Patterned structure of back-contact solar cells, back-contact solar cells and solar cell modules

Abstract

This invention relates to the field of photovoltaic technology, specifically to the patterned structure of a back-contact solar cell, a back-contact solar cell, and a solar cell module. If the minority carrier lifetime at the center of the silicon wafer is greater than that at the edge, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from the center to the edge of the back-contact solar cell; the grid spacing also decreases from the center to the edge of the back-contact solar cell. Conversely, if the minority carrier lifetime at the center is less than that at the edge, and the difference is greater than 100 μs, then the opposite is true. This effectively improves the problem of high current-carrying recombination losses in back-contact solar cells, thereby enhancing their performance.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and more specifically, to the patterned structure of a back-contact solar cell, a back-contact solar cell, and a solar cell module. Background Technology

[0002] Back-contact solar cells are a type of solar cell technology that integrates all positive and negative metal contacts on the back side. Their grid-free design on the front side allows for greater absorption of sunlight, combining aesthetics with high power generation efficiency, making them suitable for distributed photovoltaic and commercial / industrial rooftop applications. The back-side pattern of a back-contact solar cell refers to the interlaced P- and N-region structures formed on the back of the cell using a specific process, along with the corresponding metal electrode patterns. Generally, back-contact solar cells employ a symmetrical layout of equal-width p / n functional regions, equal-width isolation regions, and equal-spacing main grids. However, in mass production, the following key defects exist: (1) large carrier recombination losses; (2) insufficient isolation reliability; and (3) uneven resistance losses.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a patterned structure for a back-contact solar cell, a back-contact solar cell, and a solar cell module. The patterned structure for the back-contact solar cell provided by this invention can effectively improve the problem of high current recombination loss in back-contact solar cells, thereby improving the performance of back-contact solar cells.

[0005] This invention is implemented as follows: In a first aspect, the present invention provides a patterned structure for a back-contact solar cell, wherein the patterned structure satisfies the following requirements: If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is greater than that at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from the center to the edge of the back contact solar cell; the fine grid spacing decreases from the center to the edge of the back contact solar cell. If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is less than the minority carrier lifetime at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from the edge to the center of the back contact solar cell; the fine grid spacing decreases from the edge to the center of the back contact solar cell. The functional regions are p-type doped functional regions and n-type doped functional regions.

[0006] In an optional implementation, the graphical structure meets the following requirements: If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is greater than that at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from (400-410) μm at the center of the back contact solar cell to (250-300) μm at the edge; the fine grid spacing decreases from (900-1200) μm at the center of the back contact solar cell to (750-860) μm at the edge. If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is less than that at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from (400-410) μm at the edge of the back contact solar cell to (250-300) μm at the center; the fine grid spacing decreases from (900-1200) μm at the edge of the back contact solar cell to (750-860) μm at the center. The functional regions are p-type doped functional regions and n-type doped functional regions.

[0007] In an optional implementation, the width of the functional area is reduced from (400-410) μm to (250-300) μm with a linear gradient of 65 μm / 30 mm.

[0008] In an optional implementation, the graphical structure meets the following requirements: If the edge doping diffusion of the functional region is greater than the center doping diffusion of the functional region, and the sheet resistance difference is greater than 4 ohms / sq, then the width of the isolation region decreases from the edge to the center of the back contact solar cell. If the edge doping diffusion of the functional region is less than the center doping diffusion of the functional region, and the sheet resistance difference is greater than 4 ohms / sq, then the width of the isolation region decreases from the center to the edge of the back contact solar cell.

[0009] In an optional implementation, the graphical structure meets the following requirements: If the edge doping diffusion amount of the functional region is greater than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the width of the isolation region shrinks from (120-170) μm at the edge of the back contact solar cell to (30-50) μm at the center. If the edge doping diffusion amount of the functional region is less than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the width of the isolation region shrinks from (120-170) μm at the center of the back contact solar cell to (30-50) μm at the edge.

[0010] In an optional implementation, the graphical structure meets the following requirements: If the edge doping diffusion amount of the functional region is greater than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the main grid spacing decreases from the edge to the center of the back contact solar cell; and the fine grid width decreases from the center to the edge of the back contact solar cell. If the edge doping diffusion amount of the functional region is less than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the main grid spacing decreases from the center to the edge of the back contact solar cell; and the fine grid width decreases from the edge to the center of the back contact solar cell.

[0011] In an optional implementation, the graphical structure meets the following requirements: If the edge doping diffusion amount of the functional region is greater than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the main grid spacing is reduced from (18-25) mm at the edge of the back contact solar cell to (10-15) mm at the center; and the fine grid width is reduced from (30-60) μm at the center of the back contact solar cell to (10-20) μm at the edge. If the edge doping diffusion amount of the functional region is less than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the main grid spacing is reduced from (18-25) mm at the center of the back contact solar cell to (10-15) mm at the edge; and the fine grid width is reduced from (30-60) μm at the edge of the back contact solar cell to (10-20) μm at the center.

[0012] Secondly, the present invention provides a back-contact solar cell, which includes the patterned structure of the back-contact solar cell described in any of the foregoing embodiments.

[0013] In an optional embodiment, the back contact solar cell includes any one of interdigitated back contact cells, tunnel oxide passivated contact back contact cells, heterojunction back contact cells, and high-low temperature composite passivated back contact cells.

[0014] Thirdly, the present invention provides a solar cell module comprising the back-contact solar cell described in the foregoing embodiments.

[0015] The present invention has the following beneficial effects: The back contact solar cell pattern structure provided by the present invention sets the width gradient of the p-type doped functional region and the n-type doped functional region in the functional region according to the minority carrier lifetime of the silicon wafer, thereby making the width of the functional region adapt to the in-plane gradient of the minority carrier lifetime of the silicon wafer, shortening the edge carrier transport distance, and thus reducing carrier recombination loss. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the patterned structure of the back-contact solar cell provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the patterned structure of the back-contact solar cell provided in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the patterned structure of the back-contact solar cell provided in Embodiment 3 of the present invention. Detailed Implementation

[0018] To make the objectives, 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] In a first aspect, the present invention provides a patterned structure for a back-contact solar cell, comprising alternating p-type doped functional regions, n-type doped functional regions, and isolation regions; further comprising a fine grid and a main grid; wherein both the p-type doped functional regions and the n-type doped functional regions are in contact with the fine grid, and both the p-type doped functional regions and the n-type doped functional regions are in contact with the main grid.

[0020] The graphic structure must meet the following requirements: If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is greater than that at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from the center to the edge of the back contact solar cell. That is, the width of the functional region decreases at equal intervals from the center to the edge of the back contact solar cell. For example, it decreases linearly from (400-410) μm at the center of the back contact solar cell to (250-300) μm at the edge; or from 410 μm at the center to 280 μm at the edge. Specifically, the width of the functional region decreases from (400-410) μm to (250-300) μm with a linear gradient of 65 μm / 30 mm. That is, it decreases by a linear gradient of 65 μm every 30 mm.

[0021] Simultaneously, the fine grid spacing is reduced, that is, it is reduced from the center to the edge of the back contact solar cell. For example, the fine grid spacing is reduced from (900-1200) μm at the center of the back contact solar cell to (750-860) μm at the edge. Specifically, for example, it is reduced from 900 μm at the center to 860 μm at the edge.

[0022] If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is less than the minority carrier lifetime at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional area and the fine grid spacing are set in the exact opposite way to the above settings.

[0023] Specifically, if the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is less than the minority carrier lifetime at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from the edge to the center of the back contact solar cell; for example, from (400-410) μm at the edge to (250-300) μm at the center. The fine grid spacing decreases from the edge to the center of the back contact solar cell; for example, from (900-1200) μm at the edge to (750-860) μm at the center.

[0024] It should be noted that the minority carrier lifetime mentioned above was tested using a minority carrier lifetime tester.

[0025] The functional regions are p-type doped functional regions and n-type doped functional regions. That is, the width of the functional region is the width of the p-type doped functional region and the width of the n-type doped functional region.

[0026] When the graphic structure meets the above requirements, it can adapt to the in-plane gradient of minority carrier lifetime, shorten the carrier transmission distance at the edge, and reduce carrier recombination loss.

[0027] In this embodiment of the invention, the graphic structure meets the following requirements: If the edge doping diffusion of the functional region is greater than the center doping diffusion, and the sheet resistance difference is greater than 4 ohms / sq, then the width of the isolation region decreases from the edge to the center of the back contact solar cell. In this case, the width of the isolation region adopts a gradual change from narrow at the center to wide at the edge. For example, it decreases from (120-170) μm at the edge to (30-50) μm at the center.

[0028] The opposite is true if the edge doping diffusion of the functional region is less than the center doping diffusion. Specifically, if the edge doping diffusion of the functional region is less than the center doping diffusion, and the sheet resistance difference is greater than 4 ohms / sq, then the width of the isolation region decreases from the center to the edge of the back contact solar cell. In this case, the width of the isolation region adopts a gradual width of "wider at the center and narrower at the edge". For example, it decreases from (120-170) μm at the center to (30-50) μm at the edge.

[0029] When the pattern structure meets the above requirements, it can further address the lateral diffusion deviation of doped elements in the functional area, thereby reducing edge leakage current or central dead zone area and improving isolation reliability.

[0030] It should be noted that the doping diffusion amount of the functional region refers to the concentration of boron doped in the p-type doped functional region or the concentration of phosphorus doped in the n-type doped functional region.

[0031] The doping diffusion amount is obtained through sheet resistance testing, which is generally performed during the process debugging stage. This testing method is an existing testing method and will not be described in detail in this invention.

[0032] In this embodiment of the invention, the pattern structure meets the following requirements: the edge doping diffusion amount of the functional region is greater than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohms / sq; then the main grid spacing decreases from the edge of the back contact solar cell to the center; that is, the main grid spacing adopts a non-equidistant layout of "dense at the center and sparse at the edge". For example, the (18-25) mm at the edge is reduced to (10-15) mm at the center.

[0033] At the same time, the width of the fine grid decreases from the center to the edge of the back contact solar cell; that is, the width of the fine grid is "wider at the center and narrower at the edge". For example, the width at the center is reduced from (30-60) μm to (10-20) μm at the edge.

[0034] If the edge doping diffusion of the functional region is less than the center doping diffusion, and the sheet resistance difference is greater than 4 ohms / sq, then the opposite is true. Specifically, if the edge doping diffusion of the functional region is less than the center doping diffusion, and the sheet resistance difference is greater than 4 ohms / sq, then the main grid spacing decreases from the center to the edge of the back contact solar cell; in this case, the main grid spacing is "sparser at the center and denser at the edge." For example, it decreases from (18-25) mm at the center to (10-15) mm at the edge. At the same time, the fine grid width decreases from the edge to the center of the back contact solar cell; that is, the fine grid width is "narrower at the center and wider at the edge." For example, it decreases from (30-60) μm at the edge to (10-20) μm at the center.

[0035] When the pattern structure meets the above requirements, it can further adapt to the current density gradient of large-size silicon wafers, thereby balancing resistance loss.

[0036] The present invention also provides a method for preparing the above-mentioned back-contact solar cell, comprising: 1. Double-sided alkaline etching (removing mechanical damage to the silicon wafer surface and forming a smooth plane); 0.5%~10% NaOH or KOH + 0.1%~5% additives, with the balance being water, reaction temperature 60~80℃, time 100~500s, after etching, the silicon wafer forms a smooth surface with a base of 15~50μm.

[0037] 2. LPCVD 1 (deposition of a-Si on both sides of silicon wafer); deposition temperature 500~700℃, time 10~100min, deposition of 100~500nm i-poly layer.

[0038] 3. Boron diffusion (double insertion, preparation of P-doped layer on the back side, p poly, forming PN junction); deposition temperature 750~900℃, time 5~60min, drive temperature 800~1000℃, time 10~60min; forming a p poly layer with sheet resistance of 50~400 ohm / sq and surface doping concentration of 1E19~9E19 atm / cm3.

[0039] 4. Patterning 1 (backside film opening, removal of n-region and isolation region BSG): Based on the sheet resistance distribution in step 3, design patterns with different widths and line spacings, and remove the surface BSG layer according to the patterns.

[0040] 5. Chain cleaning (removal of BSG coating on the front side); 40%-80% HF solution to remove the BSG layer on the front side until the front side is completely hydrophobic.

[0041] 6. Alkali etching (removal of p-poly in the N-region and isolation region on the back side and p-poly around the front side); 5%~20% NaOH or KOH + 0.1%~5% additives, with the balance being water, reaction temperature 60~85℃, time 100~500s. After etching, a smooth surface of 25~60μm is formed on the front side of the silicon wafer, and the p-poly in the patterned area 1 on the back side is completely etched, with a height difference of 0.5~3μm between it and the unetched area.

[0042] 7. LPCVD 2 (backside deposition of a-Si); deposition temperature 500~700℃, time 10~100min, deposition of 50~300nm poly layer.

[0043] 8. Phosphorus diffusion (forming an N-doped layer on the back side, n poly); deposition temperature 650~900℃, time 5~60min, drive-through temperature 700~900℃, time 10~60min; forming an n poly layer with a sheet resistance of 20~200 ohm / sq and a surface doping concentration of 1E20~1E21 atm / cm3.

[0044] 9. Patterning 2 (backside film opening, removal of PSG layer on top of p-area and isolation area): Combining the pattern design of Patterning 1 and the sheet resistance distribution in step 8, design patterns with different widths and line spacings, and remove the surface PSG layer according to the pattern.

[0045] 10. Chain cleaning (removal of PSG wrapped around the front side); 40%-80% HF solution to remove the BSG layer on the front side until the front side is completely hydrophobic.

[0046] 11. Texturing (removing the back P-area and isolation area n-poly and the front n-poly coating, forming a textured surface on the front and isolation areas); 5%~20% NaOH or KOH + 0.1%~5% additives, the balance being water, reaction temperature 60~85℃, time 100~500s. After etching, a smooth surface with a base of 25~60μm is formed on the front of the silicon wafer, and the p-poly in the patterned area 1 on the back is completely etched, with a height difference of 0.5~3μm between it and the unetched area.

[0047] 12. ALD: AlOx is deposited on both sides of a silicon wafer with a thickness of 3~20nm and a refractive index of 1.4~1.7.

[0048] 13. PECVD: Deposit SiNx antireflective coatings on both sides of a silicon wafer, with a thickness of 60~110nm and a refractive index of 1.9~2.2.

[0049] 14. Screen printing: Match the pattern design 1 and pattern design 2 for the N and P regions on the back of the silicon wafer, and print the metal grid lines respectively to complete the fabrication of the back contact solar cell.

[0050] Secondly, the present invention provides a back-contact solar cell, which includes the patterned structure of the back-contact solar cell described in any of the foregoing embodiments. This back-contact solar cell includes IBC (Interdigitated BackContact), TBC (Tunneling Oxide Passivated Contact BackContact), HBC (Heterojunction Back Contact), HIBC (Hybrid Interdigitated Back Contact), etc.

[0051] Thirdly, the present invention provides a solar cell module comprising the back-contact solar cell described in the foregoing embodiments.

[0052] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0053] Example 1 This embodiment provides a TBC (Transient Carbon-Based Cell) using an n-type Cz-Si silicon wafer. The minority carrier lifetime at the center of the wafer is greater than that at the edges, with a center minority carrier lifetime of 1450 μs and an edge minority carrier lifetime of 1200 μs. The doping diffusion at the edges of the functional regions is greater than that at the center, with a sheet resistance of ~98 ohms / sq for the p-region at the edge and ~110 ohms / sq for the p-region at the center; the sheet resistance of the n-region at the edge is ~29 ohms / sq, and the sheet resistance of the n-region at the center is ~41 ohms / sq. The wafer pattern is designed with gradients from the center to the edges. The pattern structure of this TBC cell is shown below. Figure 1 .

[0054] The graphic parameters are as follows: Functional regions: The silicon wafer is divided into three equal parts from its edge to its center, parallel to the fine gate direction. The p-type and n-type doped functional regions are designed with equal width. Extending 30mm from both edges towards the center, the width of the functional region is designed to be 280μm, named Width 1. Extending 30mm from Width 1 towards the center, the width of the functional region is designed to be 345μm, named Width 2. Extending Width 2 to the center, the width of the functional region is designed to be 410μm, named Width 3. Simultaneously, the fine gate spacing is expanded from 800μm at the edge of the silicon wafer (named Fine Gate Spacing Width 1) to 830μm (named Fine Gate Spacing Width 2) and 900μm (named Fine Gate Spacing Width 3) at the center.

[0055] Isolation area: Matches the gradient of the functional area. The width of the isolation area from the edge to the center is 120μm (named Isolation area width 1), 70μm (named Isolation area width 2), and 40μm (named Isolation area width 3).

[0056] Main grid spacing: The fine grid and the main grid adopt an 85° acute angle; the main grid spacing matches the functional area gradient, with the center to edge being 10mm (named main grid spacing 1), 18.4mm (named main grid spacing 2), and 25mm (named main grid spacing 3); the fine grid width is 50μm (named fine grid 1), 35μm (named fine grid 2), and 20μm (named fine grid 3) from the center to the edge.

[0057] This embodiment also provides a method for preparing the above-mentioned TBC battery, including: 1. Double-sided alkaline etching; 3% NaOH + 0.9% additive (purchased from companies such as Shichuang / Topband / Xiaochen), with the remainder being water, reaction temperature 72℃, time 180s, after etching, a smooth surface of 25μm is formed on the silicon wafer.

[0058] 2. LPCVD 1; deposition temperature 600℃, time 75min, deposition of 300nm i-poly layer.

[0059] 3. Boron diffusion; deposition temperature 800℃, time 25 min, drive-through temperature 930℃, time 35 min; sheet resistance 105 ohm / sq, surface doping concentration 3E19 atm / cm 3 p poly layer.

[0060] 4. Graphicalization 1: Based on the sheet resistance distribution in step 3, design graphics with different widths and line spacings, and remove the surface BSG layer according to the graphics.

[0061] 5. Chain cleaning (removal of BSG coating on the front side); remove the BSG layer on the front side with 70% HF solution until the front side is completely hydrophobic.

[0062] 6. Alkali etching: 9% NaOH + 1.8% additive, balance water, reaction temperature 82℃, time 210s. After etching, a smooth surface of 40μm is formed on the front side of the silicon wafer, and the p poly in the patterned area 1 on the back side is completely etched, with a height difference of 1.7μm between it and the unetched area.

[0063] 7. LPCVD 2; deposition temperature 595℃, time 45min, deposition of 230nm i-poly layer.

[0064] 8. Phosphorus diffusion; deposition temperature 760℃, time 20 min; drive-up temperature 830℃, time 30 min; sheet resistance 35 ohm / sq; surface doping concentration 5E20 atm / cm 3 n poly layers.

[0065] 9. Graphicalization 2: Combining the graphic design of Graphicalization 1 with the sheet resistance distribution in step 8, design graphics with different widths and line spacings, and remove the surface PSG layer according to the graphics.

[0066] 10. Chain cleaning: Remove the front-side BSG layer with 70% HF solution until the front side is completely hydrophobic.

[0067] 11. Texturing: 2% KOH + 1.5% additives, balance water, reaction temperature 75℃, time 530s. After etching, a pyramid structure is formed in the isolation areas on the front and back sides of the silicon wafer. The p-poly in the patterned area 1 on the back side is completely etched, and there is a 3μm height difference with the unetched area.

[0068] 12. ALD: AlOx is deposited on both sides of a silicon wafer with a thickness of 5.1 nm and a refractive index of 1.56.

[0069] 13. PECVD: Deposition of SiNx antireflective coatings on both sides of a silicon wafer, with a thickness of 80 nm and a refractive index of 2.07.

[0070] 14. Screen printing: Match the pattern design 1 and pattern design 2 for the N and P regions on the back of the silicon wafer, and print the metal grid lines respectively to complete the fabrication of the back contact solar cell.

[0071] Performance tests were conducted on the aforementioned back-contact solar cells: Electrical properties: V oc =745mV, J sc =42.8mA / cm², FF=85.2%, conversion efficiency=27.17%.

[0072] Yield: Laser film opening yield 99.95%, screen printing yield 99.98%, overall yield 98.1%.

[0073] Comparative Example 1 This comparative example provides a patterned structure, which is an existing equal-width patterned structure. Specifically, the width of both the n-type doped functional region and the p-type doped functional region is 410 μm, the width of the isolation region is 80 μm, and the line spacing is 980 μm. Its performance test results are as follows: Electrical performance: V oc =743mV, J sc =42.62mA / cm², FF=84.73%, conversion efficiency=26.83%. Yield: laser film opening yield 99.75%, screen printing yield 99.17%, overall yield 96.8%.

[0074] Comparing Example 1 and Comparative Example 1, it can be seen that the gradient-set functional region width shortens the edge carrier transport distance, reduces recombination loss, and increases Voc by 2mV. The fine gate width gradient reduces the transport resistance of the highly doped region; at the same time, the non-equidistant main gate spacing balances the resistance loss, together increasing FF by 0.47%. The overall efficiency is improved by 0.34%. The gradient isolation zone reduces edge leakage rate and the risk of silicon wafer cracking; the 85° angle electrode between the main gate and the fine gate improves printing yield, resulting in an overall yield improvement of more than 1%. Example 2 This embodiment provides a TBC (Transient Carbon-Based Cell) using an n-type Cz-Si silicon wafer. The minority carrier lifetime at the center of the wafer is greater than that at the edges, with a center minority carrier lifetime of 1450 μs and an edge minority carrier lifetime of 1200 μs. The doping diffusion at the edges of the functional regions is greater than that at the center, with a sheet resistance of ~98 ohms / sq for the p-region at the edge and ~110 ohms / sq for the p-region at the center; the sheet resistance of the n-region at the edge is ~29 ohms / sq, and the sheet resistance of the n-region at the center is ~41 ohms / sq. The wafer pattern is designed with gradients from the center to the edges. The pattern structure of this TBC cell is shown below. Figure 2 .

[0075] The graphic parameters are as follows: Functional regions: The silicon wafer is divided into three equal parts from its edge to its center, parallel to the fine gate direction. The p-type and n-type doped functional regions are designed with equal width. Extending 30mm from both edges towards the center, the width of the functional region is designed to be 280μm, named Width 1. Extending 30mm from Width 1 towards the center, the width of the functional region is designed to be 345μm, named Width 2. Extending Width 2 to the center, the width of the functional region is designed to be 410μm, named Width 3. Simultaneously, the fine gate spacing is expanded from 800μm at the edge of the silicon wafer (named Fine Gate Spacing Width 1) to 830μm (named Fine Gate Spacing Width 2) and 900μm (named Fine Gate Spacing Width 3) at the center.

[0076] Isolation area: Matches the gradient of the functional area. The width of the isolation area from the edge to the center is 120μm (named Isolation area width 1), 70μm (named Isolation area width 2), and 40μm (named Isolation area width 3).

[0077] Main grid spacing: The fine grid and the main grid adopt an 85° acute angle; the main grid spacing matches the functional area gradient, with the center to edge being 10mm (named main grid spacing 1), 18.4mm (named main grid spacing 2), and 25mm (named main grid spacing 3); the fine grid width is 50μm (named fine grid 1), 35μm (named fine grid 2), and 20μm (named fine grid 3) from the center to the edge.

[0078] A vertical fine gate edge gradually transitions towards the center, and a through functional area (region 1) is set to connect the edge main gate, thereby maximizing the utilization of the silicon wafer area.

[0079] The TBC battery is prepared according to the preparation method in Example 1.

[0080] Performance tests were conducted on the aforementioned back-contact solar cells: Electrical performance: Voc=747mV, Jsc=42.8mA / cm², FF=85.5%, conversion efficiency=27.34%.

[0081] Yield: Laser film opening yield 99.95%, screen printing yield 99.98%, overall yield 98.9%.

[0082] Comparative Example 2 This comparative example provides a patterned structure, which is an existing equal-width patterned structure. Specifically, the width of both the n-type doped functional region and the p-type doped functional region is 410 μm, the width of the isolation region is 80 μm, and the line spacing is 980 μm. Its performance test results are as follows: Electrical performance: V oc =743mV, J sc =42.62mA / cm², FF=84.73%, conversion efficiency=26.83%. Yield: laser film opening yield 99.75%, screen printing yield 99.17%, overall yield 96.8%.

[0083] Comparing Example 2, Example 1, and Comparative Example 2, it can be seen that by gradient-setting the functional region width from the edge to the center of the entire silicon wafer, the edge carrier transport distance is shortened, recombination loss is reduced, and Voc is increased by 4mV. The fine gate width gradient reduces the transport resistance of the highly doped region; simultaneously, the non-equidistant main gate spacing balances the resistance loss, together increasing FF by 0.77%. The overall efficiency is improved to 27.34%. The gradient isolation region reduces edge leakage and the risk of wafer cracking; the 85° angled electrodes between the main gate and the fine gate improve printing yield. Overall yield is further improved to over 98%.

[0084] Example 3 This embodiment provides a TBC (Transient Carbon-Based Cell) using an n-type Cz-Si silicon wafer. The minority carrier lifetime at the center of the wafer is greater than that at the edges, with a center minority carrier lifetime of 1450 μs and an edge minority carrier lifetime of 1200 μs. The doping diffusion at the edges of the functional regions is greater than that at the center, with a sheet resistance of ~98 ohms / sq for the p-region at the edge and ~110 ohms / sq for the p-region at the center; the sheet resistance of the n-region at the edge is ~29 ohms / sq, and the sheet resistance of the n-region at the center is ~41 ohms / sq. The wafer pattern is designed with gradients from the center to the edges. The pattern structure of this TBC cell is shown below. Figure 3 .

[0085] The graphic parameters are as follows: Functional regions: The silicon wafer is divided into three equal parts from its edge to its center, parallel to the fine gate direction. The p-type and n-type doped functional regions are designed with equal width. Extending 30mm from both edges towards the center, the width of the functional region is designed to be 280μm, named Width 1. Extending 30mm from Width 1 towards the center, the width of the functional region is designed to be 345μm, named Width 2. Extending Width 2 to the center, the width of the functional region is designed to be 410μm, named Width 3. Simultaneously, the fine gate spacing is expanded from 800μm at the edge of the silicon wafer (named Fine Gate Spacing Width 1) to 830μm (named Fine Gate Spacing Width 2) and 900μm (named Fine Gate Spacing Width 3) at the center.

[0086] Isolation area: Matches the gradient of the functional area. The width of the isolation area from the edge to the center is 120μm (named Isolation area width 1), 70μm (named Isolation area width 2), and 40μm (named Isolation area width 3).

[0087] Main gate spacing: The fine gate and the main gate are perpendicular to each other; the main gate spacing in different areas is 18mm; the fine gate width in different areas is 35μm.

[0088] The TBC battery is prepared according to the preparation method in Example 1.

[0089] Performance tests were conducted on the aforementioned back-contact solar cells: Electrical performance: Voc=745mV, Jsc=42.64mA / cm², FF=84.9%, conversion efficiency=26.97%.

[0090] Yield: Laser film opening yield 99.95%, screen printing yield 98.68%, overall yield 97.3%.

[0091] Compared with Comparative Example 1, Example 3 shows that the gradient setting shortens the edge carrier transport distance and reduces recombination loss, resulting in a 2mV increase in Voc, thus improving efficiency. However, the setting of equal width for the fine gate and equal spacing between the main gates does not significantly improve carrier collection; therefore, the efficiency of Comparative Example 1 is only improved by 0.14%. The gradient isolation zone reduces edge leakage current and the risk of silicon wafer cracking. Overall yield is further improved to over 97%.

[0092] In summary, the graphic structure provided by this invention has the following advantages: 1. Efficiency Improvement: Gradient setting of functional area width shortens the edge carrier transport distance, reducing recombination loss by 0.2%. – Fine gate width gradient setting reduces the transport resistance of highly doped regions, improving FF by 0.15%. Non-equidistant main gate spacing balances resistance loss, further improving FF by 0.2%. Overall efficiency improvement is over 0.5%. 2. Yield Improvement: Gradient isolation areas reduce edge leakage rate by 40% and wafer cracking risk by 1.5%. Sharp-angle electrodes improve printing yield by 3% and reduce short-circuit rate by 2.5%. Overall yield improvement is over 1.5%. 3. High process compatibility: No additional equipment modification is required. It can be directly imported into existing TBC battery mass production lines and is compatible with the complete process chain of "dual insertion LPCVD - dual doping - dual laser film opening".

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A patterned structure for a back-contact solar cell, characterized in that, The graphic structure must meet the following requirements: If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is greater than that at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from the center to the edge of the back contact solar cell; the fine grid spacing decreases from the center to the edge of the back contact solar cell. If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is less than the minority carrier lifetime at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from the edge to the center of the back contact solar cell; the fine grid spacing decreases from the edge to the center of the back contact solar cell. The functional regions are p-type doped functional regions and n-type doped functional regions.

2. The patterned structure of the back-contact solar cell according to claim 1, characterized in that, The graphic structure must meet the following requirements: If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is greater than that at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from (400-410) μm at the center of the back contact solar cell to (250-300) μm at the edge; the fine grid spacing decreases from (900-1200) μm at the center of the back contact solar cell to (750-860) μm at the edge. If the minority carrier lifetime at the center of the silicon wafer forming the back contact solar cell is less than that at the edge of the silicon wafer, and the difference is greater than 100 μs, then the width of the functional region decreases linearly from (400-410) μm at the edge of the back contact solar cell to (250-300) μm at the center; the fine grid spacing decreases from (900-1200) μm at the edge of the back contact solar cell to (750-860) μm at the center. The functional regions are p-type doped functional regions and n-type doped functional regions.

3. The patterned structure of the back-contact solar cell according to claim 2, characterized in that, The width of the functional area decreases from (400-410) μm to (250-300) μm with a linear gradient of 65 μm / 30 mm.

4. The patterned structure of the back-contact solar cell according to any one of claims 1-3, characterized in that, The graphic structure must meet the following requirements: If the edge doping diffusion of the functional region is greater than the center doping diffusion of the functional region, and the sheet resistance difference is greater than 4 ohms / sq, then the width of the isolation region decreases from the edge to the center of the back contact solar cell. If the edge doping diffusion of the functional region is less than the center doping diffusion of the functional region, and the sheet resistance difference is greater than 4 ohms / sq, then the width of the isolation region decreases from the center to the edge of the back contact solar cell.

5. The patterned structure of the back-contact solar cell according to claim 4, characterized in that, The graphic structure must meet the following requirements: If the edge doping diffusion amount of the functional region is greater than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the width of the isolation region shrinks from (120-170) μm at the edge of the back contact solar cell to (30-50) μm at the center. If the edge doping diffusion amount of the functional region is less than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the width of the isolation region shrinks from (120-170) μm at the center of the back contact solar cell to (30-50) μm at the edge.

6. The patterned structure of the back-contact solar cell according to any one of claims 1-3, characterized in that, The graphic structure must meet the following requirements: If the edge doping diffusion amount of the functional region is greater than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the main grid spacing decreases from the edge to the center of the back contact solar cell; and the fine grid width decreases from the center to the edge of the back contact solar cell. If the edge doping diffusion amount of the functional region is less than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the main grid spacing decreases from the center to the edge of the back contact solar cell; and the fine grid width decreases from the edge to the center of the back contact solar cell.

7. The patterned structure of the back-contact solar cell according to claim 6, characterized in that, The graphic structure must meet the following requirements: If the edge doping diffusion amount of the functional region is greater than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the main grid spacing is reduced from (18-25) mm at the edge of the back contact solar cell to (10-15) mm at the center; and the fine grid width is reduced from (30-60) μm at the center of the back contact solar cell to (10-20) μm at the edge. If the edge doping diffusion amount of the functional region is less than the center doping diffusion amount of the functional region, and the sheet resistance difference is greater than 4 ohm / sq, then the main grid spacing is reduced from (18-25) mm at the center of the back contact solar cell to (10-15) mm at the edge; and the fine grid width is reduced from (30-60) μm at the edge of the back contact solar cell to (10-20) μm at the center.

8. A back-contact solar cell, characterized in that, It includes the patterned structure of the back-contact solar cell as described in any one of claims 1-7.

9. The back-contact solar cell according to claim 8, characterized in that, The back-contact solar cell includes any one of the following: interdigitated back-contact cell, tunnel oxide passivated contact back-contact cell, heterojunction back-contact cell, and high-low temperature composite passivated back-contact cell.

10. A solar cell module, characterized in that, It includes the back-contact solar cell as described in claim 8 or 9.

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