Preparation method of thin grid side edge morphology of solar cell and solar cell

Abstract

The invention discloses a solar cell fine grid side edge morphology preparation method and a solar cell, and belongs to the field of solar cells. Laser parameters are set, the energy density of a light spot center is higher than the energy density of a light spot edge, a cell piece is subjected to graphical processing along a fine grid, alkali etching is carried out on the back face of the cell piece, and the thin grid side edge morphology of the cell piece is obtained. And the shape of the side edge of the thin grid of the battery piece is a slope type structure, a step type structure or a slope type and step type combined structure. According to the invention, the energy density of the center of the laser spot is high, and the energy density of the edge is low, so that the applied energy of the edges of the two sides of the laser area is less, and the fine grid side morphology of the cell is etched to form a slope type structure, a step type structure or a slope type and step type combined structure in cooperation with a subsequent wet etching process. A passivation film is easier to deposit on the side edge of the junction of the laser area and the non-laser area of the battery piece in the subsequent process, and the overall passivation effect of the battery piece is improved.

Description

Technical Field

[0001] The present invention relates to the field of solar cells, and in particular to a method for preparing a fine grid side profile of a solar cell and a solar cell. Background Art

[0002] Tunneling oxide passivated contact (TOPCon) solar cell technology, a novel solar cell technology, has attracted considerable attention in the photovoltaic field. TOPCon cells utilize a passivation structure composed of an ultrathin silicon oxide layer and a heavily doped polysilicon layer on the backside of the silicon wafer, achieving excellent surface passivation and selective carrier collection, significantly improving cell performance. However, current TOPCon solar cell technology still faces numerous challenges. From a cell performance perspective, further reducing the surface recombination rate and improving passivation effectiveness remain pressing challenges. In practical applications, cell efficiency loss primarily stems from optical and electrical losses, with a portion of electrical loss arising from electron-hole recombination losses. Reducing these recombination losses through passivated contact technology is a key efficiency improvement measure for TOPCon cells. Currently, TOPCon passivated contact structures primarily reduce recombination losses through the deposition of a SiO2 thin film to achieve the tunneling effect, the deposition of a doped polysilicon layer to achieve field passivation, and the provision of good electron conductivity. However, there is still room for improvement. Furthermore, while TOPCon cells have achieved some significant efficiency breakthroughs, there is still significant potential for improvement compared to the theoretical efficiency limit. PECVD-based TOPCon cells also require effective control of the explosive film of polysilicon and reduction of parasitic absorption in the material to further enhance photoelectric conversion efficiency.

[0003] Currently, to improve the parasitic absorption problem of the backside Poly layer of TOPCon solar cells, the conventional method is to use laser debonding combined with alkaline etching to remove the Poly layer in the non-gateline area. Although this method can solve the parasitic absorption problem of the backside Poly layer, the micromorphology cannot be precisely controlled during the etching process, resulting in steeper side etching. Since the steep side cannot be deposited with a passivation film in the subsequent process, the passivation effect of the side will be seriously affected, resulting in low conversion efficiency of the cell. In this case, how to improve the steep side of the solar cell and prevent the deposition of the passivation film in the subsequent process has become an urgent problem to be solved. Summary of the Invention

[0004] To improve the problem of solar cells using laser film opening combined with alkaline etching to eliminate backside poly parasitic absorption, resulting in steep sides of the solar cell fine grid and the inability to deposit a passivation film in subsequent processes, the present application provides a method for preparing the side morphology of the solar cell fine grid and a solar cell, the technical solution of which is as follows:

[0005] A method for preparing the side morphology of a solar cell fine grid comprises the following steps:

[0006] Step 1: Set the laser parameters: the energy density at the center of the spot is 300~500µJ / cm 2 , the energy density at the edge of the light spot is 3~25% lower than the energy density at the center of the light spot;

[0007] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0008] Step three: alkaline-etching the cell so that the edge of the junction between the laser area and the non-laser area of ​​the cell has a slope structure, a step structure, or a combination of a slope and a step structure.

[0009] Preferably, the shape of the light spot in step 1 is one of a rectangle, a rectangle with rounded / arc corners, or an ellipse.

[0010] Preferably, the light spot in step 1 is in a rectangular shape with a length of 100-800 μm and a width of 30-600 μm.

[0011] Preferably, in step 1, the area of ​​the edge of the light spot accounts for 1-30% of the area of ​​the light spot.

[0012] Preferably, in step 1, the wavelength of the laser is 532 nm, the power is 60-250 W, the frequency is 100-800 KHz, and the laser scanning speed is 10-100 m / s.

[0013] Preferably, the vertical height of the sloped structure, the stepped structure, or the combined sloped and stepped structure is 100-180 nm.

[0014] Preferably, the slope of the sloped structure is 90-170°.

[0015] Preferably, the alkaline etching in step three is specifically performed by using an alkaline solution of NaOH or KOH with a volume concentration of 1-5% to etch the cell for 50-500 seconds.

[0016] Preferably, the following steps are also included before step 1: sequentially cleaning and texturing the cell, diffusing boron on the front side, etching and alkali polishing, depositing SiO2 and a polysilicon layer on the back side, and diffusing phosphorus.

[0017] Preferably, after step three, the method further includes the following steps: sequentially pickling the cell, depositing a front aluminum oxide layer, a front silicon nitride layer and a back silicon nitride layer, screen printing and sintering.

[0018] The present invention also provides a solar cell, the side morphology of which is manufactured using the above-mentioned manufacturing method.

[0019] The beneficial effects produced by the technical solution of the present invention are as follows:

[0020] The present invention adjusts the energy distribution of the laser spot to have a high energy density at the center and a low energy density at the edge, thereby reducing the amount of energy acting on the edge of the laser area of ​​the cell. In conjunction with the subsequent etching process, the junction between the laser area and the non-laser area of ​​the cell is etched to form a sloped structure, a stepped structure, or a combination of a sloped and stepped structure, making it easier to deposit a passivation film on the side of the cell in the subsequent process, thereby improving the overall passivation effect of the cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 Schematic diagram of the sloped structure of the edge of the battery cell in Example 1;

[0023] Figure 2 Schematic diagram of the stepped structure of the edge of the battery cell in Example 3. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] This embodiment sets the laser parameters to make the energy density at the center of the spot higher than the energy density at the edge of the spot to pattern the cell, and then performs alkaline etching on the back of the cell to form a sloped structure, a stepped structure, or a combination of sloped and stepped structures on the left and right sides of the cell laser area. This makes it easier to deposit a passivation film on the sides of the cell in subsequent processes, thereby improving the overall passivation effect of the cell. Specific embodiments are as follows:

[0026] A method for preparing the side morphology of a solar cell fine grid comprises the following steps:

[0027] Step 1: Set the laser parameters: the energy density at the center of the spot is 300~500µJ / cm 2 , the energy density at the edge of the light spot is 3~25% lower than the energy density at the center of the light spot;

[0028] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0029] Step three: alkaline-etching the cell so that the edge of the junction between the laser area and the non-laser area of ​​the cell has a slope structure, a step structure, or a combination of a slope and a step structure.

[0030] As a preferred embodiment, the shape of the light spot in step 1 is a rectangle, a rectangle with rounded / arc corners, or an ellipse.

[0031] As a preferred embodiment, the light spot in step 1 is in a rectangular shape with a length of 100-800 μm and a width of 30-600 μm.

[0032] As a preferred implementation manner, the area of ​​the edge of the light spot in the step 1 accounts for 1-30% of the area of ​​the light spot.

[0033] As a preferred embodiment, in the step 1, the wavelength of the laser is 532 nm, the power is 60-250 W, the frequency is 100-800 KHz, and the laser scanning speed is 10-100 m / s.

[0034] As a preferred embodiment, the vertical height of the sloped structure, the stepped structure, or the sloped and stepped combined structure is 100-180 nm.

[0035] As a preferred embodiment, the slope of the sloped structure is 90-170°.

[0036] As a preferred embodiment, the alkaline etching in step three is specifically performed by using an alkaline solution of NaOH or KOH with a volume concentration of 1-5% to etch the cell for 50-500 seconds.

[0037] As a preferred embodiment, the following steps are also included before step one: cleaning and texturing the cell, diffusing boron on the front side, etching and alkali polishing, depositing SiO2 and a polysilicon layer on the back side and diffusing phosphorus.

[0038] As a preferred embodiment, after step three, the following steps are also included: acid-washing the cell in sequence, depositing a front aluminum oxide layer, a front silicon nitride layer and a back silicon nitride layer, screen printing and sintering.

[0039] The present invention also provides a solar cell, the side morphology of which is manufactured using the above-mentioned manufacturing method.

[0040] The following further reviews the method for preparing the side morphology of the fine grid of a solar cell and the beneficial effects of the solar cell provided by the present invention through several groups of embodiments.

[0041] Example 1:

[0042] This embodiment 1 provides a method for preparing the side morphology of a thin grid of a solar cell, comprising the following steps:

[0043] Step 1: Set the laser parameters: the spot shape is rectangular, the length is 100μm, the width is 30μm, and the energy density at the center of the spot is 300μJ / cm 2 , the energy density at the edge of the spot is 3% lower than that at the center of the spot, where the area of ​​the edge of the spot accounts for 2% of the spot area;

[0044] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0045] Step 3: Alkaline etching is performed on the cell. Specifically, the cell is etched with 1% volume concentration of NaOH for 50 seconds to form a slope structure at the junction of the laser area and the non-laser area of ​​the cell. The slope of the slope structure is 131.71° and the vertical height is 100nm. Figure 1 shown.

[0046] Example 2:

[0047] This embodiment 2 provides a method for preparing the side morphology of a thin grid of a solar cell, comprising the following steps:

[0048] Step 1: Set the laser parameters: the spot shape is rectangular, the length is 200μm, the width is 100μm, and the energy density at the center of the spot is 350μJ / cm 2 , the energy density at the edge of the spot is 8% lower than that at the center of the spot, where the area of ​​the edge of the spot accounts for 5% of the spot area;

[0049] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0050] Step three, alkaline etching is performed on the cell, specifically using alkaline solution NaOH with a volume concentration of 2% to etch the cell for 100s, forming a sloped structure at the edge of the junction between the laser area and the non-laser area of ​​the cell, with a slope of 90° and a vertical height of 120nm.

[0051] Example 3:

[0052] This embodiment 3 provides a method for preparing the side morphology of a solar cell fine grid, comprising the following steps:

[0053] Step 1: Set the laser parameters: the spot shape is rectangular, the length is 300μm, the width is 200μm, and the energy density at the center of the spot is 400µJ / cm 2 , the energy density at the edge of the spot is 10% lower than that at the center of the spot, where the area of ​​the edge of the spot accounts for 10% of the spot area;

[0054] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0055] Step 3: Alkaline etching is performed on the cell. Specifically, the cell is etched with 3% volume concentration of NaOH for 100s to form a step-like structure at the junction of the laser area and the non-laser area of ​​the cell. The vertical height of the step-like structure is 139nm. Figure 2 shown.

[0056] Example 4:

[0057] This embodiment 4 provides a method for preparing the side morphology of a thin grid of a solar cell, comprising the following steps:

[0058] Step 1: Set the laser parameters: the spot shape is rectangular, the length is 400μm, the width is 300μm, and the energy density at the center of the spot is 450µJ / cm 2 , the energy density at the edge of the spot is 15% lower than that at the center of the spot, where the area of ​​the edge of the spot accounts for 20% of the spot area;

[0059] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0060] Step three, alkaline etching is performed on the cell, specifically using alkaline solution NaOH with a volume concentration of 4% to etch the cell for 200s, forming a step-like structure at the edge of the junction between the laser area and the non-laser area of ​​the cell, and the vertical height of the step-like structure is 150nm.

[0061] Example 5:

[0062] This embodiment 5 provides a method for preparing the side morphology of a solar cell fine grid, comprising the following steps:

[0063] Step 1: Set the laser parameters: the spot shape is rectangular, the length is 600μm, the width is 500μm, and the energy density at the center of the spot is 500µJ / cm 2 , the energy density at the edge of the spot is 20% lower than that at the center of the spot, where the area of ​​the edge of the spot accounts for 25% of the spot area;

[0064] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0065] Step three, alkaline etching is performed on the cell, specifically using alkaline solution NaOH with a volume concentration of 5% to etch the cell for 300s, forming a sloped structure at the edge of the junction between the laser area and the non-laser area of ​​the cell, with a slope of 150° and a vertical height of 170nm.

[0066] Example 6:

[0067] This embodiment 6 provides a method for preparing the side morphology of a thin grid of a solar cell, comprising the following steps:

[0068] Step 1: Set the laser parameters: the spot shape is rectangular, the length is 800μm, the width is 600μm, and the energy density at the center of the spot is 500µJ / cm 2 , the energy density at the edge of the spot is 25% lower than that at the center of the spot, where the area of ​​the edge of the spot accounts for 30% of the spot area;

[0069] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0070] Step three, alkaline etching is performed on the cell, specifically using alkaline solution NaOH with a volume concentration of 5% to etch the cell for 500s, forming a sloped and stepped combination structure at the edge of the junction between the laser area and the non-laser area of ​​the cell, with a vertical height of 180nm.

[0071] Comparative Example 1:

[0072] This comparative example 1 provides a method for preparing the side morphology of a solar cell fine grid, comprising the following steps:

[0073] Step 1: Set the laser parameters: the spot shape is rectangular, the length is 300μm, the width is 200μm, and the energy density of the spot is 400µJ / cm 2 ;

[0074] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0075] Step three: performing alkaline etching on the cell, specifically etching the cell with an alkaline solution NaOH having a volume concentration of 3% for 100 seconds to obtain a cell.

[0076] Comparative Example 2:

[0077] This comparative example 2 provides a method for preparing the side morphology of a solar cell fine grid, comprising the following steps: Step 1, setting the laser parameters: the spot shape is rectangular, the length is 400 μm, the width is 300 μm, and the energy density of the spot is 450 μJ / cm 2 ;

[0078] Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction.

[0079] Step three: performing alkaline etching on the cell, specifically etching the cell with alkaline solution NaOH having a volume concentration of 4% for 200 seconds to obtain a cell.

[0080] The solar cells obtained in the above examples and comparative examples were subjected to performance tests, and the results are as follows:

[0081] Table 1 Electrical performance test results of solar cells prepared in Examples and Comparative Examples

[0082] 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

[0083] Examples 1-6 of the present application utilize a laser spot with high energy density at the center and low energy density at the edges, combined with a subsequent etching process, to achieve a sloped, stepped, or combined structure at the junction of the laser and non-laser regions on the cell's fine grid edges. Comparative Examples 1-2 utilize a conventional laser process combined with a subsequent etching process to achieve steeper cell grid edges. As shown in Table 1, the cell photoelectric conversion efficiencies of Examples 1-6 of the present application are superior to those of Comparative Examples 1-2.

[0084] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing the side morphology of a solar cell fine grid, characterized in that: The steps include: Step 1: Set the laser parameters: the energy density at the center of the spot is 300~500µJ / cm 2 , the energy density at the edge of the light spot is 3~25% lower than the energy density at the center of the light spot; Step 2: Patterning with laser: Use laser spot to pattern the back of the cell along the electrode grid direction to form laser areas and non-laser areas that are alternately arranged along the grid direction. Step three: alkaline-etching the cell so that the edge of the junction between the laser area and the non-laser area of ​​the cell has a slope structure, a step structure, or a combination of a slope and a step structure.

2. The method for preparing the side morphology of the solar cell fine grid according to claim 1, characterized in that: The shape of the light spot in step 1 is one of a rectangle, a rounded / arc-cornered rectangle or an ellipse.

3. The method for preparing the side profile of a solar cell fine grid according to claim 2, characterized in that: The light spot in step 1 is in a rectangular shape with a length of 100-800 μm and a width of 30-600 μm.

4. The method for preparing the side morphology of the solar cell fine grid according to claim 1, characterized in that: The area of ​​the edge of the light spot in step 1 accounts for 1-30% of the area of ​​the light spot.

5. The method for preparing the side morphology of the solar cell fine grid according to claim 1, characterized in that: In the step 1, the wavelength of the laser is 532 nm, the power is 60-250 W, the frequency is 100-800 KHz, and the laser scanning speed is 10-100 m / s.

6. The method for preparing the side morphology of the solar cell fine grid according to claim 1, characterized in that: The vertical height of the sloped structure, the stepped structure, or the sloped and stepped combined structure is 100-180 nm.

7. The method for preparing the side profile of a solar cell fine grid according to claim 6, characterized in that: The slope of the sloped structure is 90-170°.

8. The method for preparing the side morphology of the solar cell fine grid according to claim 1, characterized in that: The alkaline etching in step three is specifically performed by using an alkaline solution of NaOH or KOH with a volume concentration of 1-5% to etch the cell for 50-500 seconds.

9. A solar cell, characterized in that: The fine grid side morphology of the solar cell is obtained by the preparation method according to any one of claims 1 to 8.

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