Solar cell

Abstract

The back surface of the solar cell is provided with metal grid lines located in a grid line area and alignment marks located in a non-grid line area. The solar cell further comprises a patterned passivation contact structure, the passivation contact structure only comprises a first area located in the grid line area and a second area located at the position where the alignment marks are formed, the metal grid lines are located in the first area, and the alignment marks are located in the second area. According to the utility model, the alignment mark is arranged on the second area of the non-grid line area, so that the contrast around the alignment mark can be increased, the point grabbing precision is improved, and good grid line alignment can be realized.

Description

Technical Field

[0001] The utility model relates to the photovoltaic field, in particular to a solar cell with high back light utilization rate and high metal grid line alignment accuracy. Background Art

[0002] TOPCon (Tunnel Oxide Passivated Contact) solar cells are a new type of photovoltaic cells. Their market share has increased rapidly in recent years and they have gradually developed into the mainstream technology of solar cells.

[0003] The back of the silicon substrate of the TOPCon battery is provided with a thin tunneling oxide layer and a doped polysilicon layer, which together form a passivation contact structure, forming a field passivation effect, increasing the probability of electron tunneling, reducing contact resistance, and increasing the open circuit voltage and short circuit current of the battery, thereby improving the battery conversion efficiency.

[0004] The inventors have found that the parasitic absorption of light by the doped polysilicon layer will reduce the utilization rate of light and affect the conversion efficiency of the battery; in the related technology, removing the doped polysilicon layer in the non-gate line area can improve the efficiency to a certain extent, but it poses a challenge to the alignment of the metal gate line and the remaining passivation contact structure.

[0005] In view of this, it is necessary to provide an improved solar cell to solve the above technical problems. Utility Model Content

[0006] In order to solve one of the technical problems existing in the related art, the utility model provides a solar cell to improve the contrast between the alignment mark and the surrounding area, thereby improving the printing accuracy of the metal grid line.

[0007] In order to achieve one of the above-mentioned purposes of the utility model, the utility model adopts the following technical solutions:

[0008] A solar cell has a metal grid line located in a grid line area and an alignment mark located in a non-grid line area on its back; the solar cell also includes a patterned passivation contact structure, the passivation contact structure only includes a first area located in the grid line area and a second area located at a position where the alignment mark is formed, the metal grid line is located in the first area, and the alignment mark is located in the second area.

[0009] Furthermore, the second area is spaced apart from the first area.

[0010] Furthermore, the second region is located between two adjacent first regions, and the second region is connected to the adjacent first region on at least one side.

[0011] Further, the distance from the edge of the alignment mark to the edge of the second region is not less than 200 μm, and / or the distance from the edge of the alignment mark to the edge of the second region is not more than 350 μm.

[0012] Furthermore, the size of the alignment mark is not less than 300 μm and is smaller than the distance between two adjacent metal gate lines.

[0013] Furthermore, the alignment mark is a patterned groove mark, and the groove depths at different positions of the groove mark are consistent, or the groove depth at the edge of the groove mark is greater than the groove depth in the inner area;

[0014] Alternatively, the alignment mark is a patterned printed mark.

[0015] Furthermore, the alignment mark is in the shape of a cross, a polygon, an ellipse or a circle.

[0016] Furthermore, the reflectivity of the second region is different from that of other regions of the non-gate line region, and the reflectivity of the second region is different from that of the alignment mark.

[0017] Furthermore, the difference in reflectivity between the alignment mark and the second area is between 20% and 40%; or

[0018] The reflectivity of the area outside the second region in the non-gate line region is between the reflectivity of the second region and the reflectivity of the alignment mark.

[0019] Furthermore, the back side of the solar cell also has a back side passivation layer located on the back side of the passivation contact structure; the front side of the solar cell has an emitter, a front side passivation layer and a front side electrode.

[0020] The beneficial effects of the utility model are as follows: the utility model sets the alignment mark on the second area of ​​the non-grid line area, which can increase the contrast around the alignment mark, improve the grasping point accuracy, and achieve good grid line alignment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the back side of a solar cell in one embodiment of the utility model;

[0022] Figure 2 for Figure 1 The local schematic diagram of the A in the middle;

[0023] Figure 3 is a partial schematic diagram of point A in another embodiment;

[0024] Figure 4 is a partial schematic diagram of point A in another embodiment;

[0025] Figure 5It is a local schematic diagram of point A in the related technology.

[0026] Among them, 100 is a solar cell, 1 is a passivation contact structure, 11 is a first region, 12 is a second region, and 2 is an alignment mark. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below in conjunction with the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional changes made by a person skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0028] In the various drawings of the present invention, for the convenience of illustration, some dimensions of structures or parts are exaggerated relative to other structures or parts, and therefore, are only used to illustrate the basic structure of the subject matter of the present invention.

[0029] The inventors further discovered that the doped polysilicon layer on the back of the TOPCon cell is opened to remove the doped polysilicon layer in the non-gate line area to avoid its parasitic absorption of light; only the tunneling oxide layer and the doped polysilicon layer in the gate line area are retained to isolate the direct contact between the metal gate line and the silicon substrate and reduce metal recombination; this can improve the efficiency of the cell. However, the width of the passivation contact structure 1 retained after opening the film is narrow. If the deposited metal gate line is to be well aligned with the passivation contact structure 1, in addition to the camera accuracy of the screen printing machine itself and the contrast of different light sources, the design of the alignment mark 2 (mark point) also plays a crucial role.

[0030] Based on this, the utility model optimizes the structure of the back of the TOPCon battery. Figures 1 to 4 As shown, a solar cell 100 of a preferred embodiment of the utility model is provided with a patterned passivation contact structure 1, a metal grid line located in the grid line area (not shown), and an alignment mark 2 located in the non-grid line area on the back side. When the metal grid line is formed, the alignment mark 2 plays a positioning role.

[0031] In the present invention, the patterned passivation contact structure 1 only includes a first region 11 located in the gate line region and a second region 12 located at a position where the alignment mark 2 is formed. The metal gate line is located on the first region 11, and the alignment mark 2 is located on the second region 12. This structural design can improve the recognition of the alignment mark 2 while removing the doped polysilicon in the non-gate line region on the back side, thereby ensuring that the metal gate line and the passivation contact structure 1 are well aligned.

[0032] It should be noted that the first region 11 can be consistent with the metal gate line but not completely consistent. Based on the metal gate line formation process, the gate line area and the first region 11 are slightly wider than the width of the metal gate line to prevent the metal gate line from directly contacting the silicon substrate when it is deflected due to process errors.

[0033] The second area 12 is located in the non-gate line area, but is not completely consistent with the alignment mark 2, but is slightly larger than the alignment mark 2. The alignment mark 2 is formed on the second area 12, and the alignment mark 2 forms a clear contrast with other positions of the second area 12, which can improve the recognition of the alignment mark 2 and further improve the forming accuracy of the metal gate line.

[0034] In a preferred embodiment, Figure 2 As shown, the second area 12 is spaced apart from the first area 11 to ensure a certain distance between the alignment mark 2 and the metal grid line; damage to the grid line area is avoided when the alignment mark 2 is formed by grooving, and the secondary grid paste (burn-through type) is avoided from spreading to the alignment mark 2 to affect the passivation performance of the battery cell.

[0035] In another preferred embodiment, Figure 3 and Figure 4 As shown, the second region 12 is located between two adjacent first regions 11, and the second region 12 is connected to at least one adjacent first region 11. Specifically, a plurality of metal grid lines / second regions 12 are arranged in parallel, the second region 12 is located between two adjacent first regions 11 in the arrangement direction of the metal grid lines, and the second region 12 can be connected to the first regions 11 on one side or both sides thereof into one piece.

[0036] Please refer to Figure 2 As shown, when the second area 12 is spaced apart from the first area 11, only the second area 12 is used as a quasi-area for forming the alignment mark 2. Figure 3 As shown, when the second region 12 is connected to the first region 11 adjacent to one side thereof only, the first region 11 and the second region 12 connected to the second region 12 can be used together as a quasi-region for forming the alignment mark 2, that is, part of the first region 11 is also used as a part of the quasi-region; therefore, under the premise that the required quasi-region area is certain, the area of ​​the second region 12 located in the non-gate line area can be reduced, more doped polysilicon layers can be removed, and the parasitic absorption of light can be reduced; or it is equivalent to expanding the area of ​​the quasi-region, which can increase the size of the alignment mark 2 and improve its recognition.

[0037] Please refer to Figure 4As shown, when the second area 12 is connected to the first area 11 adjacent to both sides, it is equivalent to expanding the area of ​​the quasi-area, so the alignment mark 2 can be maximized between two adjacent gate lines, and the recognition degree of the large-area alignment mark 2 is significantly higher than that of the small-area alignment recognition.

[0038] It should be noted that the enlargement of the quasi-region area only improves the recognition between the alignment mark and the surrounding area, and the alignment mark 2 is still located on the second region 12 to avoid damage to the gate line region.

[0039] Preferably, the distance between the edge of the alignment mark 2 and the edge of the second region 12 is not less than 200 μm, so that a second region 12 with a larger area is provided around the alignment mark 2 to ensure an obvious contrast effect; and / or, the distance between the edge of the alignment mark 2 and the edge of the second region 12 is not greater than 350 μm. On the basis of being able to identify the alignment mark 2, the area of ​​the second region 12 is minimized as much as possible, that is, the area of ​​the retained doped polysilicon layer is reduced, thereby reducing its parasitic absorption of light and improving light utilization.

[0040] The alignment mark 2 is located between two adjacent metal grid lines, and the size of the alignment mark 2 is not less than 300 μm, and is smaller than the distance between the two metal grid lines, ensuring that the alignment mark 2 is spaced apart from the metal grid lines, thereby avoiding damage to the grid line area when the grooves are formed to form the alignment mark 2, and also avoiding the secondary grid slurry (burn-through type) from spreading to the alignment mark 2 to affect the passivation performance of the battery cell.

[0041] In the present invention, the alignment mark 2 is in the shape of a cross, a polygon, an ellipse or a circle.

[0042] The alignment mark 2 is a groove mark formed in the second area 12, and various groove methods in the related art can be used, such as laser groove, etching groove, mechanical groove, etc. Taking laser groove as an example, the groove depth can be controlled by controlling laser parameters, scanning times, etc.

[0043] In a preferred embodiment, the groove depths at different positions of the groove mark are consistent, the process parameters are consistent, and the control is simple. In other preferred embodiments, the groove depth at the edge of the groove mark is greater than the groove depth in the inner area, forming a stronger visual contrast with the surrounding second area 12, thereby improving the recognition of the edge of the alignment mark 2.

[0044] The solar cell 100 of the present invention can be formed by referring to but not limited to the following process.

[0045] A tunneling oxide layer and a doped polysilicon layer are formed on the back of the silicon substrate to form a passivation contact structure 1 on the entire surface; a laser groove is made at the non-gate line area corresponding to the mask on the back of the passivation contact structure 1, and the mask corresponding to the second area 12 in the gate line area and the non-gate line area is retained; a laser groove is made on the mask of the second area 12 to form a groove consistent with the pattern of the alignment mark 2; after wet etching, the doped polysilicon layer in the laser grooved area is etched away, while the doped polysilicon layer in the gate line area and the area outside the alignment mark 2 in the second area 12 is retained to form a patterned passivation contact structure 1, and the alignment mark 2 has a strong contrast with the surrounding second area 12, which can realize screen printing point grabbing. The above-mentioned mask can be an oxide layer naturally formed when forming the passivation contact structure or silicon oxide formed by additional deposition.

[0046] Please refer to Figure 5 In the related process of first laser grooving the entire non-metallic area and then laser-forming the alignment mark 2 in the local area, after wet etching, the contrast difference between the position of the alignment mark 2 and the surrounding area is not large. When screen printing, it is difficult to match the points and it is difficult to achieve mass production printing. In this utility model, please refer to Figure 2 to Figure 4 As shown, the second area 12 is retained when the non-metallic area is laser-opened. After wet etching, there is a strong contrast between the alignment mark 2 and the second area 12. With the cooperation of the white ring light source, the accuracy is controlled within ±10μm.

[0047] Alternatively, the patterned passivation contact structure 1 is directly formed on the back side of the silicon substrate with the aid of a mask, and then the alignment mark 2 is formed by laser grooving on the second area 12. The alignment mark 2 also has a strong contrast with the surrounding second area 12, and a screen printing point can be realized.

[0048] The alignment mark 2 may also be a patterned printed mark, which can also form a sharp contrast with the surrounding second area 12 .

[0049] Regardless of which of the above methods is used, the reflectivity of the second area 12 is different from that of other areas of the non-gridline area, and the reflectivity of the second area 12 is different from that of the alignment mark 2, forming three obviously different areas in one visual area, and the alignment mark 2 is very prominent.

[0050] Preferably, the difference in reflectivity between the alignment mark 2 and the second area 12 is 20% to 40%, which has high recognition and can reduce the resolution requirement of the camera.

[0051] Preferably, the reflectivity of the area outside the second region 12 in the non-gate line area is between the reflectivity of the second region 12 and the reflectivity of the alignment mark 2 , which can improve the resolution of the alignment mark 2 and the alignment rate between the gate line and the first region 11 .

[0052] In addition, the back of the solar cell 100 also has a back passivation layer located on the back of the passivation contact structure 1; the front of the solar cell 100 has an emitter, a front passivation layer and a front electrode. Other structures and their formation methods can adopt related technologies and will not be repeated here.

[0053] In summary, the present invention sets the alignment mark 2 on the second area 12 of the non-gridline area, which can increase the contrast around the alignment mark 2, improve the gripping accuracy, and achieve good gridline alignment with an accuracy within ±10μm.

[0054] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0055] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the utility model. They are not intended to limit the protection scope of the utility model. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. A solar cell, wherein the back side of the solar cell is provided with metal grid lines in the grid line area and alignment marks in the non-grid line area; characterized in that: The solar cell further includes a patterned passivation contact structure, which includes only a first region located in the gate line region and a second region located at a position where the alignment mark is formed, the metal gate line is located in the first region, and the alignment mark is located in the second region.

2. The solar cell according to claim 1, characterized in that: The second area is spaced apart from the first area.

3. The solar cell according to claim 1, characterized in that: The second region is located between two adjacent first regions, and the second region is connected to the adjacent first region on at least one side.

4. The solar cell according to any one of claims 1 to 3, characterized in that: The distance from the edge of the alignment mark to the edge of the second region is not less than 200 μm, and / or the distance from the edge of the alignment mark to the edge of the second region is not more than 350 μm.

5. The solar cell according to any one of claims 1 to 3, characterized in that: The size of the alignment mark is not less than 300 μm and is smaller than the distance between two adjacent metal grid lines.

6. The solar cell according to any one of claims 1 to 3, characterized in that: The alignment mark is a patterned groove mark, and the groove depths at different positions of the groove mark are consistent, or the groove depth at the edge of the groove mark is greater than the groove depth in the inner area; Alternatively, the alignment mark is a patterned printed mark.

7. The solar cell according to any one of claims 1 to 3, characterized in that: The alignment mark is in the shape of a cross, a polygon, an ellipse or a circle.

8. The solar cell according to any one of claims 1 to 3, characterized in that: The reflectivity of the second region is different from that of other regions of the non-gate line region, and the reflectivity of the second region is different from that of the alignment mark.

9. The solar cell according to claim 8, characterized in that: The difference in reflectivity between the alignment mark and the second area is between 20% and 40%; or The reflectivity of the area outside the second region in the non-gate line region is between the reflectivity of the second region and the reflectivity of the alignment mark.

10. The solar cell according to claim 1, characterized in that: The back side of the solar cell also has a back side passivation layer located on the back side of the passivation contact structure; the front side of the solar cell has an emitter, a front side passivation layer and a front side electrode.

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