WO2017128670A1

WO2017128670A1 - Crystalline silicon solar cell

Info

Publication number: WO2017128670A1
Application number: PCT/CN2016/092197
Authority: WO
Inventors: 何凤琴; 张思远
Original assignee: 张甘霖
Priority date: 2016-01-28
Filing date: 2016-07-29
Publication date: 2017-08-03
Also published as: CN105679850A

Abstract

A crystalline silicon solar cell, comprising a cell body (1), as well as a front electrode (2) positioned at the front face of the cell body (1) and a rear electrode (3) positioned at the rear face of the cell body (1), the front electrode (2) comprising multiple secondary grid lines (10) extending in a first direction and arranged in rows at regular intervals, and the front electrode (2) also comprising a number M of fine grid lines (20) extending in a second direction and arranged in rows at regular intervals, the width of the fine grid lines (20) being 0.10-0.25mm; 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), the welding contacts (30) being circular, and length of the diameter of a circle being greater than the width of the fine grid line (20); the rear electrode (3) comprises a number N×M of electrode units (31), the electrode units (31) and welding contacts (30) corresponding one-to-one, and the length of each electrode unit (31) along the first direction and the second direction being no shorter than the length of a welding contact (30) along the corresponding direction. Light-blocking area is thus reduced.

Description

Crystal silicon solar cell

Technical field

The present invention relates to the field of solar cell technologies, and in particular, to 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 front electrode and the battery ribbon can be soldered well, but the light shielding area is also large. In recent years, for In order to reduce the light-shielding area of the front electrode, the industry has proposed a front electrode structure without a main gate, which mainly removes three main gate lines in the front electrode structure, and only retains the sub-gate line. After the battery is completed, the use is extremely fine. The cylindrical ribbon is directly soldered 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 crystalline silicon solar cell. By improving the structure of the front electrode, the front electrode structure can achieve the purpose of reducing the shading area and ensuring smooth current export; further, corresponding The back electrode structure in the solar cell is improved, and the amount of silver paste in the back electrode structure is saved.

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

A crystalline silicon solar cell includes a battery body and a front electrode on a front surface of the battery body and a back electrode on a back surface of the battery body, wherein the front electrode includes a plurality of sub-gate lines spaced apart from each other in the first direction, and further includes The M gate lines are arranged in the second direction, 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; wherein 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 a circle, the diameter of the circle is in the range of 0.2 to 1 mm, and the diameter of the circle is larger than the width of the fine grid line; wherein, N = 5 to 15; the back electrode includes N × M electrode units, the electrode units are in one-to-one correspondence with the soldering contacts, and the lengths of the electrode units in the first direction and the second direction are respectively not less than the length of the soldering contacts in the corresponding direction.

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 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, the width of the fine grid line is 0.2 mm; the diameter of the circular soldering contact is 0.8 mm; Where M=15 and N=10.

Further, the electrode unit includes a first electrode portion, a second electrode portion, and a third electrode portion spaced apart from each other in the first direction, and in the first direction, the length of the second electrode portion is greater than The length of one electrode portion and the third electrode portion.

Further, in a first direction, a ratio of lengths of the first electrode portion, the second electrode portion, and the third electrode portion is (0.4 to 0.6): 1: (0.4 to 0.6).

Further, in the first direction, the length of the second electrode portion is 0.6 to 1 mm, and the distance between the second electrode portion and the first electrode portion and the third electrode portion is 0.3 to 0.6 mm.

Compared with the prior art, the crystalline silicon solar cell provided by the embodiment of the present invention uses a larger number of fine gate lines with smaller widths instead of the main gate lines in the front electrode, and the overall shading area is smaller. , reducing the optical 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, stacking on the fine grid line There is a large circular welding contact, which 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 ribbon and the battery. Further, the back electrode is divided into electrode units that are in one-to-one correspondence with the solder contacts, and the electrode unit is segmented, which effectively reduces the amount of silver paste in the back electrode structure.

DRAWINGS

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

2 is a schematic structural view of a front electrode in an embodiment of the present invention;

Figure 3 is an enlarged schematic view of a portion A of Figure 2;

4 is a schematic structural view of a back electrode in an embodiment of the present invention;

Fig. 5 is a schematic structural view of an electrode unit in an embodiment of the present invention.

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.

Here, it should also be noted that in order to avoid obscuring the present invention due to unnecessary details, Only the structural and/or processing steps closely related to the solution according to the invention are shown in the figures, while other details which are not relevant to the invention are omitted.

As shown in FIG. 1 , this embodiment firstly provides a crystalline silicon solar cell mainly comprising a battery body 1 and a front electrode 2 located on the front surface of the battery body 1 and a back electrode 3 located on the back surface of the battery body 1 . The battery body 1 mainly uses a silicon wafer to prepare a PN junction battery formed by a texturing process, a diffusion process, and an etching process. The front electrode 2 and the back electrode 3 are mainly formed on both sides of the battery body 1 by a screen printing process for outputting the electric energy converted by the battery body 1.

2 and FIG. 3, the front electrode 2 in this embodiment includes a plurality of sub-gate lines 10 spaced apart from each other in the first direction (in the Y direction in FIG. 2) and arranged in parallel, along the second direction (eg, A plurality of fine gate lines 20 spaced apart from each other and arranged in parallel in the X direction in FIG. 2, the plurality of sub-gate lines 10 and the plurality of fine gate lines 20 being 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 solder contact 30 is circular. 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 gate lines 20 can be selected in the range of 10 to 20, and the width D1 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 gate lines 20 may be selected to be in the range of 5 to 15, and the diameter R of the soldering contacts 30 may be selected to be in the range of 0.2 to 1 mm, and the soldering contacts 30 are to be satisfied. The diameter R is larger than the width of the fine grid 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 D1 of the fine gate lines 20 is 0.2 mm; each fine gate The number of solder contacts 30 on line 20 is N = 10, and the shape of solder contact 30 is circular with a diameter R of 0.8 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. 2, the plurality of sub-gate lines 10 are arranged at equal intervals in a first direction (such as the Y direction in FIG. 2), and the M thin gate lines 20 are in a second direction ( Arranged at equal intervals in the X direction as in FIG. 2, 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. 2, 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 shape of the solder contact is circular and its diameter R is 0.8 mm. Then: the shielding area of 10 fine grid lines to sunlight is 0.2mm×15×156mm=468mm ² ; the obstruction of sunlight by the sub-grid line and 4 frames is 0.04mm×(90+2)×(153.5mm-0.2mm ×15)+0.04mm×2×153.5mm=566.12mm ² , the circular pattern of 0.8mm diameter except the fine grid line occludes sunlight [π×0.4 ² mm ² -(0.8mm-0.2mm)×0.04 Mm-π×0.4 ² mm ² ×29°×2÷360°-0.2×0.4×sin14.5]×150=56.64mm ² , the total shielding area is 468mm ² +566.12mm ² +56.64mm ² =1090.76mm ² . The front electrode provided by the embodiment of the invention has a reduced light-shielding area of 1262.6 mm ² -1090.76 mm ² =171.84 mm ² compared to the front electrode of the existing three-main gate.

Further, referring to FIG. 4 and FIG. 5, the back electrode 3 in this embodiment includes N×M electrode units 31, that is, the number of the electrode units 31 and the soldering contacts 30 are equal, and the electrodes The unit 31 has a one-to-one correspondence with the welding contacts 30, and the lengths of the electrode units 31 in the first direction (such as the Y direction in FIG. 4) and the second direction (in the X direction in FIG. 4) are not less than The length of the soldering contact in the corresponding direction. Specifically, the length of the electrode unit 31 in the first direction and the second direction is not less than the diameter of the circular soldering contact 30, respectively.

Wherein, as shown in FIG. 5, the electrode unit 31 includes the first electrode portion 311, the second electrode portion 312, and the third electrode portion 313 spaced apart from each other in the first direction, and in the first direction, Second electrode The length of the portion 312 is greater than the length of the first electrode portion 311 and the third electrode portion 313, respectively. In the present embodiment, in the first direction, the ratio of the lengths of the first electrode portion 311, the second electrode portion 312, and the third electrode portion 312 is L21: L22: L23 = (0.4 - 0.6): 1: ( 0.4 to 0.6). The length L21 of the second electrode portion 312 may be selected to be 0.6 to 1 mm, and the distances D21 and D22 between the second electrode portion 312 and the first electrode portion 311 and the third electrode portion 313 may be selected to be 0.3. ~0.6mm. Among them, L21 and L23 can be selected as equal values, and D21 and D22 can be selected as equal values. Specifically, in this embodiment, the values of the respective parameters are as follows: L21=L23=0.5mm, L22=1mm, D21=D22=0.5mm; the length L24 of the electrode unit 31 in the second direction and the soldering contact 30 The diameter is equal, that is, L24 = 0.8mm.

The back electrode of the existing three-main grid solar cell generally comprises three columns, each column comprising three electrode blocks having a size of 21 mm x 3 mm, and the overall area of the back electrode is: 21 mm x 3 mm x 9 = 567 mm ² .

The back electrode structure provided by the above specific embodiment of the present invention includes 10×15=150 electrode units, the width of the electrode unit is L24=0.8 mm, the length is L21+L22+L23=2 mm, and the overall area of the back electrode is: 2 mm × 0.8 mm × 150 = 240 mm ² .

The back electrode provided by the embodiment of the present invention has an overall area reduced by 567 mm ² -240 mm ² = 327 mm ² compared with the back electrode of the existing three main grid solar cell, and under the same screen printing process, the silver paste The dosage is reduced by more than 50%, which greatly reduces the cost.

In summary, the crystalline silicon solar cell provided by the above embodiment has a smaller number of narrow gate lines instead of the prior art main gate lines in the front electrodes, and the overall shading area is smaller and smaller. The optical 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 the power loss; in addition, the area on the fine grid line is set to be thinner. Large round welded contacts increase the contact area of the solder joints and the height of the solder joints. When soldering the solder ribbon, there is less problem of abnormal soldering of the solder ribbon and the battery. Further, the back electrode is divided into electrode units that are in one-to-one correspondence with the solder contacts, and the electrode unit is segmented, which effectively reduces the amount of silver paste in the back electrode structure.

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. In the absence of more restrictions, the elements defined by the statement "including one..." are not excluded from including the There are other similar elements in the process, method, article or equipment.

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

A crystalline silicon solar cell includes a battery body and a front electrode on a front surface of the battery body and a back electrode on a back surface of the battery body, wherein

The front electrode includes a plurality of sub-gate lines spaced apart from each other in the first direction, and further includes M thin gate lines arranged in a spaced relationship from each other in the second direction, the fine gate lines being electrically connected to the sub-gate lines, The width of the fine gate line is 0.10-0.25 mm; wherein, M=10-20; wherein each fine grid line is further provided with N soldering contacts spaced apart from each other, and the solder contact stack is disposed at The fine gate line is electrically connected to the fine grid line, the shape of the solder contact is circular, the diameter of the circle is 0.2 to 1 mm, and the diameter of the circle is larger than Describe the width of the fine grid line; wherein, N = 5 to 15;

The back electrode includes N×M electrode units, and the electrode unit has a one-to-one correspondence with the soldering contacts, and the lengths of the electrode units in the first direction and the second direction are not less than the soldering contacts respectively. Corresponding to the length in the direction.
The crystalline silicon solar cell of claim 1, wherein the solder contact is formed on the fine gate line by a secondary printing process.
The crystalline silicon solar cell of claim 1 , wherein the plurality of sub-gate lines are equally spaced along a first direction, and the M fine gate lines are equally spaced along a second direction, the second direction being The first directions are perpendicular to each other.
The crystalline silicon solar cell of claim 3, wherein the solder contact is disposed at a position where the fine gate line intersects the sub-gate line.
The crystalline silicon solar cell of claim 4, wherein the N solder contacts on each of the fine gate lines are equally spaced along the length of the thin gate lines.
The crystalline silicon solar cell of claim 5 wherein all of the solder contacts in the front side electrode are distributed in an array of N rows x M columns.
The crystalline silicon solar cell of claim 6, wherein the fine gate line has a width of 0.2 mm; the circular solder contact has a diameter of 0.8 mm; wherein M = 15, N = 10.
The crystalline silicon solar cell of claim 1, wherein the electrode unit includes a first electrode portion, a second electrode portion, and a third electrode portion spaced apart from each other in a first direction, and in a first direction, The length of the second electrode portion is greater than the length of the first electrode portion and the third electrode portion, respectively.
The crystalline silicon solar cell according to claim 8, wherein a ratio of lengths of the first electrode portion, the second electrode portion, and the third electrode portion in the first direction is (0.4 to 0.6): 1: (0.4 to 0.6).
The crystalline silicon solar cell according to claim 9, wherein the second electrode portion has a length of 0.6 to 1 mm in the first direction, and the second electrode portion and the first electrode portion and the third electrode portion The distance between the intervals is 0.3 to 0.6 mm.
The crystalline silicon solar cell according to claim 2, wherein the electrode unit includes the first electrode portion, the second electrode portion, and the third electrode portion spaced apart from each other in the first direction, and in the first direction, The length of the second electrode portion is greater than the length of the first electrode portion and the third electrode portion, respectively.
The crystalline silicon solar cell according to claim 11, wherein a ratio of lengths of the first electrode portion, the second electrode portion, and the third electrode portion in the first direction is (0.4 to 0.6): 1: (0.4 to 0.6).
The crystalline silicon solar cell according to claim 12, wherein the second electrode portion has a length of 0.6 to 1 mm in the first direction, and the second electrode portion and the first electrode portion and the third electrode portion The distance between the intervals is 0.3 to 0.6 mm.
The crystalline silicon solar cell according to claim 3, wherein the electrode unit includes the first electrode portion, the second electrode portion, and the third electrode portion spaced apart from each other in the first direction, and in the first direction, The length of the second electrode portion is greater than the length of the first electrode portion and the third electrode portion, respectively.
The crystalline silicon solar cell according to claim 14, wherein a ratio of lengths of the first electrode portion, the second electrode portion, and the third electrode portion in the first direction is (0.4 to 0.6): 1: (0.4 to 0.6).
The crystalline silicon solar cell according to claim 15, wherein the second electrode portion has a length of 0.6 to 1 mm in the first direction, and the second electrode portion and the first electrode portion and the third electrode portion The distance between the intervals is 0.3 to 0.6 mm.
The crystalline silicon solar cell of claim 4, wherein the electrode unit includes the first electrode portion, the second electrode portion, and the third electrode portion spaced apart from each other in the first direction, and in the first direction, The length of the second electrode portion is greater than the length of the first electrode portion and the third electrode portion, respectively.
The crystalline silicon solar cell according to claim 17, wherein the ratio of the lengths of the first electrode portion, the second electrode portion, and the third electrode portion in the first direction is (0.4 to 0.6): 1: (0.4 to 0.6).
The crystalline silicon solar cell according to claim 18, wherein the second electrode portion has a length of 0.6 to 1 mm in the first direction, and the second electrode portion and the first electrode portion and the third electrode portion The distance between the intervals is 0.3 to 0.6 mm.