Solar cell with ramp or step fine grid side edge morphology

Abstract

This invention discloses a solar cell with a sloped or stepped grid side morphology, belonging to the field of solar cells. It includes a solar cell and a grid uniformly arranged on the back of the solar cell. The back of the solar cell includes alternating laser and non-laser regions arranged along the direction of the grid. The grid is attached to the non-laser region. The boundary between the laser and non-laser regions has a sloped structure, a stepped structure, or a combination of sloped and stepped structures. This invention, by etching the boundary between the laser and non-laser regions into a sloped structure, a stepped structure, or a combination of sloped and stepped structures, makes it easier to deposit a passivation film on the side of the solar cell in subsequent processes, improving the overall passivation effect of the solar cell.

Description

Technical Field

[0001] This utility model relates to the field of solar cells, and more specifically, to a solar cell with a sloped or stepped grid side morphology. Background Technology

[0002] Tunneling oxide passivated contact (TOPCon) solar cell technology, as a novel solar cell technology, has attracted much attention in the photovoltaic field. TOPCon cells achieve excellent surface passivation and selective carrier collection by constructing a passivation structure on the back of the silicon wafer consisting of an ultrathin layer of silicon oxide and a layer of heavily doped polycrystalline silicon, significantly improving cell performance. However, current TOPCon solar cell technology still faces many challenges. From the perspective of cell performance, how to further reduce the surface recombination rate and improve the passivation effect remains an urgent problem to be solved. In practical applications, the efficiency loss of solar cells mainly stems from optical and electrical losses. A portion of the electrical loss comes from the recombination loss of electrons and holes, and the core efficiency improvement method for TOPCon cells is to reduce recombination losses through passivation contact technology. Currently, the passivation contact structure of TOPCon mainly reduces recombination losses through three methods: depositing a SiO2 thin film to achieve the tunneling effect, depositing a doped polycrystalline silicon layer to achieve the field passivation effect, and providing good electron conductivity. However, there is still room for improvement. Furthermore, regarding conversion efficiency, although TOPCon cells have achieved some breakthroughs, there is still significant potential for improvement compared to the theoretical limit. For TOPCon cells using the PECVD technology route, it is also necessary to effectively suppress the easily ruptured polycrystalline silicon film and reduce parasitic absorption in the material to further improve photoelectric conversion efficiency.

[0003] Currently, to improve the parasitic absorption problem of poly on the back side of TOPCon solar cells, a conventional approach is to use laser etching combined with alkaline etching to remove the poly in the non-grid area. While this approach can solve the parasitic absorption problem on the back side, the micro-morphology during the etching process cannot be precisely controlled, resulting in steeper etching edges. Because these steep edges cannot be deposited with passivation films in subsequent processes, the passivation effect is severely affected, leading to lower cell conversion efficiency. Therefore, how to make it easier to deposit passivation films on the edges of solar cells has become an urgent problem to be solved. Utility Model Content

[0004] To address the issue of steep grid sides in solar cells making it difficult to deposit passivation films in subsequent processes, this application provides a solar cell with a sloped or stepped grid side morphology, the technical solution of which is as follows:

[0005] A solar cell with a sloped or stepped grid side profile includes a cell and a grid uniformly arranged on the back side of the cell. The back side of the cell includes laser regions and non-laser regions arranged alternately along the direction of the grid. The grid is attached to the non-laser regions. The edge at the junction of the laser region and the non-laser region has a sloped structure, a stepped structure, or a combination of sloped and stepped structures.

[0006] Preferably, the vertical height of the ramp structure, the stepped structure, or the combination of ramp and stepped structures is 100~180nm.

[0007] Preferably, the slope of the ramp structure is 90~170°.

[0008] Preferably, the laser spot in the laser region includes a central region and an edge region, and the energy density of the central region is 300~500µJ / cm². 2 The energy density of the edge region of the light spot is 3-25% lower than that of the center region of the light spot.

[0009] Preferably, the shape of the laser spot is one of a rectangle, a rounded / arc-shaped rectangle, or an ellipse.

[0010] Preferably, the laser spot is rectangular in shape, with a length of 100~800μm and a width of 30~600μm.

[0011] Preferably, the area of ​​the edge region of the laser spot accounts for 1 to 30% of the area of ​​the laser spot.

[0012] Preferably, the laser has a wavelength of 532nm, a power of 60~250W, a frequency of 100~800KHz, and a laser scanning speed of 10~100m / s.

[0013] The fabrication method of the solar cell with the above-mentioned sloped or stepped grid side morphology includes the following steps:

[0014] Step 1: Set laser parameters: The energy density in the central region of the laser spot is 300~500µJ / cm². 2 The energy density of the edge region of the light spot is 3-25% lower than that of the center region of the light spot;

[0015] Step 2: Patterning with laser: The back of the solar cell is patterned along the direction of the electrode grid using a laser spot, forming alternating laser and non-laser areas along the direction of the grid.

[0016] Step 3: Alkaline etching is performed on the solar cell to make the edge of the junction between the laser area and the non-laser area of ​​the solar cell a sloping structure, a stepped structure, or a combination of sloping and stepped structures.

[0017] Preferably, the alkaline etching in step three specifically involves using an alkaline solution of NaOH or KOH with a volume concentration of 1-5% to etch the battery cell for 50-500 seconds.

[0018] Preferably, before step one, the following steps are also included: the battery cell is sequentially subjected to cleaning and texturing, front-side boron diffusion, and etching alkaline polishing treatment.

[0019] Preferably, after step three, the following steps are also included: acid washing of the battery cell, deposition of a front aluminum oxide layer, a front silicon nitride layer and a back silicon nitride layer, screen printing and sintering.

[0020] The beneficial effects of adopting the technical solution of this utility model are as follows:

[0021] This invention etches the edge of the boundary between the laser area and the non-laser area into a sloped structure, a stepped structure, or a combination of sloped and stepped structures, making it easier to deposit a passivation film on the side of the cell in subsequent processes and improving the overall passivation effect of the cell. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of the laser area and the non-laser area on the back of the solar cell;

[0024] Figure 2 This is a schematic diagram of the sloping structure at the boundary between the laser zone and the non-laser zone.

[0025] Figure 3 This is a schematic diagram of the stepped structure at the boundary between the laser zone and the non-laser zone.

[0026] Figure 4 This is a schematic diagram of the planar structure of the laser spot;

[0027] Figure 5 This is a schematic diagram of the sloping structure at the edge of the battery cell in Example 1;

[0028] Figure 6 This is a schematic diagram of the stepped structure at the edge of the battery cell in Example 3.

[0029] Among them: 1. Solar cell; 2. Fine grid; 3. Laser area; 4. Non-laser area; 10. Laser spot; 11. Center area of ​​spot; 12. Edge area of ​​spot. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions in the embodiments of this utility model will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of them. Therefore, the detailed description of the embodiments of this utility model provided below is not intended to limit the scope of the claimed utility model, but merely to represent selected embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0031] This embodiment adjusts the energy distribution of the laser spot, setting it so that the energy density is high at the center and low at the edges. This reduces the energy applied to the sides of the laser-treated area of ​​the solar cell. Combined with subsequent wet etching, this results in a sloping, stepped, or combined sloping and stepped structure on the sides of the laser-treated area. This makes it easier to deposit passivation films on the sides of the laser-treated area in subsequent processes, improving the overall passivation effect of the solar cell. The specific implementation is as follows:

[0032] A solar cell with a sloped or stepped grid side morphology includes a cell 1 and a grid 2 uniformly arranged on the back of the cell 1. The back of the cell 1 includes a laser region 3 and a non-laser region 4 alternately arranged along the direction of the grid 2. The grid 2 is attached to the non-laser region 4. The edge at the junction of the laser region 3 and the non-laser region 4 is a sloped structure, a stepped structure, or a combination of sloped and stepped structures.

[0033] In a preferred embodiment, the vertical height of the ramp structure, the stepped structure, or the combination of ramp and stepped structures is 100~180nm.

[0034] In a preferred embodiment, the slope of the ramp structure is 90~170°.

[0035] In a preferred embodiment, the laser spot 10 of the laser region 3 includes a central region 11 and an edge region 12, wherein the energy density of the central region 11 is 300~500µJ / cm². 2 The energy density of the edge region 12 of the light spot is 3-25% lower than that of the center region 11 of the light spot.

[0036] In a preferred embodiment, the laser spot 10 is shaped as a rectangle, a rounded / arc-cornered rectangle, or an ellipse.

[0037] In a preferred embodiment, the laser spot 10 is rectangular in shape, with a length of 100~800μm and a width of 30~600μm.

[0038] In a preferred embodiment, the area of ​​the edge region 12 of the laser spot accounts for 1 to 30% of the area of ​​the laser spot 10.

[0039] In a preferred embodiment, the laser has a wavelength of 532nm, a power of 60~250W, a frequency of 100~800KHz, and a laser scanning speed of 10~100m / s.

[0040] The fabrication method of the solar cell with the above-mentioned sloped or stepped grid side morphology includes the following steps:

[0041] Step 1, set the laser parameters: the energy density in the central region 11 of the laser spot is 300~500µJ / cm. 2 The energy density of the edge region 12 of the light spot is 3-25% lower than that of the center region 11 of the light spot;

[0042] Step 2, use laser for patterning: use laser spot 10 to pattern the back of the battery cell 1 along the direction of the electrode grid 2, forming laser area 3 and non-laser area 4 arranged alternately along the direction of the grid 2;

[0043] Step 3: Alkaline etching is performed on the battery cell 1 so that the edge at the junction of the laser region 3 and the non-laser region 4 is a sloped structure, a stepped structure, or a combination of sloped and stepped structures.

[0044] In a preferred embodiment, the alkaline etching in step three specifically involves using an alkaline solution of NaOH or KOH with a volume concentration of 1-5% to etch the battery cell for 150-500 seconds.

[0045] As a preferred embodiment, the following steps are included before step one: the battery cell 1 is sequentially cleaned and texturized, subjected to front boron diffusion, and etched alkaline polishing.

[0046] As a preferred embodiment, after step three, the following steps are also included: acid washing of the battery cell 1, deposition of a front aluminum oxide layer, a front silicon nitride layer and a back silicon nitride layer, screen printing and sintering.

[0047] The following is a further review of the beneficial effects of a solar cell with a sloped or stepped grid side morphology provided by this utility model through several examples.

[0048] Example 1:

[0049] This embodiment 1 provides a solar cell with a sloped side profile. The edge at the boundary between the laser region and the non-laser region of the cell has a sloped structure with a slope of 131.71° and a vertical height of 100 nm. Figure 3 As shown. Its preparation method includes the following steps:

[0050] Step 1: Set the laser parameters: The laser spot shape is rectangular, with a length of 100 μm and a width of 30 μm. The energy density at the center of the laser spot is 300 µJ / cm². 2 The energy density at the edge of the light spot is 3% lower than that at the center of the light spot, and the area at the edge of the light spot accounts for 2% of the total area of ​​the light spot.

[0051] Step 2: Patterning with laser: The back of the solar cell is patterned along the direction of the electrode grid using a laser spot, forming alternating laser and non-laser areas along the direction of the grid.

[0052] Step 3: Alkali etching is performed on the solar cells sequentially. Specifically, the solar cells are etched with a 1% NaOH solution for 50 seconds to form a sloping structure at the boundary between the laser area and the non-laser area of ​​the solar cells.

[0053] Example 2:

[0054] This embodiment 2 provides a solar cell with a stepped grid side morphology. The edge at the boundary between the laser region and the non-laser region of the cell has a sloping structure with a slope of 90° and a vertical height of 120 nm. Its fabrication method includes the following steps:

[0055] Step 1: Set the laser parameters: The laser spot shape is rectangular, with a length of 200 μm and a width of 100 μm. The energy density at the center of the laser spot is 350 µJ / cm². 2 The energy density at the edge of the light spot is 8% lower than that at the center of the light spot, and the area at the edge of the light spot accounts for 5% of the total area of ​​the light spot.

[0056] Step 2: Patterning with laser: The back of the solar cell is patterned along the direction of the electrode grid using a laser spot, forming alternating laser and non-laser areas along the direction of the grid.

[0057] Step 3: Alkali etching is performed on the solar cells sequentially. Specifically, the solar cells are etched with a 2% NaOH solution for 100 seconds to form a sloping structure at the boundary between the laser area and the non-laser area of ​​the solar cells.

[0058] Example 3:

[0059] This embodiment 3 provides a solar cell with a stepped grid side morphology. The boundary between the laser region and the non-laser region of the cell has a stepped structure, and the vertical height of the stepped structure is 139 nm. Its fabrication method includes the following steps:

[0060] Step 1: Set the laser parameters: the laser spot shape is rectangular, with a length of 300 μm and a width of 200 μm, and the energy density at the center of the spot is 400 µJ / cm². 2 The energy density at the edge of the light spot is 10% lower than that at the center of the light spot, and the area at the edge of the light spot accounts for 10% of the total area of ​​the light spot.

[0061] Step 2: Patterning with laser: The back of the solar cell is patterned along the direction of the electrode grid using a laser spot, forming alternating laser and non-laser areas along the direction of the grid.

[0062] Step 3: Alkali etching is performed on the solar cells sequentially. Specifically, the solar cells are etched with a 3% NaOH solution for 100 seconds to form a stepped structure at the boundary between the laser area and the non-laser area of ​​the solar cells.

[0063] Example 4:

[0064] This embodiment 4 provides a solar cell with a stepped grid side morphology. The boundary between the laser region and the non-laser region of the cell has a stepped structure, and the vertical height of the stepped structure is 150 nm. Its fabrication method includes the following steps:

[0065] Step 1: Set the laser parameters: The laser spot shape is rectangular, with a length of 400 μm and a width of 300 μm. The energy density at the center of the laser spot is 450 µJ / cm². 2 The energy density at the edge of the light spot is 15% lower than that at the center of the light spot, and the area at the edge of the light spot accounts for 20% of the total area of ​​the light spot.

[0066] Step 2: Patterning with laser: The back of the solar cell is patterned along the direction of the electrode grid using a laser spot, forming alternating laser and non-laser areas along the direction of the grid.

[0067] Step 3: Alkali etching is performed on the solar cells sequentially. Specifically, the solar cells are etched with NaOH solution with a volume concentration of 4% for 200 seconds to form a stepped structure at the edge of the boundary between the laser area and the non-laser area of ​​the solar cells.

[0068] Example 5:

[0069] This embodiment 5 provides a solar cell with a sloped side profile. The boundary between the laser region and the non-laser region of the cell has a sloped structure with a gradient of 150° and a vertical height of 170 nm. Its fabrication method includes the following steps:

[0070] Step 1: Set the laser parameters: The laser spot shape is rectangular, with a length of 600 μm and a width of 500 μm. The energy density at the center of the laser spot is 500 µJ / cm². 2 The energy density at the edge of the light spot is 20% lower than that at the center of the light spot, and the area at the edge of the light spot accounts for 25% of the total area of ​​the light spot.

[0071] Step 2: Patterning with laser: The back of the solar cell is patterned along the direction of the electrode grid using a laser spot, forming alternating laser and non-laser areas along the direction of the grid.

[0072] Step 3: Alkali etching is performed on the solar cells sequentially. Specifically, the solar cells are etched with a 5% NaOH solution for 300 seconds to form a sloping structure at the boundary between the laser area and the non-laser area of ​​the solar cells.

[0073] Example 6:

[0074] This embodiment 6 provides a solar cell with a stepped grid side morphology. The boundary between the laser region and the non-laser region of the cell has a combination of sloping and stepped structures at the edge, with a vertical height of 180 nm. Its fabrication method includes the following steps:

[0075] Step 1: Set the laser parameters: The laser spot shape is rectangular, with a length of 800 μm and a width of 600 μm. The energy density at the center of the laser spot is 500 µJ / cm². 2 The energy density at the edge of the light spot is 25% lower than that at the center of the light spot, and the area at the edge of the light spot accounts for 30% of the total area of ​​the light spot.

[0076] Step 2: Patterning with laser: The back of the solar cell is patterned along the direction of the electrode grid using a laser spot, forming alternating laser and non-laser areas along the direction of the grid.

[0077] Step 3: Alkali etching is performed on the solar cells sequentially. Specifically, the solar cells are etched with a 5% NaOH solution for 500 seconds to form a combination of sloping and stepped structures at the boundary between the laser area and the non-laser area of ​​the solar cells.

[0078] Comparative Example 1:

[0079] Comparative Example 1 provides a solar cell, the preparation method of which includes the following steps:

[0080] Step 1: Set the laser parameters: the laser spot shape is rectangular, with a length of 300 μm and a width of 200 μm, and the energy density of the laser spot is 400 µJ / cm². 2 ;

[0081] Step 2, patterning using laser: pattern the back of the solar cell along the direction of the electrode grid using a laser spot;

[0082] Step 3: The battery cells are sequentially etched with alkaline solution, specifically by etching the battery cells with a 3% (by volume) NaOH solution for 100 seconds to obtain the battery cells.

[0083] Comparative Example 2:

[0084] Comparative Example 2 provides a solar cell whose fabrication method includes the following steps:

[0085] Step 1: Set the laser parameters: the laser spot shape is rectangular, with a length of 400 μm and a width of 300 μm, and the energy density of the laser spot is 450 µJ / cm². 2 ;

[0086] Step 2, patterning using laser: pattern the back of the solar cell along the direction of the electrode grid using a laser spot;

[0087] Step 3: The battery cells are sequentially etched with alkaline solution, specifically by etching the battery cells with a 4% NaOH solution for 200 seconds to obtain the battery cells.

[0088] The performance of the solar cells obtained in the above embodiments and comparative examples is tested below, and the results are as follows:

[0089] Table 1. Electrical performance test results of the solar cells prepared in the examples and comparative examples.

[0090] Group Eta Uoc Isc FF Rs Rsh IRev2 Example 1 26.22 736.80 15.90 85.47 0.9 6364 0.02 Example 2 26.32 737.25 15.93 85.59 0.9 6702 0.02 Example 3 26.44 737.48 15.97 85.73 0.9 6576 0.02 Example 4 26.34 738.09 15.89 85.73 0.9 6757 0.02 Example 5 26.28 737.09 15.90 85.61 0.9 6464 0.02 Example 6 26.21 736.10 15.90 85.52 0.9 6150 0.02 Comparative Example 1 26.15 734.57 15.90 85.48 0.9 6272 0.03 Comparative Example 2 26.20 736.20 15.91 85.43 1.0 6286 0.02

[0091] Examples 1-6 show that the boundary between the laser and non-laser areas on the side of the fine grid of the solar cell in this application has a sloping structure, a stepped structure, or a combination of sloping and stepped structures. Comparative Examples 1-2 show that the side of the fine grid of the solar cell obtained by conventional laser process combined with subsequent etching process has a steep edge. As shown in Table 1, the photoelectric conversion efficiency of the solar cells in Examples 1-6 of this application is better than that of Comparative Examples 1-2.

[0092] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A solar cell with ramp or step fine grid side edge profile, comprising a cell piece (1) and fine grids (2) uniformly arranged on the back of the cell piece (1), characterized in that, The back of the battery cell (1) includes laser regions (3) and non-laser regions (4) arranged alternately along the direction of the fine grid (2). The fine grid (2) is attached to the non-laser region (4). The edge at the junction of the laser region (3) and the non-laser region (4) is a ramp structure, a step structure, or a combination of ramp and step structure.

2. The solar cell according to claim 1, characterized in that, The vertical height of the ramp structure, the stepped structure, or the combination of ramp and stepped structures is 100~180nm.

3. The solar cell according to claim 1, characterized in that, The slope of the sloping structure is 90~170°.

4. The solar cell of claim 1, wherein The laser spot (10) of the laser region (3) includes a central area (11) and an edge area (12). The energy density of the central area (11) is 300~500µJ / cm2, and the energy density of the edge area (12) is 3~25% lower than that of the central area (11).

5. The solar cell according to claim 4, characterized in that, The shape of the laser spot (10) is one of rectangle, rounded / arc rectangle or ellipse.

6. The solar cell of claim 4, wherein, The laser spot (10) is rectangular in shape, with a length of 100~800μm and a width of 30~600μm.

7. The solar cell of claim 4, wherein, The area of ​​the edge region (12) of the laser spot accounts for 1 to 30% of the area of ​​the laser spot (10).

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