Photovoltaic cell, photovoltaic module and preparation method thereof

Abstract

The present invention provides a photovoltaic cell, a photovoltaic module and a preparation method thereof, wherein the photovoltaic cell is provided with a front side and a back side, wherein the back side is provided with a plurality of long strip battery cells of equal size and arranged in sequence, wherein each battery cell is formed with a slot, and the slot ratio of the first and last two battery cells located at the edge of the photovoltaic cell is greater than the slot ratio of other battery cells. Compared with the prior art, the present invention changes the Voc value of the battery slice after cutting and splitting by adjusting the slot ratio or window ratio in different areas on the back side of the photovoltaic cell, thereby making the Voc values ​​of each battery slice close to or consistent, which is conducive to improving the yield rate of EL detection and is less likely to cause the problem of luminescence due to excessively high Voc values.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaics, and in particular to a photovoltaic cell sheet, a photovoltaic module and a preparation method thereof. Background Art

[0002] During the production process of photovoltaic cells, the Voc value (i.e., the open-circuit voltage value) of each cell is different, which causes the photovoltaic modules made of it to show different brightness at different positions in the EL test, resulting in poor EL display. This problem is particularly obvious in sliced ​​photovoltaic modules. Slicing technology is a commonly used technology in the photovoltaic field, that is, by cutting a photovoltaic cell of standard size into two, three or four equal parts, a plurality of cell slices are obtained, and then these cell slices are connected in a specific way, and finally made into photovoltaic modules (such as shingled photovoltaic modules). Such photovoltaic modules are more likely to have poor EL problems. The reason is that the cell slices obtained by equally cutting different areas of the standard photovoltaic cell also have different Voc values, especially the cell slices from the edge area of ​​the standard photovoltaic cell, whose Voc values ​​are usually higher, so that the position of the slice will be bright in the EL test, and then the photovoltaic module is judged as a defective product. Therefore, how to make the Voc values ​​of each cell or cell slice close to or consistent to improve the yield rate of EL detection is a problem that needs to be solved urgently. Summary of the invention

[0003] The technical problem solved by the present invention is to provide a photovoltaic cell, a photovoltaic module and a preparation method thereof, which can improve the problem of poor EL detection caused by excessively large differences in Voc values ​​between different cells or slices in the prior art.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solution: a photovoltaic cell sheet is provided, which has a front side and a back side, and the back side is provided with a plurality of elongated battery cells of equal size and arranged in sequence, each battery cell has a groove formed therein, and the groove rate of the first and last two battery cells located at the edge of the photovoltaic cell sheet is greater than the groove rate of other battery cells.

[0005] Furthermore, the slotting ratio of the first and last two battery cells is 1.0 to 1.5 times the slotting ratio of other battery cells.

[0006] Furthermore, the slotting rates of the first and last two battery cells are 3.2-3.5%.

[0007] Furthermore, the grooving rate of the entire back side of the photovoltaic cell sheet is 1-70%.

[0008] Furthermore, the battery unit is in the shape of an elongated rectangle, the length of its long side is N times the length of its short side, and N is an integer not less than 3.

[0009] Furthermore, the slot is in the shape of an elongated strip, and its extending direction is perpendicular to the long side of the battery unit.

[0010] Furthermore, the width of the grooves is 10-200 micrometers, and the spacing between two adjacent rows of grooves is 0.1-3 millimeters.

[0011] Furthermore, each slot in each row of slots is not aligned one by one with each slot in an adjacent row, but is staggered in a direction perpendicular to the length of the slots and partially overlaps.

[0012] Furthermore, cutting grooves are formed between the battery cells.

[0013] The present invention also provides a photovoltaic module, comprising a plurality of battery slices, wherein the battery slices are connected by overlapping edges, the battery slices are obtained by cutting the battery units of the photovoltaic battery sheet in the aforementioned technical solution, and the groove rate on the back side of some of the battery slices in the photovoltaic module is greater than the groove rate on the back side of the remaining battery slices.

[0014] The present invention may also adopt the following technical solution: A method for preparing a photovoltaic cell sheet, comprising:

[0015] Providing a silicon wafer;

[0016] The first laser is used to groove different areas on the back of the silicon wafer, so that the groove rate of the edge area of ​​the silicon wafer is greater than the groove rate of other areas, and the silicon wafer is used to prepare a photovoltaic cell.

[0017] Furthermore, the grooves in different areas on the back side of the silicon wafer are formed simultaneously.

[0018] Furthermore, the silicon wafer edge region is formed at two opposite edges of the silicon wafer and extends along the edges of the silicon wafer, and the width of the edge region does not exceed one third of the side length of the silicon wafer.

[0019] The present invention also provides a method for preparing a photovoltaic module, comprising:

[0020] Providing a silicon wafer;

[0021] Using a first laser to groove different areas on the back of a silicon wafer, so that the groove rate of the edge area of ​​the silicon wafer is greater than the groove rate of other areas, and using the silicon wafer to prepare a photovoltaic cell;

[0022] Using a second laser to carve a plurality of cutting grooves on the back of the photovoltaic cell sheet, the cutting grooves evenly divide the back of the photovoltaic cell sheet into a plurality of battery cells;

[0023] Applying force to the photovoltaic cell sheet so that each of the cell units is split along the cutting groove to form a plurality of independent cell slices;

[0024] The cell slices are connected into cell strings.

[0025] Furthermore, the battery slices are connected into a battery string, specifically comprising:

[0026] Applying conductive glue to the edge of each battery slice;

[0027] Overlap the edges of the battery slices to form a battery string.

[0028] Compared with the prior art, the present invention changes the Voc value of the cell slices after cutting and splitting by adjusting the grooving rate or window opening rate in different areas on the back of the photovoltaic cell, thereby making the Voc values ​​of each cell slice close to or consistent, which is beneficial to improving the yield rate of EL detection and is less likely to cause the problem of brightness due to excessively high Voc values. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the photovoltaic cell of the present invention.

[0030] Figure 2 This is a schematic diagram of the back side of the battery slice described in the present invention.

[0031] Figure 3 The figure is a schematic diagram of the connection of the cell slices in the photovoltaic module of the present invention. DETAILED DESCRIPTION

[0032] See also Figure 1 As shown, the present invention provides a photovoltaic cell 10, which has a front side and a back side, wherein the back side is divided into N areas of equal size, each area constituting a battery cell 11, and each battery cell 11 is a long rectangular strip, and the length of the long side is N times the length of the short side, and N is an integer not less than 3.

[0033] A large number of slots 12 are formed on the back of the photovoltaic cell sheet 10. The slots 12 are formed by laser and are distributed in each battery cell 11 of the photovoltaic cell sheet 10. The slots 12 are long strips, and their extending direction is perpendicular to the long side of the battery cell 11. For each battery cell 11, the ratio of the total area of ​​all the slots 12 formed therein to the back area of ​​the battery cell 11 is the slot ratio (or window ratio) of the battery cell 11.

[0034] The plurality of slots 12 are arranged in M ​​parallel rows (M is an integer) on the back of the photovoltaic cell 10, and all the slots 12 in each row are arranged in a straight line and are non-continuously distributed, that is, there are no slots between two adjacent slots 12 in the same row or between two adjacent rows of slots 12. Figure 2As shown, assuming that the width of the slot 12 is a, the length is x, the distance between two adjacent slots 12 in the same row is y, and the distance between two adjacent rows of slots 12 is z, the slot rate calculation formula is: slot rate (%) = ax / (x+y)(a+z). It can be seen that the size of the slot rate is related to the aforementioned parameters a, x, y and z, and adjusting any one of the parameters will change the size of the slot rate.

[0035] In addition, cutting grooves 13 engraved by laser are provided between the several battery cells 11 of the photovoltaic cell sheet 10. The cutting grooves 13 can be used to split the several battery cells 11 into several independent battery slices 11'. Each battery slice 11' serves as a small-sized power generation unit and can be connected with other battery slices 11' to form a string, and finally made into a photovoltaic module.

[0036] In a preferred embodiment of the present invention, the slotting rates of the battery cells 11 at different positions of the photovoltaic cell sheet 10 are different, especially the two battery cells 11 near the edge of the photovoltaic cell sheet 10, i.e., the first and last two battery cells 11, whose slotting rates are significantly higher than the slotting rates of the remaining battery cells 11. The purpose of such setting is to reduce the Voc value of the first and last two battery slices 11' after cutting, so that the Voc value is closer to or consistent with the Voc value of the battery slices 11' cut at other positions. The reason is that under normal circumstances, the two battery slices 11' at the first and last positions will have higher Voc values, which will appear to be obviously bright in EL detection. Therefore, this embodiment reduces the Voc value of the battery slice 11' after cutting by increasing the slotting rates of the two battery cells 11 at the first and last positions, so that it will not be obviously bright in EL detection, thereby improving the EL detection yield.

[0037] Preferably, the photovoltaic cell 10 described in the present invention is a PERC cell, and the grooves on the back are to achieve back contact of the PERC cell to form a back electrode. The quality of the grooves 12 will directly affect the performance of the cell. Therefore, the present invention preferably uses laser or chemical etching to perform the grooves 12.

[0038] Preferably, the width a of the slots 12 of the present invention is 10-200 microns, the offset distance b of the slots 12 is between 0 and x, the slot ratio x / (x+y) is between 0.1 and 1, that is, x:y≥1:9, and the spacing z between two adjacent rows of slots 12 is between 0.1 and 3 mm. It should be noted that each slot 12 in each row of slots 12 is not aligned with each slot 12 in the adjacent row, but is staggered in a direction perpendicular to the length of the slots 12 and partially overlaps, such as Figure 2As shown, the position of a single slot 12 corresponds to the unslotted area between two slots 12 in adjacent rows. Therefore, the offset distance b of the slot 12 specifically refers to the overlapping size of two partially overlapping slots 12 in two adjacent rows.

[0039] It can be seen that the present invention adjusts the slotting rate of a certain battery cell 11 of the photovoltaic cell 10 to reduce the Voc value of the battery slice 11' formed by the battery cell 11, so that the Voc value of the battery slice 11' is close to or consistent with that of other battery slices 11', thereby avoiding the problem of EL detection lighting. There are various methods for adjusting the slotting rate. According to the slotting rate formula: slotting rate (%) = ax / (x+y)(a+z), an example is given. For example, the slotting rate can be increased by increasing the length x of the slot 12 and shortening y; or, the slotting rate can be increased by shortening the distance z (i.e., shortening the spacing between two adjacent rows of slots 12); or, the slotting rate can be increased by increasing the width a. All of the above methods can be used to increase the slotting rate. Of course, the opposite is also possible, that is, the slotting rate can be reduced and the Voc value of the battery slice 11' can be increased according to actual needs. In short, whether reducing the slotting rate or increasing the slotting rate, the purpose is to adjust the Voc values ​​of each battery slice 11 ′ after laser cutting to be as close or equal as possible, which can effectively avoid the problem of poor EL detection due to inconsistent Voc values.

[0040] In a preferred embodiment of the present invention, the slotting rate is 1-70%, which can be adjusted according to the electrode pattern design and the size of the laser spot. For example, taking a photovoltaic cell 10 divided into five equal parts, the back of the photovoltaic cell 10 is divided into five battery cells 11. After laser slotting, the slotting rate of the entire photovoltaic cell 10 is 3-5%, among which the slotting rates of the two battery cells 11 at the first and last positions (i.e., edge positions) are 3.2-3.5% (preferably 3.25%), and the slotting rates of the remaining battery cells 11 at the middle positions are 3.0-3.2% (preferably 3.06%), which is lower than the slotting rates of the battery cells 11 at the first and last positions. Of course, the slotting rates of each battery cell 11 can be further adjusted according to actual needs, but the slotting rates of the battery cells 11 at the first and last positions are always 1.0 to 1.5 times (not including 1.0 times) of the slotting rates of the battery cells 11 at the middle positions.

[0041] The present invention also discloses a photovoltaic module, which includes a plurality of interconnected battery slices 11', wherein the battery slices 11' are obtained by cutting the photovoltaic cell sheet 10 into N equal parts, and each battery slice 11' has a long side and a short side, and the length of the long side is N times the length of the short side. In a preferred embodiment of the present invention, the plurality of battery slices 11' are interconnected in a manner of overlapping long sides, that is, in two adjacent battery slices 11', the back side of one battery slice 11' is stacked on the front side of the adjacent battery slice 11', and the two are electrically connected by a conductive adhesive, and the reference Figure 3 All the cell slices 11' in the photovoltaic module form a plurality of cell strings connected in parallel, each cell string is provided with a plurality of cell slices 11' with a higher slotting rate and a plurality of cell slices 11' with a lower slotting rate, and the number of cell slices 11' with a higher slotting rate is less than or equal to the number of cell slices 11' with a lower slotting rate. Taking the photovoltaic cell 10 cut into four equal parts as an example to prepare the photovoltaic module, each column of the cell string includes a plurality of cell slices 11' that are overlapped and connected to each other, and among the four cell slices 11' obtained by cutting into four equal parts, the back surface slotting rates of the two cell slices 11' at the edge positions are significantly higher than the back surface slotting rates of the two cell slices 11' at the middle positions. At this time, in a single column of the cell string, the number of cell slices 11' with higher slotting rates is equal to the number of cell slices 11' with lower slotting rates. Of course, if the photovoltaic cell 10 is cut into five or six equal parts, the number of cell slices 11' at the edge will be less than the number of cell slices 11' at the middle position. At this time, the number of cell slices 11' with higher slotting rates in the entire column of the cell string will be less than the number of cell slices 11' with lower slotting rates.

[0042] The invention also discloses a method for manufacturing a photovoltaic module, which comprises: first preparing a photovoltaic cell sheet, and then using the photovoltaic cell sheet to manufacture a photovoltaic module.

[0043] The preparation of photovoltaic cells specifically includes:

[0044] Providing a silicon wafer;

[0045] Using a first laser to groove different areas on the back of a silicon wafer, so that the groove rate of the edge area of ​​the silicon wafer is greater than the groove rate of other areas, and using the silicon wafer to prepare a photovoltaic cell;

[0046] Using a second laser to carve a plurality of cutting grooves on the back of the photovoltaic cell sheet, the cutting grooves evenly divide the back of the photovoltaic cell sheet into a plurality of battery cells;

[0047] Applying force to the photovoltaic cell sheet so that each of the cell units is split along the cutting groove to form a plurality of independent cell slices;

[0048] The battery slices are connected to form battery strings in an edge-overlapping manner.

[0049] When the first laser is used for grooving, the grooving rates in different areas are changed by adjusting the laser patterns corresponding to different areas, and the laser grooving in different areas is performed simultaneously, that is, a plurality of areas with different grooving rates can be formed simultaneously through a single laser grooving process 12.

[0050] In summary, the present invention adjusts the slotting rate or windowing rate in different areas on the back of the photovoltaic cell 10 to change the Voc value of the cell slice 11' after cutting and splitting, thereby making the Voc values ​​of each cell slice 11' close or consistent, which is conducive to improving the yield rate of EL detection and is less likely to cause the problem of brightness due to excessively high Voc values. This has positive significance for shingled photovoltaic modules, as each cell slice 11' can maintain a similar Voc value, making the overall performance of the photovoltaic module more outstanding.

[0051] The above is only the best embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the field can make many possible changes and modifications to the technical solution of the present invention by using the method disclosed above without departing from the scope of the technical solution of the present invention, which all fall within the scope of protection of the claims.

Claims

1. A photovoltaic cell sheet, having a front side and a back side, wherein the back side is provided with a plurality of elongated battery cells of equal size and arranged in sequence, each battery cell is formed with a slot, and the slots are arranged in parallel, characterized in that: The slotting rate of the first and last two battery cells located at the edge of the photovoltaic cell sheet is greater than the slotting rate of other battery cells, and the ratio of the slotting rate of the first and last two battery cells located at the edge of the photovoltaic cell sheet to the slotting rate of other battery cells is greater than 1 and less than or equal to 1.

5.

2. The photovoltaic cell according to claim 1, characterized in that: The slotting rates of the first and last two battery cells are 3.2-3.5%.

3. The photovoltaic cell according to claim 1, characterized in that: The grooving rate of the entire back side of the photovoltaic cell sheet is 1-70%.

4. The photovoltaic cell according to any one of claims 1 to 3, characterized in that: The battery unit is in the shape of an elongated rectangle, the length of its long side is N times the length of its short side, and N is an integer not less than 3.

5. The photovoltaic cell according to claim 4, characterized in that: The slot is in the shape of an elongated strip, and its extending direction is perpendicular to the long side of the battery unit.

6. The photovoltaic cell according to claim 5, characterized in that: The width of the grooves is 10-200 micrometers, and the spacing between two adjacent rows of grooves is 0.1-3 millimeters.

7. The photovoltaic cell according to claim 6, characterized in that: Each slot in each row of slots is not arranged one by one in alignment with each slot in an adjacent row, but is staggered in a direction perpendicular to the length of the slots and partially overlaps.

8. The photovoltaic cell according to claim 7, characterized in that: Cutting grooves are formed between the battery cells.

9. A photovoltaic module, comprising a plurality of cell slices, wherein the cell slices are connected by overlapping edges, characterized in that: The cell slices are obtained by cutting the cell units of the photovoltaic cell sheet according to any one of claims 1 to 8, and the back surface groove rate of a part of the cell slices in the photovoltaic module is greater than the back surface groove rate of the remaining cell slices.

10. A method for preparing a photovoltaic cell, characterized in that: include: Providing a silicon wafer; Using a first laser to groove different areas on the back of a silicon wafer, so that the groove rate of the edge area of ​​the silicon wafer is greater than the groove rate of other areas, and using the silicon wafer to prepare a photovoltaic cell; The ratio of the slotting rate of the first and last two battery cells located at the edge of the photovoltaic cell sheet to the slotting rate of other battery cells is greater than 1 and less than or equal to 1.

5.

11. The method for preparing a photovoltaic cell according to claim 10, characterized in that: The grooves in different areas on the back side of the silicon wafer are formed simultaneously.

12. The method for preparing a photovoltaic cell according to claim 11, characterized in that: The silicon wafer edge region is formed at two opposite edges of the silicon wafer and extends along the edges of the silicon wafer, and the width of the edge region does not exceed one third of the side length of the silicon wafer.

13. A method for preparing a photovoltaic module, characterized in that: include: Providing a silicon wafer; Using a first laser to groove different areas on the back of a silicon wafer, so that the groove rate of the edge area of ​​the silicon wafer is greater than the groove rate of other areas, and using the silicon wafer to prepare a photovoltaic cell; The ratio of the slotting rate of the first and last two battery cells located at the edge of the photovoltaic cell sheet to the slotting rate of other battery cells is greater than 1 and less than or equal to 1.5; Using a second laser to carve a plurality of cutting grooves on the back of the photovoltaic cell sheet, the cutting grooves evenly divide the back of the photovoltaic cell sheet into a plurality of battery cells; Applying force to the photovoltaic cell sheet so that each of the cell units is split along the cutting groove to form a plurality of independent cell slices; The cell slices are connected into cell strings.

14. The method for preparing a photovoltaic module according to claim 13, characterized in that: Connecting the battery slices into a battery string specifically includes: Applying conductive glue to the edge of each battery slice; Overlap the edges of the battery slices to form a battery string.

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