Crystalline silicon cell cutting edge passivation method

Abstract

The invention provides a crystalline silicon cell cutting edge passivation method, which comprises the following steps of S1, stacking and fixing a plurality of sliced cell pieces, and enabling the cutting surfaces of the plurality of cell pieces to be flush with each other; s2, placing the stacked battery pieces in an oxygen atmosphere, and scanning the cutting surfaces of the battery pieces by using laser; and S3, putting the battery piece into a nitrogen atmosphere for annealing treatment. According to the crystalline silicon cell cutting edge passivation method, in the oxygen atmosphere, laser is used for scanning the cell cutting edge to generate a compact silicon dioxide passivation layer, and high-temperature annealing treatment is carried out in the nitrogen atmosphere to form the silicon dioxide passivation layer, so that carrier recombination at the edge of the cell is reduced; the open-circuit voltage and the short-circuit current of the cell are improved, the photoelectric conversion efficiency of the cell is further improved, the efficiency loss caused by cutting is effectively made up, meanwhile, the silver grid line oxidized by oxygen in the oxygen atmosphere can be reduced and repaired in the high-temperature annealing process, and the conductivity is improved.

Description

Technical Field

[0001] This invention relates to the field of TOPCon battery production, and more particularly to a method for passivating the cutting edges of crystalline silicon batteries. Background Technology

[0002] In the production process of solar cell modules, the cells need to be welded together and then laminated and encapsulated. This is because the heat loss of the cells themselves follows the formula P=I0. 2 R represents the current, and the higher the current, the greater the power loss due to heat. Therefore, during the production of modules, it is often necessary to cut a cell into two or more halves to reduce the current of a single cell and thus reduce heat loss. Currently, the mainstream cutting method mainly uses two laser beams to cut the cell along the split line. At the same time, the cooling unit sprays cooling medium onto the split line, so that the cell is cut under relatively low internal stress.

[0003] The current TOPCon cells have undergone aluminum oxide and composite silicon nitride stack passivation on the front and sides respectively, resulting in high passivation quality. However, after the silicon wafer is back-cut, there are a large number of dangling bonds on the cut edge, which leads to a high carrier recombination rate, resulting in a decrease in the cell's open voltage and thus affecting efficiency. Data shows that the absolute efficiency of the cell decreases by about 0.2% with each cut.

[0004] Existing methods for passivating the edges of battery cutting include PECVD deposition, thermal oxidation, and photocatalytic oxidation. Among these, PECVD deposition results in poor edge coverage uniformity. The geometry of silicon wafer edges (especially rounded edges or chamfers) is complex, and the distribution of plasma at the edges is easily affected by the "shadowing effect," leading to uneven passivation layer thickness (locally too thin or too thick), and even "exposed" areas in some regions, failing to effectively suppress edge recombination. The high temperature of thermal oxidation can significantly reduce the lifespan of silicon wafers and may also trigger impurity diffusion, affecting the electrical parameters of the device. Photocatalytic oxidation relies on light intensity and catalyst activity, producing a thin oxide layer with poor density, making it difficult to form a long-term stable passivation barrier, and easily affected by environmental humidity and impurities, leading to failure.

[0005] Therefore, it is necessary to design a passivation method for the cutting edges of crystalline silicon solar cells to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a simple method for passivating the cutting edges of crystalline silicon solar cells that does not introduce new impurities.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for passivating the cutting edge of a crystalline silicon solar cell, comprising the following steps: S1. Stack and fix the multiple sliced ​​battery cells together, ensuring that the cut surfaces of the multiple battery cells are flush.

[0008] S2. Place the stacked solar cells in an oxygen atmosphere and scan the cut surfaces of the solar cells with a laser; under the action of the laser, the cut edges of the solar cells quickly generate dense silicon oxide with oxygen.

[0009] S3. Anneal the battery cells in a nitrogen atmosphere.

[0010] As a further improvement of the present invention, in step S1, the number of stacked battery cells is 2-1000.

[0011] As a further improvement of the present invention, in step S2, the molar concentration of oxygen is ≥95% and the oxygen flow rate is 5-15 L / min.

[0012] As a further improvement to the present invention, in step S2, an ultraviolet laser is used to scan the cut surface with a wavelength of 200-400nm. At the cut edge of the solar cell, the surface is not a smooth plane or a large-radius arc, but rather has a relatively sharp curved surface or localized severe curvature. This high curvature causes the edge of the solar cell to exhibit different characteristics in terms of optics and material properties compared to the flat portion of the cell, thus affecting physical processes such as light absorption. Using a short-wavelength laser, which has higher light energy absorption and conversion, can match the light absorption characteristics of the high-curvature silicon-based region at the edge of the solar cell. After the high-curvature edge forms a high-quality passivation layer through efficient light absorption by short-wavelength lasers (such as 248nm, 266nm, 355nm, 365nm, etc.), the dangling bonds are effectively saturated, extending the minority carrier lifetime. Simultaneously, the edge leakage channel is blocked, reducing the reverse saturation current, laying the foundation for improving open-circuit voltage, short-circuit current, and conversion efficiency.

[0013] As a further improvement to the present invention, in step S2, the laser pulse width is 10-50 ns and the repetition frequency is 50-100 kHz. This allows for rapid application to the cut surface, suppressing heat diffusion and preventing damage to the internal structure and the passivation layers on both sides of the battery cell.

[0014] As a further improvement to this invention, the cutting surface of the solar cell is perpendicular to the laser axis, and the laser spot diameter is 10-30 μm. This increases the energy density in the edge region and ensures the density of the generated oxide layer.

[0015] As a further improvement to the present invention, in step S3, the laser radial scanning speed is 200-600 mm / s, and the spot overlap rate is 10%-20%. This avoids heat accumulation leading to microcracks and affecting passivation performance.

[0016] As a further improvement of the present invention, in step S3, the molar concentration of nitrogen is ≥98%.

[0017] As a further improvement of the present invention, in step S3, the annealing temperature is 450℃-500℃. Annealing promotes atomic rearrangement within the silicon dioxide passivation layer, reduces lattice defects and interface state density, and enhances the bonding strength between the passivation layer and the silicon substrate. At the same time, the high-temperature process can reduce the silver gate lines oxidized by oxygen in a pure oxygen environment, repair the silver gate lines, and improve conductivity.

[0018] As can be seen from the above technical solutions, the crystalline silicon cell cutting edge passivation method of the present invention generates a dense silicon dioxide passivation layer by scanning the cutting edge of the cell with a laser in an oxygen atmosphere, and then forming the silicon dioxide passivation layer by high-temperature annealing in a nitrogen atmosphere. This reduces carrier recombination at the edge of the cell, improves the open-circuit voltage and short-circuit current of the cell, and thus improves the photoelectric conversion efficiency of the cell, effectively compensating for the efficiency loss caused by cutting. At the same time, the high-temperature annealing process can also reduce the silver grid lines oxidized by oxygen in the oxygen atmosphere, repair the silver grid lines, and improve conductivity. Attached Figure Description

[0019] Figure 1 These are test images of the initial PL brightness, PL brightness after scribing, and PL brightness after passivation of the battery in Examples 1-4 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Example 1

[0021] Step S1: Stack 50 sliced ​​battery cells together and fix them in place, ensuring that the cut surfaces of the multiple battery cells are flush. Step S2: Place the stacked solar cells in an oxygen atmosphere with a molar concentration of 99% and an oxygen flow rate of 10 L / min. Scan the cut surface of the solar cells with a laser. Use a 355 nm ultraviolet laser with a pulse width of 30 ns, a repetition rate of 75 kHz, the cut surface of the solar cells perpendicular to the laser axis, a spot diameter of 20 μm, a laser radial scanning speed of 400 mm / s, and a spot overlap rate of 15%. Step S3: Place the battery cells in a nitrogen atmosphere for annealing treatment, with a nitrogen molar concentration of 99% and an annealing temperature of 475℃. Example 2

[0022] Step S1: Stack 200 sliced ​​battery cells together and fix them in place, ensuring that the cut surfaces of the multiple battery cells are flush. Step S2: Place the stacked solar cells in an oxygen atmosphere with a molar concentration of 97% and an oxygen flow rate of 8 L / min. Scan the cut surface of the solar cells with a laser. Use a 365 nm ultraviolet laser with a pulse width of 30 ns, a repetition rate of 75 kHz, the cut surface of the solar cells perpendicular to the laser axis, a spot diameter of 20 μm, a laser radial scanning speed of 400 mm / s, and a spot overlap rate of 15%. Step S3: The battery cells are placed in a nitrogen atmosphere for annealing treatment, with a nitrogen molar concentration of 98.5% and an annealing temperature of 480℃. Example 3

[0023] Step S1: Stack 100 sliced ​​battery cells together and fix them in place, ensuring that the cut surfaces of the multiple battery cells are flush. Step S2: Place the stacked solar cells in an oxygen atmosphere with a molar concentration of 96% and an oxygen flow rate of 12 L / min. Scan the cut surface of the solar cells with a laser. Use a 355 nm ultraviolet laser with a pulse width of 20 ns, a repetition rate of 90 kHz, the cut surface of the solar cells perpendicular to the laser axis, a spot diameter of 15 μm, a laser radial scanning speed of 600 mm / s, and a spot overlap rate of 12%. Step S3: Place the battery cells in a nitrogen atmosphere for annealing treatment, with a nitrogen molar concentration of 99% and an annealing temperature of 460℃. Example 4

[0024] Step S1: Stack 500 sliced ​​battery cells together and fix them in place, ensuring that the cut surfaces of the multiple battery cells are flush. Step S2: Place the stacked solar cells in an oxygen atmosphere with a molar concentration of 98% and an oxygen flow rate of 6 L / min. Scan the cut surface of the solar cells with a laser. Use a 365 nm ultraviolet laser with a pulse width of 40 ns, a repetition rate of 60 kHz, the cut surface of the solar cells perpendicular to the laser axis, a spot diameter of 25 μm, a laser radial scanning speed of 300 mm / s, and a spot overlap rate of 18%. Step S3: Place the battery cells in a nitrogen atmosphere for annealing treatment, with a nitrogen molar concentration of 98% and an annealing temperature of 450°C. Example 5

[0025] Step S1: Stack the 10 sliced ​​battery cells together and fix them in place, ensuring that the cut surfaces of the multiple battery cells are flush. Step S2: Place the stacked solar cells in an oxygen atmosphere with a molar concentration of 95% and an oxygen flow rate of 15 L / min. Scan the cut surface of the solar cells with a laser. Use a 355 nm ultraviolet laser with a pulse width of 50 ns, a repetition rate of 50 kHz, the cut surface of the solar cells perpendicular to the laser axis, a spot diameter of 30 μm, a laser radial scanning speed of 200 mm / s, and a spot overlap rate of 20%. Step S3: Place the battery cells in a nitrogen atmosphere for annealing treatment, with a nitrogen molar concentration of 99.5% and an annealing temperature of 500℃. Comparative Example 1

[0026] Step S1: Stack 50 sliced ​​battery cells together and fix them in place, ensuring that the cut surfaces of the multiple battery cells are flush. Step S2: Place the stacked solar cells in an oxygen atmosphere with a molar concentration of 99% and an oxygen flow rate of 10 L / min. Scan the cut surface of the solar cells with a laser. Use a 532 nm laser with a pulse width of 30 ns, a repetition rate of 75 kHz, the cut surface of the solar cells perpendicular to the laser axis, a spot diameter of 20 μm, a laser radial scanning speed of 400 mm / s, and a spot overlap rate of 15%. Step S3: Place the battery cells in a nitrogen atmosphere for annealing treatment, with a nitrogen molar concentration of 99% and an annealing temperature of 475℃. Comparative Example 2

[0027] Step S1: Place one sliced ​​battery cell separately (without stacking). Step S2: Place the solar cell in an oxygen atmosphere with a molar concentration of 99% and an oxygen flow rate of 10 L / min. Scan the cut surface of the solar cell with a laser. Use a 355 nm ultraviolet laser with a pulse width of 30 ns, a repetition rate of 75 kHz, the cut surface of the solar cell perpendicular to the laser axis, a spot diameter of 20 μm, a laser radial scanning speed of 400 mm / s, and a spot overlap rate of 15%. Step S3: Place the battery cells in a nitrogen atmosphere for annealing treatment, with a nitrogen molar concentration of 99% and an annealing temperature of 475℃. Comparative Example 3

[0028] Step S1: Stack 50 sliced ​​battery cells together and fix them in place, ensuring that the cut surfaces of the multiple battery cells are flush. Step S2: Place the stacked solar cells in an oxygen atmosphere with a molar concentration of 99% and an oxygen flow rate of 10 L / min. Scan the cut surface of the solar cells with a laser. Use a 355 nm ultraviolet laser with a pulse width of 30 ns, a repetition rate of 75 kHz, the cut surface of the solar cells perpendicular to the laser axis, a spot diameter of 20 μm, a laser radial scanning speed of 400 mm / s, and a spot overlap rate of 15%. Step S3: Place the battery cells in a nitrogen atmosphere for annealing treatment, with a nitrogen molar concentration of 99% and an annealing temperature of 400℃.

[0029] Table 1 shows the parameter comparison in each embodiment and comparative example; Table 2 shows the performance test data of the battery cells before and after passivation in each of embodiments 1-4. The specific test descriptions are as follows: PL Testing: The solar cells of each embodiment and comparative example, before and after passivation, were precisely fed into a sealed test chamber via a conveyor belt. Subsequently, a pre-set LED surface light source array inside the chamber was instantly activated, uniformly illuminating the solar cells with wavelength-matched near-infrared light. The exposure time and intensity remained consistent before and after passivation. Simultaneously with the completion of exposure, a near-infrared industrial CCD camera, triggered synchronously with the light source, rapidly captured the fluorescence signal emitted by the solar cells, generating a high-resolution PL brightness image. Please refer to [link / reference] for details. Figure 1 As can be seen from the test graphs of the initial PL brightness, PL brightness after dicing, and PL brightness after passivation of the battery cells in Examples 1-4 of this invention, the PL brightness of the battery cells after passivation in the examples shows a slight increase. Please also refer to Table 2; from the brightness data, the PL brightness of the battery cells in the examples is improved after passivation, while the brightness decreases in the comparative examples.

[0030] Conversion efficiency test: The photoelectric conversion efficiency of the solar cell was calculated by taking into account the open-circuit voltage, short-circuit current and fill factor parameters. The results are shown in Table 3. Table 1 Comparison of parameters in each embodiment and comparative example.

[0031] Table 2 Comparison of brightness of battery cells after passivation in various embodiments and comparative examples.

[0032] Table 3 Performance improvement data of the solar cells after passivation in each embodiment

[0033] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. The understanding of this specification should be based on those skilled in the art. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for passivating the cutting edge of a crystalline silicon solar cell, characterized in that, Includes the following steps: S1. Stack and fix the multiple sliced ​​battery cells together, with the cut surfaces of the multiple battery cells flush. S2. Place the stacked solar cells in an oxygen atmosphere and scan the cut surfaces of the solar cells with a laser. S3. Anneal the battery cells in a nitrogen atmosphere.

2. The method for passivating the cutting edge of a crystalline silicon solar cell as described in claim 1, characterized in that: In step S1, the number of stacked solar cells is 2-1000.

3. The method for passivating the cutting edge of a crystalline silicon solar cell as described in claim 1, characterized in that: In step S2, the molar concentration of oxygen is ≥95%, and the oxygen flow rate is 5-15 L / min.

4. The method for passivating the cutting edge of a crystalline silicon solar cell as described in claim 1, characterized in that: In step S2, an ultraviolet laser is used to scan the cut surface with a laser wavelength of 200-400nm.

5. The method for passivating the cutting edge of a crystalline silicon solar cell as described in claim 1, characterized in that: In step S2, the pulse width of the laser is 10-50 ns and the repetition frequency is 50-100 kHz.

6. The method for passivating the cutting edge of a crystalline silicon solar cell as described in claim 1, characterized in that: The cut surface of the solar cell is perpendicular to the laser axis, and the laser spot diameter is 10-30μm.

7. The method for passivating the cutting edge of a crystalline silicon solar cell as described in claim 1, characterized in that: In step S3, the laser radial scanning speed is 200-600 mm / s, and the spot overlap rate is 10%-20%.

8. The method for passivating the cutting edge of a crystalline silicon solar cell as described in claim 1, characterized in that: In step S3, the molar concentration of nitrogen is ≥98%.

9. The method for passivating the cutting edge of a crystalline silicon solar cell as described in claim 1, characterized in that: In step S3, the annealing temperature is 450℃-500℃.

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