WO2017128667A1 - Front electrode of crystalline silicon solar cell - Google Patents

Abstract

A front electrode of a crystalline silicon solar cell, comprising multiple secondary grid lines (10) extending in a first direction and arranged in rows at regular intervals, said front electrode also comprising a number M of fine grid lines (20) extending in a second direction and arranged in rows at regular intervals, the fine grid lines (20) and secondary grid lines (10) being electrically connected, the width of the fine grid lines (20) being 0.10-0.25mm, and the number M = 10-20; a number N of welding contacts (30) are provided at intervals on each fine grid line (20), the welding contacts (30) being layered over the fine grid line (20) and electrically connected to said fine grid line (20), the welding contacts (30) being elliptical, the short axis of the ellipses ranging from 0.2-1mm, and the length of the short axis of each ellipse being greater than the width of a fine grid line (20); the number N = 5-15. The present front electrode structure can achieve the dual goals of reducing light-blocking area and ensuring smooth delivery of current.

Description

Front electrode of a crystalline silicon solar cell Technical field

The invention relates to the technical field of solar cells, and in particular to a front electrode of a crystalline silicon solar cell.

Background technique

A crystalline silicon solar cell is an electronic component that converts solar energy into electrical energy. The preparation of crystalline silicon solar cells is generally carried out by processes such as texturing, diffusion, coating, screen printing, and sintering. The velvet is divided into single crystal and polycrystalline velvet. The single crystal battery is formed by the method of alkali velvet to form a pyramid suede on the surface of the silicon wafer, and the polycrystalline battery is formed by using an acid etching method to form a pitted surface on the surface of the silicon wafer. The suede surface of the silicon surface can increase the absorption of sunlight on the surface of the battery to achieve the light trapping effect; the diffusion process forms a PN junction into the interior of the silicon wafer by means of thermal diffusion, so that when light is irradiated, a voltage can be formed inside the silicon wafer. It is the basis of solar cell power generation; the coating process is to reduce the composite of minority carriers on the surface of the battery, and can improve the conversion efficiency of the crystalline silicon solar cell; the screen printing process is to make the electrode of the solar cell, so that when the light is irradiated It is possible to derive the current. Screen printing is one of the most widely used processes in the preparation of crystalline silicon cells. The process sequence is to first print and dry the back electrode, then print and dry the aluminum back field, and finally print and dry the front electrode. When sintering is performed, the silver paste used for preparing the electrode is brought into contact with the battery.

In the front electrode of the crystalline silicon solar cell, the electrode structure generally includes a main gate line and a sub-gate line which are criss-crossed, and the main gate line is electrically connected to the sub-gate line. When there is light, the battery generates a current, and the current flows through the internal emitter to the surface electrode sub-gate line, collects through the sub-gate line and then flows to the battery main grid for export. The current will be lost during the collection of the secondary gate line, which we call the power loss of the resistor. The main grid line and the sub-gate line of the battery are on the light-receiving surface of the battery, which inevitably blocks a part of the light from being irradiated on the surface of the battery, thereby reducing the effective light-receiving area of the battery, which is called optical loss. Regardless of whether it is a P-type or an N-type battery, as long as the electrode structure exists on the front side of the battery, it is necessary to consider the continuous optimization of the electrode structure to achieve the purpose of reducing the shading area and ensuring smooth current export.

In the conventional front electrode structure, the number of main gate lines is usually three, and the width thereof is about 1.5 mm; the number of the sub-gate lines is usually 80 to 100, and the width thereof is about 40 μm. The width of the main gate line is wide, so that The strip of the front electrode and the battery can be soldered well, but the shading area is also large. In recent years, in order to reduce the light-shielding area of the front electrode, a front electrode structure without a main gate is proposed in the industry, mainly to remove three main gate lines in the front electrode structure, leaving only the sub-gate line, after the battery is completed, A very thin cylindrical ribbon is used to directly solder to the secondary grid, and the current is directly extracted by the ribbon. In the welding process of the extremely thin soldering strip and the sub-gate line, the power of the photovoltaic module is lowered due to the abnormality of the soldering or the inability to solder due to the small width of the sub-gate line and the sub-gate line being too low.

Summary of the invention

In view of the deficiencies of the prior art, the present invention provides a front electrode of a crystalline silicon solar cell, which can achieve the purpose of reducing the shading area and ensuring smooth current export.

In order to achieve the above object, the present invention adopts the following technical solutions:

A front electrode of a crystalline silicon solar cell, comprising a plurality of sub-gate lines arranged at a distance from each other in a first direction, wherein the front electrode further comprises M thin gate lines arranged in a spaced relationship from each other in a second direction, the thin The gate line is electrically connected to the sub-gate line, and the width of the fine gate line is 0.10-0.25 mm; wherein M=10-20; wherein each fine grid line is provided with N solders spaced apart from each other a contact point, the solder contact stack is disposed on the fine gate line and electrically connected to the fine gate line, the shape of the solder contact is elliptical, and a length range of the short side of the ellipse It is 0.2 to 1 mm, and the length of the short side of the ellipse is larger than the width of the fine grid line; wherein N = 5 to 15.

Further, the soldering contact is formed on the fine grid line by a secondary printing process.

Further, the plurality of sub-gate lines are equally spaced along the first direction, the M fine gate lines are equally spaced along the second direction, and the second direction is perpendicular to the first direction.

Further, the number of the sub-gate lines is 80 to 100.

Further, the soldering contact is disposed at a position where the fine gate line intersects the sub-gate line.

Further, N solder contacts on each of the fine gate lines are arranged at equal intervals along the length direction of the thin gate lines.

Further, all of the solder contacts in the front electrode are distributed in an array of N rows x M columns.

Further, in the elliptical welding contact, the long side thereof extends in the first direction, and the short side extends in the second direction.

Further, the length of the long side of the elliptical welding contact ranges from 0.5 to 1.2 mm.

Further, the width of the fine grid line is 0.2 mm; among the elliptical solder contacts, the long side is 1 mm and the short side is 0.6 mm; wherein, M=15, N=10.

Compared with the prior art, in the front electrode of the crystalline silicon solar cell provided by the embodiment of the present invention, a fine gate line with a larger number of smaller widths is used instead of the main gate line in the prior art, and the overall shading area is smaller. The optical loss is reduced, and a larger number of fine grid lines are evenly distributed on the front surface of the solar cell, so that the current collected by the sub-gate lines can be more smoothly derived, reducing power loss; The large-area elliptical welding contact increases the contact area of the solder joint and the height of the solder joint. When soldering the solder ribbon, there is less problem of abnormal soldering of the solder strip and the battery.

DRAWINGS

1 is a schematic structural view of a front electrode of a solar cell according to an embodiment of the present invention;

Figure 2 is an enlarged schematic view of a portion A of Figure 1.

detailed description

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these embodiments are exemplified in the drawings. The embodiments of the invention shown in the drawings and described in the drawings are merely exemplary, and the invention is not limited to the embodiments.

In this context, it is also to be noted that in order to avoid obscuring the invention by unnecessary detail, only the structures and/or processing steps closely related to the solution according to the invention are shown in the drawings, and the Other details that are not relevant to the present invention.

Referring to FIG. 1 and FIG. 2, the present embodiment provides a front electrode of a crystalline silicon solar cell. As shown in FIG. 1, the front electrode includes two rows spaced apart from each other in the first direction (such as the Y direction in FIG. 1). a plurality of sub-gate lines 10, a plurality of thin gate lines 20 spaced apart from each other in the second direction (in the X direction in FIG. 1), the plurality of sub-gate lines 10 and the plurality of fine gate lines 20 are electrically connected to each other. The sub-gate line 10 is mainly used to collect the photo-generated current generated by the solar cell, and the fine-gate line 20 is used to collect and output the current collected by the sub-gate line 10. Further, each of the fine gate lines 20 is further provided with a plurality of soldering contacts 30 spaced apart from each other, and the soldering contacts 30 are stacked on the fine gate lines 20 and electrically connected to the fine grid lines 20. Connected, the shape of the soldering contact 30 is elliptical. The soldering contact 30 is mainly used for soldering connection to the solder ribbon after the battery is fabricated.

The number of the sub-gate lines 10 may be selected from the range of 80 to 100, and the width may be selected to be in the range of 30 to 50 μm. The number M of the fine grid lines 20 can be selected in the range of 10 to 20, which is wide The degree D can be selected in the range of 0.10 to 0.25 mm. The number N of the soldering contacts 30 provided on each of the fine grid lines 20 may be selected to be in the range of 5 to 15. In the elliptical soldering contacts 30, the long sides thereof extend in the first direction (in the Y direction in FIG. 1). The short side extends in the second direction (such as the X direction in FIG. 1), and the length L11 of the long side can be selected in the range of 0.5 to 1.2 mm, and the length L12 of the short side can be selected in the range of 0.2 to 1 mm, and The length of the short side is satisfied to be larger than the width D of the fine gate line 20. In the present embodiment, the number of the sub-gate lines 10 is 90, the width of the sub-gate lines 10 is 40 μm; the number of the fine gate lines 20 is M=15, and the width D of the fine gate lines 20 is 0.2 mm; each fine gate The number of welding contacts 30 on the wire 20 is N = 10, and in the elliptical welding contact 30, the long side L11 is 1 mm and the short side L12 is 0.6 mm.

The solder contacts 30 are stacked on the fine gate lines 20. Specifically, in the preparation of the front electrode structure, the sub-gate lines 10 and the fine gate lines 20 are first prepared by a single printing process, and then the solder contacts 30 are prepared on the fine gate lines 20 by a secondary printing process.

In this embodiment, as shown in FIG. 1, the plurality of sub-gate lines 10 are arranged at equal intervals in a first direction (such as the Y direction in FIG. 1), and the M thin gate lines 20 are in a second direction ( The X direction in FIG. 1 is equally spaced, and the second direction is perpendicular to the first direction. Further, the soldering contact 30 is disposed at a position where the fine gate line 20 intersects the sub-gate line 10, and N soldering contacts 30 on each of the fine gate lines 20 along the thin grid line 20 is arranged at equal intervals in the longitudinal direction.

More specifically, in the present embodiment, as shown in FIG. 1, the arrangement pitch of the N solder contacts 30 on each of the fine gate lines 20 is equal, and therefore, in the entire front electrode structure, all the solder contacts 30 are provided. An array of N rows x M columns.

The front electrode of the crystalline silicon solar cell provided by the above embodiments can effectively reduce the light shielding area. Taking the square of the front surface of the solar cell of 156 mm×156 mm as an example, the shading area is calculated according to the front electrode of the existing three main grid and the front electrode structure provided by the embodiment of the present invention:

1. The front electrode structure of the existing three main grids. In the conventional structure of three 1.5mm wide main gate lines and 90 40μm sub grid lines, the main gate lines can be designed in a hollow form to reduce the silver paste used for printing, but all areas of the main grid will still be soldered to a width of about 1.5 mm during soldering. The welding strip blocks the sunlight. Therefore, the shielding area of the sun at the main grid is 1.5 mm × 3 × 156 mm = 702 mm ² ; the shielding area of the sub grid and the four frames is 0.04 mm × (90 + 2) × (153.5 mm - 1.5 mm × 3) + 2 ×153.5 mm × 0.04 mm = 560.6 mm ² . The total occlusion area of the conventional three-main gate front electrode is 1262.6 mm ² .

2. The front electrode structure provided by the embodiment of the invention. According to a specific example, the number of sub-gate lines is 90 and the width is 40 μm; the number of fine gate lines is 15 and the width is 0.2 mm; the number of solder contacts on each fine grid line is 10 The elliptical welded contacts have a long side of 1 mm and a short side of 0.6 mm. Then: the shielding area of the 15 fine grid lines to the sunlight is 0.2mm×10×156mm=468mm ² ; the obstruction of the sun by the sub-grid line and the 4 frames is 0.04mm×(90+2)×(153.5mm-0.2mm ×15)+0.04mm×2×153.5mm=566.12mm ² , except for the fine grid line, the elliptical pattern with a long side of 1mm and a short side of 0.6mm is estimated to be [π×0.5mm×0.3 Mm-0.2 mm x 1 mm] x 150 = 40.65 mm ² , total occlusion area is 468 mm ² + 566.12 mm ² + 40.65 mm ² = 1074.77 mm ² . The front electrode provided by the embodiment of the invention has a reduced light-shielding area of 1262.6 mm ² -1074.77 mm ² =187.83 mm ² compared to the front electrode of the existing three-main gate.

In summary, in the front electrode of the crystalline silicon solar cell provided by the above embodiment, a larger number of fine gate lines with smaller widths are used instead of the main gate lines in the prior art, and the overall shading area is smaller and reduced. Light loss, and a larger number of fine grid lines are evenly distributed on the front side of the solar cell, so that the current collected by the sub-gate line can be more smoothly derived, reducing power loss; in addition, the laminated area on the fine grid line is larger. The elliptical welding contact increases the contact area of the solder joint and the height of the solder joint. When the solder ribbon is soldered, there is less problem of abnormal soldering of the solder strip and the battery.

It should be noted that, in this context, relational terms such as first and second are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply such entities or operations. There is any such actual relationship or order between them. Furthermore, the term "comprises" or "comprises" or "comprises" or any other variations thereof is intended to encompass a non-exclusive inclusion, such that a process, method, article, or device that comprises a plurality of elements includes not only those elements but also Other elements, or elements that are inherent to such a process, method, item, or device. An element that is defined by the phrase "comprising a ..." does not exclude the presence of additional equivalent elements in the process, method, item, or device that comprises the element.

The above description is only a specific embodiment of the present application, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present application. It should be considered as the scope of protection of this application.

Claims (20)

A front electrode of a crystalline silicon solar cell, comprising a plurality of sub-gate lines arranged at a distance from each other in a first direction, wherein The front surface electrode further includes M thin gate lines which are arranged at intervals in the second direction, and the fine gate lines are electrically connected to the sub-gate lines, and the width of the fine gate lines is 0.10-0.25 mm; M=10～20; Wherein, each of the fine gate lines is further provided with N soldering contacts spaced apart from each other, and the soldering contact stack is disposed on the fine gate line and electrically connected to the fine gate lines, the soldering contacts The shape of the dot is elliptical, the length of the short side of the ellipse is 0.2 to 1 mm, and the length of the short side of the ellipse is larger than the width of the fine grid line; wherein N = 5 to 15. The front electrode of a crystalline silicon solar cell according to claim 1, wherein the solder contact is formed on the fine gate line by a secondary printing process. The front surface electrode of the crystalline silicon solar cell according to claim 1, wherein the plurality of sub-gate lines are arranged at equal intervals in a first direction, and the M fine gate lines are arranged at equal intervals in a second direction, the The two directions are perpendicular to the first direction. The front surface electrode of a crystalline silicon solar cell according to claim 3, wherein the number of the sub-gate lines is 80 to 100. The front surface electrode of a crystalline silicon solar cell according to claim 1, wherein the soldering contact is disposed at a position where the fine gate line intersects the sub-gate line. The front electrode of a crystalline silicon solar cell according to claim 5, wherein the N solder contacts on each of the fine gate lines are arranged at equal intervals along the length direction of the thin gate lines. The front electrode of a crystalline silicon solar cell according to claim 6, wherein all of the solder contacts in the front electrode are distributed in an array of N rows x M columns. The front electrode of a crystalline silicon solar cell according to claim 6, wherein the elliptical solder contact has a long side extending in a first direction and a short side extending in a second direction. The front electrode of a crystalline silicon solar cell according to claim 8, wherein the length of the long side of the elliptical solder contact is in the range of 0.5 to 1.2 mm. The front surface electrode of the crystalline silicon solar cell according to claim 8, wherein the width of the fine grid line is 0.2 mm; wherein the elliptical solder contact has a long side of 1 mm and a short side of 0.6 mm; Where M=15 and N=10. The front surface electrode of a crystalline silicon solar cell according to claim 2, wherein the soldering contact is disposed at a position where the fine gate line intersects the sub-gate line. A front surface electrode of a crystalline silicon solar cell according to claim 11, wherein N solder contacts on each of the fine gate lines are arranged at equal intervals along the length direction of the thin gate lines. The front electrode of a crystalline silicon solar cell according to claim 12, wherein all of the solder contacts in the front electrode are distributed in an array of N rows x M columns. The front electrode of a crystalline silicon solar cell according to claim 12, wherein said elliptical solder contact has a long side extending in a first direction and a short side extending in a second direction. The front electrode of a crystalline silicon solar cell according to claim 14, wherein the length of the long side of the elliptical solder contact is in the range of 0.5 to 1.2 mm. The front electrode of a crystalline silicon solar cell according to claim 3, wherein the soldering contact is disposed at a position where the fine gate line intersects the sub-gate line. A front surface electrode of a crystalline silicon solar cell according to claim 16, wherein N solder contacts on each of the fine gate lines are arranged at equal intervals along the length direction of the thin gate lines. The front electrode of a crystalline silicon solar cell according to claim 17, wherein all of the solder contacts in the front electrode are distributed in an array of N rows x M columns. A front surface electrode of a crystalline silicon solar cell according to claim 17, wherein in said elliptical solder contact, a long side thereof extends in a first direction and a short side extends in a second direction. The front electrode of a crystalline silicon solar cell according to claim 19, wherein a length of the long side of the elliptical solder contact is in the range of 0.5 to 1.2 mm.

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