (N≥1) from left to right. For example, the vertical double-sided laminated module in Figure 3 contains a total of 6 long battery strings, which are respectively marked as strings A, B, C, D, E, and F.

In the laminated assembly, any ribbon that connects multiple battery strings at the positive and negative ends of the module is called a bus bar; any ribbon that is located at the middle potential of the module and connects multiple battery strings is called a parallel ribbon; The ribbon that is connected to the parallel ribbon, runs parallel to the battery string, and is connected to the bypass diode is called the bypass ribbon.

Figure 5 is a front and back metallization pattern of a single-sided laminated battery. The front pattern includes 5 solid continuous main grid lines and several sub-grid lines perpendicular to it, and the back pattern includes 5 solid continuous back electrodes and a back field between the back electrodes. Both the main grid line and the auxiliary grid line in the front pattern are made of paste containing silver, the back electrode in the back pattern is composed of paste containing silver, and the back field is composed of paste containing aluminum. The above-mentioned front silver paste, back silver paste, and aluminum paste are all made on the surface of the cell by screen printing.

Figure 6 is a front and back metallization pattern of a double-sided laminated battery. The front pattern includes 6 solid continuous front main grid lines and several sub-grid lines perpendicular to it, and the back graphic includes 6 solid continuous back main grid lines, a sub-grid line parallel to and adjacent to the main grid line, and Several secondary grid lines perpendicular to it. Both the main grid line and the auxiliary grid line in the front pattern are composed of silver-containing paste, the main grid line in the back pattern is composed of silver-containing paste, and the auxiliary grid line is composed of aluminum-containing paste. Both the silver paste and the aluminum paste mentioned above are made on the surface of the battery sheet by screen printing.

There are two disadvantages with the prior art. (1) The consumption of silver paste is large, resulting in high battery cost. (2) For some types of conductive adhesives, there is a risk of glue overflow or seepage. Details are as follows.

Since both the front busbars and the back busbars in the prior art solution adopt a solid rectangular design, the consumption of silver paste is relatively large. Silver paste is the main source of cost in battery production, and high silver paste consumption will directly lead to an increase in battery cost.

In the production process of laminated modules, when the upper and lower cells overlap each other, the conductive adhesive between the two cells may be deformed due to the upper and lower extrusion, resulting in the widening of the conductive adhesive pattern, as shown in Figure 7 Show. The degree of broadening is related to the type of conductive adhesive and the surface characteristics of the cell. There are some conductive pastes that have much higher wetting and diffusion rates on the silicon nitride-covered textured side of the cell than on the metal paste. For this part of the conductive adhesive, it is necessary to limit its contact with silicon nitride, otherwise the part in contact with silicon nitride will obviously expand outward, and if it exceeds the overlapping part of the two cells, overflow or seepage will occur. glue.

In order to prevent glue overflow or seepage, the main grid line needs to be made wider to ensure that the conductive adhesive only contacts the main grid line. But this will further increase the consumption of silver paste and battery cost.

Contents of the invention

The present invention aims to provide a solar cell grid structure, a solar battery sheet and a solar laminate assembly, the battery grid structure is a metallization pattern scheme of laminated cells with low cost and anti-overflow or glue penetration characteristics, The conductive adhesive pattern corresponding to this structure can effectively prevent glue overflow or glue seepage, without making the main grid line wider, it can ensure the contact between the conductive adhesive and the main grid line, and at the same time reduce the consumption and consumption of silver paste. battery cost.

For realizing the above object, technical solution of the present invention is:

A solar cell grid line structure, including several sub-grid lines arranged on a silicon wafer, and main grid lines perpendicular to the sub-grid lines; the main grid lines are composed of a grid-shaped porous structure, and the main grid lines are coated with conductive When glueing, part of the conductive glue is filled in the mesh holes of the grid-like porous structure; the busbar is a continuous or segmented structure.

The grid-like porous structure is formed by intersecting a plurality of thin lines, and the thin lines include one or more arbitrary combinations of straight lines, broken lines and curves.

The characteristic length of the pores in the grid-like porous structure is 10 microns to 2000 microns, and the width of the entire busbar is 100 to 1500 microns.

The thin line has a width of 5 microns to 1500 microns and a height of 5 microns to 100 microns,

The thin lines include longitudinal thin lines and transverse thin lines.

Below the grid-shaped porous structure of the main grid line, a metal layer or a non-metal layer is provided, and the metal layer or non-metal layer is in contact with the silicon nitride passivation layer on the surface of the cell, such as silicon nitride or other oxide layers. ; The thickness of the metal layer or non-metal layer is between 0.002 microns and 100 microns.

The passivation layer or the oxide layer on the surface of the silicon chip is etched to form a gap, and the grid-shaped porous structure of the busbar passes through the gap to contact the silicon chip substrate.

In the segmented structure of the busbar, the length of each segmented electrode is 80 microns to 150 mm, and the number of segmented electrodes on each busbar is 2-240.

A solar battery sheet, the front and/or back of the solar battery sheet adopts the grid wire structure of any one of the above solar cells.

A solar stack assembly, which is made of the solar cells.

The beneficial effects of the present invention are:

The grid structure of the solar cell of the present invention replaces the solid busbars in the existing solution by adopting busbars in the form of cross grids. Since the materials that make up the conductive glue and the busbars have good electrical conductivity, when the above-mentioned grid cross lines are dense enough, using a cross grid instead of a solid pattern will not have a serious impact on the electrical performance of the component. The deformation of the conductive adhesive and the diffusion on the suede surface covered with silicon nitride are confined within the grid pattern due to the limitation of the busbar pattern, thereby avoiding the occurrence of glue overflow and glue seepage.

Further, as long as it has a porous structure, the deformation of the conductive adhesive and the diffusion on the suede surface covered with silicon nitride are both limited by the porous structure, which can avoid the occurrence of glue overflow and glue seepage.

Further, the main grid line is composed of two layers of materials, the bottom layer material is a solid metal material or non-metal material, and the top layer material is the above-mentioned cross grid, because the silicon nitride texture of the cell in the cross grid is covered by the bottom metal layer Or non-metallic layer covering prevents the contact between the conductive adhesive and the silicon nitride textured surface, so it has a better anti-overflow and adhesive penetration effect than the simple preparation of cross grids.

Further, remove the passivation layer such as silicon nitride or oxide layer such as silicon oxide at the position of the main grid line, and then prepare the main grid line in the shape of a cross grid, which can also achieve better anti-overflow than simply using a cross grid Adhesive penetration effect, and the amount of metal paste required to prepare the busbar is not higher than the scheme of using the cross grid alone.

Furthermore, the above-mentioned solutions can be combined with the busbar electrode structure of the segmented design, which can further reduce the amount of metal paste used for preparing the electrode busbar,

Description of drawings

Figure 1: Laminated interconnection of cells;

Figure 2: Cell with chamfer (left) cut into 5 cell slices (right);

Figure 3: Horizontal (left) and vertical (right) lamination components;

Figure 4: Circuit diagram of a laminated assembly with 2 diodes;

Figure 5: A diagram of the front and back metallization scheme of a single-sided laminated battery;

Figure 6: A diagram of the front and back metallization scheme of a double-sided laminated battery;

Figure 7: Changes in the thickness and width of the conductive adhesive before and after the lamination process;

Figure 8: Schematic diagram of grid main grid lines - front view; a is a schematic diagram of the structure of auxiliary grid lines and main grid lines, and b is a schematic diagram of several common grid main grid lines;

Figure 9: Schematic diagram of grid busbars - side view;

Figure 10: The hindering effect of grid bus lines on glue overflow;

Figure 11: Schematic diagram of a mesh busbar with a metal layer;

Figure 12: Schematic diagram of a mesh busbar with a non-metallic layer;

Fig. 13: A partial schematic diagram of a solar cell metallization pattern composed of multi-segment main grid lines 2 and auxiliary grid lines;

Figure 14: A conductive adhesive pattern corresponding to the metallization pattern of the battery sheet in Figure 13;

Figure 15: A single-sided laminated module using solar cells with the above metallization pattern;

Figure 16: A bifacial laminate using solar cells with the metallization pattern described above. The installation position of the junction box in the figure is in the dotted box, and the bypass ribbon and bus bar lead-out wires pass through the glass opening.

Among them: 1-sub grid line, 2-main grid line, 3-back main grid line, 4-aluminum back field, 5-back sub grid line, 6-conductive adhesive, 7-thin line, 8-longitudinal thin line ( Perpendicular to the auxiliary grid line), 9-horizontal thin line (parallel to the auxiliary grid line), 10-metal layer, 11-non-metal layer, 12-bus bar, 13-welding strip, 14-bypass welding strip, 15- Parallel ribbon, 16-junction box, 17-back panel.

Detailed ways

The technology of the present invention is described in detail below in conjunction with accompanying drawing:

The battery metallization pattern scheme of the present invention is shown in FIG. 8 , which includes main grid lines 2 and auxiliary grid lines 1 in the form of a cross grid. The busbar 2 is a network structure composed of interlaced thin lines 7, and the thin lines 7 are one or more combinations of straight lines, broken lines and curves; grooves are formed in the grid of the network structure, and the busbar 2 When the conductive glue 6 is applied, part of the conductive glue 6 is filled in the grooves of the grid.

As shown in FIG. 8( b ), the thin lines 7 of the bus bars 2 may be composed of straight lines, broken lines or curved lines. The width of the thin line 7 ranges from 5 microns to 1500 microns, the height of the thin line 7 ranges from 5 microns to 100 microns, the characteristic length of the grid holes ranges from 10 microns to 2000 microns, and the entire busbar 2 area The width range is 100 to 1500 microns. The shape of the grid can be polygon (consisting of H sides, 3≤H≤100), circle, ellipse or other shapes. The main grid lines 2 may be parallel to, perpendicular to, or at any angle with the edge of the battery sheet.

It is preferably a mesh hole structure formed by a plurality of longitudinal fine lines 8 and transverse thin lines 9 intersecting each other. (The grid-shaped main grid lines 2 will be described below.) F sub-grid lines 1 perpendicularly intersect with the grid main grid lines 2 (20≤F≤200).

The width and height of the same busbar line 2 are constant, and can also vary within the range of the above width and height. The width and height of different busbars 2 of the same battery can be the same or different. The spacing between different busbars 2 on the same battery can be the same or different. As shown in FIG. 9 , the distance between the horizontal thin lines 9 parallel to the auxiliary gate lines and the distance between the vertical thin lines 8 perpendicular to the auxiliary gate lines may be the same or different. Busbars with cross-grid graphics can be prepared by printing methods such as screen printing and stencil printing, valve dispensing, screw dispensing, air pressure dispensing and other dispensing methods, as well as electroplating, direct laying and other methods. .

Since the materials that make up the conductive glue and the busbars have good electrical conductivity, when the above-mentioned grid cross lines are dense enough, using a cross grid instead of a solid pattern will not have a serious impact on the electrical performance of the component.

As shown in Figure 10, the deformation of the conductive glue 6 and the diffusion on the suede surface covered with silicon nitride are limited within the grid pattern due to the restriction of the busbar 2 pattern, thereby avoiding glue overflow and glue seepage happened.

Another scheme has a better anti-overflow glue seepage effect than the above scheme one. The method is to adopt the method of secondary preparation of busbars. First, a metal paste layer with a solid pattern is prepared at the position of busbars, referred to as metal layer 10, and the height of the metal layer is between 0.002 microns and 100 microns. Then the aforementioned cross grid is prepared on the solid metal layer, as shown in FIG. 11 . In this solution, since the suede covered by silicon nitride in the cross grid is also covered by the first metal layer 10 , it has a better effect of preventing overflow and glue seepage than the solution one. The disadvantage is that a secondary preparation process is required, and the consumption of silver paste may be higher than that of option one. The consumption of silver paste can be reduced by reducing the thickness of the metal layer prepared for the first time, or reducing the height or density of the busbar lines 2 prepared for the second time. The graphics preparation method in this scheme, in addition to the several methods mentioned in scheme one, can also be prepared by other methods such as chemical vapor deposition, sol-gel method, evaporation or sputtering for the first metal layer . The material used may be other metals or alloy materials other than silver.

Another solution is to use non-metallic layer 11 made of non-metallic conductive materials, such as graphene, indium tin oxide, etc., or semiconductor materials such as amorphous silicon (thickness is not required), or insulating materials (thickness requirements are relatively thin, In this way, even if it cannot conduct electricity, the charge can conduct electricity through the non-metallic layer) such as silicon oxide, etc. Prepare the first layer of solid busbar pattern with a thickness ranging from 0.002 microns to 100 microns, and then prepare a cross grid structure on the pattern, such as Figure 12 shows.

Another solution is to use physical or chemical etching to remove the passivation layer such as silicon nitride or oxide layer such as silicon oxide, aluminum oxide, etc. at the position of the main gate line to form a gap, and then prepare the main gate line in the shape of a cross grid. grating. The grid-like porous structure of the busbar 2 passes through the gap and contacts the silicon substrate.

For the above four busbar pattern schemes, the segmented busbar scheme can be superimposed at the same time. As shown in Figure 13, the length of the segmented electrodes ranges from 80 microns to 150 mm, and the segmented electrodes on the same extension line The number of electrodes ranges from 2 to 240, and the lengths of each segment can be the same or different.

The above four graphics schemes and the segmented busbar scheme can be used not only for the busbar pattern on the front of the battery, but also for the silver electrode pattern on the back of the single-sided battery, or the busbar pattern on the back of the double-sided laminated battery .

All the above-mentioned schemes can be used for cells with chamfers or without chamfers.

The above solutions are applicable to various monocrystalline silicon solar cells, polycrystalline silicon solar cells, P-type crystalline silicon PERC cells, N-type crystalline silicon PERT cells, heterojunction cells, TOPCON cells, and back contact cells.

A conductive adhesive pattern scheme corresponding to the above battery metallization pattern scheme is shown in FIG. 14 . It can be prepared on the busbar on the front of the battery, or on the silver electrode or busbar on the back of the battery by printing or dispensing.

Figure 15 shows a single-sided laminated battery made of a single-sided laminated battery using the above-mentioned battery metallization pattern. Figure 16 shows a double-sided laminated assembly made of a double-sided laminated battery using the above-mentioned battery metallization pattern. In the laminated assembly, it is divided into N long battery strings (N≥1) from left to right. The vertical double-sided laminated module contains a total of 6 long battery strings, which are respectively marked as strings A, B, C, D, E, and F. In the laminated assembly, any ribbon that connects multiple battery strings at the positive and negative ends of the module is called a bus bar 12; any ribbon that is located at the middle potential of the module and connects multiple battery strings is called a parallel ribbon 14 ; All the welding strips that are connected with parallel welding strips, run parallel to the battery string, and connect bypass diodes are called bypass welding strips 15 .

In addition, the above-mentioned embodiments of the present invention are examples, and technical solutions having the same technical idea as the claims of the present invention and exerting the same effects are included in the present invention.

Claims (10)

1. A solar cell grid line structure, characterized in that it comprises several sub-grid lines (1) arranged on a silicon chip, main grid lines (2) perpendicular to the sub-grid lines (1); said main grid lines (2) It consists of a grid-like porous structure. When the busbar (2) is coated with conductive glue (6), part of the conductive glue (6) is filled in the grid holes of the grid-like porous structure; the main The grid line (2) is a continuous or segmented structure. 2. A solar cell grid wire structure according to claim 1, characterized in that the grid-like porous structure is formed by a plurality of thin lines (7) intersecting each other, and the thin lines (7) include straight lines , polyline and curve in any combination of one or more. 3. A solar cell grid wire structure according to claim 1, characterized in that, the characteristic length of the holes in the grid-like porous structure is 10 microns to 2000 microns, and the entire busbar (2) width is 100 to 1500 microns. 4. A solar cell grid wire structure according to claim 2, characterized in that the thin wire (7) has a width of 5 microns to 1500 microns and a height of 5 microns to 100 microns. 5. A solar cell grid wire structure according to claim 2, characterized in that, the thin wires (7) include longitudinal thin wires (8) and transverse thin wires (9). 6. A kind of solar cell grid line structure according to claim 1, characterized in that, under the grid-like porous structure of the described main grid line (2), a metal layer (10) or a non-metallic layer ( 11), the metal layer (10) or non-metal layer (11) is in contact with the passivation layer or oxide layer on the surface of the cell; the thickness of the metal layer (10) or non-metal layer (11) is between 0.002 microns and 100 microns between. 7. A kind of grid line structure of a solar cell according to claim 1, characterized in that, the passivation layer or oxide layer on the surface of the silicon wafer is etched to form gaps, and the grid-like porous structure of the main grid line (2) The structure contacts the silicon wafer substrate through the gap. 8. A solar cell grid wire structure according to claims 1 to 7, characterized in that, in the segmented structure of the main grid wire (2), the length of each segmented electrode is 80 microns to 150 mm, the number of segment electrodes on each busbar (2) is 2-240. 9. A solar cell, characterized in that the solar cell grid structure according to any one of claims 1 to 8 is used on the front and/or back of the solar cell. 10. A solar stack assembly, characterized in that the stack assembly is made of the solar battery sheet according to claim 9.